McMaster University, Hamilton, Ontario, Canada
Mark Tarnopolsky, MD, PhD
There has been an ongoing debate on the merits of jogging. When deaths occur during, or shortly after, this seemingly benign activity, the published headlines tend to convey a message that is often exaggerated and out of context. However, when examining the evidence relating jogging to premature death, there really does not appear to be any reason for concern. Our first abstract seems to reconfirm that jogging does, in fact, promote health rather than shorten life. In a cohort of 4,658 Danish men who were followed over 5 years, the relative risk of death in persistent joggers was significantly lower than that in nonjoggers.
A further debate in the sport medicine literature has focused on a possible causal relationship between physical exercise and the onset, or acceleration, of osteoarthritis (OA). Many of the published studies that have examined this association have used runners as the index population and have focused specifically on OA of the hips and knees. Nuances in study design, outcome selection and measurement, and management of confounding variables make it difficult to subject the available studies to metaanalysis, and so what we are left with are a number of studies of differing size that require individual interpretation, and which, when taken together, do not yet provide a clear message on the causation issue. Our second abstract is a meaningful addition to this literature. It summarizes a prospective study, over 10 years, in which 12,888 men and 4,073 women, in the age range of 20 to 87 years, were followed. Although the authors themselves identified potential limitations in their methodology (e.g., self-reporting by study participants and possible compromise in the generalizability of the results), the study design, in general, was appropriate and the study was well executed. What was found was that walking or running more than 20 miles per week was associated with an increased incidence of OA of the hip or knee in men under 50. This association was not evident in older men or in women of any age.
Our third abstract deals with the impact of different types of knee braces on speed and agility in football players. In a randomized, controlled crossover trial, 30 junior college players were assigned to wearing each of six braces (and no brace) in random order. The effects of the braces on speed and agility were variable. Also variable was the tendency of the brace to migrate, which might adversely affect its protective function and reduce athletic performance.
While the epidemiology of (ice) hockey injuries in men is well documented, the women's game seems to have attracted much less attention. The study by Dryden et al., which is summarized in our fourth abstract, is therefore timely and pertinent. It describes the nature and incidence of hockey-related injuries in a cohort of female hockey players in Edmonton, Alberta. Of the 314 players who were studied, 102 reported injuries. Most of these injuries were to the lower extremity and, for all injuries, regardless of anatomic location, most were the result of player contact (from collisions or body checks).
The fifth abstract in our Journal Club deals with the effect of recombinant erythropoietin (rhEPO) on serum levels of soluble transferrin receptors (sTfR) in a group of 20 healthy, well-trained male athletes. Although the study design was sound and the conclusions are compelling, Dr. Norman Gledhill, in his accompanying commentary, draws attention to some important qualifications in interpreting these results. He cautions that testing for sTfR lacks sensitivity and specificity for detecting rhEPO abuse, and that, therefore, as with any currently available technique for detecting rhEPO, it would only be useful in random out-of-competition testing.
The study objective in our final abstract was to determine whether iron supplementation is associated with an increase in endurance capacity in nonanemic women. Forty-nine physically active, untrained women, ages 19 to 35 years, who were iron depleted but not anemic, participated in the study. They were randomized to groups that received iron supplementation or placebo. The primary outcome measure was change in minutes required to cycle 15 km at an individually standardized resistance. The authors concluded that iron supplementation was associated with an improved response to endurance training in iron-depleted, nonanemic women.