Osteoarthritis (OA) is a degenerative joint disease, which affects many older adults. According to the World Health Organization, approximately 45% of women over the age of 65 years1 have OA. In New Zealand, over 30% of women and 20% of men aged 65 to 74 years have OA.2 Symptoms include joint pain and stiffness; the large weight-bearing joints of the hips, knees, and spine are most often affected although joints in the hands are also a common site.3 Older adults with OA are less physically active than older adults without OA,4 and the majority of adults with all forms of arthritis are not sufficiently active to meet the public health guidelines relative to physical activity levels.5 Low levels of physical activity exacerbate age-related physiological changes such as loss of muscular strength and endurance as well as reduced balance ability, all of which contribute to an increase in fall risk and a reduced ability to perform activities of daily living.6,7 Consequently, older adults with OA are particularly vulnerable to age-related reductions in muscle strength, functional ability and balance, and related declines in independence and perceived quality of life.
Aqua-based exercise is recommended for adults with OA by numerous organizations such as the American College of Rheumatology.8 Performing exercise in an aqua environment reduces joint loading, and water immersion has been associated with decreased pain symptoms because of increased sensory input and decreased joint compression.9 A number of studies investigating the potential health benefits of aqua-based exercise for older adults with OA have focused on hydrotherapy (HT)-based exercise programs10–12 rather than aqua fitness (AF) exercise classes, which are more commonly available in community-based swimming pools. HT is typically an individualized, therapist-supervised program that focuses on strength and range of motion exercises,13 usually in water temperatures between 92 and 96°F.14 Although HT-based programs have been shown to improve physical function15 and reduce pain11,16 among adults with OA, HT classes are often expensive and not always widely available because of the requirement of specialized staff and facilities. AF classes take place at many community swimming pools, and classes consist of partial weight-bearing aerobic and strengthening exercises performed to music.
In a review of literature, Rahmann17 noted that aqua-based exercise is often recommended for people with OA, but that there is no evidence to establish whether a physiotherapist-supervised HT program is more effective than a generic aqua exercise program, such as AF, at improving strength and function. The purpose of this randomized controlled trial was to investigate the effects of an AF program—compared with a seated, HT-type program—on strength, function, balance, fear of falling, and perceived quality of life among older adults with OA.
Volunteers aged 60 years and older with OA were recruited by advertisements on the Arthritis New Zealand website, in local community groups, general practitioners' rooms, at the orthopedic ward at the local public hospital, and in the local newspaper. Interested participants were provided with an information sheet, which they were asked to read before signing informed consent. Participants with OA were included if they had radiological diagnosis of OA in the hips, knees, spine and/or hands; had current and chronic (>1 year) pain, and were able to obtain medical clearance to participate in the study. Exclusion criteria included joint replacement surgery in the past 12 weeks, physical therapy intervention in the preceding 12 weeks, current participation in an organized exercise program twice a week or more, inability to safely enter and exit pool, and cognitive ability of providing informed consent.
Participants were randomly allocated using computer software to either the AF exercise group or the control group. Participants were assessed in the week preceding the first exercise classes and within a week of completing the 12-week exercise program. A 12-week intervention was selected as several previous aqua-based exercise interventions have also investigated a program of this length.15,18,19 The same assessor conducted measurements across all assessment points. The assessor was not blinded to group allocation but was blinded to measurement data from prior assessments.
The AF program consisted of aerobic and strength-based exercises performed twice weekly for 12 weeks (see Appendixes 1 and 2). Each session lasted for approximately 45 to 60 minutes. Intensity and length of sessions increased progressively over the 12-week period. Music was used to motivate and aid synchronization of participants as well as pace the velocity of movements.20 The beats per minute (bpm) of the music tracks were used to help quantify the velocity of the movements, and the instructor encouraged increased movement range as the program progressed. An experienced aqua instructor supervised each session, with a maximum of 10 participants per group. Average water temperature was 87°F; exercises were performed at a depth of 3′11″ to 4′11″ depending on participants' height, so that the water level was at chest height.
