Latest Clinical Research Published by ACSM

Football Increases Future Risk for Symptomatic Radiographic Knee Osteoarthritis This study published in the April 2020 issue of Medicine & Science in Sports & Exercise® (MSSE), took data from the Osteoarthritis Initiative (OAI) to examine the association between a history of American football participation and the development of knee osteoarthritis (OA) (1). The OAI is a multicenter observational cohort study that was originally designed to look at biomarkers of OA. The cohort for this study was men ages 45 to 79 years at the time of recruitment in 2006 to 2008. Information about physical activity history, including football participation, were taken from a modified physical activity questionnaire assessed at the 96-month follow-up. Specifically, subjects were asked to identify the three most frequently performed activities (from a list of 37) that were performed at least 20 min within a given day at least 10 times during different age periods. Questions also were asked about the frequency of participation for each identified activity. The major independent variable was “football participant” defined as participation in football during any age period. Analysis also was done using football participation in the 12 to 18 years age group specifically. Primary outcomes were OA on knee radiographs and pain assessment at the 48-month follow-up. Covariates were age, body mass index (BMI), and history of knee injuries, surgeries, and total knee replacements. Football participants also were categorized into three groups based on tertiles of frequency of participation for each age group: low participation, medium participation, and high participation. A total of 1,166 men had complete information for analysis. Baseline average age was 63.7 with an average BMI of 28.6. Thirty-one percent (365) of the subjects participated in football during any age group — 364 participated during the 12 to 18 years age group. Of these subjects, 223 (65%) played at least 5 years within the age range. Football participants at any age did not significantly differ from nonfootball participants in BMI, but had significantly more total knee replacements, ligamentous repairs, meniscal surgeries, and a history of knee injuries. When adjusted for age, BMI, and prior knee injury, football participants were 1.6 times more likely to report frequent knee pain and 1.5 times more likely to have symptomatic radiographic knee OA (SROA) than nonparticipants. The trend from lowest to highest participation was statistically significant for both frequent knee pain (OR, 2.2 for high participation) and SROA (OR, 2.2 for high participation). As is true for all cohort studies, an association does not prove causation. Men who chose to play football could have associated factors that caused them to be more likely to develop SROA. The study attempted to control for the obvious ones, such as BMI and other activities, but self-reported recalled events and activities from several years prior are fraught with inaccuracy. The mechanism by which playing football induces SROA is speculative. Prior injury was associated with a significantly increased risk of frequent knee pain and SROA, but when controlled for in the regression model, did not change the OR by more than 10%. This indicates that the majority of the risk for SROA found with football participation could not be explained by the increased prevalence of knee injuries. Bottom Line Participation in American football increased the risk of developing frequent knee pain and SROA later in life by 60%, even when controlling for BMI and prior knee injuries. How this increased risk compares with the risk of other activities (or inactivity) is not known. Evaluation of Early Submaximal Exercise Tolerance in Adolescents with Symptomatic Sport-Related Concussion Exercise intolerance is a well-documented feature of the postconcussive syndrome. Symptoms, such as headache, dizziness, and nausea, can limit exercise, but the question remains if there are cardiorespiratory response differences that accompany these symptoms that limit exercise in the postconcussive period. Morissette and colleagues from Winnipeg investigated this question by comparing the cardiorespiratory response to exercise of symptomatic sport-related concussion (SSRC) adolescents to that of healthy similarly aged controls, in the April 2020 issue of MSSE (2). The SSRC subjects were taken from patients of a multidisciplinary concussion program in Winnipeg. Subjects ranged from ages 13 to 19 years, had a previous diagnosis of concussion, and were symptomatic at the time of exercise testing. The control group consisted of a convenience sample of asymptomatic physically active adolescents. Subjects in both groups underwent exercise treadmill testing using the Buffalo Concussion Treadmill Testing protocol. Heart rate (HR), blood pressure (BP), oxygen consumption (V˙O2), carbon dioxide production (VCO2), and minute ventilation (Ve) were directly measured. The exercise tests were stopped at volitional fatigue or when postconcussive symptoms increased by at least 2 on a 10-point Likert scale. The number and severity of postconcussive symptoms was assessed both preexercise and postexercise using the Post-Concussion Symptom Scale (PCSS). There were a total of 34 SSRC subjects, 19 males and 15 females, with an average age of 16.4 years. Average time between the incident concussion and the exercise test was 45 days, with a range of 16 to 144 days. SSRC subjects averaged 12 symptoms with a symptom severity of 28 on the PCSS. The control group consisted of 40 subjects, 13 males and 27 females, with an average age of 15.9 years. In the SSRC group, 25 of the 34 subjects (74%) stopped the test due to worsening symptoms. There was no change in number of symptoms or symptom severity on the PCSS after exercise in either group. The control group went longer on the protocol, reached higher RPE, achieved higher max HR and SBP, and higher V˙O2, VCO2, and Ve. At comparable workloads, however, the only significant difference was higher RPE in the SSRC group. There were no differences in cardiorespiratory variables at comparable workloads. The study had several limitations. The postconcussive symptoms in the SSRC patients were quite prolonged, averaging 45 days at the time of testing. Responses of athletes with less prolonged or severe symptomatology may be different. The groups' cardiorespiratory changes were compared only for the first five stages of the exercise protocol, the earliest point at which SSRC subjects developed worsening symptoms. There may be cardiorespiratory differences at higher workloads that were not reported. In addition, the study may not have been powered to detect small but clinically significant differences in cardiorespiratory response. Bottom Line Exercise intolerance in symptomatic sports-related concussion athletes does not appear to be due to changes in the cardiorespiratory response to exercise.

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