Activity capacity and activity performance: time to be specific?

The importance of exercise to improve the long-term health of people with cerebral palsy (CP) cannot be underestimated given the high prevalence of many preventable chronic diseases among this population. Aerobic exercise and strength training have proven to be effective at improving cardiorespiratory and muscular fitness respectively. Not surprisingly, however, once exercise programmes end, fitness levels are quick to regress to baseline values. This suggests that while the very act of participating in exercise interventions increases physical activity in the short-term, exercise interventions fail to change longterm physical activity behaviour in people with CP. Their difficulty in changing physical activity behaviour may largely be due to environmental and personal barriers that prevent participation in exercise and physical activity, such as lack of access, unsuitable facilities, time and financial restrictions. Mitchell et al. attempted to overcome environmental barriers to participation in exercise by delivering a webbased therapy programme to children and adolescents with unilateral CP. Not only did this programme eliminate difficulties with accessibility, financial barriers were removed by providing participants with a computer and internet if necessary. The benefit of implementing a webbased programme that included children from a large geographical area and a range of socio-demographic backgrounds is visible in the relatively high recruitment rate and large sample size. Further, difficulties with arranging personnel and facilities to deliver face-to-face training were eliminated, so both the frequency and length of the programme exceeded many previous exercise interventions in the literature. The lack of face-to-face contact, however, may also have contributed to poor adherence, with participants completing on average 32.4 hours of a potential 60 hours of training. Despite the relatively low adherence rate, improvements in functional strength and walking endurance were observed. It must be noted that although participants completed only half of the prescribed dose, the vast majority of participants completed more than 20 hours of training. This exceeds the dose prescribed in many previous studies of exercise interventions and this high volume of exercise likely contributed to the positive effect. Further, researchers were able to individually progress each child’s training programme, ensuring that the intensity was adequate to induce adaptations in fitness across the 20 weeks. Although adherence was only 54% on average, it varied significantly across participants, which suggests that while the web-based programme wasn’t acceptable for some children, it was for many others. Even though the programme resulted in improvements in activity capacity, activity performance was not altered. This is not surprising given that no intervention to date in the literature has had any meaningful impact on the low levels of habitual physical activity that are present among people with CP of all ages. The result of this study emphasises the complexity of changing physical activity behaviour in this population. Because the intervention did not include any component that specifically targeted activity performance, it was perhaps unrealistic to expect changes in physical activity. It is time to accept that while exercise interventions will by their very nature increase physical activity in the short-term, alone they rarely change long-term physical activity habits. Further, there was a steady decline in log-ins across the 20 week programme, indicating that participation in physical activ-