The rationale for having the control group attend weekly exercise classes was to facilitate social interaction with their peers, similar to that experienced in the AF class.21 This was considered important, as social interaction has been associated with maintenance of function among older adults.22 Seated exercises in warm water were chosen because warm water immersion and gentle movements may improve acute OA symptoms,14 which was considered to be an appropriate motivator to attend these classes. The control group attended a once-weekly HT-type exercise session, during which they performed a random selection of exercises from the Arthritis Foundation Arthritis Water Exercise DVD (see Appendix 3 for exercises) for 12 weeks. Each session lasted for approximately 35 to 40 minutes; there was no progression of exercises and all sessions were performed while seated. The emphasis was on range of motion and relaxation, and an experienced aqua instructor oversaw each session with a maximum of 10 participants per group. Average water temperature was 97.7°F.
The primary outcome measure was the timed up-and-go (TUG) test, which has been shown to be a valid and reliable measure of functional mobility.11,23 The TUG has been widely used in previous studies investigating aqua-based exercise for older adults with OA.15,18,19 In addition to having a high correlation with lower extremity strength,24 it has been identified as a useful tool for identifying older adults who are at risk for falls.25 Participants were allowed one practice trial; thereafter, the best time from 2 timed trials was used for analysis. Secondary outcome measures included the 15-second step test, which was used as a measure of dynamic balance. The step test has been identified as a valid clinical test for dynamic balance with good test-retest reliability26 and which can identify previous fallers from healthy older adults.27 Participants were instructed to stand unsupported with feet parallel and 5 cm in front of a 7.5-cm (2.95″) block. Participants were advised which leg to step with and instructed to place the whole foot onto the block and then return it fully down to the floor. This was repeated as many times as possible in 15 seconds. After a short break, participants changed legs and repeated the test with the opposite foot stepping. The 30-second sit-to-stand (STS) test is recommended by the Osteoarthritis Research Society International (OARSI) as a functional measure of lower body strength and balance for older adults with OA.28 The STS has been validated as a reliable measure of these modalities.29 The test was performed on a straight-backed, armless chair, 43 cm (16.93″) in height. Participants were instructed to sit in the chair with their arms crossed across the chest. On the word “go,” participants stood up and sat down as many times as possible in 30 seconds. Handgrip dynamometry has been identified as a useful screening tool for health outcomes in older adults30 and a valid and reliable measure of muscle strength.31 A Jamar dynamometer (0-200 lb, Sammons Preston Inc, Bolingbrook, Illinois) was used to measure grip strength using the methodology employed by Ranganathan et al.32 Participants were seated and were instructed to grip the device with their maximal effort. Grip strength in each hand was assessed 3 times; the highest value from each hand was used for statistical analysis. The 400-m walk test was chosen to assess functional limitations,33 walking endurance, and cardiorespiratory fitness.34 Although the OARSI recommend the 6-minute walk test as a performance outcome measure for older adults with OA,28 the 400-m walk test has been identified as a comparable test that may be easier to administer.35 Furthermore, Simonsick et al34 suggested that a predetermined distance, as given in the 400-m walk test, may be more motivating for older adults than a timed test. Participants were instructed to walk as quickly as possible over 400 m, walking back and forth between 2 cones set 25 m apart. Participants were informed that they may slow down, stop, and rest as necessary but should resume walking as soon as they were able. Time taken to complete 400 m was recorded and used for analysis. The Arthritis Impact Measurement Scale 2-Short Form (AIMS2-SF) questionnaire was chosen to assess perceived quality of life and pain levels of the participants. This questionnaire has been shown to be a valid and reliable tool to assess the quality of life and pain levels of patients with OA.36 As well as providing a disease-specific assessment of quality of life, the questionnaire is easily administered.37 The questionnaire contains 4 domains—physical, symptoms, affects and social—with scores from all domains also added together to give a total score. Fear of falling was assessed using the Falls Efficacy Scale-International (FES-I), which has been found to be a valid and reliable measure of fear of falling and sensitive to change in older adults.38 This questionnaire is simple and easy to administer.39 Physical activity levels were assessed by the Rapid Assessment of Physical Activity (RAPA) questionnaire. The RAPA is considered an easy-to-use, valid measure of physical activity for use in clinical practice with older adults that is sensitive to change and allows categorization of physical activity levels.40 The questionnaire consists of questions relating to activity levels in 2 separate domains—aerobic exercise and strength and flexibility exercise—a higher score indicates a higher level of physical activity. Individuals' physical activity levels were categorized as “sedentary,” “insufficiently active,” or “active,” similar to previous research.41
Participants were not excluded from the study if they changed their medication. However, they were asked to keep a log of arthritis-related medication taken throughout the study.
