Journal of Aging and Physical Activity, 2015, 23, 1-8 http://dx.doi.org/10.1123/JAPA.2013-0038 © 2015 Human Kinetics, Inc.
Official Journal of ICAPA www.JAPA-Journal.com ORIGINAL RESEARCH
Association of Muscle-strengthening Activity With Knee and Low Back Pain, Falls, and Health-related Quality of Life Among Japanese Older Adults: A Cross-sectional Survey Kazuhiro Harada, Ai Shibata, Koichiro Oka, and Yoshio Nakamura This study aimed to examine the association of muscle-strengthening activity with knee and low back pain, falls, and health-related quality of life among Japanese older adults. A cross-sectional survey targeted 3,000 people. The response rate was 52% and 208 respondents did not meet the inclusion criteria. Therefore, 1,351 individuals were analyzed. Muscle-strengthening activity (exercise using equipment and body weight, lifestyle activities), knee and low back pain, falls over the past year, health-related quality of life (SF-8), and potential confounders were assessed. Individuals engaging in exercise using body weight and lifestyle activity (≥ 2 days/week) were more likely to have knee pain. Engaging in exercise using equipment and body weight was associated with higher scores of general health. These results indicate that exercise using equipment and body weight might have a positive effect on health-related quality of life, but muscle-strengthening activities are associated with knee pain in older people. Keywords: accidental falls, musculoskeletal pain, public health, quality of life, resistance training, sports medicine
Current physical activity guidelines recommend musclestrengthening activity for health promotion among all adults, including older people (Canadian Society for Exercise Physiology [CSEP], 2011a, 2011b; United States Department of Health and Human Services [USDHHS], 2008). In Japan, the increase in the number of frail older adults is a critical issue for the health system. The Japan Ministry of Health, Labor, and Welfare (JMHLW) recognized the importance of reducing knee and lower back pain, and the prevention of falls, for maintaining the physical functioning of older adults (JMHLW, 2009b). They recommended muscle-strengthening activity for the reduction of pain and fall risk among older adults (JMHLW, 2009b). In addition, the JMHLW (2009b) indicated that the improvement of these conditions by muscle-strengthening activity could lead to a positive change in health-related quality of life among older adults. In support of these guidelines, intervention studies have suggested that muscle-strengthening activity is effective for reducing knee and lower back pain, risk of fall, and improving health-related quality of life among older adults (Cassilhas et al., 2007; de Vreede et al., 2007; Gillespie et al., 2012; Hayden, van Tulder, & Tomlinson, 2005; Lange, Vanwanseele, & FiataroneSingh., 2008; Kimura et al., 2010; Sherrington, Tiedemann, Fairhall, Close, & Lord, 2011). Despite general agreement about the value of muscle-strengthening activity for older adults, experimental interventions have been largely conducted in controlled environments (e.g., careful management of adverse events, incentives, usage of special equipment) and lasted only 3 to 6 months (Liu & Latham, 2009). Therefore, they may not reflect typical real-world muscle-strengthening activity patterns and their impact on health in an uncontrolled environment. The impact of muscle-strengthening activity under normal Harada is with the Section for Physical Function Activation, National Center for Geriatrics and Gerontology, Obu 474-8511, Japan. Shibata is with the Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba 305-8574, Japan. Oka and Nakamura are with the Faculty of Sport Sciences, Waseda University, Tokorozawa 359-1192, Japan. Address author correspondence to Kazuhiro Harada at [email protected].
conditions can be obtained from a randomly sampled observational study where participants report on their customary engagement in muscle-strengthening activity. A few large cross-sectional studies of adults have examined the association of metabolic risk (Churilla, Magyari, Ford, Fitzhugh, & Johnson, 2012), body composition and obesity (Trudelle-Jackson, Jackson, & Morrow, 2011), insulin sensitivity (Cheng et al., 2007), and self-rated health (Ciccolo, Pettee Gabriel, Macera, & Ainsworth, 2010) with muscle-strengthening activity. However, although many previous studies have examined the associations of muscle-strengthening activities with health outcomes of older adults in controlled environments (e.g., Lange et al., 2008), few studies have examined whether muscle-strengthening activities engaged in daily life are also associated with health outcomes of older adults. Therefore, the purpose of this study was to examine the association of muscle-strengthening activity with knee and low back pain, falls, and health-related quality of life among Japanese older adults using a randomly sampled cross-sectional survey.
Methods Participants and Procedures A cross-sectional questionnaire survey was distributed via the postal system to 3,000 people aged 65 to 74 years living in the Tokyo metropolis. The Tokyo metropolis consists of two blocks; the Special Ward of Tokyo and Western Tokyo. One thousand five hundred people were randomly sampled from the each block. A registry of residential addresses was used for the random sampling. Of the 3,000 individuals, 1,559 responded to the questionnaire (response rate: 52.0%). From the respondents, 1,351 individuals had no restrictions regarding their engagement in physical activity from physicians. The data from these individuals were analyzed. Because individuals were asked to reply anonymously to the questionnaire, informed consent was implied not by signature but by return of the questionnaire. This study received prior approval from the Waseda University Ethics Committee (2010-238). 1
2 Harada et al.
Measures
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Muscle-strengthening Activities. Current physical activity
guidelines (CSEP, 2011a, 2011b; USDHHS, 2008; JMHLW, 2006, 2009b) recommend that older adults participate in musclestrengthening activities that include regular exercise as well as lifestyle activities (e.g., climbing stairs, carrying groceries, and gardening). Therefore, muscle-strengthening exercise (using equipment and body weight) and muscle-strengthening lifestyle activity were measured in this study. The selections of muscle-strengthening exercises and musclestrengthening lifestyle activities were made according to the definitions of exercise and physical activity (Caspersen, Powell, & Christenson, 1985) and the U.S. guidelines (USDHHS, 2008). Listed examples of these exercises and activities were obtained from physical activity guidelines (CSEP, 2011a, 2011b; USDHHS, 2008; JMHLW, 2006, 2009b). Exercise using equipment was defined as exercise that had the aim of strengthening muscles and was intentionally planned and structured (i.e., muscle group, number of repetitions). Exercise using portable equipment such as dumbbells and exercise tubes and that using machines or barbells located in sports facilities were listed as examples in the questionnaire. Similar to exercise using equipment, exercise using body weight was defined as body weight exercise performed for the purpose of strengthening muscles and was intentionally planned and structured. Listed examples of this type of muscle-strengthening activity included sit-ups, push-ups, and squats. For the definition of lifestyle activity, the following instruction was included in the questionnaire according to that described by Caspersen et al. (1985), the USDHHS (2008) and the JMHLW (2006): “Among various lifestyle activities, some involve a moderate-to-high level of intensity or effort for a major muscle group. Improvement in muscle strength can be expected through engaging in such activities.” Listed examples in the questionnaire included carrying groceries, climbing stairs and slopes, and heavy gardening. Respondents were asked to report how many days they participated in each type of activity during a typical week. For those reporting ≥ 1 day, the perceived intensity of each activity was also identified (light, moderate, or high). Current physical activity guidelines state that any activity can be counted as a musclestrengthening activity if it involves a moderate-to-high level of intensity or effort (USDHHS, 2008). Therefore, respondents who reported light intensity or effort were regarded as not participating in muscle-strengthening activity. Based on the guidelines, the cut-off points regarding the frequency of muscle-strengthening activities were dichotomized into < 2 days/week and ≥ 2 days/week and these were used in the analyses.
