Journal of Aging and Physical Activity, 2015, 23, 78-89 http://dx.doi.org/10.1123/JAPA.2012-0326 © 2015 Human Kinetics, Inc.

Official Journal of ICAPA www.JAPA-Journal.com ORIGINAL RESEARCH

Comparative Effects of Horse Exercise Versus Traditional Exercise Programs on Gait, Muscle Strength, and Body Balance in Healthy Older Adults Silvia Aranda-García, Albert Iricibar, Antoni Planas, Joan A. Prat-Subirana, and Rosa M. Angulo-Barroso This study evaluates the separate effect and retention of 12-week traditional (TE) and horse (HE) exercise programs on physical function in healthy older participants (61 to 87 years old). Thirty-eight participants were randomly assigned to three groups: TE (n = 17), HE (n = 10), and control group (n = 11). TE and HE underwent a supervised exercise program (3 day/week). Maximal gait speed, muscle strength, and body balance were assessed at weeks 0, 12, and 16. Only TE and HE displayed significant improvements (P < .05) in knee extensor strength, and only HE had faster gait speed. Marginal balance improvements were found only in HE in the medial-lateral direction. However, TE showed larger improvements in handgrip than HE. The largest retention was in knee extensor strength but most of the exercise effects were lost in the follow-up. Besides TE, exercise with a horse may be an alternative option to older adults, provided that they want to interact with the animal. Keywords: elderly, physical activity, horse exercise, follow-up study, rural community

Aging is associated with significant reductions in physical function, defined as the ability to perform activities of daily living independently without motor impairments (Kelly-Hayes, Jette, Wolf, D’Agostino, & Odell, 1992; Laukkanen, Leskinen, Kauppinen, Sakari-Rantala, & Heikkinen, 2000; Shinkai et al., 2000). Furthermore, age-related physical dysfunction can be exacerbated by disease or physical inactivity (McGuire et al., 2001). Gait is a good marker of physical function in older adults because it is necessary in most activities of daily living and is also an indicator of disability, physical independence, and even survival (Cress et al., 1995; Kelly-Hayes et al., 1992; Laukkanen et al., 2000; Shinkai et al., 2000; Studenski et al., 2011). Some physical components, such as muscle strength or balance, are related to gait (Buchner et al., 1996; Callisaya et al., 2009; Kline Mangione, Craik, Lopopolo, Tomlinson, & Brenneman, 2008; Kluding & Gajewski, 2009; Lord, Lloyd, & Li, 1996). Compared with adults, older adults show a decline in muscle strength (Andrews, Thomas, & Bohannon, 1996; Bohannon, 1997a; Danneskiold-Samsøe et al., 2009) and body balance (Era et al., 2006; Masui et al., 2005), which leads to a decline in gait speed (Bohannon, 1997b; Lopopolo, Greco, Sullivan, Craik, & Mangione, 2006). This decline is not necessarily inevitable, because it is well known that regular exercise and an active lifestyle may help to delay or minimize the negative effects of aging (McGuire et al., 2001; Nelson et al., 2007). In fact, there is well established evidence of improved gait (Lopopolo et al., 2006; Mian, Baltzopoulos, Minetti, & Narici, 2007) and muscle strength (Latham, Bennett, Stretton, & Anderson, 2004; Vogel et al., 2009) in older adults in comparison with adults after exercise programs. However, certain controversy over the impact of exercise interventions in older adults on body Aranda-García is with the School of Health and Sports Science, Universitat de Girona, Girona, Spain and the Health and Applied Sciences Department, INEFC-Barcelona, Universitat de Barcelona, Barcelona, Spain. Iricibar, Planas, and Prat-Subirana are with the Health and Sports Management Department, INEFC-Lleida, Universitat de Lleida, Lleida, Spain. Angulo-Barroso is with the Health and Applied Sciences Department, INEFC-Barcelona, Universitat de Barcelona, Barcelona, Spain. Address author correspondence to Silvia Aranda-García at [email protected] 78