Combined, these measures provide insight into the effects of an AF program on physical well-being as well as perceived quality of life and fear of falling, all of which contribute to ongoing independence among older adults with OA.
As each section of the AIMS2-SF questionnaire contains a Guttman Scale, items were scored separately and then the score for each section was standardized to a scale of 0 to 10 using standardized formula.37 After scoring for each dimension of the questionnaire, a total score was calculated by summing the scores from each section of the questionnaire. Raw scores from the FES-I were added together to give a total score. Raw scores from the RAPA were recoded to produce Likert scale values for analysis.
A power analysis was conducted using the TUG as the primary outcome measure. This power analysis indicated that a sample size of 30 would give 80% power, with a 5% chance of type I error to detect significant differences between aqua exercise groups.
Statistical analysis was initially performed on an intention-to-treat basis, using the last-observation-carried-forward methodology.42 Outcome measures were applied as dependent variables (TUG, step test, STS, handgrip strength, 400-m walk, AIM2-SF, FES-I, and RAPA) for each individual at a particular time point.10
Data were checked for normality and homogeneity of variance before analyses; baseline data were compared between groups with independent t tests. Repeated-measures analysis of variance was performed with the group (AF versus control) as the between-subject variable and time (0 and 12 weeks) as the within-subject variable.
Because of high rates of dropout from baseline to completion of the intervention among the exercise intervention group (31.6%), further analysis was carried out solely for participants who completed the 12-week intervention, using baseline and postintervention scores. Repeated-measures analysis of variance was performed with the group (AF versus control) as the between-subject variable and time (0 and 12 weeks) as the within-subject variable. All statistical analyses were performed on SPSS, version 19.0, with significance set at P ≤ 0.05.
To calculate effect size, Cohen's d was calculated for each outcome measure. Standardized changes of <0.2, <0.6, <1.2, and <2.0 were interpreted as trivial, small, moderate, and large effects, respectively, on the basis of a modification43 of Cohen's thresholds of 0.2, 0.5, and 0.8.44
Of the 73 individuals initially screened by telephone, 35 participants were enrolled in the study and randomly allocated to the AF group (n = 19) or the control group (n = 16). Twenty-five of those enrolled in the study completed the 12-week intervention. Six participants withdrew from the AF group and 4 from the control group. Figure 1 shows the flow of participants through the study.
One participant in the AF group reported exacerbation of hip pain during the intervention; no other adverse results were reported. Baseline characteristics are shown in Table 1; independent t tests revealed that there were no significant differences between the groups at baseline for any of the outcome measures.
No statistically significant between-group differences were found for any of the outcome measures after the 12-week intervention using the intention–to-treat analysis, as outlined in Table 2.
When data were reanalyzed to include baseline and postintervention values only for participants who completed the 12-week intervention, the AF group demonstrated a significant improvement in falls efficacy (P = 0.04) compared with the control group. There were no other statistically significant between-group differences. All results including within-group analysis are summarized in Table 3.
Cohen's effect size calculations demonstrated moderate, positive changes in step test (right and left legs), STS, and 400-m walk time for the AF group. There were small positive changes in the FES-I score and trivial, positive changes in the TUG and AIMS2-SF total score for the AF group. Trivial declines in handgrip strength were demonstrated for both hands at 12 weeks for both the AF and control groups. Self-reported physical activity levels showed no change in the activity status (classified as “sedentary,” “insufficiently active,” or “active”) postintervention for either group (see Table 4).
