Fitness, obesity and risk of asthma among Army trainees.

BACKGROUND: Epidemiological data suggest an association between overweight/obesity and asthma. However, less is known about the relationship between physical fitness and asthma. AIMS: To enumerate new-onset asthma diagnoses in Army recruits during the first 2 years of service and determine associations with fitness and excess body fat (EBF) at military entrance. METHODS: New asthma diagnoses over 2 years in Army recruits at six entrance stations were obtained from military health and personnel records. Poisson regression models were used to determine associations of asthma diagnosis with pre-accession fitness testing, EBF and other potential factors. RESULTS: In 9979 weight-qualified and 1117 EBF entrants with no prior history of asthma, 256 new cases of asthma were diagnosed within 2 years of military entry. Low level of fitness, defined by a step test and EBF, was significantly associated with new asthma diagnosis [adjusted incidence rate ratio (IRR), 1.47; 95% confidence interval (CI) 1.11-1.96 and adjusted IRR, 1.53; 95% CI 1.06-2.20, respectively]. CONCLUSIONS: Individuals with low fitness levels, EBF or both are at higher risk of asthma diagnosis in the first 2 years of military service.

Fitness, obesity and risk of heat illness among army trainees.

BACKGROUND: Exertional heat illness (EHI) affects military personnel, athletes and occupational groups such as agricultural workers, despite knowledge of preventive measures. AIMS: To evaluate EHI diagnoses during US Army basic training and its associations with fitness and body fat on entering military service. METHODS: From February 2005 to September 2006, US Army recruits at six different military entrance stations took a pre-accession fitness test, including a 5-min step test scored as pass or fail. Subsequent EHI incidence and incidence rate ratios were analysed with reference to subjects' fitness (step test performance) and whether they met (weight qualified [WQ]) or exceeded body fat (EBF) standards. RESULTS: Among the 8621 WQ and 834 EBF male subjects, there were 67 incidents of EHI within 180 days of entering military service. Among WQ subjects, step test failure was significantly associated with EHI (odds ratio [OR] 2.00, 95% confidence interval [CI] 1.13, 3.53). For those passing the step test, the risk of EHI was significantly higher in EBF than in WQ subjects (OR 3.98, 95% CI 2.17, 7.29). Expected ORs for the joint effects of step test failure and EBF classification under additive and multiplicative models were 4.98 and 7.96, respectively. There were too few women to evaluate their data in detail. CONCLUSIONS: This study demonstrated that fitness and body fat are independently associated with incident EHI, and the effect of both was substantially higher. Those with low fitness levels and/or obesity should be evaluated further before engaging in intense physical activity, especially in warmer months.