# Energy Expenditure of Special Forces Soldiers in Relation to Equipment Load and Movement Speed

## TL;DR

This study examines how carrying a 20-kg backpack and movement speed affect the energy expenditure of special forces soldiers.

## Contribution

The study quantifies the impact of load and speed on energy expenditure in special forces soldiers using breath-by-breath metabolic measurements.

## Key findings

- A 20-kg backpack increased energy expenditure by 20% at all speeds.
- Heart rate and oxygen uptake rose significantly with added load.
- Energy expenditure tripled at higher speeds with and without the backpack.

## Abstract

Background/Objectives: Additional load is associated with a significant increase in energy expenditure during soldiers’ movement. The level of energy expenditure during military tasks depends on the speed at which soldiers move. The aim of the study was to determine how the speed of movement and military load in the form of a 20-kg backpack affect the energy expenditure of special forces operators. Methods: The study included a group of 24 special forces operators. The energy expenditure of participants was measured using a portable Cosmed K5 gas analyzer operating in “breath-by-breath” mode. Energy expenditure was calculated based on VO2 and VCO2 data. Respiratory exchange ratio (RER) was recorded in parallel with VO2 and VCO2 and used to calculate the oxidation of energy substrates. The soldiers moved in 6-min intervals at the following speeds: 4.5 km/h, 6.5 km/h, 8.5 km/h, 10.5 km/h. First, the soldiers covered each speed without a load, and then with a 20 kg tactical military backpack. Results: The analysis showed that increasing speed and the use of an external load significantly increased all physiological and metabolic responses. Speed × load interactions were observed for some metabolic variables, whereas no such interactions were found for heart rate. Conclusions: Adding a 20 kg tactical backpack causes a significant increase in energy expenditure at all speed levels. The additional load resulted in an average increase of 10% in heart rate (%HRmax) and 20% in oxygen uptake (%VO2max). A more than threefold increase in energy expenditure was recorded (14.77 kcal/min without load and 17.70 kcal/min with a backpack at a speed of 10.5 km/h vs. 5.01 kcal/min and 6.35 kcal/min at a speed of 4.5 km/h).