Only 28% of participants returned their medication diary at the end of the intervention; returned diaries indicated no change in OA medication during the study.
The aims of this study were to investigate the potential physiological and psychological benefits of AF as an exercise mode for older adults with OA and to compare these outcomes with a seated aqua-based exercise program. Participants in the AF group, who completed the 12-week intervention, significantly reduced their fear of falling, determined by improved scores in the FES-I, compared with the control group. Although other outcome measures did not demonstrate statistical significance between groups, several outcomes did demonstrate a significant within-group improvement. Furthermore, effect size calculations revealed that the AF group demonstrated a moderate practical improvement in several outcome measures, and clinically important improvements were observed for the step test and STS test.
Although the TUG was the primary outcome measure, results for this test did not improve in either group postintervention, there was no difference between the groups and Cohen's effect size was trivial. Previous studies have reported mixed results for older adults with OA; Hale et al19 found no improvement in TUG after an aqua-based exercise intervention, whereas Fransen et al15 noted a significant improvement in TUG after a 12-week HT intervention. On the basis of reference values for the TUG,45 the baseline scores in the current study' participants were better than the normative data derived from older adults without musculoskeletal disease. Therefore, improvements for this measure may not have been possible for this group because of a ceiling effect for this test.
The likelihood of falling and sustaining injury increases with age.46 Previous fallers are more likely to have a fear of falling, and similarly older adults with hip OA tend to have low falls efficacy.47 Fear of falling is often associated with avoidance of physical activity.48 Furthermore, low falls efficacy has been related to reduced quality of life,49,50 depression, and social isolation.51 Improving falls efficacy and balance ability among older adults with OA may help improve functional ability and reduce avoidance of activity, helping to minimize the associated negative impact on physiological and psychosocial outcomes.
Participants in the AF group significantly improved the number of steps performed during the step test from baseline, in right and left legs by 3.1 and 3.3 steps, respectively, postintervention. Effect size calculations suggested a moderate practical effect (d = 0.87 and 0.89). Furthermore, previous research has indicated that an improvement of 3 steps may be considered clinically meaningful.52 The step test is a measure of dynamic balance—when these improvements in stepping ability are considered alongside the significant improvement in falls efficacy demonstrated postintervention—the combined results are promising.
The number of chair stands performed during the STS test increased by a mean of 2.5 postintervention in the AF group, an effect size of moderate practical effect (d = 0.73). In addition, previous data suggested that an increase of 2 repetitions could be considered clinically important for the 30-second STS test.53 Arnold and Faulkner18 found that STS scores improved after an aqua-based exercise intervention when combined with a weekly educational session but not when the exercises were performed without the educational session. The authors postulated that the educational session gave participants the opportunity to practice the movements performed in water while on land because carryover from an aqua environment to land may be difficult. The authors also suggested that the improvements in STS scores might be linked to improved falls efficacy. In the current study, falls efficacy improved significantly postintervention for the AF group. Although the relationship between these measures was not calculated, previous research noted that adults with a balance disorder performed STS more slowly than those without a balance disorder.54 Improved balance ability and falls efficacy are likely to be related to the improvement observed in functional capacity, as seen in the STS test.
Participants in the AF group demonstrated a mean reduction in 400-m walk time of 65 seconds, which indicated a significant improvement from baseline. Furthermore, Cohen's effect size value (d = 0.90) suggested a moderate practical improvement. Kwon et al55 have reported meaningful change in physical performance among older, sedentary adults aged 70 to 89 years. The authors found that minimally clinically important changes in 400-m walk time were 20 to 30 seconds, with improvements of 50 to 60 seconds classified as substantial. The HT group also significantly improved 400-m walk time from baseline; however, on the basis of the classifications by Kwon et al,55 this improvement of 21 seconds would be considered only minimally significant. A number of factors affect sustained walk performance in older adults including leg strength,56 aerobic fitness,57 and self-efficacy toward the task.58 Falls efficacy has also been linked to self-reported walking performance.59 Again, no analysis of any association between falls efficacy and 400-m walk time was made in the current study, and it can only be hypothesized that a reduced fear of falling had a positive effect on this measure of functional performance.