balance still remains. It seems that exercise interventions specifically designed to improve balance tend to be successful (Howe, Rochester, Jackson, Banks, & Blair, 2007; Orr, Raymond, & Fiatarone Singh, 2008), whereas a more generic exercise intervention has failed to improve balance in older men (Bellew, Yates, & Gater, 2003). Discrepancies among the effects of different exercise programs may be explained by the sample age and type, duration, frequency, and intensity of the intervention (Bellew et al., 2003; Cadore, Rodríguez-Mañas, Sinclair, & Izquierdo, 2013; Howe et al., 2007; Orr et al., 2008). Different ways to implement exercise in older adults could be classified into traditional exercise programs (Daniels, van Rossum, de Witte, Kempen, & van den Heuvel, 2008; Gillespie et al., 2009; Rydwik, Frandin, & Akner, 2004) or alternative programs such as those with an animal (Raina, Waltner-Toews, Bonnett, Woodward, & Abernathy, 1999; Toigo, Leal Júnior, & Ávila, 2008). Traditional interventions are performed in a group under the direction of a kinesiologist. These exercise interventions are heterogeneous and can yield physical function benefits to gait, including physical components such as muscle strength and body balance in older adults (Daniels et al., 2008; Gillespie et al., 2009; Rydwik et al., 2004). In contrast, exercise with animals (e.g., walking a pet) may imply improvements in active lifestyle in older adults (Raina et al., 1999) or indirect physical and mental health benefits (Cutt, GilesCorti, Knuiman, & Burke, 2007). Specifically, it is well established that exercise interventions with horses that focus on a therapeutic purpose can improve certain diseases at different ages. Most of these studies involved children with cerebral palsy (Kwon et al., 2011; Zadnikar & Kastrin, 2011), autism (Bass, Duchowny, & Llabre, 2009), and Down syndrome (Champagne & Dugas, 2010), while a few involved adults with multiple sclerosis (Bronson, Brewerton, Ong, Palanca, & Sullivan, 2010; Hammer et al., 2005), back pain (Hakanson, Moller, Lindstrom, & Mattsson, 2009), and poststroke hemiparetic patients (Beinotti, Correia, Christofoletti, & Borges, 2010). Participants of these studies improved aspects related to functioning of daily life and quality of life (Zadnikar & Kastrin, 2011), mainly body balance (Bronson et al., 2010; Hammer et al.,

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Horse Exercise Versus Traditional Exercise   79

2005; Kwon et al., 2011; Zadnikar & Kastrin, 2011). None of these studies involved older adults with pathology. Given the known benefits of exercise with horses in participants with certain diseases, and the benefits of other types of exercise intervention in older adults, it could be expected that healthy older adults could also improve their physical function (i.e., gait, muscle strength, and balance) after an exercise intervention with horses. To our knowledge, only one study presented results after an exercise program with horses in healthy older participants (Toigo et al., 2008). In this study, 10 women aged from 60 to 74 years participated in eight sessions (2 sessions/week, 30 min each session) of exercise with a horse. Despite their low sample size and the methodological characteristics of this study (i.e., quasi-experimental design, low exercise doses: number, duration, and frequency of exercise sessions), Toigo et al. (2008) reported some static balance improvements after the horse intervention. Given the scarce evidence of horse interventions with healthy older participants, and the lack of comparative studies examining whether the expected benefits are higher or lower than those found in other types of interventions such as traditional exercise programs, further research is warranted. Furthermore, the physical function benefits obtained in older adults via different exercise interventions may or may not be retained after their termination (Giné-Garriga et al., 2010; Protas & Tissier, 2009; Serra-Rexach et al., 2011). After a short detraining period (≤ 4 weeks), cardiovascular function has been shown to decrease (Mujika & Padilla, 2001a) and muscular function can be maintained or can be reduced (Mujika & Padilla, 2001b). Bosquet et al. (2013) suggested that retention of a training effect after its cessation was related to training level and detraining time and age, and that older people presented worse retention than adults. Unfortunately, only a few number of exercise intervention studies in older adults include follow-up assessments (Giné-Garriga et al., 2010; Protas & Tissier, 2009; Serra-Rexach et al., 2011), and none were interventions with horses. Although these studies involved different interventions and follow-up durations, they found that improvements in physical functioning were retained at follow-up (Giné-Garriga et al., 2010; Protas & Tissier, 2009), while muscle strength was partially retained for a period half as long as the intervention and completely lost in follow-up periods that were longer than half the intervention (Giné-Garriga et al., 2010; Protas & Tissier, 2009; Serra-Rexach et al., 2011). The objective of the current study was to examine the potentially larger benefits and superior retention of a horse exercise intervention in comparison with a traditional exercise intervention and a control group on maximal gait speed, leg extensor muscle strength, handgrip, and balance in healthy older adults.

Methods Participants Eligible participants were older adults aged 60 or over with independent ambulation and a desire to participate in an exercise program and interact with a horse. Exclusion criteria were a history of falls in the last six months, chronic disabling disease, obesity (defined as BMI ≥ 33 kg·m–2), or a low range of motion (shoulder: < 30° flex-extension or abduction-adduction; hip: < 30° flex-extension or < 20° abduction-adduction; ankle: < 30° flex-extension) (Escalante, Lichtenstein, Dhanda, Cornell, & Hazuda, 1999; Lark, Buckley, Jones, & Sargeant, 2004; Swank, Funk, Durham, & Roberts, 2003). A total of 1,025 older adults living in a rural town were contacted via mail to participate in a meeting to explain the study. Four

hundred and fifty people attended the meeting, and 61 of them volunteered for a clinical assessment. Six of these adults were excluded by the exclusion criteria (three with no independent ambulation, one with uncontrolled diabetes mellitus, one with < 30° flexionextension hip range of motion, and one with severe cardiovascular disease). Consequently, 55 healthy older adults participated in our study (15 men and 40 women, 77.1 ± 5.7 and 70.2 ± 6.3 years ± SD, respectively). Participants were stratified (balanced randomization with three stratification factors: sex, age, and maximal gait speed­­—men and women, < 72 and ≥ 72 years, and < 1.6515 and ≥ 1.6515 m/s) and randomized into three groups. Initially, there were 19 participants in the traditional exercise group (TE), 20 participants in the horse exercise group (HE), and 16 participants in the control group (C). However, 13 participants dropped out of the study (one from TE, seven from HE, and five from C), and four additional participants were excluded from the statistical analysis (one from TE and three from HE). Finally, 38 participants were analyzed (TE = 17, HE = 10, C = 11). Reasons for dropping out and a summary of the recruitment process are detailed in Figure 1, following the Consolidated Standards of Reporting Trials (ConSORT) flow diagram (Moher, Schulz, & Altman, 2001). The local ethics committee approved our project. All participants signed informed consent forms before starting the study.

