Journal of Physical Activity and Health, 2014, 11, 1162  -1169 http://dx.doi.org/10.1123/jpah.2012-0321 © 2014 Human Kinetics, Inc.

Official Journal of ISPAH www.JPAH-Journal.com ORIGINAL RESEARCH

A Physical Activity Program for Swedish Physically Inactive Female High School Students: A Controlled Intervention Study Yvonne Kahlin, Suzanne Werner, and Marie Alricsson Background: Physical activity and sport participation often decline during adolescence. Aim: To investigate if physical exercise during 6 months could lead to a positive behavior of physical activity, improve physical fitness and self-related health in physically inactive female high school students. Methods: A prospective cluster-randomized controlled intervention study included 104 physically inactive female high school students, 60 in an intervention group and 44 controls. At baseline there were no group differences regarding self-related health. The intervention group exercised at least once per week. A questionnaire and physical fitness tests were used for evaluation, at baseline and 6 months later. Results: The intervention group improved their self-related health compared with the controls (P = .012). When divided into a regular (n = 27) and an irregular training group (n = 33) the regular training group improved their self-related health compared with the controls, while the irregular training group did not differ from the other groups. Maximal oxygen consumption was improved in the intervention group compared with the controls (P < .001). No group differences were found in muscle strength and endurance. Conclusion: Physical exercise at least once per week during 6 months improved physical fitness (maximal oxygen consumption) and self-related health in physically inactive female high school students. Keywords: adolescent, after school hour, health, physical exercise, sport center Physical activity provides fundamental health benefits and regular physical activity is important to prevent a number of chronic diseases such as diabetes, osteoporosis, cardiovascular diseases and obesity, for instance.1,2 Worldwide one-third of adults and 80.3% of adolescents do not reach public health guidelines for recommendation levels of physical activity.3 Increased sedentary behavior in adolescents might increase health problem in adulthood.1 Physical activity and sport participation often decline during adolescence,4,5 while sedentary behaviors often increase.6 In general, female adolescents are less physically active than their male counterparts.3,7 A positive relationship has been reported between physical education at school and physical activity.4 Adolescents with a positive attitude to physical education were found to be more physically active.8 A physical behavior during adolescence has been reported to increase the probability of a physically active healthy behavior also in adulthood.4 A positive interaction between cardiovascular physical fitness and physical self-concept was reported in a school based physical activity intervention study.9 Physical activity may also contribute to both a high physical wellbeing and self-esteem.10 Simon et al11 reported that a multilevel 6-month physical activity intervention led to improved attitude toward physical activity and behavior as well as level of physical activity in middle-school adolescents. There are several intervention studies on physical activity showing increased level of physical activity in adolescents.12 In a Kahlin ([email protected]) is with the Dept of Neurobiology, Care Sciences, and Society, Division of Physiotherapy, Karolinska Institute, Stockholm, Sweden. Werner is with the Dept of Molecular Medicine and Surgery, Karolinska Institute, Stockholm, Sweden. Alricsson is with the School of Education, Physiology and Sports Science, Linnaeus University, Kalmar, Sweden. 1162

systematic review van Sluijs et al12 reported that multilevel school based physical activity was more effective to improve physical activity behavior than single physical activities. A meta-analysis based on intervention studies with physical activity as a primary outcome showed that after-school physical activity could improve physical activity level and physical fitness.13 Thus, it’s important to support adolescents to establish positive physical behavior and a positive attitude toward physical activity. To encourage physically inactive adolescents to become physically active, especially physically inactive female adolescents is important. The aim of the current study was to evaluate whether a 6-month physical activity program could influence the behavior of physical activity, improve physical fitness and self-related health in physically inactive female high school students. We hypothesized that physical activity for 6 months can stimulate physically inactive female high school students to a physically active behavior, improved physical fitness and thereby self-related health.

Methods Ethical Considerations The Ethics Committee at Linköping University, Linköping, Sweden, approved the current study (Dnr: 2010/72 to 31). All subjects received both written and oral information about the study and were informed that all data would be treated confidentially. Since most subjects were below 18 years their parents also received the same information and decided together with their daughters whether to accept the invitation to participate.

Subjects A Swedish keep-fit organization with several facilities in Stockholm city and surroundings was contacted and accepted the invitation to

Swedish Physical Inactive Female Students   1163

support the study. Public high schools in the vicinity to these facilities received an invitation to participate and written information about the study was sent to the headmaster at these high schools. Twelve high schools were contacted and 4 accepted the invitation to participate. The purpose of the study, the process of recruitment of the participants, the evaluation methods and the physical activity program were presented at meetings with the school nurses and the physical education teachers. The study was cluster-randomized (ie, the high schools, but not the students, were randomly assigned to either an intervention or a control group). The high schools were comparable with both practical and theoretical programs and the students at the high schools performed the same physical education program.