Outcome Variables. Falls, presence of knee and low back pain, and health-related quality of life were measured as outcome variables. Regarding falls, the respondents were asked to answer whether they had experienced a fall during the past year. They were categorized into those with or without fall experience. Knee and low back pain were assessed by asking the respondents whether they had experienced knee or low back pain during the past month. They were then categorized into those with or without knee or low back pain. To assess the health-related quality of life (HRQOL), the Japanese version of the Medical Outcomes Study Short Form 8-Item Health Survey (SF-8) was administered (Fukuhara & Suzukamo, 2004). The SF-8 is divided into an eight-dimension health profile: physical function, role functioning-physical, bodily pain, general health perception, vitality, social functioning, role functioningemotional, and mental health. Each item is assessed using a 5- or
6-point Likert scale. The eight-domain scaled scores range from 0 to 100, with 100 representing optimal health and functioning (Fukuhara & Suzukamo, 2004). The reliability of the Japanese version of the SF-8 by an alternate-forms method was adequate (Spearman r = .70 to 0.88), and the correlation coefficient of each eight-domain scale score between SF-8 and SF-36 was appropriate (Spearman r = .56 to 0.87) (Fukuhara & Suzukamo, 2004). Potential Confounders. Potential confounders included gender,
age, household economy (good or bad), educational background (4 years of college, 2 years of college or equivalent, high school, junior high school), current marital status (no or yes), current smoking habit (no or yes), residential area (Special Ward of Tokyo or Western Tokyo), BMI (< 25 or ≥ 25), decline of lower limb function, and total physical activity level. Decline of lower limb function was assessed using three questions: “Are you able to go upstairs without holding a rail or wall?”, “Are you able to stand up from the chair without any aid?”, and “Are you able to keep walking for about 15 minutes?” These three questions formed part of the checklist for the screening of frail older adults and was developed by the Japan Ministry of Health, Labour, and Welfare (2009a). The respondents answered “yes” or “no” to each question. Individuals who answered “no” for at least one question were regarded as demonstrating a decline in lower limb function. Individuals who answered “yes” to all three questions were considered to have no decline in lower limb function. For total physical activity level, the Japanese short version of the International Physical Activity Questionnaire was used (Murase, Katsumura, Ueda, Inoue, & Shimomitsu, 2002). According to the guidelines for data processing and analysis of this questionnaire (The International Physical Activity Questionnaire Group [TIPAQG], 2005), respondents were categorized into a low, middle, or high activity group. The detail regarding the categorization was summarized elsewhere (TIPAQG, 2005).
Statistical Analysis The analyses examined the associations between the outcome variables and total muscle-strengthening activity and the classifications of exercise using equipment, exercise using body weight, and lifestyle activity. The relationship between potential confounders and the outcome variables (low back pain, knee pain, and fall experiences) were examined using chi-squared tests, and multivariate effects (Wilks’ lambda) of multivariate analyses of variance were examined for HRQOL. Unadjusted and adjusted logistic regression analyses were then conducted to examine the association of muscle-strengthening activity with the presence of low back pain, presence of knee pain, and fall experiences. Adjustments were made for all potential confounders that were significantly associated with low back pain, presence of knee pain, or fall experiences. The association between muscle-strengthening activity and the SF-8 score was then examined using multivariate analyses of covariance (MANCOVA). The independent variable for the MANCOVA was muscle-strengthening activity and the dependent variables were the SF-8 scores. Potential confounders significantly associated with HRQOL were used as covariates. If the multivariate effects of MANCOVA were significant, analyses of covariance were conducted for each SF-8 score. If there was a significant association between muscle-strengthening activity and an outcome variable, additional subgroup analyses were performed. In the additional analyses, the frequency of musclestrengthening activity was categorized into five groups (no, 1 day/
Muscle-strengthening Activity and Health 3
week, 2 to 3 days/week, 4 to 5 days/week, or 6 to 7 days/week) and the intensity of muscle-strengthening activity was categorized into three groups (< 2 days/week, ≥ 2 days/week at a moderate intensity, or ≥ 2 days/week at a high intensity). Cochran-Armitage trends tests (low back pain, knee pain, fall experiences) and Jonckheere-Terpstra trend tests (SF-8) were then conducted to examine whether there were dose-response relationships between the health outcomes and muscle-strengthening activity. The primary analyses were performed using SPSS 18.0 software (IBM, Chicago, IL, USA), and additional subgroup analyses
were performed using College Analysis 4.5 software (Hiroshima, Japan). The level of significance was set at P < .05.
Results Characteristics of the Respondents Table 1 presents the characteristics of the respondents and the associations between muscle-strengthening activity and the potential confounders.
Table 1 Characteristics of the Respondents and their Associations with the Health Outcomes
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Associations with Health Outcomes (p Value) n
%
Men
681
50.4
Women
670
49.6
Gender
Age (years) 65–69
691
51.1
70–74
660
48.9
Household income Good
1100
82.0
Bad
241
18.0
4 years college
346
25.7
2 years college or equivalent
180
13.4
High school
598
44.5
Junior high school
220
16.4
Educational background
Current marital status No
363
27.0
Yes
980
73.0
Current smoking habit No
1173
87.5
Yes
167
12.5
Special Ward of Tokyo
654
48.4
Western Tokyo
697
51.6
Residential area
BMI (kg/m2) < 25
1099
82.4
≥ 25
235
17.6
Low
299
23.8
Middle
579
46.1
High
379
30.2
Total physical activity level
Decline of lower limb function No
1022
77.9
Yes
290
22.1
HRQOLa
Presence of Knee Painb
Presence of Low Back Painb
Fall Experienceb
.004
< .001
.616
.026
.012
< .001
.770
.032
< .001
.042
.002
.051
< .001
< .001
.112
.100
.282
.020
.993
.932
.080
.076
.700
.519
.774
.608
.267
.796
.027
< .001
.318
.071
< .001
.572
.010
.171
< .001
< .001
< .001
< .001
Note. Sample sizes vary because of missing values. HRQOL = health-related quality of life; BMI = body mass index. a Chi-squared tests. b Multivariate analysis of variance (Wilks’ lambda).
4 Harada et al.
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Overall, 73.8% of respondents reported participating in muscle-strengthening activity at least twice per week. For the types of muscle-strengthening activity, 9.2% participated in exercise using equipment, 26.2% participated in exercise using body weight, and 70.2% participated in lifestyle activity. Among them, 65.5% engaged in one activity, 27.1% engaged in two activities, and 7.3% engaged in three activities. Among all the respondents, 45.4% had knee pain, 58.6% had low back pain, and 19.4% had experienced falls in the past year. Means (standard errors) of the health-related quality scores were 51.3 (0.18) for general health, 49.9 (0.16) for physical function, 50.2 (0.18) for role physical, 50.3 for body pain, 52.1 (0.16) for vitality, 49.6 (0.23) for social function, 51.4 (0.17) for mental health, and 50.4 (0.17) for role emotional.
Associations of Muscle-strengthening Activity With Knee and Low Back Pain, Falls, and Healthrelated Quality of Life Table 2 presents the association of muscle-strengthening activity with knee pain, low back pain, and fall experience. Those individuals engaging in total muscle-strengthening activity, exercise using body weight, and lifestyle activity were significantly more likely to have knee pain. The prevalence of knee pain in those engaging in muscle-strengthening activities ≥ 2 days/week and in those not engaging in these activities is shown in Figure 1. Regarding HRQOL, after adjustment for potential confounders, significant multivariate effects were found for total musclestrengthening activity (P = .034), exercise using equipment (P = .038), and exercise using body weight (P = .015). No significant multivariate effect was observed for lifestyle activity (P = .158). Therefore, ANCOVAs were performed on all the muscle-strengthening activities except for lifestyle activity (Table 3). The ANCOVA results indicated that those who engaged in exercise using equipment and body weight were more likely to have higher general health scores. Although the multivariate effect was significant, significant relationships between total muscle-strengthening activity and each HRQOL scale were not found. In addition, subgroup analyses were conducted to examine the association of the frequency and intensity of the three types of muscle-strengthening activities (total muscle-strengthening activity, exercise using body weight, and lifestyle activity) with knee pain, and the association of the frequency and intensity of two types of muscle-strengthening activity (exercise using equipment, exercise using body weight) with general health (not shown in table). There were no significant trend associations between knee pain and muscle-strengthening activity for high frequency (p-for-trend = .114 in total muscle-strengthening activity; .148 in exercise using body weight; .142 in lifestyle activity) and high intensity (p-for-trend = .061 in total muscle-strengthening activity; .163 in exercise using body weight; .138 in lifestyle activity). In contrast, both high frequency (p-for-trend < .001 in exercise using equipment; < .001 in exercise using body weight) and high intensity (p-for-trend < .001 in exercise using equipment; < .001 in exercise using body weight) of muscle-strengthening activity were significantly associated with higher general health scores. We found the same results when they were stratified by knee and low back pain. Higher frequencies and higher intensities of exercise using equipment and body weight were significantly associated with a higher general score in individuals with and those without knee and low back pain.