Procedures and Measurements Participants were assessed at baseline, at 12 weeks (postintervention), and at 16 weeks (retention: 4 weeks after the intervention). These assessments were conducted by researchers who were trained in the procedures by an expert before the data collection period and who were blind to the purpose of the study and the participants’ group membership. General information (i.e., sex, date of birth, height, body mass, and level of physical activity) was collected at baseline, postintervention, and retention. We used the Physical Activity Scale for the Elderly (PASE) to estimate the level of physical activity (Washburn, Smith, Jette, & Janney, 1993). In all the assessments, we also collected data related to physical function: maximal gait speed, muscle strength of arms and legs, and body balance. The order for upper and lower extremity strength and balance conditions was randomized per participant, as well as the order of gait, strength, and balance measurements. The established order per participant was kept the same for postintervention and retention. Gait Speed.  Maximal gait speed was collected as participants walked as fast as they safely could on a marked 16-m walkway with a photocell timing system. Participants started and finished walking two meters before and after the walkway to ensure the participants reached a steady state gait speed across it (Macfarlane & Looney, 2008). Participants performed three consecutives trials and the times were registered. To analyze the best trial, the lowest value of time was selected as the variable for further analysis. Muscle Strength.  Maximal isometric muscle strength was measured on both sides over a 4-s period. The force production of knee extensor muscles was assessed with a dynamometer (Cybex 6000; Cybex Inc., Ronkomkoma, NY) and handgrip test was assessed with a hand dynamometer (Jamar J00105; Sammons Preston Rolyan, Bolingbrook, IL). For these strength measurements we followed the standard guidelines established in the literature (Neder et al., 1999; Ruiz-Ruiz, Mesa, Gutierrez, & Castillo, 2002). Participants executed three consecutive trials with at least a 30-s resting period between each trial. These variables were normalized

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80  Aranda-García et al.

Figure 1 — Flowchart of participants’ recruitment and trial design.

by body mass and the best trial was selected as the variable for further analysis. We assessed first the right side and then the left side. Data on knee extensors were collected under two conditions of knee flexion: 60 and 90 degrees (full knee extension was 0°). The order was: (1) right knee extensors at 60°, (2) right knee extensors at 90°, (3) left knee extensors at 60°, and (4) left knee extensors at 90°. To analyze the best trial in each condition, the highest value was selected for further analysis. Balance.  Balance during quiet standing was measured with a

force platform (Dinascan IBV, model 600M, Valencia, Spain) at a frequency of 500 Hz. Participants stood barefoot on the force platform with a comfortable and self-chosen separation between their feet. Data were collected under three conditions: quiet standing with eyes open (EO), with eyes closed (EC), and dual task (DT; with the additional cognitive task of counting backward). Three 20-s trials were collected per condition with at least a 30-s rest period between trials. To calculate the base of support and to maintain the feet in the same position across all trials, the outlines of the feet were traced on adhesive paper placed over the force platform. The sway of the center of pressure (CoP) was computed with a custom-made Matlab program (Matlab 7.0.1; Mathworks, Natick, MA) in the anterior-posterior (AP) and medial-lateral (ML) directions for every 20-s trial. For each direction, maximal distance (MaxD) and peak velocity (PkV) of CoP were computed. These variables were normalized by the base of support in each direction. To use representative value of the trials in the balance variables and given that no significant differences across trials were found (nonsignificant one-way ANOVAs for MaxD and PkV), the average of three trials per condition was calculated and considered for further analysis, as other authors have done previously (Rooks, Kiel, Parsons, & Hayes, 1997; Wayne et al., 2012).

Interventions Both experimental groups participated in a 12-week supervised exercise program of 60-min sessions three times a week on alternate days (Monday, Wednesday, and Friday). Meanwhile, the control group continued with their usual daily life activities (caring for grandchildren, gardening, farming, cleaning the home, watching television, and more) with no additional visits beyond the scheduled assessments. The exercise sessions for both experimental groups were funoriented and whole body workouts. The HE objectives were the same as for TE, but with different exercises involving the horse (see Table 1). The sessions of each program were designed and conducted by kinesiologists who were specialists in older adults. In addition, the kinesiologist who designed the HE sessions was an expert in exercise with horses. Each session was structured in three parts: an initial warm-up including 10 min of joint movements of progressively larger amplitude and progressive aerobic exercises to prepare participants for the main workout, 40 to 45 min of exercises to achieve the objectives of the session, and a final cool-down during which participants performed stretching exercises for the major muscle groups (5 to 10 min). Moreover, two days per week, participants performed specific back stretching exercises, which are critical to improve the trunk’s flexibility and mobility. Traditional Exercise (TE) Intervention Group.  TE participants

exercised in a supervised program with sessions held at a sports center. Cardiovascular capacity was trained each session in the pavilion with exercises with different displacements involving the whole body: one session per week with a volume of 30 min (10 to 15 min at vigorous intensity and 20 to 15 min at moderate