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Procedure All students (grade 1 and 2, 16 to 19 years old) at the 4 high schools completed a questionnaire about their physical activity behavior, “A questionnaire for senior high school students” that has a high test-retest reliability, r = 1.0.14 The questionnaire was used as an indicator of physical activity behavior. The females were asked questions regarding self-related health, the level of physical activity and sport participation. It consists of questions regarding a) self-related health: How do you judge your general health condition? Very good Relatively good Neither good nor poor Relatively poor Poor b) behavior of physical activity: Mark how often you performed physical activity at a high level? Mark how often you performed physical activity at a moderate level? Mark how often you performed physical activity at a low level? Three times or more weekly Twice weekly Once weekly Occasionally Never. The questionnaire was answered during school hours and was followed by an oral information about the study.

Inclusion/Exclusion Criteria The following criteria were necessary for inclusion: • Female students that were not active in any sports and/or had a low physical activity level • Female students who participated in ordinary physical education program at the high school • Female students who were able to exercise without any medical restrictions. The following criteria were considered for exclusion: • Physically active female students, who participated in physical activity at a moderate and/or a high level • Female students that were members of a sport-team or a sport center • Female students with medical problems including eating disorders.

A total of 494 students answered the questionnaire and 185 reported that they were physically inactive. An information letter was sent out to these students describing the purpose of the study. Out of the 185 students 104 accepted to participate (Figure 1). The students were assigned to an intervention group (n = 60) or a control group (n = 44). Mean age of the intervention group was 17.2 (SD 0.55) and the control group 16.1 (SD 0.34). Mean Body Mass Index (BMI) was 20.56 (SD 2.76) in the intervention group and 19.73 (SD 2.17) in the control group. There were no significant differences in baseline characteristics between the intervention group and the control group regarding age and BMI.

Evaluation Instruments All subjects of both groups answered “A questionnaire for senior high school students” at the start of the physical activity intervention (baseline) and after 6 months (6-month follow-up).

Physical Fitness Tests Data about level of physical fitness were collected. All tested subjects were supervised by the research leader. The physical fitness tests were performed in the same order at both test occasions and the research leader gave the same verbal encouragement to all subjects. One-Leg Hop Test.  One-leg hop test is a functional test suggested to measure muscle function and postural control in the lower extremity.15 From a starting position standing on 1 leg with the other knee flexed and the arms behind the back, the subjects jumped straight ahead as far as possible and landed on the same foot. The test has a high test-retest reliability (r = .96).15 The same procedure was repeated with the other leg. One trial per leg was allowed. Modified Sit-Ups in Three Steps.  Sit-ups are suggested to mea-

sure strength, particularly of the abdominal muscles, but also of the hip flexors. In a standardized way the subjects performed a maximum number of sit-ups in 3 different steps and hand positions.16

A Modified Sorensen Test.  The Sorensen test is suggested to mea-

sure endurance of global back extensor muscles and hip extensors.17 The test has been shown to have a good validity and a satisfactory test-retest reliability.17 From the starting position, lying prone on a rounded pad, the subjects performed a back extension to a horizontal position and maintained in this position as long as possible. A Modified Core Muscle Strength and Stability Test (CMSST).  A

modified CMSST was carried out by measuring the maximal time that the subjects were able to keep the body in a horizontal prone position supported by the forearms and toes in a straight line from the head to the toes.18

One-Mile Track Walk Test.  One-mile track walk test is a valid submaximal field test used to estimate maximal oxygen consumption (VO2max; test-retest r = .93 in adults).19 A moderate evidence was reported in a systematic review that the one-mile track walk test in youth is a valid test.20 The subjects walked 1 mile (1609 m) as fast as possible with a steady pace, while their heart rate was recorded with Polar heart rate monitor. The subjects also estimated their heart rate with the Ratings of Perceived Exertion scale.21

Physical Activity Intervention Intervention Group.  The intervention group participated in a

physical activity intervention running for a 6-month period. The subjects were instructed and encouraged to exercise at least once

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1164  Kahlin, Werner, and Alricsson

Figure 1 — Flowchart, female high school students: physically active females, physically inactive females, intervention group, and control group.

