Whole-body passive heating at moderate hyperthermic state impairs static and dynamic balance in healthy females

Whether static and dynamic balances can be impaired with increasing core temperature in female participants remains unknown.

We tested the hypothesis that static and dynamic balances can be further impaired with systematic increases of core temperature by Δ1 °C and Δ 2 °C using whole-body passive heating.

Eighteen female participants underwent a control trial (Con) and two progressive passive heating trials with Δ 1 °C and Δ 2 °C increase of oral temperature (T_Oral) using 45 °C water bath. In each trial, we assessed static balance with both eye open and closed and assessed dynamic balance using obstacle crossing at 10 %, 20 % and 30 % of the participant's leg length.

Static balance was not different between Con and Δ1 °C but was different between Δ1 °C and Δ 2 °C in an eye closed condition. Furthermore, Δ 2 °C greatly impaired both static and dynamic balances when compared to Con. The joint angles and toe clearance increased while leading heel-obstacle distance decreased during crossing obstacles at the height of 20 % and 30 % leg length with leading limbs in the Δ2 °C compared to Δ 1 °C and Con (All P < 0.05). However, no differences in joint kinematics and toe clearance with trailing limbs were observed (All P > 0.05).

In female participants, static and dynamic balances only became impaired when T_Oral increased 2 °C from baseline.