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Content Second Weekly Session

Third Weekly Session

• Muscle strengthening activity focused on trunk

• Muscle strengthening activity focused on arm

• Flexibility exercise involving major muscle groups in each session. In addition, two days/week focusing on the back.

• Balance exercises in each session, 3–5 min

(15–30 min combining moderate and vigorous intensity exercises: 8–10 exercises, 8–12 repetitions, resting time depending on perceived effort)

• Muscle strengthening activity focused on leg

• Aerobic activity (30 min • Aerobic activity (15–20 combining moderatemin moderate intensity vigorous intensity exercises) exercises)

• Aerobic activity (15–20 min moderate intensity exercises)

• Progressive aerobic exercise and joint movements in each session.

First Weekly Session

Static stretching of the major muscle groups of arms, trunk, and legs while using a partner, a fitball, or a spaldier as support or to provide resistance.

Maintain static positions in different conditions (e.g., eyes closed, unstable surface, remembering something). Walking around obstacles.

Up and down a bench. Squat and get up to pick balls. Hold a medicinal ball with arms. Isometric exercises involving different abdominal muscles.

Walking along a cone marked circuit at moderate intensity. Participating in a playful game with displacements at vigorous intensity.

Static stretching of the major muscle groups of arms, trunk, and legs while using the horse as support or to provide resistance.

While standing beside the horse, embrace its chest and maintain balance in different conditions (e.g., one foot, eyes closed, thinking about something) while the horse is breathing.

Grooming the horse, which encouraged participants to bend while maintaining muscle activation. Mount and dismount a horse repeatedly.

Walking the horse in a circuit of cones at moderate intensity. Walking beside, in front of, or around the horse in a circular circuit at vigorous intensity while the horse slightly pushed or pulled the participant.

From slow to fast walking along with the horse. Joint rotations next to the horse including shoulders or hips.

Horse Exercise

Exercise Examples From slow to fast walking with different forms of displacements (forward, backward, sideways). Joint rotations like shoulders, hips.

Traditional Exercise

Note. Moderate intensity exercise was at a 5–6 and vigorous intensity exercise was at a 7–8 on a 10-point scale; min = minutes.

Final (5–10 min)

Principal (40–45 min)

Initial (10 min)

Session

Table 1  Weekly Session Content by Session Parts and Exercise Examples by Type of Intervention

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intensity) and two sessions per week with 15 to 20 min of moderate intensity exercise (see Table 1). The exercise’s intensity was indicated by verbal instructions, where moderate intensity involved efforts of 5 to 6 on a 10-point scale (where sitting was 0 and all-out effort was 10) and produced a noticeable increase in breathing. Vigorous intensity involved efforts of 7 to 8 on the same scale and produced large increases in breathing (ChodzkoZajko et al., 2009; Nelson et al., 2007). In addition, trunk, arm, and leg resistance were trained one session per week each (15 to 30 min, 8 to 10 exercises, 8 to 12 repetitions involving exercises between moderate and vigorous intensity). Examples of strength training can be consulted in Table 1. Moreover, in each session exercises were included to enhance body balance and gross and fine body coordination (3 to 5 min) (see Table 1).

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Horse Exercise (HE) Intervention Group.  The HE group partici-

pated in a supervised program with horses specially trained for exercise with people. The sessions took place at a riding center. Two kinds of horse-related exercises were used to complete the program: exercises with the participant on the ground while interacting with the horse and exercises with the participant on the horse. Examples of exercises with the feet on the ground were grooming the horse, which encouraged participants to bend, and exercises walking beside, in front of, or around the horse in a circuit (see Table 1). The exercises on the horse were performed bareback (i.e., without a saddle) while the horse was walking or trotting, or simply by moving the trunk, arms, and head of participants while the horse was steady. Experts in exercise using a horse claim that more proprioceptive and more muscle activity is required without a saddle, although we are not aware of any scientific evidence. The same cardiovascular, strength, flexibility, body balance, and coordination program objectives seen in TE were achieved (Table 1).

