Exercise as it relates to Disease/Exercise adherence in sedentary women: The SWEAT Study

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This is a critique of an article for the University of Canberra unit: Health, Disease and Exercise.

The article: Cox KL, Burke V, Gorely TJ, Beilin LJ, Puddey IB. Controlled Comparison of Retention and Adherence in Home- vs. Center-Initiated Exercise in Women Ages 40-65 Years: The S.W.E.A.T. Study (Sedentary Women Exercise Adherence Trial). Preventative Medicine. 2002; 36: p.17-29.

Background[edit]

The current Australian physical activity guidelines recommend 150-300 minutes of moderate intensity exercise per week[1]. Fifteen years ago when this study was conducted only 40% of Australian women met the then-current recommendations[2]. A challenge for those in the health and fitness fields is to initiate physical activity in groups of people and individuals, and once there, how to maintain that level of physical activity. We know that when it comes to exercise a little goes a long way: from a public health point of view, it is better to encourage the inactive to be active rather than increase the activity of the already-active[3].

One way to do this is through exercise classes, but these are expensive to run as they need qualified staff and a venue with appropriate equipment. Another way is through home exercise, but although some people prefer to exercise alone, there is less accountability and potentially less adherence to an exercise program. This study looks at adherence to the exercise programs by middle-aged and older women, both exercise classes and home exercise, and at both moderate and high intensities. It specifically selected women, because at the time most of research was from studies done on males or on mixed groups, and had focussed on vigorous activity rather than moderate exercise[3].

Where is the research from?[edit]

The study was conducted through the University of Western Australia in 2002 on Australian women, aged between 40-65, who were sedentary but otherwise healthy. It was supported by the National Heart Foundation of Australia and the Western Australian Health Promotion Foundation.

Study design[edit]

The study was a 2 way factorial design. Participants were randomly assigned to centre-based or home-based by computer-generated random numbers.

Methods[edit]

Participants were assigned to either home- or centre-based exercise, and either moderate or vigorous intensity exercise. Centre-based participants attended 3 supervised group sessions a week, while the home-based participants attended 10 sessions in the first 5 weeks and were home-based thereafter. Participants were taught how to measure their radial heart rate during these sessions so as to have an idea of the exercise intensity. All subjects were home-based from 6-18 months. The prescribed exercises included walking, circuits, and aerobics, and participants were taught how to warm up, cool down, stretch, and how to effectively complete the prescribed exercises. All exercise sessions were logged, as well as the type, duration, frequency, and RPE.

In the first 2 weeks, participants worked up to 30 minutes of slow walking, and in the next 6 weeks, progressed to 40-55% HRR. Those in the moderate intensity groups stayed at this intensity, and the vigorous intensity groups progressed to working at 65-88% HRR. In the home-based phases, participants were contacted by telephone to discuss progress and have their questions answered. The telephone calls were fairly frequent at the beginning (2 phone calls every second week) and became less frequent as the study went on (contact every 6 weeks). Moderate intensity exercisers were required to complete 5 sessions a week, while those in the vigorous group were required to complete 3 sessions a week.

Compliance with the study was defined as the number of sessions completed at, above, or below the required heart rate. Retention rate was defined as the number of subjects participating in the study at a each time point (6, 12, and 18 months). Adherence was defined as the number of sessions completed compared to the number of sessions combined. Logbooks that were not filled out or returned were deemed non-adherent.

There were limitations in the format of the study, mainly due to the self reporting of the exercise: despite participants being shown how to take their heart rate and also being issued with heart rate monitors for some periods of the study, there is a slight possibility that the intensity of the exercise was overestimated. Since there were also logbooks that were not filled out or returned, there is another limitation to the study, as this was counted as non-adherence, whether or not the exercise session was actually completed.

Results[edit]

Retention was measured at 6, 12, and 18 months into the study. The centre-based moderate intensity group lost no participants, but at the end of the study (18 months), the other three groups had each lost 12 [see fig. 1][3]. At the 6 and 12 month marks, the home-based groups had lost more than the centre-based groups[3].

The intensity of the moderate groups tended to be in the upper range of what was prescribed, and the intensity of the vigorous groups tended to be in the lower prescribed range.

The most common reason participants dropped out of the study was illness/injury (50%), closely followed by ‘no time’ (31%)[3]. Other reasons included relocation to another state (8%) and family reasons (5%)[3].

Figure 1. Participant flow[edit]

Centre-based moderate exercise (N=31) Centre-based vigorous exercise (N=33) Home-based moderate exercise (N=32) Home-based vigorous exercise (N=30)
Lost to study at 6 months (N=0) Lost to study at 6 months (N=2) Lost to study at 6 months (N=4) Lost to study at 6 months (N=4)
Lost to study at 12 months (N=0) Lost to study at 12 months (N=4) Lost to study at 12 months (N=7) Lost to study at 12 months (N=8)
Lost to study at 18 months (N=0)
Assessed at 18 months (N=31)
Lost to study at 18 months (N=12)
Assessed at 18 months (N=21)
Lost to study at 18 months (N=12)
Assessed at 18 months (N=20)
Lost to study at 18 months (N=12)
Assessed at 18 months (N=18)

Conclusions[edit]

It appears obvious that people will adhere to group fitness classes more than home-based exercise, because along with group fitness comes a sense of community and routine, which can become habit. As well as social support, access to immediate feedback and encouragement from exercise leaders and trainers may increase a sense of achievement and thus motivate participants to return, especially since an exercise program can be individualised in person.

The difference in prescribed versus actual intensity seems to indicate that people will exercise at a level that is comfortable or sustainable for them. Although the discrepancy could have been due to resting from injuries, it also highlights the fact that vigorous intensity exercise is hard, especially for those unused to it. Perhaps, had the study continued, the vigorous intensity groups might have settled into a higher heart rate simply from becoming used to the required intensity.

Practical advice[edit]

Despite its age, the study is still hugely relevant and does have implications for how we might run exercise interventions for those who need them, but also how we might encourage people who have been previously inactive to begin and continue to participate in physical activity. Centre-based moderate intensity exercise is more expensive and more difficult logistically, but had better adherence rates than home-based or vigorous intensity exercise.

Further reading[edit]

References[edit]

  1. Department of Health (2014) 'Australia's Physical Activity and Sedentary Behaviour Guidelines'
  2. Booth M et al (1995) 'Active and inactive Australians. Assessing and understanding levels of physical activity.' Department of Environment, Sport and Territories: Commonwealth of Australia, Canberra, ACT
  3. a b c d e f Cox KL et al (2002) 'Controlled Comparison of Retention and Adherence in Home- vs Center-Initiated Exercise Interventions in Women Ages 40–65 Years: The S.W.E.A.T. Study (Sedentary Women Exercise Adherence Trial)'. Preventative Medicine. vol. 36; p.17-29