Author(s): VARESCO, G., OJANEN, T., VAARA, J., MARTIN, A., VAN CUTSEM, J., PATTYN, N., SIMONELLI, G., Institution: UNIVERSITÉ DE MONTREAL, Country: CANADA, Abstract-ID: 370

INTRODUCTION:
Military operations in cold environments impose significant physiological and psychological stress, including fatigue and impaired cognitive and physical performance. Sleep, a critical factor for recovery, is often disrupted in field conditions, yet its relationship with fatigue and task performance under varying operational roles and accommodations remains understudied.
METHODS:
This field study investigated perceived fatigue, physical performance (jump length), cognitive performance (20-minute Psychomotor Vigilance Task), and sleep (actigraphy) in first- and second-year military cadets during a winter training camp in Finland. Cadets were assigned roles reflecting combat (first-year) or officer duties (i.e. supervision, coordination; second-year) and housed in either heated tents or barracks. Training workload and environmental conditions including temperature and air quality were recorded across two training blocks differing in intensity.
RESULTS:
First-year cadets accumulated significantly more physical activity (p=0.005) and obtained less total sleep per night compared to second-years, with more second-year cadets achieving >5 hours of sleep (p=0.017). No significant difference was found in the number of cadets obtaining >7 hours of continuous sleep (p=0.16). Fatigue increased significantly post first training block only in first-year cadets (p=0.003). First-years demonstrated a notable decline in Psychomotor Vigilance Task (PVT) reaction time (p<0.001) and countermovement jump performance (p=0.001), with no recovery after the second block. Second-year cadets also showed a PVT decline (p<0.001), but exhibited partial recovery (p=0.001). Sleep duration correlated positively with PVT performance (p=0.043). Accommodation conditions influenced sleep quality, with tents showing larger temperature fluctuations (~30°C) and elevated particulate matter (PM10), and barracks experiencing increased CO2 proportional to occupancy.
CONCLUSION:
Sleep combined with high training loads impairs fatigue resistance and performance during cold-environment military training. Optimizing sleep continuity and accommodation conditions is essential. Cognitive performance tasks may serve as sensitive fatigue monitoring tools. Future research should test interventions to enhance sleep and operational readiness in field settings.