Smoking and Biochemical, Performance, and Muscle Adaptation to Military Training

To determine whether physical performance adaptation is impaired in smokers during early stages of military training and to examine some of the putative mechanistic candidates that could explain any impairment.

We examined measures of oxidative stress (malondialdehyde [MDA], lipid hydroperoxides), inflammation (C-reactive protein, interleukin-6), antioxidants (vitamins A and E and carotenes) and hormones (cortisol, testosterone, insulin-like growth factor-1) in 65 male British Army Infantry recruits (mean ± SD age, 21 ± 3 yr; mass, 75.5 ± 8.4 kg; height, 1.78 ± 0.07 m) at week 1, week 5, and week 10 of basic training. Physical performance (static lift, grip strength, jump height, 2.4 km run time, and 2-min press up and sit up scores) was examined and lower-leg muscle and adipose cross-sectional area and density measured by peripheral Quantitative Computed Tomography.

Basic military training, irrespective of smoking status, elicited improvement in all physical performance parameters (main time effect; P < 0.05) except grip strength and jump height, and resulted in increased muscle area and decreased fat area in the lower leg (P < 0.05). MDA was higher in smokers at baseline, and both MDA and C-reactive protein were greater in smokers during training (main group effect; P < 0.05) than nonsmokers. Absolute performance measures, muscle characteristics of the lower leg and other oxidative stress, antioxidant, endocrine, and inflammatory markers were similar in the two groups.

Oxidative stress and inflammation were elevated in habitual smokers during basic military training, but there was no clear evidence that this was detrimental to physical adaptation in this population over the timescale studied.