a week and they could either choose a sport center near school or close to their home. The physical activity program was carried out after school hours, weekdays or weekends. The intervention was done in collaboration with a Swedish keep-fit organization that offers a wide range of all-round training activities as well as more specific forms of exercises, aerobic training and gym training. Four sport centers were included in the study. The subjects were equipped with a free membership card and offered the opportunity, with help from instructors, to receive an individualized physical training program to meet their specific interests and needs. The goal was to exercise at least once a week and they were free to exercise as many times as they wanted per week and to decide what physical exercises that they wanted to do at the sport center. The Trans Theoretical Model (TTM) was used in this study. This is a common theory-based behavioral change model on physical activity and health.22 TTM explains exercise behavior and the underlying motive for adopting and maintaining physical activity. Monthly telephone calls from the research leader was used as a

strategy to maintain a high compliance over the whole intervention period.23 These telephone calls were also used to encourage the subjects to stay physically active and to try different types of physical activities at the sport center. Each subject reported the frequency and type of training every month by using a physical activity diary and also by having this information automatically filled in on a computer when entering the sport center. Control Group.  The control group continued with their ordinary physical education program at school. No alternative physical activity was organized for this group. Neither did they have any telephone calls from the research leader.

Data Analysis All analyses were completed using SPSS 19.0. All data were summarized using standard descriptive statistics such as mean, standard deviation and frequency. The distributions were checked for skewness or outliers. If the distribution was approximately normal (skewness index < 1.75), the group differences in levels and change

Swedish Physical Inactive Female Students   1165

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was analyzed with analysis of variance for repeated measurements, in which the differences in change appeared as an interaction effect (group * time). Differences at baseline were analyzed with the oneway analyses of variance. Post hoc tests were performed with the Tukey HSD test. In case of skewed distributions a nonparametric strategy was applied on the baseline variables or differences in change with the KruskalWallis H test. The significance level in all analyses was set at 5% (two-tailed). Based on the following presumptions: a 10% improvement of VO2max, a standard deviation of 5.25 of the change, a significance level of 5%, and a power of 0.85; it was determined that 22 subjects should be included in each group (intervention and control). With a dropout rate of 25% 30 subjects should be included at baseline. To be able to conduct a subgroup analysis with satisfactory power more than 50 subjects in each group would be desirable.

Results Fifty-five out of sixty subjects (91.6%) in the intervention group compared with 39 out of 44 (88.6%) in the control group completed the 6-month follow-up test. A total of 33 out of 60 subjects in the intervention group performed irregular training at the sport center. The intervention group therefore was split into 2 groups, 1 regular training group (n = 27) and 1 irregular training group (n = 33). Subjects in the regular training group had exercised regularly (one or more times per week) at the sport center, whereas those in the irregular training group had not trained regularly. Each month the subjects in the intervention group reported selfestimated physical activity level and physical activity behavior to the research leader. Lack of time, too much school work and absence of motivation were common (barriers) comments from the subjects of the irregular training group, when questioned why they did not carry out the exercise regularly.

Self-Related Health There were no significant group differences at baseline between the intervention groups, (regular and irregular training group) and the control group regarding self-related health, P = .236. There were significant group differences in self-related health from baseline to follow up, P = .012. The regular training group had a greater increase in terms of better self-related health than the control group according to the post hoc Tukey HSD test, while the irregular training group did not differ from either the control group or the regular training group, Table 1.

Physical Fitness Tests At baseline there were no significant group differences regarding physical performance, except for more sit-ups (modified sit-ups in 3 steps) in the intervention groups (mean = 25) than in the control group (mean = 19) group P = .001. In the analyses of muscle strength and muscle endurance at the 6-month follow up none of the analyses yielded any significant group differences, Table 1. Improved performance was observed in all 3 groups in terms of the sit-ups and the one-leg hop test, P < .001. VO2max (one-mile track walk test) was significantly improved in both intervention groups (regular and irregular training group) as compared with the control group, P < .001. The subjects of the intervention groups walked their mile faster than the control group,

P = .002. There were no significant differences between the 2 intervention groups (regular and irregular training group) in any of the post hoc analysis, although both intervention groups differed from the control group, Table 1. The effect sizes (z scores) in terms of BMI, self-related health, and physical fitness tests in the regular training group, the irregular training group and the control group are reported in Figure 2. The effect sizes in terms of changes as a result of the intervention were found to be higher in self-related health (regular training group and control group), time to walk 1 mile minutes (irregular training group and control group) and one-mile track walk test, VO2max (irregular training group and control group).

