Effects of body size and countermeasure exercise on estimates of life support resources during all-female crewed exploration missions.

Employing a methodology reported in a recent theoretical study on male astronauts, this study estimated the effects of body size and aerobic countermeasure (CM) exercise in a four-person, all-female crew composed of individuals drawn from a stature range (1.50- to 1.90-m) representative of current space agency requirements (which exist for stature, but not for body mass) upon total energy expenditure (TEE), oxygen (O) consumption, carbon dioxide (CO) and metabolic heat (H) production, and water requirements for hydration, during space exploration missions.

The Role of Long-Term Head-Down Bed Rest in Understanding Inter-Individual Variation in Response to the Spaceflight Environment: A Perspective Review.

Exposure to the spaceflight environment results in profound multi-system physiological adaptations in which there appears to be substantial inter-individual variability (IV) between crewmembers. However, performance of countermeasure exercise renders it impossible to separate the effects of the spaceflight environment from those associated with exercise, whilst differences in exercise programs, spaceflight operations constraints, and environmental factors further complicate the interpretation of IV. In contrast, long-term head-down bed rest (HDBR) studies isolate (by means of a control group) the effects of mechanical unloading from those associated with countermeasures and control many of the factors that may contribute to IV.

Body size and its implications upon resource utilization during human space exploration missions.

The purpose of this theoretical study was to estimate the effects of body size and countermeasure (CM) exercise in an all-male crew composed of individuals drawn from a height range representative of current space agency requirements upon total energy expenditure (TEE), oxygen (O) consumption, carbon dioxide (CO) and metabolic heat (H) production, and water requirements for hydration, during space exploration missions. Using a height range of 1.50- to 1.

High-Intensity Interval Training: A Potential Exercise Countermeasure During Human Spaceflight.

High-intensity interval training (HIT) is an effective approach for improving a range of physiological markers associated with physical fitness. A considerable body of work has demonstrated substantial improvements in cardiorespiratory fitness following short-term training programmes, while emerging evidence suggests that HIT can positively impact aspects of neuromuscular fitness. Given the detrimental consequences of prolonged exposure to microgravity on both of these physiological systems, and the potential for HIT to impact multiple components of fitness simultaneously, HIT is an appealing exercise countermeasure during human spaceflight.

Introduction to the Frontiers Research Topic: Optimization of Exercise Countermeasures for Human Space Flight - Lessons From Terrestrial Physiology and Operational Considerations.

Exercise in space has evolved from rudimental testing into the multi-modal countermeasure (CM) program used on the International Space Station (ISS). However, with the constraints of future exploration missions, replicating this program will be a significant challenge. Recent ISS data suggest that crew now experience only relatively moderate levels of microgravity (μG)-induced adaptation, although significant variation remains, with some crew displaying marked changes despite significant time/effort investment.

Spinal Health during Unloading and Reloading Associated with Spaceflight.

Spinal elongation and back pain are recognized effects of exposure to microgravity, however, spinal health has received relatively little attention. This changed with the report of an increased risk of post-flight intervertebral disc (IVD) herniation and subsequent identification of spinal pathophysiology in some astronauts post-flight. Ground-based analogs, particularly bed rest, suggest that a loss of spinal curvature and IVD swelling may be factors contributing to unloading-induced spinal elongation.

Parathyroid Hormone Secretion Is Controlled by Both Ionized Calcium and Phosphate During Exercise and Recovery in Men.

Context: The mechanism by which PTH is controlled during and after exercise is poorly understood due to insufficient temporal frequency of measurements.

Objective: The objective of the study was to examine the temporal pattern of PTH, PO4, albumin-adjusted calcium, and Ca(2+) during and after exercise.

Design And Setting: This was a laboratory-based study with a crossover design, comparing 30 minutes of running at 55%, 65%, and 75% maximal oxygen consumption, followed by 2.

Blood pressure, vascular resistance, and +Gz tolerance during repeated +Gz exposures.

Background: Cardiovascular reflexes that regulate blood pressure (BP) adapt during repeated exposure to +Gz acceleration separated by short (< 20 s) breaks, but whether this effect is preserved with longer intervals remains unknown.

Methods: There were 17 subjects who completed 5 repeated gradual onset (0.1 G x s(-1)) runs (GOR1-5) to 60 degrees peripheral light loss (PLL) on a human centrifuge, separated by 2 min.

