Active Voice: The Influence of Weight on the Pain Response After Exercise in Adolescents
By Stacy C. Stolzman, Ph.D., P.T. and Marie Hoeger Bement, Ph.D., P.T.
Stacy C. Stolzman, Ph.D., P.T., is a pediatric physical therapist and post-doctoral fellow in the Department of Physical Therapy at Marquette University, Milwaukee, Wisconsin. This study was part of her dissertation work through the Clinical and Translational Rehabilitation Health Sciences Ph.D. Program at Marquette University. Her research examines the influence of anthropometrics on health status and response to exercise in pediatric populations.
Marie Hoeger Bement, Ph.D., P.T., is an associate professor in the Department of Physical Therapy at Marquette University. Dr. Hoeger Bement’s research focuses on the pain-relieving benefits of exercise in healthy and patient populations, including the contribution of age and physical activity levels.
This commentary presents the views of these authors in a research article published in the November 2015 issue of Medicine & Science in Sports & Exercise® (MSSE).
While a large body of literature shows that exercise decreases pain in adults, there is limited evidence in pediatric populations. Even more surprising is the lack of information regarding the influence of weight status. This is problematic because individuals with increasing weight status (overweight and/or obese) tend to report more pain in general and with physical activity than normal weight individuals. Thus, in our study reported in the November 2015 MSSE, pain reports were measured before and after exhaustive treadmill running in both normal weight and overweight/obese adolescents.
Physical activity and fitness levels also were assessed because these factors may impact how a person reports pain. In young and older adults, we previously have shown that those individuals who report greater levels of physical activity modulate pain better than individuals with less physical activity. Interestingly, in our more recent study which is the subject of this commentary, we found that normal weight and overweight/obese adolescents both reported similar levels of physical activity. But, paradoxically, the adolescent subjects with more body fat actually reported less physical activity! This discrepancy in self-reported physical activity may be due to combining the overweight and obese adolescents into one group resulting in an overall higher average of physical activity. When measured with accelerometers, physical activity levels were similar between normal weight and overweight/obese adolescents. However, we also found with our accelerometry data that the overweight/obese adolescents had longer periods of time in which they were sedentary. Important physical activity data, particularly moderate-to-vigorous levels, are missing because many of the adolescent athletes in both weight groups were told to remove the monitors during organized competitive sporting practices and events.
For our evaluation protocol, we chose a maximal aerobic exercise test, with the purpose of determining whether the adult parameters for exercise to relieve pain were similar for adolescents, and to allow us to analyze for independent influences of physical fitness. When discussing this protocol, we were intrigued by the range of opinions expressed by trained health care professionals. The responses to whether obese individuals should run on a treadmill ranged from “of course” to “never.” In this study, not only did all of the adolescents complete and tolerate exhaustive treadmill running, but pain decreased similarly for the normal weight and overweight/obese groups. It is important to note, though, that the adolescents were fairly fit and also had relatively high physical activity levels.
To our surprise, normal weight and overweight/obese adolescents reported similar experimental (pressure pain thresholds) and clinical pain at rest. We suspect that differences would likely occur with a clinical population, rather than the community-based population used for this study and if more adolescents in our sample were in the obese range. In relation to pain, self-reported quality of life was similar for the weight groups. Furthermore, our findings suggest that physical fitness levels have a greater impact on quality of life than weight status. Thus, some appraisal of physical fitness should be integrated into routine health assessments, along with weight status.
While this study helps us to understand how exercise can relieve pain across weight status, further investigation is needed. To enhance the translation of our findings to rehabilitation, future studies should incorporate clinical populations that better delineate weight status groupings, so as to capture the potential increase in pain with increasing weight status. Our study with a combined group of overweight/obese adolescents may have masked this effect. Incorporating individuals with higher levels of obesity and examining specific obesity classifications would likely influence exercise tolerance and physical activity levels as well.