Comprehensive assessment of physiological responses in women during the ESA dry immersion VIVALDI microgravity simulation.

Astronauts in microgravity experience multi-system deconditioning, impacting their inflight efficiency and inducing dysfunctions upon return to Earth gravity. To fill the sex gap of knowledge in the health impact of spaceflights, we simulate microgravity with a 5-day dry immersion in 18 healthy women (ClinicalTrials.gov Identifier: NCT05043974). Here we show that dry immersion rapidly induces a sedentarily-like metabolism shift mimicking the beginning of a metabolic syndrome with a drop in glucose tolerance, an increase in the atherogenic index of plasma, and an impaired lipid profile. Bone remodeling markers suggest a decreased bone formation coupled with an increased bone resorption. Fluid shifts and muscular unloading participate to a marked cardiovascular and sensorimotor deconditioning with decreased orthostatic tolerance, aerobic capacity, and postural balance. Collected datasets provide a comprehensive multi-systemic assessment of dry immersion effects in women and pave the way for future sex-based evaluations of countermeasures.

An ergonomics assessment of three simulated 120 m ladder ascents: A comparison of novice and experienced climbers.

This study investigated the ergonomics of three simulated 120 m vertical ladder ascents and differences between novice (NC) and experienced climbers (EC). Seven EC and 10 NC undertook three 120 m climbs; comprising of four 30 m climbs. Ascending 120 m was reported as a high physical demand, supported by high peak HRs (~173 b.min-1 across the three climbs) and V˙ O2 (~3.1 L.min-1 across the three climbs). Grip strength and endurance were significantly (p < 0.05) impaired by ascents. With multiple ascents, toe clearance was reduced (Climb 1 - 0.0515 m; Climb 3 - 0.046 m), and participants reached higher with their arms (shoulder angle: Climb 1 - 117°; Climb 3 - 136°). NC demonstrated less range of movement through the hips (NC - 46°; EC - 58°), and higher muscle activation in the upper body (NC - 60%; EC - 49%). Experience reduced cumulative climbing times (exercise + rest), whilst maintaining the same physiological demand as NC and maintained optimised movement patterns for longer.

Thermoregulation and markers of muscle breakdown in malignant hyperthermia susceptible volunteers during an acute heat tolerance test.

OBJECTIVES: The study was undertaken to compare the thermal and biochemical responses to a heat tolerance test (HTT) of malignant hyperthermia (MH) susceptible individuals, volunteers who have suffered heat illness (HI) and control volunteers. METHODS: Three groups of male volunteers (n=6 in each group) were recruited to the study: MHS - civilian volunteers previously diagnosed as MH susceptible; EHI - military volunteers with a history of exertional HI; CON - military volunteers with no history of HI or MH. For the HTT, volunteers walked on a treadmill at 60% maximal oxygen uptake in a hot environment. Measurements were made of core and skin temperatures, heat flow, whole body sweat rate and serum lactate, creatine kinase and myoglobin concentrations. RESULTS: There were no differences in deep body temperature, oxygen uptake or serum lactate and creatine kinase concentrations between the three groups. One MHS volunteer and two EHI volunteers failed to achieve thermal balance with rectal temperature continuing to rise throughout the test and reaching 39.5°C, the rectal temperatures of the other volunteers plateaued at a mean (SD) of 38.7 (0.4)°C demonstrating thermal tolerance on this test. Serum myoglobin concentration and the increase in serum myoglobin was higher in MHS than EHI and CON Post HHT (P<0.05). CONCLUSION: MH susceptibility does not always predispose an individual to heat intolerance during an acute HTT, but does appear to increase muscle breakdown. The inclusion of serum myoglobin measurements to a HTT may help to distinguish patients that are potentially MHS, and who otherwise demonstrate thermal tolerance.