Effect of cooling strategies on overall performance of a hybrid personal cooling system incorporated with phase change materials (PCMs) and electric fans

The effect of four cooling strategies on cooling performance of a hybrid personal cooling system (HPCS) incorporated with phase change materials (PCMs) and electric fans in a hot environment (i.e., T_air = 36 ± 0.5 °C, RH = 59 ± 5%) was investigated. Twelve healthy young male participants underwent four 90-min trials comprising 70 min walking and 20 min resting periods. Cooling strategies adopted in this work were CON (control), PCM-control (PCMs were removed at the end of exercise), Fan-control (fans were switched OFF during the initial 20 min) and PCM&Fan-control (fans were turned ON after 20 min exercising and PCMs were removed after the 70-min exercise). Results demonstrated that the control of electric fans could suppress the mean skin temperature rise to 34.0 °C by over 15 min and also cut down the energy consumption of the HPCS from 15.6 W h to 12.1 W h over the entire 90-min trials. Thus, it is recommended that fans should be turned off at the beginning of hot exposure and switched on once participants felt warm. Our findings also showed that the removal of fully melted PCM packs from the HPCS could enhance the evaporative cooling effect brought about by air circulation. The removal of melted PCMs significantly reduced the physical load by 37.3% and ratings of perceived exertion (RPE) were decreased by 3.5-4.2 RPE units. This could also help quickly restore the PCM energy for future usage. In summary, cooling strategies demonstrated in this work could improve HPCS's overall cooling performance on workers while working in the studied hot environment.

Autonomic and perceptual thermoregulatory responses to voluntarily engaging in a common thermoregulatory behaviour

We examined whether partial clothing removal is an effective thermoregulatory behaviour to attenuate both thermoregulatory and perceptual strain in a moderate environment (23 °C, 65% RH) during and after exercise. Ten healthy males (age: 21.9 (0.9) years; height: 173.9 (6.2) cm; mass: 62.3 (8.2) kg; body surface area: 1.8 (0.1) m²; VO₂max: 51.8 (13.3) mL.kg^-1.min^-1) wore a long sleeve polyester shirt and performed two randomized cycling trials for 40 min at 40% VO₂max followed by 20 min recovery. In one trial, they were permitted to roll up their sleeves at any time they wanted (Roll) whereas in the other trial, they were instructed to remain with long sleeves (No Roll) until the end of the recovery. Thermoregulatory variables were measured continuously whilst thermal perceptions (forearm wettedness perception (WP_Forearm), forearm and whole-body thermal discomfort (TD_Forearm, TD_Whole), local and whole-body thermal sensation (TS_Forearm, TS_Whole) and whole-body wettedness perception (WP_whole)) were measured every 10 min. All subjects behaved by rolling up their sleeves at 21.6 (4.7) minutes. T_skin (32.3 (0.2) °C, vs 32.0 (0.1) °C, p = 0.03), local sweat rate on the forearm (0.24 (0.08) mg.cm^-2.min^-1 vs 0.2 (0.04) mg.cm^-2.min^-1, p = 0.05), WP_Forearm, TD_Forearm, TS_Forearm and WP_Whole were all lower in Roll than No Roll (all p < 0.05) whilst T_core and cutaneous vascular conductance (CVC) on the forearm were not different (all p > 0.7) throughout the entire trial. We conclude that this behavioural response is an effective thermoregulatory behaviour to modulate local sudomotor function and thermal perceptions, WP_Whole during exercise but only T_sk, TD_Forearm WP_Forearm and WP_Whole persisted throughout the recovery in a moderate environment.

Aerobic exercise with blood flow restriction affects mood state in a similar fashion to high intensity interval exercise

We investigated the acute effects of aerobic exercise with blood flow restriction (BFR) on mood state in American football athletes. Twenty-two male American football athletes were randomly assigned to three experimental conditions: 1) aerobic exercise (AE: 40% VO_2max), 2) aerobic exercise with BRF (AE + BFR: 40% VO_{2 max}), and 3) high-intensity interval exercise (HIIE: 80% and 40% VO_2max during exercise and the active intervals, respectively). Mood state and total mood disturbance (TMD) were assessed before, immediately post, and 1 h post-exerciser. Ratings of perceived exertion (RPE) were measured 30 min post-exercise. AE + BFR and HIIE significantly (p < 0.05) increased fatigue and tension compared to baseline immediately post-exercise, whereas vigor significantly (p < 0.05) decreased at the same time point for both conditions. TMD increased significantly (p < 0.05) for AE + BFR and HIIE immediately post-exercise and it remained elevated up to 1 h post-exercise for AE + BFR. AE did not significantly (p > 0.05) affect mood state or TMD and it was significantly (p < 0.05) lower than AE + BFR and HIIE. AE + BFR and HIIE also elicited significantly (p < 0.05) greater RPE levels than AE 30 min post-exercise. Therefore, AE + BFR induces acute impairments in mood state and RPE levels in a similar fashion to HIIE.