+Gz tolerance, with and without muscle tensing, following loss of anti-G trouser pressure.

Background: Fast jet aircrew are heavily reliant on anti-G trousers (AGT) and failure of the garment or its pressure supply would expose them to high levels of +Gz acceleration without protection. A previous study demonstrated the severity of this event at high +Gz, but no data exists as to the maximum +Gz level which could be tolerated.

Methods: : While relaxed and with lower body muscle tensing, 10 experienced centrifuge subjects had their AGT deflated after 5 and 30 s of +Gz exposure.

Treadmill running reduces parathyroid hormone concentrations during recovery compared with a nonexercising control group.

Context: Lower PTH concentrations reported in the hours after acute, endurance exercise compared with preexercise levels might be influenced by factors such as circadian fluctuations.

Objective: The objective of the study was to compare postexercise PTH concentrations with a nonexercising control group.

Design And Setting: A laboratory-based study with a crossover design, comparing a 60-minute (at 10:30 am) bout of treadmill running at 65% of the maximal rate of oxygen uptake (exercise) with semirecumbent rest (CON).

Subjective and objective measures of relaxed +Gz tolerance following repeated +Gz exposure.

Background: Repeated exposure to +Gz acceleration provokes cardiovascular adaptations of potential benefit to pilots' +Gz tolerance, but whether such changes actually improve human tolerance to +Gz acceleration is uncertain. This study assessed +Gz tolerance before and after repeated exposure to +Gz at two different intensities as the role of frequency of +Gz exposure in adaptation also remains unknown.

Methods: In a cross-over design, 10 experienced male centrifuge volunteers completed two experimental conditions separated by at least 3 wk.

Garment fit and protection from sustained +Gz acceleration with 'full-coverage' anti-G trousers.

Introduction: Garment fit may influence the effectiveness with which Full-Coverage Anti-G Trousers (FCAGT) transmit pressure to the skin surface, and hence provide protection from sustained +Gz acceleration. A search of the available literature, however, did not reveal any prior work quantifying this effect.

Methods: Three related studies were performed.

Cytokine response to acute running in recreationally-active and endurance-trained men.

To compare the cytokine response to exhaustive running in recreationally-active (RA) and endurance-trained (ET) men. Eleven RA men (VO2max 55 ± 7 mL·min(-1)·kg(-1)) and 10 ET men (VO₂max 68 ± 7 mL·min(-1)·kg(-1)) followed a controlled diet and refrained from volitional exercise for 8 days. On the fourth day, participants completed 60 min of treadmill running (65 % VO₂max), followed by intermittent running to exhaustion (70 % VO₂max).

Effect of recovery duration between two bouts of running on bone metabolism.

Purpose: Strenuous endurance exercise increases biochemical markers of bone resorption but not formation, although the effect of recovery duration between consecutive bouts of exercise is unknown. We examined the effect of recovery duration on the bone metabolic response to two bouts of running.

Methods: Ten physically active men completed two 9-d trials.

Effect of fasting versus feeding on the bone metabolic response to running.

Individuals often perform exercise in the fasted state, but the effects on bone metabolism are not currently known. We compared the effect of an overnight fast with feeding a mixed meal on the bone metabolic response to treadmill running. Ten, physically-active males aged 28 ± 4y (mean ±SD) completed two, counterbalanced, 8d trials.

Effect of exercise intensity on the cytokine response to an acute bout of running.

Purpose: We compared the effects of exercise intensity (EI) on the cytokine response to an acute bout of running.

Methods: Ten males (mean ± SD VO(2max)= 56.2 ± 8.

The role of exercise intensity in the bone metabolic response to an acute bout of weight-bearing exercise.

We compared the effects of exercise intensity (EI) on bone metabolism during and for 4 days after acute, weight-bearing endurance exercise. Ten males [mean ± SD maximum oxygen uptake (Vo(2max)): 56.2 ± 8.

The effect of training status on the metabolic response of bone to an acute bout of exhaustive treadmill running.

Context: Strenuous exercise increases bone resorption but not formation. The effect of improved training status is unknown.

Objective: Our objective was to examine the metabolic response of bone to strenuous running in recreationally active (RA) and endurance-trained (ET) men.