Metabolic Cost of a Proposed NMES Spaceflight Countermeasure Compared to Walking in Active Adults.

Astronauts exercise to reduce microgravity-induced bone loss, but the resultant skeletal loading may not be sufficient to reduce fracture risk on an extended Mars mission. Adding additional exercise increases the risk of a negative caloric balance. Neuromuscular electrical stimulation (NMES) induces involuntary muscle contractions, which load the skeleton.

Potential of Neuromuscular Electrical Stimulation as a Bone Loss Countermeasure in Microgravity.

For future long-duration spaceflight missions, additional methods of loading the skeleton may be required to supplement exercise to minimize bone loss. Neuromuscular electrical stimulation (NMES) can elicit muscular contractions that create strain on bone. However, the potential effectiveness of NMES on the proximal femur during disuse is not known.

Longitudinal Impacts of Simulated Long-Duration Spaceflight Missions on Operationally Relevant Measures of Human Performance Using a Portable Simulation Platform.

Objective: This project quantifies operationally relevant measures of flight performance and workload in a high-fidelity long-duration spaceflight analog, longitudinally across mission duration, using a portable simulation platform.

Background: Real-time performance measures allow for the objective assessment of task performance and the timely identification of performance degradations.

Methods: Measures of flight performance on a piloted lunar lander task were collected on 32 total crewmembers across 8 simulated space missions of 45 days each (623 total sessions).

Effect of Athletic Training on Fatigue During Neuromuscular Electrical Stimulation.

The purpose of this study was to explore the effect an individual's exercise training type will have on muscle fatigability during repetitive contractions induced by Neuromuscular Electrical Stimulation (NMES). Thirty-four subjects comprising of competitive athletes and controls were recruited into three cohorts: Endurance (runners/cyclists) = 13; nine male, four female; 27 ± 8 years old, Explosive (Lifters/Sprinters) = 11; nine male, two female; 30 ± 7 years old, and controls = 10, six male, four female, 26 ± 4 years old. Subjects were placed in a custom-made leg extension rig, and received NMES against a fixed resistance (NMES-FR), to the Vastus Medialis muscle resulting in isometric leg extensions, at a duty cycle of 1 s on/3 s rest, for 20 min.

A Closed-Loop Model of Operator Visual Attention, Situation Awareness, and Performance Across Automation Mode Transitions.

Objective: This article describes a closed-loop, integrated human-vehicle model designed to help understand the underlying cognitive processes that influenced changes in subject visual attention, mental workload, and situation awareness across control mode transitions in a simulated human-in-the-loop lunar landing experiment.

Background: Control mode transitions from autopilot to manual flight may cause total attentional demands to exceed operator capacity. Attentional resources must be reallocated and reprioritized, which can increase the average uncertainty in the operator's estimates of low-priority system states.

The Variable Vector Countermeasure Suit (V2Suit) for space habitation and exploration.

The "Variable Vector Countermeasure Suit (V2Suit) for Space Habitation and Exploration" is a novel system concept that provides a platform for integrating sensors and actuators with daily astronaut intravehicular activities to improve health and performance, while reducing the mass and volume of the physiologic adaptation countermeasure systems, as well as the required exercise time during long-duration space exploration missions. The V2Suit system leverages wearable kinematic monitoring technology and uses inertial measurement units (IMUs) and control moment gyroscopes (CMGs) within miniaturized modules placed on body segments to provide a "viscous resistance" during movements against a specified direction of "down"-initially as a countermeasure to the sensorimotor adaptation performance decrements that manifest themselves while living and working in microgravity and during gravitational transitions during long-duration spaceflight, including post-flight recovery and rehabilitation. Several aspects of the V2Suit system concept were explored and simulated prior to developing a brassboard prototype for technology demonstration.

Squat exercise biomechanics during short-radius centrifugation.

Introduction: Centrifuge-induced artificial gravity (AG) with exercise is a promising comprehensive countermeasure against the physiological de-conditioning that results from exposure to weightlessness. However, body movements onboard a rotating centrifuge are affected by both the gravity gradient and Coriolis accelerations. The effect of centrifugation on squat exercise biomechanics was investigated, and differences between AG and upright squat biomechanics were quantified.

Motion sickness: a cholinomimetic agent hypothesis.

Motion sickness has been defined as a set of physiological signs and symptoms produced as a result of prolonged sensory conflict in central nervous system vestibular centers. It has long been noted that the particular pattern of motion sickness signs and symptoms does not fit the conventional "fight or flight vs. rest and digest" autonomic synergy.