Discussion In the present investigation, it was found that a 6-month physical activity program influenced the behavior of physical activity and improved physical fitness (maximal oxygen consumption) and thereby self-related health in physically inactive female high school students. In an analog to a previous meta-analysis investigation,13 the current study showed that after school hour physical activity is effective and can improve physical fitness and the physical activity level. Furthermore, based on the current study it was found that females who exercised at least 1 time per week improved both physical fitness and self-related health when compared with those who did not perform any physical activity. A 2-year school based physical activity intervention in girls from 36 middle schools led to increased physical activity when compared with controls without any physical activity.24 In contrast to earlier physical intervention studies that resulted in increased physical activity in adolescents the current study primarily was focused on physically inactive females. It is difficult to compare studies about physical activity level since some authors describe physical activity level in the intervention and other authors describe an overall physical activity level. The heterogeneity of physical activity interventions in adolescents makes it difficult to determine the effects (positive and negative) and thereby to compare different studies.12,13 Adolescents nowadays seem to spend more time in front of the computer and television than to carry out physical activities or sports.25 A meta-analysis on changes of sedentary behavior in young people showed that a combination of self-reported and objectively reported sedentary behavior led to a reduced sedentary behavior.25 This strategy was also used in the current study, where the females in the intervention group self-reported their physical activities at the same time as their activities were objectively recorded computer wise at the sport center. In a 6-month health behavior intervention with a counseling approach self-reported physical activity was increased in adolescents.26 This was also studied in the present investigation by a monthly oral contact between the females of the intervention group and the research leader. This contact was a further opportunity for the research leader to ask questions about the compliance of the physical activity program. The characteristic of the TTM is that the change process is based on the following 5 stages: precontemplation (not intending to make a change), contemplation, preparation, action, and maintenance (sustaining change over time).22 The process in the intervention group of the current study runs from unhealthy physical activity to preparation and furthermore to action (irregular training group) and maintenance (regular training group).

1166

a

91.8 24.1

One leg hop test in cms, left, follow-up

Number of modified sit-ups in 3 steps, baseline

151.2 11.6 10.9 14.1 13.4 46.7 48.9

Heart rate after 1-mile walk, baseline

Heart rate after 1-mile walk, follow-up

Rating of perceived exertion scale, baseline

Rating of perceived exertion scale, follow-up

One mile walk in mins, baseline

One mile walk in mins, follow-up

VO2max, one-mile track walk test baseline

VO2max, one-mile track walk test follow-up

Tukey HSD test ≤ 0.10.

47.8 152.7

Modifies CMSST in secs, follow-up

54.4

80.3

One leg hop test in cms, left, baseline

113.4

97.4

One leg hop test in cms, right, follow-up

Modified CMSST in secs, baseline

84.9

One leg hop test in cms, right, baseline

Modified Sorensen test in secs, follow-up

3.93

Rating of self-related health, follow-up

28.2

3.48

Rating of self-related health, baseline

107.2

21.1

BMI, follow-up

Modified Sorensen test in secs, baseline

20.6

BMI, baseline

Number of modified sit-ups in 3 steps, follow-up

Mean

Physical test

3.87

3.09

0.84

0.75

2.24

1.70

15.78

17.04

22.50

33.35

43.07

49.57

10.67

6.16

18.83

26.61

16.13

27.06

0.385

0.802

2.23

2.42

SD

Regular training group (n = 27)

49.6

44.9

13.5

14.5

11.1

12.0

146.3

156.0

45.4

45.9

118.0

104.5

27.6

23.2

96.0

85.7

99.4

86.6

3.68

3.39

21.0

20.6

Mean

4.16

4.78

0.99

1.24

1.85

2.03

15.40

20.74

16.73

27.17

56.06

52.20

8.69

9.71

13.26

28.58

11.57

27.27

0.819

0.956

3.22

3.26

SD

Irregular training group (n = 28)

43.8

45.1

14.8

14.5

11.6

12.7

161.0

160.0

55.8

60.0

125.1

135.4

21.0

19.4

93.3

79.0

96.8

82.2

3.59

3.74

20.1

19.8

Mean

4.69

3.34

1.54

1.07

2.06

1.96

16.89

18.50

29.75

26.36

77.98

63.70

7.64

6.12

21.63

33.73

21.85

34.98

0.785

0.751

2.48

2.30

SD

Control group (n = 39)

Table 1  Body Mass Index (BMI), Self-Related Health, and Physical Fitness, Baseline and 6-Month Follow Up

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7.21

7.14

1.18

2.63

C

NS

(IRT > C)a

NS

NS

NS

NS

RT > C

NS

Tukey HSD test

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Swedish Physical Inactive Female Students   1167

Figure 2 — Effect sizes in terms of Body Mass Index (BMI), self-related health and physical fitness: the regular training group (n = 27), the irregular training group (n = 28), and the control group (n = 39).

