Musculoskeletal adaptations to weightlessness and development of effective countermeasures

Abstract

A Research Roundtable, organized by the American College of Sports Medicine with sponsorship from the National Aeronautics and Space Administration, met in November 1995 to define research strategies for effective exercise countermeasures to weightlessness. Exercise was considered both independently of, and in conjunction with, other therapeutic modalities (e.g., pharmacological nutritional, hormonal, and growth-related factors) that could prevent or minimize the structural and functional deficits involving skeletal muscle and bone in response to chronic exposure to weightlessness, as well as return to Earth baseline function if a degree of loss is inevitable. Musculoskeletal deficits and countermeasures are described with respect to: 1) muscle and connective tissue atrophy and localized bone loss, 2) reductions in motor performance, 3) potential proneness to injury of hard and soft tissues, and 4) probable interaction between muscle atrophy and cardiovascular alterations that contribute to the postural hypotension observed immediately upon return from space flight. In spite of a variety of countermeasure protocols utilized previously involving largely endurance types of exercise, there is presently no activity-specific countermeasure(s) that adequately prevent or reduce musculoskeletal deficiencies. It seems apparent that countermeasure exercises that have a greater resistance element, as compared to endurance activities, may prove beneficial to the musculoskeletal system. Many questions remain for scientific investigation to identify efficacious countermeasure protocols, which will be imperative with the emerging era of long-term space flight.

Mechanical Stimulation Modifies Canopy Architecture and Improves Volume Utilization Efficiency in Bell Pepper: Implications for Bioregenerative Life-support and Vertical Farming

“…Humans require significant countermeasure interventions to reduce the negative impacts of microgravity on bone and muscle tissue (Baldwin et al 1996); it stands to reason that crop plants making up part of a bioregenerative life-support system may also benefit from microgravity countermeasures. In the absence of a significant gravity vector plant cell walls and, by elaboration, supporting tissues (e.g., branches supporting fruit) can be modified, although consensus on the degree and direction of the modifications is elusive (de Micco et al 2008, Ferl et al 2002, Hoson 2014, Levine et al 2001, Matía et al 2010, Ruyters & Braun 2013.…”

Molecular pathways mediating mechanical signaling in bone

“…One of the most striking effects of long-duration human exposure to space is a dramatic loss of bone tissue (Baldwin et al, 1996;Carmeliet et al, 2001), reaching as much as a 2% bone density loss in the hip per month, while the upper extremities, which experience less dramatic changes in loading input, show negligible changes (Lang et al, 2004). Disuse, such as occurs in paralysis or prolonged bed rest, also can lead to a rapid loss of bone, with rates of loss approaching that realized during long-duration spaceflight (Gross and Rubin, 1995).…”

Applied horizontal force increases impact loading in reduced-gravity running

“…Chronic exposure to microgravity degrades the structural integrity of the lower extremity bones (for reviews see Baldwin et al, 1996;Vernikos, 1996). This could have catastrophic consequences during mission operations requiring even modest amounts of strength, during emergency escape procedures, and can also increase the risk of fracture after returning to Earth (Baldwin et al, 1996).…”