Influence Of Hypothermia And Cold Stress On Ability To Adhere To A Prescribed Stepping Cadence

Cold-wet stress, which occurs during water immersion or rain exposure, accelerates body heat loss and undermines optimal function. The current work focuses on warfighters’ ability to adhere to a stepping cadence during rewarming while in varying states of cold stress and hypothermia. PURPOSE: To evaluate the relationship between body heat loss and ability to follow a prescribed stepping cadence. METHODS: Sixteen male military personnel (mean ± SD, 30 ± 7 yr, 175 ± 8 cm, 85 ± 13 kg; body fat: 19 ± 7%) were immersed to the neck for 10 min in an outdoor pond (air: −4.2 °C; water: 1.3 °C) clothed in shorts and T-shirts. Upon exiting the water, participants changed into dry clothes and completed a 60-s postural stability test using a force platform. Participants then began a 40-min step exercise (8-in step) to rewarm. They were given metronome headsets and asked to adhere to a prescribed cadence representing either 30% or 45% of their estimated VO2max. Stepping cadence compliance was determined using data from an accelerometer secured to their chest. Core temperature (Tc) was measured each minute with ingestible sensors. During analysis, groups were developed based on magnitude of heat loss: slight cold stress (CS-S: Tc > 36 °C), moderate cold stress (CS-M: Tc 35-36 °C), and hypothermic (HYP: Tc < 35 °C). Path length (balance), sway area (balance), foot temperature (Tfoot), and thermal sensation (TS) were compared among groups using one-way ANOVAs with a significance level set at p < .05. RESULTS: Step cadence adherence was not influenced by magnitude of heat loss, as no differences in cadence compliance were observed (CS-S: 83 ± 9%, CS-M: 91 ± 11%, or HYP: 98 ± 14%; p = .133). Participants’ TS ratings (CS-S: −2.2 ± 1.8, CS-M: −3.2 ± 1.0, HYP: −3.3 ± 0.3; p = .280), Tfoot (CS-S: 16.4 ± 2.8 °C, CS-M: 17.0 ± 2.1 °C, HYP: 16.3 ± 2.9 °C; p = .890), and sway area (CS-S: 15 ± 6 cm2, CS-M: 35 ± 28 cm2, HYP: 30 ± 16 cm2; p = .203) did not differ between groups. Path length was different between groups (CS-S: 198 ± 93 cm, CS-M: 279 ± 245 cm, HYP: 638 ± 315 cm; p = .019). CONCLUSION: Preliminary findings indicate that the magnitude of body heat loss does not negatively impact one’s ability to adhere to a prescribed stepping cadence, suggesting that operational performance in cold-wet environments may be maintained for physical tasks that involve simple, repetitive motion.