Data Analysis The normal distribution of each variable was checked with the Kolmogorov-Smirnov test. The nonnormal variables were logarithmically transformed for the statistical analysis and back-log transformed to be reported in raw units. Descriptive statistics were conducted for all variables. To examine baseline group differences, one-way ANOVAs were conducted for all continuous variables and chi-square tests were used for categorical variables. To test whether any general or anthropometric variable could be included as a covariable in the ANOVAs, we checked the baseline differences of potential covariables between groups with a one-way ANOVA and the correlations of these variables with the dependent variables of interest (Raab, Day, & Sales, 2000). Body mass and BMI showed differences between groups at baseline. However, these variables did not correlate with the dependent variables and were not included as covariables (P = ns) (Vincent, 2005). For gait speed and strength variables, 3 (group: TE, HE, C) × 3 (time: baseline, postintervention, retention) ANOVAs with repeated measures on the time factor were performed to determine the effect of group, time, and their interaction. Focused analyses were performed when interactions were significant, calculating the effect size (ŋ2) (Richardson, 2011; Thomas & Nelson, 2007) and conducting Bonferroni post hoc or planned comparisons when necessary. For the balance variables, 3 (group: TE, HE, C) × 3 (time: baseline, postintervention, retention) × 3 (conditions: EO, EC, DT) ANOVAs with repeated measures on the time and condition factors were performed to determine the effect of group, time, condition,

and their interactions. Focused analyses were performed when interactions were significant, calculating the effect size (ŋ2) and doing Bonferroni post hoc or planned comparisons when necessary. We considered results statistically significant when P < .05. Analyses were conducted using SPSS for Windows version 15.0 (IBM, Chicago, IL).

Results Participants’ Characteristics at Baseline The anthropometric values and the level of physical activity of the three groups at baseline are presented in Table 2. Initially, the three groups did not differ significantly in baseline characteristics, except for body mass (P = .007) and BMI (P = .017). HE participants’ body mass was lower than that of the other two groups and HE participants’ BMI was also lower than the BMI in TE participants (posthocs, all P < .05).

Adherence to the Intervention Participants were required to complete > 65% sessions to be considered for further analyses. As shown in Figure 1, only two participants were excluded for this reason. The adherence to the intervention in the experimental groups, understood as the mean attendance, was 85.7% in HE (SD = 11.9, range: 65.7–100.0%) and 86.0% in HE (SD = 10.9, range: 67.6–100.0%) for the total sessions.

Maximal Gait Speed At baseline, there was no significant difference in maximal gait speed between TE, HE, and C groups (see Table 3). A significant group-by-time interaction was detected for maximal gait speed with 13.0% of its variance explained by the interaction (F4,70 = 2.74, P = .036, ŋ2 = .130). The focused analysis revealed that the interaction was explained by changes in HE, which increased significantly from baseline to postintervention (8.7%), while TE and C did not change significantly (see Table 3 and Figure 2A). Although not significant, the gait speed improvement in HE remained above baseline value at retention time (4 weeks postintervention), since gait speed for HE improved by 6.2% and was larger than that of baseline at retention (see Table 3 and Figure 2A). This 6.2% retention meant that HE participants maintained 71.3% of the total improvement due to the four weeks of intervention. Table 2  Baseline Characteristics of Traditional Exercise (TE), Horse Exercise (HE), and Control (C) Groups TE (N = 17)

HE (N = 10)

C (N = 11)

p

Sex

Variable

12 F, 5 M

7 F, 3 M

7 F, 4 M

ns

Age (yr)

70.5 ± 7.1

72.2 ± 7.7

71.9 ± 5.4

ns

Height (m)

1.6 ± 0.1

1.5 ± 0.1

1.6 ± 0.1

ns

Body mass (kg)

75.0 ± 9.7

62.7 ± 8.9

76.5 ± 12.6

.007

BMI (kg/m2)

30.4 ± 3.5

26.3 ± 2.2

29.7 ± 4.3

.017

Level PA (range)

88.3 ± 46.4

77 ± 55

104.1 ± 42.0

ns

Note. Values are means ± SD. N = number of individuals; F = female; M = male; BMI = body mass index; PA = physical activity; ns = not significant. p values are the statistical probability from the one-way ANOVA for continuous variables or chi-square for sex variable.

83

139.78 ± 53.98 143.19 ± 39.60 143.42 ± 31.38

HE C

151.85 ± 43.34

C TE

140.79 ± 32.09

HE

29.70 ± 8.03

C 139.30 ± 53.75

30.14 ± 6.56

TE

25.85 ± 7.11

TE

1.68 ± 0.11

C HE

1.61 ± 0.22

HE

SD

1.76 ± 0.25

Mean

TE

Group

SD

138.93 ± 25.20

161.11 ± 39.04

155.49 ± 51.00

150.27 ± 42.19

176.38 ± 34.82

169.35 ± 59.96

33.54 ± 5.88

31.14 ± 5.06

33.17 ± 7.20

1.65 ± 0.13

1.75 ± 0.16

1.83 ± 0.26

Mean

Postintervention (W12) SD

141.41 ± 26.29

150.00 ± 44.94

140.93 ± 47.82

160.33 ± 41.42

156.39 ± 40.58

167.42 ± 61.21

28.24 ± 9.24

28.87 ± 8.57

27.73 ± 9.25

1.72 ± 0.17

1.71 ± 0.3

1.75 ± 0.29

Mean

Retention (W16)

Group × time

Group × time

Group × time

Group × time

Effect Tested

p

.090

.013

.047

.036

HE: W0 < W12

TE: W0 < W12 > W16

HE: W0 < W12

TE: W0 < W12, W16

C: W0 < W12 > W16

TE: W0 < W12 > W16

HE: W0 < W12

Focused Analysis

Note. Values are means ± SD. The three groups were TE = traditional exercise (N = 17); HE = horse exercise (N = 10); and C = control (N = 11). Assessment time points are indicated by W0 = week zero; W12 = week 12; and W16 = week 16. p values indicate the significance of 3 (group) by 3 (time) ANOVAs. When p was significant, focused analyses were performed.