Discussion This is the first randomly sampled observational study to examine the association between muscle-strengthening activity in daily life and health outcomes among older adults. The results will assist in providing a better understanding of the role of muscle-strengthening activity in health promotion for older adults. Although many intervention studies have shown health effects of muscle-strengthening activity performed in controlled conditions, few studies have focused on muscle-strengthening activity performed under normal conditions among older adults. Some population-based observational studies investigated muscle-strengthening activity among adults (Cheng et al., 2007; Churilla et al., 2012; Ciccolo et al., 2010; Trudelle-Jackson et al., 2011), but they did not target older adults. The results demonstrated that older adults engaging in musclestrengthening exercise two or more days per week had a better health-related quality of life, specifically in the general health subscale. Additional subgroup analyses revealed that higher frequency and intensity of muscle-strengthening exercises were associated with better general health, and these associations were observed in individuals with and those without knee and low back pain. Significant differences in general health (2.4 points in exercise using equipment; 1.1 points in exercise using body weight) would be relatively small because the minimum important difference of it in the SF-36 English version (the SF-8 is an abbreviated version of the SF-36) is suggested as 3 points (Ware et al., 2007). However, the findings of the current study suggested that muscle-strengthening exercises might have positive effects on HRQOL, at least in the general health of older adults, regardless of knee and low back pain. Previous experimental intervention studies examined the effects of muscle-strengthening activity on HRQOL (Cassilhas et al., 2007; de Vreede et al., 2007; Kimura et al., 2010). The present results suggest that the findings from the intervention studies can be generalized to muscle-strengthening exercises using both equipment and body weight. Regarding the SF-8 subscales, positive associations were observed between general health and both equipment and body weight exercises. From the intervention studies (Cassilhas et al., 2007; de Vreede et al., 2007; Kimura et al., 2010), it remains unclear which subscales of the HRQOL are most strongly affected. For example, de Vreede et al. (2007) reported positive effects on physical function, Kimura et al. (2010) reported on mental health, and Cassilhas et al. (2007) reported on general health and vitality. According to Kimura et al. (2010), further studies (both experimental intervention studies and observational studies) are required to provide conclusive explanations regarding the relationship between muscle-strengthening exercise and the subscales of HRQOL among older adults. Except for exercise using equipment, this study found that muscle-strengthening activities were associated with knee pain among older adults. However, a review of intervention studies concluded that muscle-strengthening activity could reduce knee pain (Lange et al., 2008). An explanation for the finding of the current study is that engagement in muscle-strengthening activity without supervision might be associated with knee pain. In support of this, a recent review reported that most of the adverse events related to muscle-strengthening activity in older adults were musculoskeletal problems such as joint pain (Liu & Latham, 2010). Therefore, engagement in inappropriate muscle-strengthening activity would relate to pain. The majority of the intervention studies supporting the reduction of knee pain using muscle-strengthening activity were
5
1,011
≥ 2 days/week
124
≥ 2 days/week
352
≥ 2 days/week
930
≥ 2 days/week
70.2
29.8
26.2
73.8
9.2
90.8
76.2
23.8
%
1.31 (1.05–1.70)*
1.00
1.29 (1.01–1.66)*
1.00
1.16 (0.80–1.69)
1.00
1.48 (1.14–1.92)**
1.00
COR (95% CI)
1.44 (1.11–1.87)**
1.00
1.38 (1.06–1.79)*
1.00
1.34 (0.91–1.98)
1.00
1.70 (1.28–2.26)***
1.00
AOR (95%
CI)a
0.96 (0.76–1.23)
1.00
0.81 (0.63–1.04)
1.00
0.79 (0.54–1.14)
1.00
1.02 (0.79–1.33)
1.00
COR (95% CI)
for household economy, total physical activity level, and decline of lower limb function.
for gender, age, and decline of lower limb function.
b Adjusted
c Adjusted
*P < .05, **P < .01, ***P < .001.
for gender, age, household economy, educational background, current marital status, BMI, and decline of lower limb function.
a Adjusted
1.19 (0.91–1.57)
1.00
0.89 (0.68–1.16)
1.00
0.98 (0.66–1.47)
1.00
1.29 (0.97–1.73)
1.00
AOR (95%
CI)b
Presence of Low Back Pain
Note. Sample sizes vary because of missing values. COR = crude odds ratio; AOR = adjusted odds ratio; 95% CI = 95% confidence interval.
394
< 2 days/week
Lifestyle activity
989
< 2 days/week
Exercise using body weight
1,225
< 2 days/week
Exercise using equipment
315
< 2 days/week
Total muscle-strengthening activity
n
Presence of Knee Pain
1.02 (0.75–1.37)
1.00
0.79 (0.57–1.08)
1.00
0.85 (0.52–1.38)
1.00
0.86 (0.63–1.17)
1.00
1.09 (0.80–1.49)
1.00
0.81 (0.58–1.12)
1.00
0.85 (0.51–1.41)
1.00
0.92 (0.67–1.28)
1.00
AOR (95% CI)c
Fall Experience COR (95% CI)
Table 2 Association of Muscle-strengthening Activity with Knee, Low Back Pain, and Falls in Japanese Older Adults
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6 Harada et al.
Figure 1 — Associations between knee pain and muscle-strengthening activity among Japanese older adults. *P < .05 **P < .01.
conducted under professional supervision (Lange et al., 2008). However, a population-based survey revealed that the majority of older adults engage in muscle-strengthening activity without professional supervision (Harada et al., 2008). Therefore, there is a possibility that older adults do not engage in muscle-strengthening activity safely. Another explanation for the result could be the existence of a reverse causal relationship between muscle-strengthening activity and knee pain. There is a possibility that older adults with knee pain engage in muscle-strengthening activity for the treatment of their pain. Therefore, to identify the role of muscle-strengthening activity in the reduction of knee pain, well-designed prospective cohort studies are needed. A significant association between muscle-strengthening activity and low back pain was not found in this study. A meta-analysis indicated that exercise therapy, including muscle-strengthening activity, is effective for the treatment of low back pain (Hayden et al., 2005), but also that supervised exercise is more effective than unsupervised exercise. Similar to knee pain, lack of supervision may have influenced the results for the relationship between muscle-strengthening activity and low back pain. This study also failed to identify a relationship between muscle-strengthening activities with fall experience. According to a Cochrane review (Gillespie et al., 2012) and another review (Sherrington et al., 2011), engagement in both muscle-strengthening activity and balance training is more effective for the prevention of falls. Therefore, for future studies, the measurement of balance training may help in the examination of the relationship between falls and muscle-strengthening activity.
