Disuse-Induced Muscle Loss and Rehabilitation: The National Aeronautics and Space Administration Bed Rest Study.

Objectives: The time course and magnitude of atrophic remodeling and the effects of an acute rehabilitation program on muscle atrophy are unclear. We sought to characterize bed rest-induced leg muscle atrophy and evaluate the safety and efficacy of an acute rehabilitation program.

Design: Prespecified analysis of a randomized controlled trial.

High intensity training during spaceflight: results from the NASA Sprint Study.

Historically, International Space Station (ISS) exercise countermeasures have not fully protected astronauts' musculoskeletal and cardiorespiratory fitness. Although these losses have been reduced on more recent missions, decreasing the time required to perform in-flight exercise would permit reallocation of that time to other tasks. To evaluate the effectiveness of a new training prescription, ISS crewmembers performed either the high intensity/lower volume integrated Sprint resistance (3 d wk) and aerobic (interval and continuous workouts, each 3 d wk in alternating fashion) exercise program ( = 9: 8M/1F, 48 ± 7 y, 178 ± 5 cm, 77.

Exercise and Testosterone Countermeasures to Mitigate Metabolic Changes during Bed Rest.

Background/objectives: Exercise is a front-line countermeasure used to maintain astronaut health during long-duration spaceflight; however, reductions in metabolic health still occur. Accordingly, we evaluated serial changes in metabolic parameters in a spaceflight analog and evaluated the efficacy of exercise with or without the addition of low-dose testosterone treatment on mitigating adverse metabolic changes.

Subjects/methods: Healthy young (<55 years) men were randomly assigned to one of three groups during 70-days of strict, diet controlled, 6° head-down bed rest: Control (CON, n=9), exercise plus testosterone countermeasure (TEX, n=8), or exercise countermeasure plus placebo (PEX, n=9).

A novel approach for establishing fitness standards for occupational task performance.

Purpose: To identify strength and performance thresholds below which task performance is impaired.

Methods: A new weighted suit system was used to manipulate strength-to-body-weight ratio during the performance of simulated space explorations tasks. Statistical models were used to evaluate various measures of muscle strength and performance on their ability to predict the probability that subjects could complete the tasks in an acceptable amount of time.

Physiological and Functional Alterations after Spaceflight and Bed Rest.

Introduction: Exposure to microgravity causes alterations in multiple physiological systems, potentially impacting the ability of astronauts to perform critical mission tasks. The goal of this study was to determine the effects of spaceflight on functional task performance and to identify the key physiological factors contributing to their deficits.

Methods: A test battery comprised of seven functional tests and 15 physiological measures was used to investigate the sensorimotor, cardiovascular, and neuromuscular adaptations to spaceflight.

Panoramic ultrasound: a novel and valid tool for monitoring change in muscle mass.

Background: The strong link between reduced muscle mass and morbidity and mortality highlights the urgent need for simple techniques that can monitor change in skeletal muscle cross-sectional area (CSA). Our objective was to examine the validity of panoramic ultrasound to detect change in quadriceps and gastrocnemius size in comparison with magnetic resonance imaging (MRI) in subjects randomized to 70 days of bed rest (BR) with or without exercise.

Methods: Panoramic ultrasound and MRI images of the quadriceps and gastrocnemius muscles were acquired on the right leg of 27 subjects (26 male, 1 female; age: 34.

Integrated resistance and aerobic exercise protects fitness during bed rest.

Introduction: The current exercise countermeasures have not fully protected astronauts' preflight aerobic and muscular fitness levels during International Space Station (ISS) missions, prompting a need to optimize the exercise prescription to improve or maintain astronauts' ability to perform critical tasks and eventually extend the duration of missions.

Purpose: To test the hypothesis that an integrated resistance and aerobic exercise prescription performed with exercise equipment similar to that on the ISS can be tolerated and maintain cardiovascular and muscular fitness during 14 d of exposure to a model of microgravity.

Methods: Subjects (n = 9) participated in 14-21 d of pre-bed rest training and familiarization, 14 d of bed rest + iRAT exercise, and 7 d of ambulatory recovery.

Influence of muscle strength to weight ratio on functional task performance.

Existing models of muscle deconditioning such as bed rest are expensive and time-consuming. We propose a new model utilizing a weighted suit to manipulate muscle strength, power, or endurance relative to body weight. The aims of the study were to determine as to which muscle measures best predict functional task performance and to determine muscle performance thresholds below which task performance is impaired.

Reliability and validity of panoramic ultrasound for muscle quantification.

This study examined the reliability and validity of using customized templates to acquire panoramic ultrasound (US) images for determining cross-sectional area (CSA) and volume in the vastus lateralis (VL), rectus femoris (RF), medial gastrocnemius (MG) and lateral gastrocnemius (LG). Panoramic US and magnetic resonance imaging (MRI) images were analyzed by two trained investigators. The inter-experimenter reliability (coefficient of variation [CV]) of panoramic US ranged from 2.

Test battery designed to quickly and safely assess diverse indices of neuromuscular function after unweighting.

Adequately describing the functional consequences of unweighting (e.g., bed rest, immobilization, spaceflight) requires assessing diverse indices of neuromuscular function (i.