Overnight heart rate variability responses to military combat engineer training

Area of Science:

• Physiology
• Sports Science
• Military Medicine

Background:

• Military training imposes significant physical and psychological stress.
• Monitoring physiological responses like heart rate variability (HRV) can offer insights into stress and recovery.
• Understanding the relationship between workload, stress, and physiological markers is crucial for optimizing performance and well-being.

Purpose of the Study:

• To investigate if overnight heart rate variability (HRV) accurately reflects workload and stress levels during military training.
• To compare the recovery rates of HRV with subjective wellbeing measures post-training.

Main Methods:

• A 15-day assessment period involving 32 combat engineers during military training.
• Collection of data on cognitive load, perceived exertion, physical activity, nocturnal HRV, cognitive performance, and sleep.
• Phased training including PRE, FIELD, BASE, and RECOVERY, incorporating sleep deprivation and restriction.

Main Results:

• The FIELD phase showed increased mood disturbance, perceived exertion, physical activity, and HRV, alongside reduced sleep quantity.
• Heart rate variability (HRV) measures returned to baseline levels faster than subjective wellbeing indicators.
• Sleep duration and physical activity were significant predictors in the HRV model, highlighting their role as primary stressors.

Conclusions:

• Overnight HRV serves as a physiological indicator of workload and stress during demanding military training.
• Distinct recovery trajectories for HRV and subjective wellbeing suggest differing physiological and psychological adaptation processes.
• HRV monitoring can provide objective insights into trainee stress and recovery, complementing subjective assessments.