Introduction Habitual smoking is highly prevalent in military populations despite its association with poorer training outcomes. Smoking imposes challenges on the immune and endocrine systems which could alter how smokers acutely respond to, and recover from, intensive exercise particularly over multiple days of training.
Methods Over a two-day period, 35 male British Army recruits (age 22±3 years; mass 76.9±8.0 kg; height 1.78±0.06 m; 15 smokers) completed a 16.1 km loaded march (19.1 kg additional mass) on the first morning and a best-effort 3.2 km ‘log race’ (carrying a 60 kg log between six and eight people) on the subsequent morning. Blood samples were obtained on waking and immediately postexercise on both days and analysed for C reactive protein (CRP), interleukin 6 (IL-6), testosterone to cortisol ratio and insulin-like growth factor 1 (IGF-1).
Results Independent of smoking group, the exercise bouts on both days evoked significant increases in IL-6 (p<0.001) and decreases in testosterone to cortisol ratio (p<0.05). CRP concentrations on day 2 were significantly higher than both time points on day 1 (p<0.001), and a 9% decline in IGF-1 occurred over the two-day period, but was not significant (p=0.063). No significant differences were observed between smokers and non-smokers (p>0.05).
Conclusions Military-specific tasks elicited inflammatory and endocrine responses, with systemic CRP and IGF-1 indicating that the physiological stress generated during the first training day was still evident on the second day. Despite the well-established impacts of smoking on resting levels of the markers examined, responses to two days of arduous military-specific training did not differ by smoking status.
- sports medicine
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Contributors All authors made substantial contributions to the conception or design of the work, or the acquisition, analysis or interpretation of data. All were involved in drafting, critically reviewing and revising the manuscript. All authors have seen and approved the final manuscript and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
Funding This work was funded by the Army Recruiting and Initial Training Command (formerly Army Recruiting and Training Division), UK Ministry of Defence (grant ID no: 100278024).
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The study was approved by the Ministry of Defence Research Ethics Committee (MODREC/0911/236).
Provenance and peer review Not commissioned; internally peer reviewed.
Data availability statement Data may be obtained from a third party and are not publicly available. Data remain the property of the UK Ministry of Defence, but can be made available subject to appropriate request and approval.