Knee extensors 60º (N·m/kg·100)

Knee extensors 90º (N·m/kg·100)

Handgrip (%)

Gait speed (m/s)

Baseline (W0)

Table 3  Gait Speed and Muscle Strength at Baseline, Postintervention, and Retention by Group

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84  Aranda-García et al.

Figure 2 — Box plots of the changes in gait speed and muscle strength by time (baseline: week 0; postintervention: week 12; and retention: week 16) and by group (traditional exercise [TE], horse exercise [HE], and control [C]).

Muscle Strength At baseline, there was no significant difference in muscle strength (knee extensor strength at 90°, knee extensor strength at 60°, handgrip) between the three groups (see Table 3). A significant group-by-time interaction was detected for knee extensor strength at 90° and handgrip, explaining 12.9% and 9.4% of their variances, respectively (F4,58 = 3.48, P = .013, ŋ2 = .129 and F4,66 = 2.55, P = .047, ŋ2 = .094; respectively). The interaction in knee extensor strength at 90° was explained by significant improvements in both intervention groups, while the C group remained unchanged. TE participants improved by 21.6% and HE participants by 25.3% in postintervention compared with baseline values. The retention of this effect was almost complete in TE participants (20.2% improvement from baseline to retention) and still remained above baseline value in HE (11.1% improvement from baseline to retention) (see Table 3 and Figure 2C). These retention values meant that TE participants retained 93.5% of the intervention improvements, while HE participants retained 43.9%. Results for knee extensor strength at 60° showed similar trends as those seen in the 90° condition, but with no significant change (F4,58 = 2.12, P = .078, ŋ2 = .106) (see Figure 2D). The group-by-time interaction in handgrip was explained by a significant increase between baseline and postintervention in TE (28.3%, P < .001) and no significant changes in HE (3.3%, P =

1.00) and in C (12.9%, P = .054). The handgrip change in TE was significantly lower in the retention period than postintervention (83.6%, P = .001); however, this retention value did not returned to the baseline level given it was 7.3% higher (see Table 3 and Figure 2B).

Body Balance At baseline, there were no significant differences in balance variables (MaxD and PkV) between groups (TE, HE, and C), conditions (EO, EC, and DT), or directions (AP and ML) (see baseline data on Table 4). For PkV in the ML direction only, a significant groupby-time-by-condition interaction was detected, explaining 9.3% of its variance (F8,64 = 2.77, P = .011, ŋ2 = .093) in the 3 (group) by 3 (time) by 3 (condition) ANOVA (see Figure 3). The 3 (group) by 3 (time) focused analysis on PkV in the ML direction did not reveal any significant interaction (F4,66 = 2.21, P = .078, ŋ2 = .118). However, planned comparisons by groups showed that HE participants’ balance worsened 24.4% in the DT condition only when the intervention period had finished. The other two groups remained unchanged across time in all conditions (see Figure 3C). Furthermore, planned comparisons for the time factor on the PkV in the ML direction yielded significant time effects only in the EC condition, explaining 6.3% of its variance (F2,33 = 5.91, P = .001, ŋ 2 = .063). Post hoc analysis revealed greater PkV

Horse Exercise Versus Traditional Exercise   85

Table 4  Baseline Body Balance by Condition, Direction, and Group Group

Eyes Open (EO)

Eyes Closed (EC)

Mean

Mean

SD

SD

Dual Task (DT) Mean

SD

Maximum distance AP direction

ML direction

TE

0.063 ± 0.018

0.079 ± 0.020

0.089 ± 0.044

HE

0.072 ± 0.034

0.090 ± 0.041

0.108 ± 0.065

C

0.058 ± 0.012

0.083 ± 0.018

0.072 ± 0.016

TE

0.035 ± 0.019

0.041 ± 0.022

0.051 ± 0.022

HE

0.048 ± 0.041

0.068 ± 0.075

0.072 ± 0.055

C

0.046 ± 0.033

0.055 ± 0.030

0.056 ± 0.028

Peak velocity (s–1)

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AP direction

ML direction

TE

0.129 ± 0.039

0.189 ± 0.094

0.208 ± 0.096

HE

0.154 ± 0.083

0.232 ± 0.168

0.222 ± 0.119

C

0.121 ± 0.022

0.176 ± 0.058

0.184 ± 0.055

TE

0.068 ± 0.033

0.090 ± 0.044

0.099 ± 0.045

HE

0.116 ± 0.111

0.134 ± 0.139

0.135 ± 0.098

C

0.081 ± 0.049

0.087 ± 0.037

0.101 ± 0.040

Note. Values are means ± SD. All data normalized by base of support. Directions were AP = anterior-posterior and ML = medial-lateral. The three groups were TE = traditional exercise (N = 17); HE = horse exercise (N = 10); and C = control (N = 11). EO, EC, and DT were the three balance conditions. Postintervention and retention results are not provided because differences were not significant, with the exception of those presented in Figure 3.