Although both types of muscle-strengthening exercise were positively associated with general health, desirable relationships between muscle-strengthening lifestyle activities and health outcomes were not identified. While current physical activity guidelines recommend that some lifestyle activities should form a part of muscle-strengthening activity (CSEP, 2011a, 2011b; USDHHS, 2008; JMHLW, 2006, 2009b), no epidemiological studies have examined the relationships between health outcomes and musclestrengthening lifestyle activity. The results from the current study fail to support the recommendations regarding engagement in muscle-strengthening lifestyle activities for health. The current study has several limitations. First, the validity and reliability of the questionnaire measuring the muscle-strengthening activity are unclear. Moreover, the questionnaire method for the measurement of muscle-strengthening activity might have caused no significant associations in the frequency or intensity of musclestrengthening activity with knee pain. Second, details regarding the muscle-strengthening activity were not measured. Third, retrospective falls recalled over 12 months can lead to an underestimation of fall events. This may have an effect on associations of muscle-strengthening activity with falls. Therefore, in addition to examining the validity and reliability of the muscle-strengthening activity questionnaire, longitudinal research is required to examine the specific details regarding the optimal muscle-strengthening activity required for promoting health. Despite the limitations, the study provides unique findings regarding the association between muscle-strengthening activity and health outcomes in older adults. The current study found
7
124
124
352
≥ 2 days/week
26.2
73.8
9.2
90.8
53.0 (0.32)**
51.9 (0.19)**
53.8 (0.53)**
52.0 (0.17)**
52.5 (0.19)***
51.2 (0.34)***
Unadjusted
52.6 (0.33)
51.9 (0.20)
53.0 (0.55)
52.0 (0.18)
52.2 (0.20)
51.8 (0.36)
Adjusteda
52.1 (0.37)***
51.0 (0.22)***
53.5 (0.62)***
51.1 (0.20)***
51.5 (0.22)
50.8 (0.41)
Vitality
52.5 (0.36)***
50.9 (0.22)***
54.2 (0.60)***
51.1 (0.19)***
51.8 (0.21)***
50.0 (0.38)***
Unadjusted
50.0 (0.33)
49.7 (0.19)
50.3 (0.54)
49.8 (0.17)
49.9 (0.20)
49.6 (0.36)
50.7 (0.44)***
49.3 (0.27)***
51.1 (0.74)*
49.6 (0.24)*
50.1 (0.26)***
48.3 (0.47)***
Unadjusted
50.2 (0.46)
49.7 (0.27)
50.6 (0.76)
49.8 (0.24)
50.1 (0.27)
49.1 (0.50)
Adjusteda
Social Function
50.3 (0.32)*
49.5 (0.19)*
50.7 (0.53)
49.7 (0.17)
50.0 (0.19)**
48.9 (0.34)**
Unadjusted
Adjusteda
Physical Function
50.7 (0.34)
50.2 (0.21)
51.0 (0.57)
50.3 (0.18)
50.6 (0.20)
49.8 (0.38)
51.5 (0.33)
51.4 (0.20)
52.2 (0.56)
51.3 (0.18)
51.6 (0.20)
51.1 (0.36)
Unadjusted
51.3 (0.35)
51.6 (0.21)
51.6 (0.58)
51.5 (0.18)
51.5 (0.21)
51.7 (0.38)
Adjusteda
Mental Health
51.0 (0.34)*
50.0 (0.20)*
51.3 (0.57)
50.2 (0.18)
50.6 (0.20)***
49.1 (0.36)***
Unadjusted
Adjusteda
Role Physical
50.1 (0.45)
50.7 (0.27)
51.2 (0.75)
50.5 (0.24)
50.3 (0.27)
51.4 (0.49)
Adjusteda
50.8 (0.33)
50.4 (0.20)
51.2 (0.55)
50.4 (0.18)
50.7 (0.19)*
49.8 (0.35)*
Unadjusted
50.5 (0.33)
50.7 (0.20)
50.8 (0.56)
50.6 (0.18)
50.7 (0.20)
50.5 (0.37)
Adjusteda
Role Emotional
50.2 (0.43)
50.4 (0.26)
51.5 (0.73)
50.2 (0.23)
50.3 (0.26)
50.5 (0.46)
Unadjusted
Body Pain
for gender, age, household economy, educational background, BMI, total physical activity level, and decline of lower limb function.
*P < .05, **P < .01, ***P < .001 for difference between those in < 2 days/week and those in ≥ 2 days/week.
a Adjusted
Note. Sample sizes vary because of missing values. Values represent mean (standard error) of each eight-domain scale score of Short Form 8-Item Health Survey (SF-8). Higher scores represent higher health-related quality of life (range: 0–100). The results of lifestyle activity were not shown because multivariate effect (Wilks’ lambda) was not significant (P = .158).
989
< 2 days/week
Exercise using body weight
1,225
< 2 days/week
76.2
1,011
≥ 2 days/week
Exercise using equipment
≥ 2 days/week
< 2 days/week
23.8
n 315
%
352
≥ 2 days/week
Total muscle-strengthening activity
26.2
989
73.8
9.2
90.8
< 2 days/week
Exercise using body weight
1,225
76.2
1,011
≥ 2 days/week
23.8
%
315
< 2 days/week
Exercise using equipment
≥ 2 days/week
< 2 days/week
Total muscle-strengthening activity
n
Adjusteda
General Health
Table 3 Association of Muscle-strengthening Activity with Health-related Quality of Life in Japanese Older Adults
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8 Harada et al.
that muscle-strengthening exercise may have positive effects on HRQOL, specifically in general health, but that muscle-strengthening activities could be associated with knee pain in older adults. Further well-designed observational studies are required to confirm whether muscle-strengthening activity is effective for health promotion in older adults. Acknowledgments
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This work was supported by a Grant-in-Aid for Research Fellows of the Japan Society for the Promotion of Science (No. 20-633, 23-7878); Waseda University Grant for Special Research Projects (No. 2010A-093); and Global COE Program “Sport Sciences for the Promotion of Active Life” from the Japan Ministry of Education, Culture, Sports, Science, and Technology. We wish to thank Masamitsu Kamada (Brigham and Women’s Hospital, Harvard Medical School) and Kuniko Araki (Faculty of Sport Sciences, Waseda University) for helpful comments in conceiving this study.
References Canadian Society for Exercise Physiology (CSEP). (2011a). Canadian Physical Activity Guidelines. Retrieved February 25, 2013, from: http://www.csep.ca/CMFiles/Guidelines/CSEP-InfoSheetsCompleteENG.pdf Canadian Society for Exercise Physiology (CSEP). (2011b). Canadian Physical Activity Guidelines: Glossary of Terms. Retrieved February 25, 2013, from: http://www.csep.ca/CMFiles/Guidelines/ PAGuidelinesGlossary_E.pdf Caspersen, C.J., Powell, K.E., & Christenson, G.M. (1985). Physical activity, exercise, and physical fitness: definitions and distinctions for health-related research. Public Health Reports, 100, 126–131. PubMed Cassilhas, R.C., Viana, V.A., Grassmann, V., Santos, R.T., Santos, R.F., Tufik, S., & Mello, M.T. (2007). The impact of resistance exercise on the cognitive function of the elderly. Medicine and Science in Sports and Exercise, 39, 1401–1407. PubMed doi:10.1249/ mss.0b013e318060111f Cheng, Y.J., Gregg, E.W., De Rekeneire, N., Williams, D.E., Imperatore, G., Caspersen, C.J., & Kahn, H.S. (2007). Muscle-strengthening activity and its association with insulin sensitivity. Diabetes Care, 30, 2264–2270. PubMed doi:10.2337/dc07-0372 Churilla, J.R., Magyari, P.M., Ford, E.S., Fitzhugh, E.C., & Johnson, T.M. (2012). Muscular strengthening activity patterns and metabolic health risk among U.S. adults. Journal of Diabetes, 4, 77–84. PubMed doi:10.1111/j.1753-0407.2011.00172.x Ciccolo, J.T., Pettee Gabriel, K.K., Macera, C., & Ainsworth, B.E. (2010). Association between self-reported resistance training and self-rated health in a national sample of U.S. men and women. Journal of Physical Activity and Health, 7, 289–298. PubMed de Vreede, P.L., van Meeteren, N.L., Samson, M.M., Wittink, H.M., Duursma, S.A., & Verhaar, H.J. (2007). The effect of functional tasks exercise and resistance exercise on health-related quality of life and physical activity. A randomised controlled trial. Gerontology, 53, 12–20. PubMed doi:10.1159/000095387 Fukuhara, S., & Suzukamo, Y. (2004). Manual of the SF- 8 (Japanese edition). Kyoto: Institute for Health Outcomes & Process Evaluation Research. (in Japanese) Gillespie, L.D., Robertson, M.C., Gillespie, W.J., Sherrington, C., Gates, S., Clemson, L.M., & Lamb, S.E. (2012). Interventions for preventing falls in older people living in the community. Cochrane Database of Systematic Reviews, 9, CD007146. PubMed
