# Effect of hyperthermia on simulated muscle activation in female when crossing obstacle

## TL;DR

This study found that higher body heat increases muscle activation in women when crossing obstacles of moderate height or higher.

## Contribution

The study reveals how increasing hyperthermia affects muscle activation in females during obstacle crossing.

## Key findings

- Greater hyperthermia (Δ2°C) increased lower limb muscle activation for obstacle heights of 20% and 30% leg length.
- Muscle activation was not significantly different between mild hyperthermia (Δ1°C) and control conditions.
- Higher muscle activation at Δ2°C suggests a compensatory mechanism for safety and stability during obstacle crossing.

## Abstract

It is well known that hyperthermia greatly impairs neuromuscular function and dynamic balance. However, whether a greater level of hyperthermia could potentially alter the lower limb simulated muscle activation when crossing an obstacle in female participants remains unknown. Therefore we examined the effect of a systematic increase in oral temperature on lower limb simulated muscle activation when crossing an obstacle in female participants. Eighteen female participants were recruited where they underwent a control trial (Con) and two progressive passive heating trials with Δ 1°C and Δ 2°C increase of oral temperature (Toral) using a 45°C water bath. In each trial, we assessed lower limb simulated muscle activation when crossing an obstacle height of 10%, 20%, and 30% of the participant’s leg length and toe-off, toe-above-obstacle and heel-strike events were identified and analyzed. In all events, the lower limb simulated muscle activation were greater in Δ2°C than Δ1°C and Con when both leading and trailing limbs crossed the obstacle height of 20% and 30% leg length (all p < 0.001). However, the lower limb simulated muscle activation were not different between Δ1°C and Con across all obstacle heights (p > 0.05). This study concluded that a greater level of hyperthermia resulted in a greater lower limb simulated muscle activation to ensure safety and stability when females cross an obstacle height of 20% leg length or higher.