Figure 3 — Box plots of the changes in peak velocity of center of pressure (in medial-lateral [ML] direction) by time (baseline: week 0; postintervention: week 12; and retention: week 16), group (traditional exercise [TE], horse exercise [HE], and control [C]), and condition (eyes open [EO]; eyes closed [EC]; and dual task [DT]). Note. Outliers are not included in the graph.

in the ML direction in baseline than postintervention and retention, considering all groups together (P = .023 and P = .004, respectively) (see Figure 3B).

Body Composition A 3 (group) by 3 (time) ANOVA showed a significant time difference in body mass (F2,34 = 16.02, P < .001, ŋ2 = .274) and BMI (F2,34 = 49.10, P < .001, ŋ2 = .275). The post hoc test and the planned analysis showed that changes in body mass were explained by decreases in both intervention groups (HE and TE) between baseline and postintervention (all P < .001), while the C group remained unchanged. Changes in BMI were explained by smaller values in

postintervention and retention than at baseline for all groups (all P < .001).

Discussion The major finding of our study was that a horse exercise program is a viable form to implement exercise in healthy older adults who choose to interact with an animal, as our results yielded some benefits related to physical function, such as maximal gait speed and maximal isometric knee extensor muscle strength. As a result of the exercise intervention, maximal gait speed improved in the

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86  Aranda-García et al.

HE group as it was hypothesized, but such improvement was not observed in the TE group. The potential reasons for the increase in gait speed only in the HE group were unclear, but could be related to the characteristics of the practice location and the principle of specificity of training (Matveyev, 1977). Compared with the TE group, HE participants had to walk longer distances in the riding center because of its size. Related to knee extensor strength, we hypothesized larger improvements in the HE group than in the TE group, with no changes in the C group. Our results mainly supported this hypothesis, as participants from both exercise interventions improved their maximal isometric knee extensor strength at 90° knee joint angle (21.6% in TE and 25.3% in HE), while the C group did not change. However, these benefits were not greater in the HE group than in the TE group. Comparison of our results with previous studies should be made with caution due to methodological differences (e.g., wide variety of methods for assessing muscle strength and multiple exercise protocols) (Buchner et al., 1997; Giné-Garriga et al., 2010; Rooks et al., 1997; Serra-Rexach et al., 2011; Sipila, Multanen, Kallinen, Era, & Suominen, 1996; Sousa & Sampaio, 2005). Previous authors stated that different exercise interventions improved the leg strength of older adults (Buchner et al., 1997; Giné-Garriga et al., 2010; Rooks et al., 1997; Serra-Rexach et al., 2011; Sipila et al., 1996; Sousa & Sampaio, 2005), such as in our study. These studies showed a wide range of improvements in knee extensor strength (6–65%). None of the studies we could find measured knee extension at 90°; however, when comparing our results to only those with assessment of leg muscle strength or intervention duration most similar to ours (Giné-Garriga et al., 2010; Rooks et al., 1997; Sipila et al., 1996; Sousa & Sampaio, 2005), our improvements seemed lower for the 60° knee joint angle condition. Giné-Garriga et al. (2010) measured the maximal isometric knee extensor strength with 60° of knee flexion after 12 weeks of functional circuit training and reported 19% improvement in the left leg muscle strength, while in our study there were no relevant changes in this joint angle. Sipila et al. (1996) measured maximal isometric knee extensor strength with a 60° knee joint angle and found 19% improvement in the strength exercise training group and 31% in the endurance training group after 18 weeks of intervention. Finally, Sousa and Sampaio (2005) recorded 46% improvement in knee extensor strength in older participants after a 12-week progressive strength training program. Possible reasons for the greater improvement in muscle strength in other studies compared with ours could be related to the specificity of the interventions (Giné-Garriga et al., 2010; Sousa & Sampaio, 2005), the duration of the intervention (Sipila et al., 1996), or the age of the participants (Giné-Garriga et al., 2010). Although muscle strength was assessed with isometric tests and in a particular muscle group, limiting generalization, studies assessing isometric strength in older adults are common and related to physical function (Giné-Garriga et al., 2010; Marko, Neville, Prince, & Ploutz-Snyder, 2012; Rantanen et al., 2002; Sipila et al., 1996; Vaapio, Salminen, Vahlberg, & Kivela, 2011). According to our results, horse exercise seemed to be an effective alternative option to improve knee extensor strength in older adults but it was not effective to increase handgrip strength. Handgrip improved in the TE group (28.3%) while it did not change significantly in the HE and C groups. It is noteworthy that although changes in the C group were not significant, it represented a substantial percentage of change (around 13%). The results in the C group could be related to the participants’ activities of daily living, which included farming and gardening during the intervention period. In fact, due to the