Harada, K., Oka, K., Shibata, A., Ota, A., Okada, J., & Nakamura, Y. (2008). Factors associated with the stages of change for strength training behavior. International Journal of Sport and Health Science, 6, 251–263. http://dx.doi.org/10.5432/ijshs.IJSHS20070313 Hayden, J.A., van Tulder, M.W., & Tomlinson, G. (2005). Systematic review: strategies for using exercise therapy to improve outcomes in chronic low back pain. Annals of Internal Medicine, 142, 776–785. PubMed doi:10.7326/0003-4819-142-9-200505030-00014 Japan Ministry of Health, Labour and Welfare (JMHLW). (2006). Exercise and physical activity guide for health promotion 2006. Retrieved February 25, 2013, from: http://www.nih.go.jp/eiken/programs/pdf/ exercise_guide.pdf Japan Ministry of Health, Labour and Welfare (JMHLW). (2009a). Kaigo yobo no tame no Seikatsu yobo hyoka ni kannsuru manyuaru. [Revised manual for the assessment of physical function]. (in Japanese). Retrieved February 25, 2013, from: http://www.mhlw.go.jp/ topics/2009/05/dl/tp0501-1c.pdf Japan Ministry of Health, Labour and Welfare (JMHLW). (2009b). Undouki no kino kojo manyuaru. [Revised manual for the improvement of motor function]. (in Japanese). Retrieved February 25, 2013, from: http:// www.mhlw.go.jp/topics/2009/05/dl/tp0501-1d.pdf Kimura, K., Obuchi, S., Arai, T., Nagasawa, H., Shiba, Y., Watanabe, S., & Kojima, M. (2010). The influence of short-term strength training on health-related quality of life and executive cognitive function. Journal of Physiological Anthropology, 29, 95–101. PubMed doi:10.2114/ jpa2.29.95 Lange, A.K., Vanwanseele, B., & Fiatarone-Singh, M.A. (2008). Strength training for treatment of osteoarthritis of the knee: a systematic review. Arthritis and Rheumatism, 59, 1488–1494. PubMed doi:10.1002/ art.24118 Liu, C.J., & Latham, N.K. (2009). Progressive resistance strength training for improving physical function in older adults. Cochrane Database of Systematic Reviews, 3, CD002759. PubMed Liu, C.J., & Latham, N.K. (2010). Adverse events reported in progressive resistance strength training trials in older adults: 2 sides of a coin. Archives of Physical Medicine and Rehabilitation, 91, 1471–1473. PubMed doi:10.1016/j.apmr.2010.06.001 Murase, N., Katsumura, T., Ueda, C., Inoue, S., & Shimomitsu, T. (2002). International standardization of physical activity level – Reliability and validity study of the Japanese version of the International Physical Activity Questionnaire (IPAQ). Journal of Health and Welfare Statistics, 49, 1–9. Sherrington, C., Tiedemann, A., Fairhall, N., Close, J.C., & Lord, S.R. (2011). Exercise to prevent falls in older adults: an updated metaanalysis and best practice recommendations. New South Wales Public Health Bulletin, 22, 78–83. PubMed doi:10.1071/NB10056 The International Physical Activity Questionnaire Group (TIPAQG). (2005). Guidelines for Data Processing and Analysis of the International Physical Activity Questionnaire (IPAQ). Retrieved February 25, 2013, from: http://www.ipaq.ki.se/scoring.pdf Trudelle-Jackson, E., Jackson, A.W., & Morrow, J.R., Jr. (2011). Relations of meeting national public health recommendations for muscular strengthening activities with strength, body composition, and obesity: the Women’s Injury Study. American Journal of Public Health, 101, 1930–1935. PubMed doi:10.2105/AJPH.2011.300175 United States Department of Health and Human Services (USDHHS). (2008). 2008 Physical Activity Guidelines for Americans. 2008. Retrieved January 16, 2012, from: http://www.health.gov/paguidelines/pdf/paguide.pdf Ware, J.E., Jr., Kosinski, M., Bjorner, J.B., Turner-Bowker, D.M., Gandek, B., & Maruish, M.E. (2007). User’s manual for the SF-36v2 health survey (2nd ed.). Lincoln: QualityMetric Incorporated.
Official Journal of ICAPA www.JAPA-Journal.com ORIGINAL RESEARCH
Association of Muscle-strengthening Activity With Knee and Low Back Pain, Falls, and Health-related Quality of Life Among Japanese Older Adults: A Cross-sectional Survey Kazuhiro Harada, Ai Shibata, Koichiro Oka, and Yoshio Nakamura This study aimed to examine the association of muscle-strengthening activity with knee and low back pain, falls, and health-related quality of life among Japanese older adults. A cross-sectional survey targeted 3,000 people. The response rate was 52% and 208 respondents did not meet the inclusion criteria. Therefore, 1,351 individuals were analyzed. Muscle-strengthening activity (exercise using equipment and body weight, lifestyle activities), knee and low back pain, falls over the past year, health-related quality of life (SF-8), and potential confounders were assessed. Individuals engaging in exercise using body weight and lifestyle activity (≥ 2 days/week) were more likely to have knee pain. Engaging in exercise using equipment and body weight was associated with higher scores of general health. These results indicate that exercise using equipment and body weight might have a positive effect on health-related quality of life, but muscle-strengthening activities are associated with knee pain in older people. Keywords: accidental falls, musculoskeletal pain, public health, quality of life, resistance training, sports medicine
Current physical activity guidelines recommend musclestrengthening activity for health promotion among all adults, including older people (Canadian Society for Exercise Physiology [CSEP], 2011a, 2011b; United States Department of Health and Human Services [USDHHS], 2008). In Japan, the increase in the number of frail older adults is a critical issue for the health system. The Japan Ministry of Health, Labor, and Welfare (JMHLW) recognized the importance of reducing knee and lower back pain, and the prevention of falls, for maintaining the physical functioning of older adults (JMHLW, 2009b). They recommended muscle-strengthening activity for the reduction of pain and fall risk among older adults (JMHLW, 2009b). In addition, the JMHLW (2009b) indicated that the improvement of these conditions by muscle-strengthening activity could lead to a positive change in health-related quality of life among older adults. In support of these guidelines, intervention studies have suggested that muscle-strengthening activity is effective for reducing knee and lower back pain, risk of fall, and improving health-related quality of life among older adults (Cassilhas et al., 2007; de Vreede et al., 2007; Gillespie et al., 2012; Hayden, van Tulder, & Tomlinson, 2005; Lange, Vanwanseele, & FiataroneSingh., 2008; Kimura et al., 2010; Sherrington, Tiedemann, Fairhall, Close, & Lord, 2011). Despite general agreement about the value of muscle-strengthening activity for older adults, experimental interventions have been largely conducted in controlled environments (e.g., careful management of adverse events, incentives, usage of special equipment) and lasted only 3 to 6 months (Liu & Latham, 2009). Therefore, they may not reflect typical real-world muscle-strengthening activity patterns and their impact on health in an uncontrolled environment. The impact of muscle-strengthening activity under normal Harada is with the Section for Physical Function Activation, National Center for Geriatrics and Gerontology, Obu 474-8511, Japan. Shibata is with the Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba 305-8574, Japan. Oka and Nakamura are with the Faculty of Sport Sciences, Waseda University, Tokorozawa 359-1192, Japan. Address author correspondence to Kazuhiro Harada at [email protected].
conditions can be obtained from a randomly sampled observational study where participants report on their customary engagement in muscle-strengthening activity. A few large cross-sectional studies of adults have examined the association of metabolic risk (Churilla, Magyari, Ford, Fitzhugh, & Johnson, 2012), body composition and obesity (Trudelle-Jackson, Jackson, & Morrow, 2011), insulin sensitivity (Cheng et al., 2007), and self-rated health (Ciccolo, Pettee Gabriel, Macera, & Ainsworth, 2010) with muscle-strengthening activity. However, although many previous studies have examined the associations of muscle-strengthening activities with health outcomes of older adults in controlled environments (e.g., Lange et al., 2008), few studies have examined whether muscle-strengthening activities engaged in daily life are also associated with health outcomes of older adults. Therefore, the purpose of this study was to examine the association of muscle-strengthening activity with knee and low back pain, falls, and health-related quality of life among Japanese older adults using a randomly sampled cross-sectional survey.
