Infection in Athletes

An epidemiologic study of Los Angeles Marathon (LAM) applicants was conducted to investigate the relationship between self-reported infectious episodes (IE), training data, and LAM participation. Eight days before the LAM, 4926 of 12,200 applicants were randomly selected, and sent a pilot-tested four page questionnaire, which was received 7 days after the LAM. The 2311 respondents were found to be 2.0 yr older and 7.6 min faster than other LAM finishers (p less than .01). Univariate and multivariate analyses (logistic regression) were conducted to test the relationship between IE and km/wk of running (6 total categories). The final model tested controlled for age, marital status, reported sickness in other members of the runner's home, perceived feelings of stress in response to personal training regimens, and the suppressive effect of sickness on regular training. In runners training greater than or equal to 97 vs less than 32 km/wk, the odds ratio (OR) for IE during the 2 month period prior to the LAM was 2.0 (95% confidence interval (CI) 1.2-3.4). A test for trend showed an increase in OR with increase in km/wk category (p = .04) which was largely explained by the increased odds of reported sickness in the greater than or equal to 97 km/wk category. Of the 1828 LAM participants without IE before the LAM, 236 (12.9%) reported IE during the week following the LAM vs 3 of 134 (2.2%) similarly experienced runners who did not participate, OR = 5.9 (95% CI 1.9-18.8). These data suggest that runners may experience increased odds for IE during heavy training or following a marathon race.

A randomly controlled 15-wk exercise training (ET) study (five 45-min sessions/wk, brisk walking at 60% heart rate reserve) with a group of 36 mildly obese, sedentary women was conducted to investigate the relationship between improvement in cardiorespiratory fitness, changes in natural killer (NK) cell number and activity, and acute upper respiratory tract infection (URI) symptomatology. The study was conducted using a 2 (exercise and nonexercise groups) x 3 (baseline, 6-, and 15-wk testing sessions) factorial design, with data analyzed using repeated measures ANOVA. No significant change in NK cell number occurred as a result of ET as measured by the CD16 and Leu-19 monoclonal antibodies. ET did have a significant effect on NK cell activity (E:T 50:1) especially during the initial 6-wk period [F(2.68) = 12.34, p less than 0.001]. Using data from daily logs kept by each subject, the exercise group was found to have significantly fewer URI symptom days/incident than the nonexercise group (3.6 +/- 0.7 vs 7.0 +/- 1.4 days, respectively, p = 0.049). Improvement in cardiorespiratory fitness was correlated significantly with a reduction in URI symptom days/incident (r = 0.37, p = 0.025) and a change in NK cell activity from baseline to six but not 15 wks (r = 0.35, p = 0.036). In summary, moderate ET is associated with elevated NK cell activity after six but not 15 weeks, and reduced URI symptomatology in comparison to a randomized, sedentary control group.