Body Mass Index and Association of Psychological Stress with Exercise Performance in Military Members: The Cardiorespiratory Fitness and Hospitalization Events in Armed Forces (CHIEF) Study.

AIMS

To investigate the influence of body mass index (BMI) on the association between psychological stress and physical fitness.

BACKGROUND

Both obesity and psychological stress reduce exercise performance.

OBJECTIVE

It is unknown whether obesity may modify the relationship.

METHODS

A population of 4,080 military subjects in Taiwan was divided to three groups according to the BMI ≥27.0 kg/m2 (obesity), 24.0-26.9 kg/m2 (overweight) and 18.5-23.9 kg/m2 (normal weight). Normal, slight, and great psychological stress was evaluated by the Brief Symptoms Rating Scale (BSRS-5) score ≤5, 6-9, and ≥10, respectively. Aerobic and anaerobic fitness were respectively evaluated by time for a 3000-meter run and numbers of 2-minute sit-ups and 2-minute push-ups. Analysis of covariance (ANCOVA) with adjustments for age and sex was used to determine the relationship.

RESULTS

The mean time (sec) for a 3000-meter run (standard error) under slight and great stress differed from that under normal stress in the normal weight (881.0 (11.0) and 877.9 (5.8) vs. 862.2 (1.7), p=0.089 and 0.0088, respectively) and in the obesity (928.1 (16.8) and 921.8 (10.7) vs. 895.2 (1.6), p=0.054 and 0.016, respectively), while the differences were not significant in the overweight (877.1 (12.7) and 877.5 (7.1) vs. 867.1 (2.1), both p >0.5). The impacts of the BMI on 2-minute sit-ups had a similar pattern with that on a 3000-meter run whereas the impact of the BMI on 2-minute push-ups was insignificant.

CONCLUSIONS

Mental stress may not affect physical fitness in overweight military personnel. The mechanism is not clear and should be further investigated.