Methods Participants and Procedures A cross-sectional questionnaire survey was distributed via the postal system to 3,000 people aged 65 to 74 years living in the Tokyo metropolis. The Tokyo metropolis consists of two blocks; the Special Ward of Tokyo and Western Tokyo. One thousand five hundred people were randomly sampled from the each block. A registry of residential addresses was used for the random sampling. Of the 3,000 individuals, 1,559 responded to the questionnaire (response rate: 52.0%). From the respondents, 1,351 individuals had no restrictions regarding their engagement in physical activity from physicians. The data from these individuals were analyzed. Because individuals were asked to reply anonymously to the questionnaire, informed consent was implied not by signature but by return of the questionnaire. This study received prior approval from the Waseda University Ethics Committee (2010-238). 1
2 Harada et al.
Measures
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Muscle-strengthening Activities. Current physical activity
guidelines (CSEP, 2011a, 2011b; USDHHS, 2008; JMHLW, 2006, 2009b) recommend that older adults participate in musclestrengthening activities that include regular exercise as well as lifestyle activities (e.g., climbing stairs, carrying groceries, and gardening). Therefore, muscle-strengthening exercise (using equipment and body weight) and muscle-strengthening lifestyle activity were measured in this study. The selections of muscle-strengthening exercises and musclestrengthening lifestyle activities were made according to the definitions of exercise and physical activity (Caspersen, Powell, & Christenson, 1985) and the U.S. guidelines (USDHHS, 2008). Listed examples of these exercises and activities were obtained from physical activity guidelines (CSEP, 2011a, 2011b; USDHHS, 2008; JMHLW, 2006, 2009b). Exercise using equipment was defined as exercise that had the aim of strengthening muscles and was intentionally planned and structured (i.e., muscle group, number of repetitions). Exercise using portable equipment such as dumbbells and exercise tubes and that using machines or barbells located in sports facilities were listed as examples in the questionnaire. Similar to exercise using equipment, exercise using body weight was defined as body weight exercise performed for the purpose of strengthening muscles and was intentionally planned and structured. Listed examples of this type of muscle-strengthening activity included sit-ups, push-ups, and squats. For the definition of lifestyle activity, the following instruction was included in the questionnaire according to that described by Caspersen et al. (1985), the USDHHS (2008) and the JMHLW (2006): “Among various lifestyle activities, some involve a moderate-to-high level of intensity or effort for a major muscle group. Improvement in muscle strength can be expected through engaging in such activities.” Listed examples in the questionnaire included carrying groceries, climbing stairs and slopes, and heavy gardening. Respondents were asked to report how many days they participated in each type of activity during a typical week. For those reporting ≥ 1 day, the perceived intensity of each activity was also identified (light, moderate, or high). Current physical activity guidelines state that any activity can be counted as a musclestrengthening activity if it involves a moderate-to-high level of intensity or effort (USDHHS, 2008). Therefore, respondents who reported light intensity or effort were regarded as not participating in muscle-strengthening activity. Based on the guidelines, the cut-off points regarding the frequency of muscle-strengthening activities were dichotomized into < 2 days/week and ≥ 2 days/week and these were used in the analyses.
Outcome Variables. Falls, presence of knee and low back pain, and health-related quality of life were measured as outcome variables. Regarding falls, the respondents were asked to answer whether they had experienced a fall during the past year. They were categorized into those with or without fall experience. Knee and low back pain were assessed by asking the respondents whether they had experienced knee or low back pain during the past month. They were then categorized into those with or without knee or low back pain. To assess the health-related quality of life (HRQOL), the Japanese version of the Medical Outcomes Study Short Form 8-Item Health Survey (SF-8) was administered (Fukuhara & Suzukamo, 2004). The SF-8 is divided into an eight-dimension health profile: physical function, role functioning-physical, bodily pain, general health perception, vitality, social functioning, role functioningemotional, and mental health. Each item is assessed using a 5- or
6-point Likert scale. The eight-domain scaled scores range from 0 to 100, with 100 representing optimal health and functioning (Fukuhara & Suzukamo, 2004). The reliability of the Japanese version of the SF-8 by an alternate-forms method was adequate (Spearman r = .70 to 0.88), and the correlation coefficient of each eight-domain scale score between SF-8 and SF-36 was appropriate (Spearman r = .56 to 0.87) (Fukuhara & Suzukamo, 2004). Potential Confounders. Potential confounders included gender,
age, household economy (good or bad), educational background (4 years of college, 2 years of college or equivalent, high school, junior high school), current marital status (no or yes), current smoking habit (no or yes), residential area (Special Ward of Tokyo or Western Tokyo), BMI (< 25 or ≥ 25), decline of lower limb function, and total physical activity level. Decline of lower limb function was assessed using three questions: “Are you able to go upstairs without holding a rail or wall?”, “Are you able to stand up from the chair without any aid?”, and “Are you able to keep walking for about 15 minutes?” These three questions formed part of the checklist for the screening of frail older adults and was developed by the Japan Ministry of Health, Labour, and Welfare (2009a). The respondents answered “yes” or “no” to each question. Individuals who answered “no” for at least one question were regarded as demonstrating a decline in lower limb function. Individuals who answered “yes” to all three questions were considered to have no decline in lower limb function. For total physical activity level, the Japanese short version of the International Physical Activity Questionnaire was used (Murase, Katsumura, Ueda, Inoue, & Shimomitsu, 2002). According to the guidelines for data processing and analysis of this questionnaire (The International Physical Activity Questionnaire Group [TIPAQG], 2005), respondents were categorized into a low, middle, or high activity group. The detail regarding the categorization was summarized elsewhere (TIPAQG, 2005).
Statistical Analysis The analyses examined the associations between the outcome variables and total muscle-strengthening activity and the classifications of exercise using equipment, exercise using body weight, and lifestyle activity. The relationship between potential confounders and the outcome variables (low back pain, knee pain, and fall experiences) were examined using chi-squared tests, and multivariate effects (Wilks’ lambda) of multivariate analyses of variance were examined for HRQOL. Unadjusted and adjusted logistic regression analyses were then conducted to examine the association of muscle-strengthening activity with the presence of low back pain, presence of knee pain, and fall experiences. Adjustments were made for all potential confounders that were significantly associated with low back pain, presence of knee pain, or fall experiences. The association between muscle-strengthening activity and the SF-8 score was then examined using multivariate analyses of covariance (MANCOVA). The independent variable for the MANCOVA was muscle-strengthening activity and the dependent variables were the SF-8 scores. Potential confounders significantly associated with HRQOL were used as covariates. If the multivariate effects of MANCOVA were significant, analyses of covariance were conducted for each SF-8 score. If there was a significant association between muscle-strengthening activity and an outcome variable, additional subgroup analyses were performed. In the additional analyses, the frequency of musclestrengthening activity was categorized into five groups (no, 1 day/
Muscle-strengthening Activity and Health 3
week, 2 to 3 days/week, 4 to 5 days/week, or 6 to 7 days/week) and the intensity of muscle-strengthening activity was categorized into three groups (< 2 days/week, ≥ 2 days/week at a moderate intensity, or ≥ 2 days/week at a high intensity). Cochran-Armitage trends tests (low back pain, knee pain, fall experiences) and Jonckheere-Terpstra trend tests (SF-8) were then conducted to examine whether there were dose-response relationships between the health outcomes and muscle-strengthening activity. The primary analyses were performed using SPSS 18.0 software (IBM, Chicago, IL, USA), and additional subgroup analyses
were performed using College Analysis 4.5 software (Hiroshima, Japan). The level of significance was set at P < .05.
Results Characteristics of the Respondents Table 1 presents the characteristics of the respondents and the associations between muscle-strengthening activity and the potential confounders.
Table 1 Characteristics of the Respondents and their Associations with the Health Outcomes
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Associations with Health Outcomes (p Value) n
%
Men
681
50.4
Women
670
49.6
Gender
Age (years) 65–69
691
51.1
70–74
660
48.9
Household income Good
1100
82.0
Bad
241
18.0
4 years college
346
25.7
2 years college or equivalent
180
13.4
High school
598
44.5
Junior high school
220
16.4
Educational background
Current marital status No
363
27.0
Yes
980
73.0
Current smoking habit No
1173
87.5
Yes
167
12.5
Special Ward of Tokyo
654
48.4
Western Tokyo
697
51.6
Residential area
BMI (kg/m2) < 25
1099
82.4
≥ 25
235
17.6
Low
299
23.8
Middle
579
46.1
High
379
30.2
Total physical activity level
Decline of lower limb function No
1022
77.9
Yes
290
22.1
HRQOLa
Presence of Knee Painb
Presence of Low Back Painb
Fall Experienceb
.004
< .001
.616
.026
.012
< .001
.770
.032
< .001
.042
.002
.051
< .001
< .001
.112
.100
.282
.020
.993
.932
.080
.076
.700
.519
.774
.608
.267
.796
.027
< .001
.318
.071
< .001
.572
.010
.171
< .001
< .001
< .001
< .001
Note. Sample sizes vary because of missing values. HRQOL = health-related quality of life; BMI = body mass index. a Chi-squared tests. b Multivariate analysis of variance (Wilks’ lambda).