The AIMS2-SF is a self-administered questionnaire designed to assess perceived quality of life, pain, and the impact of arthritis on their lives. Participants answered questions relating to 4 domains: physical, symptoms, affect, and social aspects. Analysis revealed that there was no between-group difference in the total questionnaire score postintervention; however, individual scores improved significantly in both the intervention and control groups compared with baseline (P = 0.02). When broken down by domain, the questionnaire revealed some differences between the groups. Both groups demonstrated small improvements in the physical and symptoms domains. However, the AF group improved their affect scores, whereas the HT group's score in this domain declined. Cohen's effect size value (d = 0.64) suggested a moderate practical improvement for the AF group for affect. Interestingly, the HT group demonstrated an improvement in their social domain score, with the Cohen's effect size value (d = 0.40) suggesting a small practical effect, whereas the AF group's scores for this domain were trivial. This was initially unexpected as the AF group met twice per week, whereas the HT group only met once per week. However, the HT group exercised in a seated circle, there was no music, and movements were gentle, this may have resulted in a more relaxing experience with greater opportunity to communicate with others in the group, thus potentially enhancing the social experience.
Handgrip strength test postintervention had a tendency to decline slightly from baseline, Cohen's effect size values (d =−0.34 to −0.35 for the 2 hands) suggesting a trivial practical effect. Although trivial, these results are surprising as previous studies have reported small, moderate improvements in handgrip strength after a specific hand-exercise intervention60,61 for older adults with hand OA. In this current study, handgrip strength declined in the AF group by 13% and in the HT group by 17%, which far exceeds the estimated 2% per annum decline reported in adults aged 65 years and older.62 Some hand exercises were performed by both groups; therefore, it was anticipated that participants would increase or at least maintain their handgrip strength throughout the intervention. It should be noted that not all participants in this study had OA in their hands, but for those who did, the joints affected were not recorded. Distal and proximal interphalangeal joints are commonly affected, as is the carpometacarpal thumb joint. Pain and disability is significantly higher for those with carpometacarpal thumb joint symptoms63; however, little is known about the impact this may have on handgrip strength and whether this affected the results of the current study. Further investigation into the effects of aqua-based exercise on handgrip strength among older adults with hand OA is warranted.
Although participants were asked to keep a diary of arthritis medication taken throughout the study, only 28% of those who completed the intervention returned their medicine diary at the end of the study. Participants who did keep a medication diary for the duration of the intervention reported no change in the number or type of arthritis medication taken from baseline to postintervention. Regular telephone contact with participants has been reported to improve completion rates of health diaries,64 and this may have helped compliance in the current study. Future studies should consider weekly telephone follow-up to encourage participants to complete their diary.
Despite a relatively small sample size, the current study demonstrated promising results with regard to functional status and a reduced fear of falling among older adults with OA, after an AF exercise program. However, there are several limitations of the present study. There were a large number of dropouts, in particular from the AF group. This was believed to have reflected some of the environmental features of one of the venues which was very busy and provided no lane separation. Furthermore, data relating to affected hand joint(s) or limb were not used in analysis of the handgrip strength test or step test data. Further analysis relating to affected joint(s) could have provided useful insight into the effects of aqua-based exercise specifically on joints, which are affected by OA.
The combined measures in the current study demonstrated that an AF exercise program has the potential to produce clinically important improvements in physical function and a reduced fear of falling among older adults with OA. Although AF has not been widely investigated as an exercise mode for older adults with OA, this study indicates that this type of aqua-based exercise may offer several potential health benefits for this group and further research of long-term participation is warranted. However, the large number of dropouts may indicate that this type of aqua-based exercise is not suitable for all older adults with OA and the suitability of the venue should be carefully considered. Seated HT-type sessions, similar to those undertaken by the control group, may provide an appealing introduction to aqua-based exercise for some older adults with OA. In particular, it may provide a useful starting point for those who are less active and have low falls efficacy, allowing a transitional period of adaptation before undertaking a more intense aqua-based exercise program such as AF.
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