RESUMEN
Wet clothing is less insulative than dry clothing and increases heat loss in cold air. Tactical necessity can render removal of wet clothing impossible and/or require Warfighters to remain static to avoid detection, limiting heat production and posing a threat of hypothermia (core temperature <35°C). This study aimed to characterize body temperatures and evaluate hypothermia risk while statically exposed to 5°C air wearing three wet military uniforms. Further, low-speed loaded walking was evaluated as a strategy to raise end-static temperatures. Twelve adults (11M, 1F) randomly completed three wet-cold trials wearing either the Improved Hot Weather Combat Uniform (IHWCU), Army Combat Uniform (ACU), or ACU with silk-weight base layer (ACU+). Each trial involved 180 minutes of cold air (5.3±0.3°C, 0.8 m·s-1) exposure after a clothed 2-minute head-out immersion (34.0 ± 0.2°C). Volunteers were static for 60 minutes followed by 120 minutes of loaded walking. Rectal temperature (Tre) area under the curve did not differ among the three wet uniforms when static (p=0.431) with Tre increasing, rather than decreasing, across the 60 minutes (IHWCU: +0.26±0.19°C, ACU: +0.37±0.21°C, ACU+: +0.36±0.20°C). Hypothermia risk with 60-minute static wet-cold exposure therefore appears minimal, regardless of the military uniform worn. End-static finger temperatures (IHWCU: 9.48±2.30°C, ACU: 9.99±1.82°C, ACU+: 9.27±1.66°C, p >0.999) were reduced by ~20-23°C posing a considerable dexterity concern. Heat production of ~210 W·m2 appeared sufficient to begin to reverse negative cumulative heat storage and initiate slight elevation of rectal and peripheral temperatures, although finger temperatures increased < 2°C after 120 minutes. ClinicalTrials.gov ID:NCT05409937.
RESUMEN
BACKGROUND: It remains unknown if physical inactivity and excess adiposity increases 24-h central blood pressure and arterial stiffness in young adults. This study examined 24-h central blood pressure and indirect measures of arterial stiffness (e.g., central pulse pressure) in physically inactive young adults with and without excess adiposity. METHODS: Body fat and ambulatory 24-h blood pressure were measured in 31 young adults (men: 22±4 years, N.=15; women: 22±5 years, N=16). Multi-frequency bioelectrical impedance measured body fat. Normal adiposity was defined as <20% body fat in men and <32% body fat in women, whereas excess adiposity was defined as ≥20% and ≥32% in men and women, respectively. Ambulatory 24-h central blood pressure was calculated based on brachial blood pressure and volumetric displacement waveforms. RESULTS: By design, the normal adiposity group had a lower body fat percentage (men: 15.5±4.6%; women: 20.8±2.5%) compared to the physically inactive excess adiposity group (men: 29.8±5.4%; women: 34.3±7.5%). Men and women with excess adiposity group had elevated central blood pressure (central systolic, P<0.05 vs. normal adiposity groups). Central pulse pressure was elevated in the excess adiposity group (men: 45±5 mmHg; women: 41±9 mmHg) compared to normal adiposity groups (men: 36±4 mmHg; women: 32±3 mmHg, P<0.05 for both), while other arterial stiffness (augmentation index and ambulatory arterial stiffness index) measures trended toward significance only in men with excess adiposity. CONCLUSIONS: Physically inactive men and women with excess adiposity have increased 24h central blood pressure and pulse pressure compared to physically inactive young adults with normal adiposity.