4 Harada et al.
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Overall, 73.8% of respondents reported participating in muscle-strengthening activity at least twice per week. For the types of muscle-strengthening activity, 9.2% participated in exercise using equipment, 26.2% participated in exercise using body weight, and 70.2% participated in lifestyle activity. Among them, 65.5% engaged in one activity, 27.1% engaged in two activities, and 7.3% engaged in three activities. Among all the respondents, 45.4% had knee pain, 58.6% had low back pain, and 19.4% had experienced falls in the past year. Means (standard errors) of the health-related quality scores were 51.3 (0.18) for general health, 49.9 (0.16) for physical function, 50.2 (0.18) for role physical, 50.3 for body pain, 52.1 (0.16) for vitality, 49.6 (0.23) for social function, 51.4 (0.17) for mental health, and 50.4 (0.17) for role emotional.
Associations of Muscle-strengthening Activity With Knee and Low Back Pain, Falls, and Healthrelated Quality of Life Table 2 presents the association of muscle-strengthening activity with knee pain, low back pain, and fall experience. Those individuals engaging in total muscle-strengthening activity, exercise using body weight, and lifestyle activity were significantly more likely to have knee pain. The prevalence of knee pain in those engaging in muscle-strengthening activities ≥ 2 days/week and in those not engaging in these activities is shown in Figure 1. Regarding HRQOL, after adjustment for potential confounders, significant multivariate effects were found for total musclestrengthening activity (P = .034), exercise using equipment (P = .038), and exercise using body weight (P = .015). No significant multivariate effect was observed for lifestyle activity (P = .158). Therefore, ANCOVAs were performed on all the muscle-strengthening activities except for lifestyle activity (Table 3). The ANCOVA results indicated that those who engaged in exercise using equipment and body weight were more likely to have higher general health scores. Although the multivariate effect was significant, significant relationships between total muscle-strengthening activity and each HRQOL scale were not found. In addition, subgroup analyses were conducted to examine the association of the frequency and intensity of the three types of muscle-strengthening activities (total muscle-strengthening activity, exercise using body weight, and lifestyle activity) with knee pain, and the association of the frequency and intensity of two types of muscle-strengthening activity (exercise using equipment, exercise using body weight) with general health (not shown in table). There were no significant trend associations between knee pain and muscle-strengthening activity for high frequency (p-for-trend = .114 in total muscle-strengthening activity; .148 in exercise using body weight; .142 in lifestyle activity) and high intensity (p-for-trend = .061 in total muscle-strengthening activity; .163 in exercise using body weight; .138 in lifestyle activity). In contrast, both high frequency (p-for-trend < .001 in exercise using equipment; < .001 in exercise using body weight) and high intensity (p-for-trend < .001 in exercise using equipment; < .001 in exercise using body weight) of muscle-strengthening activity were significantly associated with higher general health scores. We found the same results when they were stratified by knee and low back pain. Higher frequencies and higher intensities of exercise using equipment and body weight were significantly associated with a higher general score in individuals with and those without knee and low back pain.
Discussion This is the first randomly sampled observational study to examine the association between muscle-strengthening activity in daily life and health outcomes among older adults. The results will assist in providing a better understanding of the role of muscle-strengthening activity in health promotion for older adults. Although many intervention studies have shown health effects of muscle-strengthening activity performed in controlled conditions, few studies have focused on muscle-strengthening activity performed under normal conditions among older adults. Some population-based observational studies investigated muscle-strengthening activity among adults (Cheng et al., 2007; Churilla et al., 2012; Ciccolo et al., 2010; Trudelle-Jackson et al., 2011), but they did not target older adults. The results demonstrated that older adults engaging in musclestrengthening exercise two or more days per week had a better health-related quality of life, specifically in the general health subscale. Additional subgroup analyses revealed that higher frequency and intensity of muscle-strengthening exercises were associated with better general health, and these associations were observed in individuals with and those without knee and low back pain. Significant differences in general health (2.4 points in exercise using equipment; 1.1 points in exercise using body weight) would be relatively small because the minimum important difference of it in the SF-36 English version (the SF-8 is an abbreviated version of the SF-36) is suggested as 3 points (Ware et al., 2007). However, the findings of the current study suggested that muscle-strengthening exercises might have positive effects on HRQOL, at least in the general health of older adults, regardless of knee and low back pain. Previous experimental intervention studies examined the effects of muscle-strengthening activity on HRQOL (Cassilhas et al., 2007; de Vreede et al., 2007; Kimura et al., 2010). The present results suggest that the findings from the intervention studies can be generalized to muscle-strengthening exercises using both equipment and body weight. Regarding the SF-8 subscales, positive associations were observed between general health and both equipment and body weight exercises. From the intervention studies (Cassilhas et al., 2007; de Vreede et al., 2007; Kimura et al., 2010), it remains unclear which subscales of the HRQOL are most strongly affected. For example, de Vreede et al. (2007) reported positive effects on physical function, Kimura et al. (2010) reported on mental health, and Cassilhas et al. (2007) reported on general health and vitality. According to Kimura et al. (2010), further studies (both experimental intervention studies and observational studies) are required to provide conclusive explanations regarding the relationship between muscle-strengthening exercise and the subscales of HRQOL among older adults. Except for exercise using equipment, this study found that muscle-strengthening activities were associated with knee pain among older adults. However, a review of intervention studies concluded that muscle-strengthening activity could reduce knee pain (Lange et al., 2008). An explanation for the finding of the current study is that engagement in muscle-strengthening activity without supervision might be associated with knee pain. In support of this, a recent review reported that most of the adverse events related to muscle-strengthening activity in older adults were musculoskeletal problems such as joint pain (Liu & Latham, 2010). Therefore, engagement in inappropriate muscle-strengthening activity would relate to pain. The majority of the intervention studies supporting the reduction of knee pain using muscle-strengthening activity were
5
1,011
≥ 2 days/week
124
≥ 2 days/week
352
≥ 2 days/week
930
≥ 2 days/week
70.2
29.8
26.2
73.8
9.2
90.8
76.2
23.8
%
1.31 (1.05–1.70)*
1.00
1.29 (1.01–1.66)*
1.00
1.16 (0.80–1.69)
1.00
1.48 (1.14–1.92)**
1.00
COR (95% CI)
1.44 (1.11–1.87)**
1.00
1.38 (1.06–1.79)*
1.00
1.34 (0.91–1.98)
1.00
1.70 (1.28–2.26)***
1.00
AOR (95%
CI)a
0.96 (0.76–1.23)
1.00
0.81 (0.63–1.04)
1.00
0.79 (0.54–1.14)
1.00
1.02 (0.79–1.33)
1.00
COR (95% CI)
for household economy, total physical activity level, and decline of lower limb function.
for gender, age, and decline of lower limb function.
b Adjusted
c Adjusted
*P < .05, **P < .01, ***P < .001.
for gender, age, household economy, educational background, current marital status, BMI, and decline of lower limb function.
a Adjusted
1.19 (0.91–1.57)
1.00
0.89 (0.68–1.16)
1.00
0.98 (0.66–1.47)
1.00
1.29 (0.97–1.73)
1.00
AOR (95%
CI)b
Presence of Low Back Pain
Note. Sample sizes vary because of missing values. COR = crude odds ratio; AOR = adjusted odds ratio; 95% CI = 95% confidence interval.