Lack of suitable places for physical exercises and environmental problems are common barriers for carrying out physical activity have been reported by inactive high school female students.27,28 To avoid these barriers, the females in the intervention group of the current study were allowed to choose a sport center close to either their high school or their home. Zaragoza et al28 found that adolescent females at a low physical activity level had more intrapersonal (lack of interest and motivation, dislike physical activity) and environmental barriers when compared with adolescent females at a high physical activity level. The instructors at the sport center made individual physical activity programs to help the females of the current study to avoid intrapersonal barriers. Furthermore, the research leader regularly encouraged them to stay physically active. It is important to customize a physical activity strategy to increase physical activity since lack of time is a common barrier. To avoid time barrier, school based and after school hours physical activity at a sport center or a sport club might attract physically inactive females to a higher extent. Another strategy is to present a

wide range of different kinds of physical activities both inside and outside school. In a longitudinal study, Jerden et al29 reported significantly lower self-related health in female adolescents when compared with male adolescents, with increasing differences throughout the adolescence. Therefore a strategy to early influence and encourage young females to stay active should be of high priority. In the current study the females of the regular training group significantly increased their self-related health compared with the controls, thereby concluding that physical activity positively influences health. Our results correspond well with those from another study on Swedish high school students, students with a moderate and high level of physical activity reported better self-related health compared with less physical active students.30 Encouraging adolescents to be physically active and to maintain a physically activity behavior throughout life is therefore crucial. A study on middle/high school students and their physical activity behavior showed that cardio respiratory fitness, VO2max, was positively associated with physical activity.31 VO2max increased

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1168  Kahlin, Werner, and Alricsson

both in the regular training group and in the irregular training group in comparison with the control group. This finding is of utmost importance since high VO2max during adolescence might decrease the risk of sustaining a cardiovascular disease in adulthood.32 In the intervention groups the VO2max increased and the time to walk 1 mile decreased when compared with the control group. A study on college students showed that one-mile track walk test overpredicted VO2max in less physically active students.33 Similar results were found in the current study, that VO2max was slightly overpredicted, higher at both test occasions, at baseline as well as at the 6-month follow up. Moreover, improvement in VO2max was found in the intervention group. An 8-month school-based physical activity intervention study in female adolescents also resulted in improvement of physical fitness, where VO2max increased both in the intervention group and the control group.34 The lack of differences in changes as measured with the physical fitness tests in the current investigation are not that surprising and can possibly be explained by the fact that the females in the intervention group practiced different types of physical activities at the sport center. In this study the intervention groups and the control group made some improvements in physical fitness (increased muscle strength and endurance), although these improvements were not statistically significant. Significant improvements were seen in all groups in terms of the sit-ups and the in one-leg hop test. Furthermore, by stating a relatively low exercise goal (at least 1 time per week) we were most likely able to reduce the number of dropouts in the intervention group. Although, the exercise level was either regular or irregular among the females in the intervention group, there were no actual dropouts at the sport center. The only dropouts were found at the 6-month follow up test. To our knowledge this is one of the first studies using an intervention that was individually designed. The females were able to choose a sport center near their home or school and each female received an individually based physical activity program. They also received a monthly telephone call from the research leader and self-reported their physical activity parallel with recordings of each time they visited the sport center. Drop-outs are often a problem in physical activity interventions.13 Fortunately, in the current study there were not that many drop-outs. This might be explained by the monthly telephone calls and the strategy that the females could choose their own physical exercises and how often they wanted to visit the sport center for training, once or more times per week. The power of the present investigation decreased somewhat when the intervention group was split into 2 smaller groups, a regular and an irregular training group. This might at least to some extent explain lack of significant results of the physical fitness tests in the different groups. Furthermore, the fitness tests were not laboratory based measures and they were done in the high schools, and dependent on the motivation of each subject. Finally, daily regular physical activities (overall physical activities) were not measured. Future studies are needed to evaluate the long-term effects of physical activity in inactive high school female students. Collaboration between different high schools and sport centers might stimulate physically inactive females to become physically active.

Conclusion The overall message of the present investigation is that regular physical activity at a sport center can influence the behavior of physical activity and improve both physical fitness and self-related health in physically inactive female high school students. It also indicates

that an individually based physical activity program increases selfrelated health and physical fitness (maximal oxygen consumption) in physically inactive female high school students. Acknowledgments This study was financially supported by grants from the Swedish Sports Confederation (Riksidrottsförbundet/Idrottslyftet).

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