When compared with both the general population and people with other types of disabilities and chronic conditions, people with SCI are considered to be at the lowest end of the physical activity spectrum (van den Berg-Emons et al. 2010). Surprisingly, few studies have actually measured physical activity in the SCI population. This lack of research is partly due to the challenges of measuring physical activity in people with SCI.
Physical activity measures used in SCI research can be categorized as technological/wearable measures or self-report measures. Technological or wearable measures are devices such as accelerometers, heart rate monitors, odometers, and other sensor-based devices that are attached to the person and/or their wheelchair. Technological/wearable measures have the advantage of being able to capture data over a long duration but are often limited by their inability to provide valid and reliable measures of the different types and intensities of activity performed by people with SCI. For instance, technological measures typically cannot distinguish between wheeling along a flat, even surface versus wheeling up steep, gravelly inclines. These two activities require different levels of effort and energy expenditure, so it is important to be able to distinguish between them in order to accurately measure physical activity. Similarly, wearable measures such as wrist-worn accelerometers or heart-rate monitors cannot reliably measure resistance exercise activities (e.g., lifting weights) or water-based activities such as swimming because most devices cannot be worn in the water. Another limitation of most technological measures is that they do not distinguish between leisure-time physical activities and other types of physical activity (e.g., occupational, household). A further limitation is a cost and convenience; it is challenging for researchers to use these types of measures in large, population-based studies of people with SCI because the devices can be expensive and difficult to distribute and retrieve from study participants.
Self-report measures of physical activity have the benefit of being inexpensive and relatively easy to administer in large samples of people with SCI. When people self-report their activity levels, researchers are able to categorize the activities as leisure time, or other types of activity (e.g., household, occupational). However, a major limitation of self-report measures is that they are susceptible to recall biases. Respondents may have difficulties remembering how much activity they performed and at what intensity. Activities that are done over a long time with lots of stops and starts (e.g., playing wheelchair rugby, gardening) might present a challenge for remembering the amount of time spent resting versus active, so respondents may over-report time spent on these types of activities. People might also self-report the perceived intensity of an activity to be different from the actual, physiological intensity, or worry about giving ‘good’ responses and adjust their reports of activity time or intensity to what they think the researcher wants to hear.
In Table 1, we summarize studies that have descriptively reported physical activity levels in a sample of people with SCI.
In the reviewed studies, the physical activity estimates are likely influenced by how physical activity was defined and measured. In some of the reviewed studies, physical activity was defined narrowly (e.g., participation in sports activities or exercise activities); in others, it was defined broadly to capture participation in all activities requiring physical exertion (e.g., leisure-time physical activity, activities of daily living). Some studies reported physical activity of a particular intensity (e.g., mild, moderate, heavy) and others reported on total physical activity, regardless of intensity. These differences introduce considerable variability into the reported estimates of physical activity participation and make it difficult to compare the results across samples and studies. All of the studies were conducted in high-income countries (particularly Canada, the US, the UK, and European countries). We have virtually no information on physical activity participation by people with SCI living in low- and middle-income countries.
All of the larger-sample studies (n > 70) utilized self-report measures of physical activity, with considerable variability in the types and amounts of physical activity information collected. This information ranged from simply the rate of participation in the sample (e.g., the percentage who achieved physical activity guidelines), to more comprehensive data on the types of physical activities performed, and in some cases, participation frequency, duration, and intensity. In studies that used technological measures, the data were reported as time spent on activity, movement behaviours (e.g., number of steps walked), energy expenditure (expressed as METs or metabolic equivalents) or percentage of time spent active. Again, these differences in reporting methods create variability in estimates and make it difficult to compare findings across studies.
Regardless of how physical activity was measured, overall, the studies indicated low average daily and weekly amounts of physical activity in samples of people with SCI. It is important to note, however, that the standard deviations were very large — typically 1 to 2 times the size of the mean (Martin Ginis, Latimer, et al. 2010; Rocchi et al. 2017; Saori Ishikawa 2011). This is an important observation that highlights the tremendous variability in physical activity participation among people with SCI.
Furthermore, large proportions of people with SCI (up to 50%) did no leisure-time physical activity whatsoever. This is an important finding to keep in mind when developing physical activity-enhancing interventions. There are at least two large sub-groups within the SCI population; a completely inactive sub-group and a sub-group that varies from minimally active to highly active (Martin Ginis, Arbour-Nicitopoulos et al. 2010). These different groups will require different interventions.
A couple of studies looked at whether people with SCI were meeting physical activity guidelines. Of note, while both the WHO (Bull et al. 2020) and the SCI exercise guidelines (Martin Ginis et al. 2018) emphasize the importance of aerobic and strength training exercises, we have very little data specifically on the amount of strength training activity performed. Most of the studies report only on aerobic activities (e.g., minutes spent walking or wheeling) or aerobic and strength training activities are combined (e.g., in studies that use technological measures, or a self-report measure of total time spent on exercise or leisure-time physical activities). Going forward, attention is needed to measure participation in both types of exercise prescribed in the guidelines.
With a couple of exceptions (Tawashy et al. 2009), most of the measurement studies have been conducted among people with chronic SCI, who are living in community settings. van den Berg-Emons et al. (2008) conducted a study in which physical activity was measured at the start of in-patient rehabilitation, at discharge, and 2 months and 1-year after discharge. This study demonstrated the sharp decline in physical activity from the in-patient phase to 1-year post-discharge, emphasizing the need to monitor physical activity and to intervene and provide support to sustain activity across in-patient/out-patient transitions and phases.