Effects of anaerobic exercise on the immune system in eight- to seventeen-year-old trained and untrained boys.

OBJECTIVES: To determine the immunologic response to a brief bout of intense exercise in children and to determine the effects of prolonged activity and maturation level of the subjects on this response. STUDY DESIGN: We determined counts of leukocytes and their subsets, counts of lymphocytes and their subsets, and natural killer (NK) cell activity and cell number before and 3 and 60 minutes after a Wingate anaerobic test (WAnT) in 16 male swimmers (9 to 17 years of age) and 17 male nonswimmers (9 to 17 years of age). Subjects were also categorized by pubertal status based on Tanner staging and by level of physical activity. The Student t test and analysis of variance were used to determine statistical significance, with values expressed as mean +/- SEM. RESULTS: Three minutes after the WAnT, all children had increases in leukocytes (28%), lymphocytes (43%), and NK cells (395%) (p < 0.01). Swimmers had less baseline NK cell activity (54 +/- 6 cytolytic units) than nonswimmers (87 +/- 10 cytolytic units) after the WAnT (p < 0.01), although both groups showed an increase to similar levels of NK activity 3 minutes after exercise. Pubertal effects on these responses were not significant. CONCLUSIONS: Our results demonstrate transient leukocytosis, lymphocytosis, and increases in NK cell number and activity in 8- to 17-year-old boys after a brief bout of intense exercise. Formal athletic training appears to be associated with a lower baseline NK cell activity, and yet such activity is still within the normal range for this age group. Further investigations are necessary to determine the impact of such training on overall health and the ability to fight infection.

A six-minute walk test for assessing exercise tolerance in severely ill children.

OBJECTIVES: The primary objective of this study was to compare exercise tolerance, heart rate, and oxyhemoglobin saturation (Sao2) between a traditional progressive maximal exercise test and a self-paced, 6-minute walk test in severely ill children. STUDY DESIGN: Seventeen patients (9 to 19 years of age) performed a progressive maximal exercise test on a cycle ergometer and a self-paced, 6-minute walk test as part of the evaluation for possible heart, lung, or combined heart and lung transplantation. Physical work capacity and peak oxygen uptake were measured during the progressive cycle test. The walk test was performed in a hospital corridor, with patients trying to cover as much distance as possible in 6 minutes at their own pace. Oxyhemoglobin saturation and heart rate were monitored continuously by pulse oximetry and compared between the two tests. RESULTS: The distance walked in 6 minutes correlated with peak oxygen uptake (r = 0.70, p < 0.01) and physical work capacity (r = 0.64, p < 0.005). The minimum (Min) Sao2 on the bike test correlated significantly with Min Sao2 on the walk test (r = 0.82, p < 0.001), with 11 of 17 patients having a lower Min Sao2 on the walk test than the bike test (mean Min Sao2, 84% and 86%, respectively). The peak heart rate did not correlate significantly between the bike and walk tests (r = 0.25), although significantly lower (p < 0.01) values were observed on the walk (148 beats/min) than bike (169 beats/min) test. CONCLUSIONS: The results suggest that the 6-minute self-paced walk test may provide an alternative method for assessing functional capacity in severely ill children, and that Sao2 measured during progressive exercise testing on a cycle ergometer may not reflect the degree of oxyhemoglobin desaturation during self-paced walking in some patients with severe cardiopulmonary disease.

Factors limiting anaerobic performance in adolescent males with cystic fibrosis.

Forty-one adolescent males (11.1-18.3 yr) with cystic fibrosis (CF) and 37 healthy adolescent males (11.1-17.9 yr) performed a Wingate Anaerobic Test (WAnT). The group with CF was subdivided by sexual maturity, nutritional status, and degree of airway obstruction. The subjects with CF had lower absolute power outputs than the healthy controls [mean power in Watts (mean +/- SD): 350.2 +/- 135.9 vs 424.5 +/- 120.4, P < 0.001; peak power: 525.2 +/- 178.4 vs 665.9 +/- 191.3, P < 0.001). When absolute power was corrected for lean body mass, the subjects with CF had lower power outputs than the healthy controls (mean power in W.kg-1: 8.9 +/- 1.7 vs 9.6 +/- 0.9, P < 0.05; peak power: 13.4 +/- 2.1 vs 15.0 +/- 1.6, P < 0.05). The subgroup with CF with a higher body mass index (BMI > 17.5 kg.m-2) had higher peak and mean power output than subjects with CF with a lower BMI in both absolute power and when power was expressed per lean body mass. When sexual maturation was considered, subjects with CF with salivary testosterone greater than 4.0 ng.dl-1 had a higher mean and peak power in both absolute terms and relative to lean body mass than subjects with CF with salivary testosterone less than 4.0 ng.dl-1. Multiple regression analysis indicated that the nutritional factor accounted for 70%-80% of the variability in power output in the subjects with CF, while testosterone accounted for 10% of the variability. Pulmonary function was not a significant independent correlate of anaerobic power. Our results suggest that nutritional status, and to a lesser extent maturational factors, may play a more important role than pulmonary function in determining anaerobic fitness in male adolescents with CF.

Physical inactivity and glucose intolerance in the multiethnic island of Mauritius.

The island nation of Mauritius, located in the southwest Indian Ocean, has a high prevalence of non-insulin-dependent diabetes mellitus (NIDDM) among all of its ethnic groups (Hindu and Muslim Indians, African-origin Creoles, and Chinese). These high rates of NIDDM among groups of varying genetic background provide strong support for the importance of environmental components in the etiology of the disease. Research in Mauritius using a simple activity scale has suggested that physical inactivity may be one of these components. The current investigation further examined the association between glucose tolerance and physical activity in middle-aged nondiabetic residents of Mauritius using a more extensive physical activity questionnaire (the Modifiable Activity Questionnaire). Excluding individuals with NIDDM, a statistically significant (P < 0.05) inverse relationship between physical activity and 2-h post-load glucose concentration was found for both males (rho = -0.14) and females (rho = -0.11). Stratifying by ethnic group, similar inverse correlations were observed in Hindu, Creole, and Chinese males, and in Hindu females (P < 0.05), as well as weaker relationships in Muslim males and Creole females (P < 0.10). Total physical activity remained an independent predictor of 2-h post-load glucose concentration after controlling for body mass index, waist-hip ratio, age, and family history of NIDDM. These data are supportive of a potentially important role of physical activity in the prevention of NIDDM in middle-aged inhabitants of Mauritius.