With regards to depression, all but two studies (Hicks et al. 2005; Warms et al. 2004) showed positive effects of exercise on depressive symptoms (Guest et al. 1997; Hicks et al. 2003; Latimer et al. 2004; 2005; Martin Ginis et al. 2003). In addition, Kennedy et al. (2006) showed significant reductions in anxiety but not depression using the Hospital Anxiety and Depression Scale with their 1 week physical activity course. Given the variety of modes of physical activity examined in these studies, the consistent findings speak to the robustness of the relationship between physical activity and depression among people living with SCI. In the studies that showed no significant effects of exercise on depression (Hicks et al. 2005; Kennedy et al. 2006; Warms et al. 2004), participants’ baseline depression scale scores were already extremely low, indicating minimal depressive symptomatology and very little room for improvement. As exercise has been shown to exert its greatest effects on people with greater depressive symptomatology, these findings are not particularly surprising.
With regards to quality of life, all of the Level 1, 2, and 4 studies showed that exercise training was associated with better quality of life (Mulroy et al. 2011; Alexeeva et al. 2011; Anneken et al. 2010; Ditor et al. 2003; Effing et al. 2006; Hicks et al. 2003; 2005; Kennedy et al. 2006; Latimer et al. 2004; 2005; Martin Ginis et al. 2003; Semerjian et al. 2005). Again, given that this association held across different types of physical activity modalities and in studies that used different measures of quality of life, the physical activity-quality of life relationship appears to be robust. However, the case-study by Effing et al. (2006) did not find quality of life improvements for two of its three participants. When contrasted with the findings of the higher quality studies, these null findings speak to the importance of examining changes in quality of life over time, and in sufficiently large and representative samples, in order to properly assess the effects of physical activity on SWB.
How does physical activity improve depression, quality of life, and potentially other aspects of SWB? This question was examined in a series of papers using data from Hicks et al.’s (2003) RCT. Overall, these studies showed that exercise-induced reductions in stress and pain mediated the effects of exercise on quality of life and depression (Latimer et al., 2004; Martin Ginis et al., 2003). In other words, exercise training led to reductions in stress and pain, which, in turn, led to improvements in quality of life and depressive symptoms. Mulroy et al. (2011) also found a reduction in shoulder pain and an increase of 10% in subjective quality of life scores and an increase in all, but two, of the SF-36 subscales in the exercise/movement optimization group post-intervention with no change in the control group. There was also evidence that among people who were experiencing stressful life events, exercise helped to buffer the effects of the stress on their SWB (Latimer et al., 2005).
In general, several of the studies examining subjective well-being are constrained by an inadequate control group, making it difficult to discern whether it is the physical activity itself or some other aspect of a structured program that may be contributing to beneficial effects. Regardless, the conclusions below are based on the relative consistency across studies, despite these limitations. Of note, the trials conducted by Hicks et al. (2003) and Latimer et al. (2004) did provide an opportunity for education about exercise to their control group participants which afforded a more effective comparison than other trials which simply asked control group participants to maintain their usual activity patterns and defer initiation of an exercise program until after the study trial. Mulroy et al. (2011) also employed an education session for their attention control group. This session included a video and brochure regarding shoulder anatomy, mechanisms of injury, managing shoulder pain, and general shoulder care.
Based on level 1 and 2 evidence from 6 studies, exercise is an effective intervention for improving two aspects of SWB;quality of life and depressive symptomatology. For the most part, the level 4 and 5 evidence also supports this conclusion.
Emerging data from these studies suggest that changes in stress and pain may be the mechanisms underlying the effects of exercise on quality of life and depression. Further research is needed to examine other aspects of SWB in relation to physical activity.
Exercise is an effective strategy for improving at least two aspects of subjective well-being – depression and quality of life.