394
< 2 days/week
Lifestyle activity
989
< 2 days/week
Exercise using body weight
1,225
< 2 days/week
Exercise using equipment
315
< 2 days/week
Total muscle-strengthening activity
n
Presence of Knee Pain
1.02 (0.75–1.37)
1.00
0.79 (0.57–1.08)
1.00
0.85 (0.52–1.38)
1.00
0.86 (0.63–1.17)
1.00
1.09 (0.80–1.49)
1.00
0.81 (0.58–1.12)
1.00
0.85 (0.51–1.41)
1.00
0.92 (0.67–1.28)
1.00
AOR (95% CI)c
Fall Experience COR (95% CI)
Table 2 Association of Muscle-strengthening Activity with Knee, Low Back Pain, and Falls in Japanese Older Adults
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6 Harada et al.
Figure 1 — Associations between knee pain and muscle-strengthening activity among Japanese older adults. *P < .05 **P < .01.
conducted under professional supervision (Lange et al., 2008). However, a population-based survey revealed that the majority of older adults engage in muscle-strengthening activity without professional supervision (Harada et al., 2008). Therefore, there is a possibility that older adults do not engage in muscle-strengthening activity safely. Another explanation for the result could be the existence of a reverse causal relationship between muscle-strengthening activity and knee pain. There is a possibility that older adults with knee pain engage in muscle-strengthening activity for the treatment of their pain. Therefore, to identify the role of muscle-strengthening activity in the reduction of knee pain, well-designed prospective cohort studies are needed. A significant association between muscle-strengthening activity and low back pain was not found in this study. A meta-analysis indicated that exercise therapy, including muscle-strengthening activity, is effective for the treatment of low back pain (Hayden et al., 2005), but also that supervised exercise is more effective than unsupervised exercise. Similar to knee pain, lack of supervision may have influenced the results for the relationship between muscle-strengthening activity and low back pain. This study also failed to identify a relationship between muscle-strengthening activities with fall experience. According to a Cochrane review (Gillespie et al., 2012) and another review (Sherrington et al., 2011), engagement in both muscle-strengthening activity and balance training is more effective for the prevention of falls. Therefore, for future studies, the measurement of balance training may help in the examination of the relationship between falls and muscle-strengthening activity.
Although both types of muscle-strengthening exercise were positively associated with general health, desirable relationships between muscle-strengthening lifestyle activities and health outcomes were not identified. While current physical activity guidelines recommend that some lifestyle activities should form a part of muscle-strengthening activity (CSEP, 2011a, 2011b; USDHHS, 2008; JMHLW, 2006, 2009b), no epidemiological studies have examined the relationships between health outcomes and musclestrengthening lifestyle activity. The results from the current study fail to support the recommendations regarding engagement in muscle-strengthening lifestyle activities for health. The current study has several limitations. First, the validity and reliability of the questionnaire measuring the muscle-strengthening activity are unclear. Moreover, the questionnaire method for the measurement of muscle-strengthening activity might have caused no significant associations in the frequency or intensity of musclestrengthening activity with knee pain. Second, details regarding the muscle-strengthening activity were not measured. Third, retrospective falls recalled over 12 months can lead to an underestimation of fall events. This may have an effect on associations of muscle-strengthening activity with falls. Therefore, in addition to examining the validity and reliability of the muscle-strengthening activity questionnaire, longitudinal research is required to examine the specific details regarding the optimal muscle-strengthening activity required for promoting health. Despite the limitations, the study provides unique findings regarding the association between muscle-strengthening activity and health outcomes in older adults. The current study found
7
124
124
352
≥ 2 days/week
26.2
73.8
9.2
90.8
53.0 (0.32)**
51.9 (0.19)**
53.8 (0.53)**
52.0 (0.17)**
52.5 (0.19)***
51.2 (0.34)***
Unadjusted
52.6 (0.33)
51.9 (0.20)
53.0 (0.55)
52.0 (0.18)
52.2 (0.20)
51.8 (0.36)
Adjusteda
52.1 (0.37)***
51.0 (0.22)***
53.5 (0.62)***
51.1 (0.20)***
51.5 (0.22)
50.8 (0.41)
Vitality
52.5 (0.36)***
50.9 (0.22)***
54.2 (0.60)***
51.1 (0.19)***
51.8 (0.21)***
50.0 (0.38)***
Unadjusted
50.0 (0.33)
49.7 (0.19)
50.3 (0.54)
49.8 (0.17)
49.9 (0.20)
49.6 (0.36)
50.7 (0.44)***
49.3 (0.27)***
51.1 (0.74)*
49.6 (0.24)*
50.1 (0.26)***
48.3 (0.47)***
Unadjusted
50.2 (0.46)
49.7 (0.27)
50.6 (0.76)
49.8 (0.24)
50.1 (0.27)
49.1 (0.50)
Adjusteda
Social Function
50.3 (0.32)*
49.5 (0.19)*
50.7 (0.53)
49.7 (0.17)
50.0 (0.19)**
48.9 (0.34)**
Unadjusted
Adjusteda
Physical Function
50.7 (0.34)
50.2 (0.21)
51.0 (0.57)
50.3 (0.18)
50.6 (0.20)
49.8 (0.38)
51.5 (0.33)
51.4 (0.20)
52.2 (0.56)
51.3 (0.18)
51.6 (0.20)
51.1 (0.36)
Unadjusted
51.3 (0.35)
51.6 (0.21)
51.6 (0.58)
51.5 (0.18)
51.5 (0.21)
51.7 (0.38)
Adjusteda
Mental Health
51.0 (0.34)*
50.0 (0.20)*
51.3 (0.57)
50.2 (0.18)
50.6 (0.20)***
49.1 (0.36)***
Unadjusted
Adjusteda
Role Physical
50.1 (0.45)
50.7 (0.27)
51.2 (0.75)
50.5 (0.24)
50.3 (0.27)
51.4 (0.49)
Adjusteda
50.8 (0.33)
50.4 (0.20)
51.2 (0.55)
50.4 (0.18)
50.7 (0.19)*
49.8 (0.35)*
Unadjusted
50.5 (0.33)
50.7 (0.20)
50.8 (0.56)
50.6 (0.18)
50.7 (0.20)
50.5 (0.37)
Adjusteda
Role Emotional
50.2 (0.43)
50.4 (0.26)
51.5 (0.73)
50.2 (0.23)
50.3 (0.26)
50.5 (0.46)
Unadjusted
Body Pain
for gender, age, household economy, educational background, BMI, total physical activity level, and decline of lower limb function.
*P < .05, **P < .01, ***P < .001 for difference between those in < 2 days/week and those in ≥ 2 days/week.
a Adjusted
Note. Sample sizes vary because of missing values. Values represent mean (standard error) of each eight-domain scale score of Short Form 8-Item Health Survey (SF-8). Higher scores represent higher health-related quality of life (range: 0–100). The results of lifestyle activity were not shown because multivariate effect (Wilks’ lambda) was not significant (P = .158).
989
< 2 days/week
Exercise using body weight
1,225
< 2 days/week
76.2
1,011
≥ 2 days/week
Exercise using equipment
≥ 2 days/week
< 2 days/week
23.8
n 315
%
352
≥ 2 days/week
Total muscle-strengthening activity
26.2
989
73.8
9.2
90.8
< 2 days/week
Exercise using body weight
1,225
76.2
1,011
≥ 2 days/week
23.8
%
315
< 2 days/week
Exercise using equipment
≥ 2 days/week
< 2 days/week
Total muscle-strengthening activity
n
Adjusteda
General Health
Table 3 Association of Muscle-strengthening Activity with Health-related Quality of Life in Japanese Older Adults
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8 Harada et al.
that muscle-strengthening exercise may have positive effects on HRQOL, specifically in general health, but that muscle-strengthening activities could be associated with knee pain in older adults. Further well-designed observational studies are required to confirm whether muscle-strengthening activity is effective for health promotion in older adults. Acknowledgments
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This work was supported by a Grant-in-Aid for Research Fellows of the Japan Society for the Promotion of Science (No. 20-633, 23-7878); Waseda University Grant for Special Research Projects (No. 2010A-093); and Global COE Program “Sport Sciences for the Promotion of Active Life” from the Japan Ministry of Education, Culture, Sports, Science, and Technology. We wish to thank Masamitsu Kamada (Brigham and Women’s Hospital, Harvard Medical School) and Kuniko Araki (Faculty of Sport Sciences, Waseda University) for helpful comments in conceiving this study.
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