Female Energy Expenditure during Load Carriage in Thermal Environments

Area of Science:

• Exercise physiology
• Environmental physiology
• Human performance

Background:

• The Load Carriage Decision Aid (LCDA) is a tool designed to estimate energy expenditure during load carriage.
• Validating the LCDA's accuracy in diverse environmental conditions is crucial for its practical application.
• Understanding energy costs associated with load carriage is vital for military and occupational settings.

Purpose of the Study:

• To cross-validate the Load Carriage Decision Aid (LCDA) in healthy, military-aged females naive to load carriage.
• To assess the LCDA's accuracy in estimating oxygen consumption (Ṁ) across a range of thermal environments.
• To determine the reliability of LCDA estimations under varying temperature and humidity levels.

Main Methods:

• Twenty-seven healthy females (18-35 years) participated in seven experimental trials.
• Participants walked at increasing speeds with and without load carriage in controlled cool to hot environments (10-45°C, 20-60% RH).
• Oxygen consumption (Ṁ) was measured using indirect calorimetry and estimated using the LCDA; differences were analyzed for bias, concordance correlation coefficient (CCC), and statistical equivalence.

Main Results:

• The LCDA demonstrated excellent accuracy in cool and dry conditions (e.g., 22°C, 20% RH; Bias ± SD, -0.01 ± 0.33 W·kg-1; CCC = 0.992).
• Acceptable precision was observed in most dry environments, but performance was unacceptable in hot, humid conditions (40°C, 60% RH).
• Statistical equivalence was confirmed across most environments, except for the 40°C, 60% RH condition.

Conclusions:

• The Load Carriage Decision Aid (LCDA) can be reliably used by females to estimate walking energy expenditure with and without load across many environments.
• Users should anticipate higher energy costs than predicted by the LCDA in hot and humid conditions.
• The LCDA provides a valuable tool for estimating energy expenditure, with specific considerations for extreme thermal environments.