{
  "abstract": "Introduction Military operations in cold environments impose significant physiological and psychological stress, resulting in 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 different operational roles and living conditions remains understudied.Methods This study investigated perceived fatigue (10 cm Visual Analogue Scale), physical performance (standing long jump), sustained attention (20-minute psychomotor vigilance task (PVT)) and sleep (actigraphy) in first-year and second-year cadets during a winter military exercise in Finland. Cadets were assigned roles reflecting combat (first-year) or officer duties (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 with second-year cadets, 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. Perceived fatigue increased post-first training block only in first-year cadets (p=0.003). First-year cadets demonstrated a notable decline in PVT reaction time (p<0.001) and 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). Increased fatigue correlated negatively with PVT performance (all p<0.043). Accommodation in tents showed large temperature fluctuations (~30 °C) and elevated particulate matter (PM10); barracks experiencing increased CO 2 proportional to occupancy.Conclusions A challenging sleep environment combined with high training loads impairs fatigue resistance and performance during cold-environment military training. Sleep continuity is crucial for fatigue and in turn sustained attention. Long (~20 min) sustained tasks might serve as sensitive fatigue monitoring tools. Improvements to sleep environment such as increased temperature comfort might improve sleep, reducing fatigue.",
  "authors": [
    {
      "affiliations": [
        "Departement of Medicine, Université de Montréal, Montreal, Québec, Canada",
        "Center for Advanced Research in Sleep Medicine, Hôpital du Sacré-Coeur de Montréal, Montreal, Québec, Canada",
        "National Institute of Sport of Québec, Montréal, Québec, Canada"
      ],
      "name": "Giorgio Varesco"
    },
    {
      "affiliations": [
        "Human Performance Division, Finnish Defence Research Agency, Lakiala, Finland",
        "Faculty of Sport and Health Sciences, Neuromuscular Research Center, University of Jyväskylä, Jyväskylä, Central Finland, Finland"
      ],
      "name": "Tommi Ojanen"
    },
    {
      "affiliations": [
        "Department of Leadership and Military Pedagogy, Finnish Defence Forces National Defence University, Helsinki, Uusimaa, Finland"
      ],
      "name": "Jani P Vaara"
    },
    {
      "affiliations": [
        "Center for Advanced Research in Sleep Medicine, Hôpital du Sacré-Coeur de Montréal, Montreal, Québec, Canada"
      ],
      "name": "Antonio Martin"
    },
    {
      "affiliations": [
        "Research Unit VIPER, Royal Military Academy, Bruxelles, Belgium",
        "Human Physiology and Sports Physiotherapy Research Group, Faculty of Physical Education and Physiotherapy, Vrije Universiteit Brussel, Brussels, Brussels, Belgium"
      ],
      "name": "Jeroen van Cutsem"
    },
    {
      "affiliations": [
        "Faculty of Health Sciences, University of Ottawa, Ottawa, Ontario, Canada"
      ],
      "name": "François Haman"
    },
    {
      "affiliations": [
        "Center for Advanced Research in Sleep Medicine, Hôpital du Sacré-Coeur de Montréal, Montreal, Québec, Canada",
        "Research Unit VIPER, Royal Military Academy, Bruxelles, Belgium"
      ],
      "name": "Nathalie Pattyn"
    },
    {
      "affiliations": [
        "Departement of Medicine, Université de Montréal, Montreal, Québec, Canada",
        "Center for Advanced Research in Sleep Medicine, Hôpital du Sacré-Coeur de Montréal, Montreal, Québec, Canada",
        "Department of Neuroscience, Université de Montréal, Montréal, Québec, Canada"
      ],
      "name": "Guido Simonelli"
    }
  ],
  "title": "The relationship between sleep, fatigue and performance during sub-Arctic operations: data from a winter military field exercise in Finland",
  "uid": "7b8b33f3-8e88-5898-93ba-93056ca3d071"
}