unavailability of the C group to attend additional social events, it represented a limitation in our design for not appropriately controlling the potential socioemotional impact of the intervention. Regarding balance, we hoped to find larger improvements due to the interventions in the HE group than in TE group (with no changes in the C group) for both directions and for all conditions, but our results marginally supported this hypothesis. We found an 8.7% improvement in the EC condition between baseline and postintervention when considering all groups together. In addition, a 24.4% deterioration only in the HE group and only in the most sensitive condition (dual task) from postintervention to retention was found for PkV in the ML direction. There were no benefits during the intervention period. Three aspects may have affected this lack of benefits: sample size, baseline level of balance, or characteristics of the exercise interventions. First, our sample size was 27, but Rydwik et al. (2004) reported in their systematic review that studies with samples with less than 50 participants may not reveal balance benefits. Second, some exercise programs among healthy older adult participants presented lack of balance changes when the balance exercise program starting point was high (Judge, Lindsey, Underwood, & Winsemius, 1993); in our study, although there were no significant differences between groups at baseline, the HE group presented the worst balance, with a larger margin for improvement. Third, time riding on the horse was probably less in the HE group than other reported horse interventions in the literature, therefore limiting the potential balance benefits reported by Toigo et al. (2008). On the other hand, it is possible that HE participants performed exercises that involved a greater component of balance than those carried out by TE participants. The HE sessions took place on irregular ground, which could promote balance training with each step, in comparison with the floor of the sports pavilion where TE participants exercised. Moreover, during exercises with the horse, imbalance can be produced by the horse pushing or pulling the participant. With the cessation of the intervention most gains were lost. The largest retention of effects in the current study was in isometric knee extensor strength, specifically in the 90° knee flexion condition in the TE group, where there was a 98.9% retention. In contrast, only part of the gain in the HE groups’ maximal gait speed (6.2%) and knee extensor strength at 90° (11.1%) still remained above baseline value in the follow-up assessment. Our retention findings were in agreement with previous authors who observed reduction of improvements in gait speed and partial or total retention of benefits in leg muscle strength at follow-up (Buchner et al., 1997, Giné-Garriga et al., 2010; Protas & Tissier, 2009; Serra-Rexach et al., 2011). Overall, results of previous authors indicate that knee extensor strength improves more when the intervention exercises are more specific, and that gait and strength benefits are progressively lost after the intervention ceases. This study is not free of limitations. First, our relatively small sample size and multiple variables analyzed imply taking our results with precaution. Second, there was a methodological limitation related to the quantification of exercise intensity. The exercise intensity was controlled by a subjective 10-point scale. However, this is a recommended method for the quantification of exercise intensity in older adults (Chodzko-Zajko et al., 2009; Nelson et al., 2007). Lastly, there was a limitation to the potential application of results of our study to the general public because of several reasons: (1) access to horse interventions is not as easy for older adults as traditional exercise, (2) horses must be specially trained, (3) a specialized center is required for practice, (4) the financial costs are greater, and (5) some people may be afraid of horses. However, only two participants dropped out from the horse intervention for

Horse Exercise Versus Traditional Exercise   87

this latter reason, while adherence was similar between the two intervention groups.

Conclusions To our knowledge, this is the first study to compare the effects and the retention of an exercise intervention using a horse with a more traditional physical exercise intervention in healthy older participants. Hence, our findings are encouraging with regard to recommending that horse exercise is a viable activity for older adults to maintain or improve physical function. Besides the more traditional exercise interventions, the horse exercise may be an alternative option for older adults, provided they want to interact with the animal.

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Ethics Committee Approval This research was approved by the ethics committee of the Hospital Arnau de Vilanova (Lleida, Spain) and the ethics committee of the Administració Esportiva de la Generalitat de Catalunya (Spain).

Acknowledgments We thank the Andromeda Fundación, the promoter of the Método Centauro, which provided hippologists to develop all the exercise interventions with horses and partially funded the project. This research was supported by the Commission for Universities and Research of the Department of Innovation, Universities and Enterprises of the Catalan Government and the European Social Fund (AGAUR). We thank INEFC Catalonia (Lleida and Barcelona) for providing student volunteers, laboratories for assessments, intervention facilities, and the other human and equipment resources needed to conduct the project. We thank Anna Requesens from Alcarràs Town Council for facilitating contact with potential participants and providing facilities for the meetings. We thank Hípica d’Alcarràs for making the exercise intervention with horses possible. We are grateful to Albert Busquets for the suggestions that helped to improve the manuscript. We are grateful to the kinesiologists who implemented the exercise interventions and participated in the assessments: Jordi Ticó, Laura and Marta, Roser Comes, Albert Permanyer, Wilka Pascual, Irene Fernández, Josep Blázquez, Vicente Beltran, Helena Frutos, Consuelo García, Divina Farreny, Valvanera Caballero, and Merxe Puertolas. Finally, special thanks to the older adults that participated in the study.

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