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.

The prognostic value of exercise testing in patients with cystic fibrosis.

BACKGROUND: Previous studies have shown female sex, impaired pulmonary function, older age, malnutrition, and colonization of the respiratory tract with Pseudomonas cepacia to be associated with a poor prognosis in patients with cystic fibrosis. We sought to determine the prognostic value of exercise testing in addition to the other prognostic factors. METHODS: A total of 109 patients with cystic fibrosis, 7 to 35 years old, underwent pulmonary-function and exercise testing in the late 1970s. They were followed for eight years to determine the factors associated with subsequent mortality. Survival rates were calculated with standard life-table methods. Cox proportional-hazards regression models were used to determine crude relative risks of mortality and relative risks adjusted for age, sex, body-mass index, forced expiratory volume in one second (FEV1) end-tidal partial pressure of carbon dioxide (PCO2) at peak exercise, and oxygen consumption at peak exercise (VO2 peak). RESULTS: Patients with the highest levels of aerobic fitness (VO2 peak, > or = 82 percent of predicted) had a survival rate of 83 percent at eight years, as compared with rates of 51 percent and 28 percent for patients with middle (VO2 peak, 59 to 81 percent of predicted) and lowest (VO2 peak, < or = 58 percent of predicted) levels of fitness, respectively. After adjustment for other risk factors, patients with higher levels of aerobic fitness were more than three times as likely to survive than patients with lower levels of fitness. Colonization with P. cepacia was associated with a risk of dying that was increased fivefold. Age, sex, body-mass index, FEV1, and end-tidal PCO2 at peak exercise were not independently correlated with mortality. CONCLUSIONS: Higher levels of aerobic fitness in patients with cystic fibrosis are associated with a significantly lower risk of dying. Although better aerobic fitness may simply be a marker for less severe illness, measurement of VO2 peak appears to be valuable for predicting prognosis. Further research is warranted to determine whether improving aerobic fitness through exercise programs will result in a better prognosis.