Author(s): SPINABELLI, S., DE LIMA, D., MARTINEZ-GONZALEZ, B., RANUNCOLI, C., BARBIERI, R., SENATORE, T., MARCORA, S.M., Institution: ALMA MATER STUDIORUM UNIVERSITY OF BOLOGNA, Country: ITALY, Abstract-ID: 2021

INTRODUCTION:
Research on the effects of caffeine supplementation in soldiers operating in cold and hypoxic environments is sparse. This pilot field study aimed to investigate the effects of such strategy on the physical and cognitive fatigue of soldiers during a 2-day military exercise on the Mont Blanc (3375m) in December 2025.
METHODS:
Twenty alpine soldiers were randomly assigned in a triple-blinded manner to either a caffeine or a placebo group with a 1:1 allocation ratio. Each day, to assess fatigue, participants were tested before and after a military exercise consisting of 4-hour technical navigation on the Gigante glacier. The pre-test included the Groningen Sleep Quality Scale (GSQS), the Italian Mood Scale (ITAMS), a 5-min psychomotor vigilance task (PVT), and a 5-min step test during which heart rate (HR), blood lactate concentration (bLA) and ratings of perceived exertion (RPE) for legs and breathing were measured. Immediately after the pre-test and 3 hours into the military exercise, participants ingested pills containing 200mg of caffeine or placebo for a total of 400 mg of caffeine. The military exercise workload was quantified with wearables and the NASA-TLX. Apart from the GSQS, the same pre-test measures were repeated after the military exercise (post-test). During nights, soldiers slept in tents and wore actigraphs to record sleep parameters. Data were analysed using mixed models with Gamma distribution; data clustered in subjects and selected as random effects intercept. Time, Drug and Day treated as fixed factors.
RESULTS:
Caffeine supplementation significantly reduced the negative effects of fatigue on reaction time (ms) [Group*Time b=-15.96; SE=6.84; CI95%=(-29.36 to -2.55); p=0.020] and number of lapses [Group*Time b=-3.34; SE=0.97; CI95%=(-5.25 to -1.43); p<.001] during the PVT, Vigor (0-16 scale) [Group*Time b=0.81; SE=0.40; CI95%=(0.02 to 1.61); p=0.044], and RPE-Legs (0-10 scale) [Group*Time b=-1.44; SE=0.55; CI95%=(-2.51 to -0.37); p=0.008]. No significant effects of caffeine were found on RPE-Breathing, HR, bLA, other mood dimensions, and sleep. The latter was poor during the nights preceding the military exercise (total sleep time 5:45±1:45; GSQS 8.2±3.9, with scores over 6 indicating poor sleep quality).
CONCLUSION:
The results of this pilot field study suggest that supplementation with 400 mg of caffeine is able to reduce the physical and cognitive fatigue experienced by soldiers operating in cold and hypoxic environments without further disrupting their sleep. Pending confirmation in larger trials, these findings extend the use of caffeine supplementation for military purposes in soldiers deployed in these extreme environments.