Stumbling reactions in hypo and hyper gravity – muscle synergies are robust across different perturbations of human stance during parabolic flights

Abstract

The control of bipedal stance and the capacity to regain postural equilibrium after its deterioration in variable gravities are crucial prerequisites for manned space missions. With an emphasize on natural orthograde posture, computational techniques synthesize muscle activation patterns of high complexity to a simple synergy organization. We used nonnegative matrix factorization to identify muscle synergies during postural recovery responses in human and to examine the functional significance of such synergies for hyper-gravity (1.75 g) and hypo-gravity (0.25 g). Electromyographic data were recorded from leg, trunk and arm muscles of five human exposed to five modes of anterior and posterior support surface translations during parabolic flights including transitional g-levels of 0.25, 1 and 1.75 g. Results showed that in 1 g four synergies accounted for 99% of the automatic postural response across all muscles and perturbation directions. Each synergy in 1 g was correlated to the corresponding one in 0.25 and 1.75 g. This study therefore emphasizes the similarity of the synergy organization of postural recovery responses in Earth, hypo- and hyper-gravity conditions, indicating that the muscle synergies and segmental strategies acquired under terrestrial habits are robust and persistent across variable and acute changes in gravity levels.

Muscle activation patterns are more constrained and regular in treadmill than in overground human locomotion

“…mechanical) or internal (e.g. aging or pathology) perturbations to locomotion, the number of synergies is not affected in both mice (Santuz et al, 2019) and humans (Maclellan et al, 2014; Santuz et al, 2018b, 2020a; Holubarsch et al, 2019; Janshen et al, 2020). Several studies have attempted in the past to highlight potential discrepancies between overground and treadmill locomotion from many perspectives concluding that spatiotemporal, kinematic, kinetic, and muscle-tendon interaction measures are scarcely influenced by the locomotion environment (Van Hooren et al, 2019).…”

Muscle Activation Patterns Are More Constrained and Regular in Treadmill Than in Overground Human Locomotion

“…2014; Santuz et al, 2018aSantuz et al, , 2020aHolubarsch et al, 2019;Janshen et al, 2020). Several studies have attempted in the past to highlight potential discrepancies between overground and treadmill locomotion from many perspectives concluding that spatiotemporal, kinematic, kinetic, and muscle-tendon interaction measures are scarcely influenced by the locomotion environment (Van Hooren et al, 2019).…”

Guest Edited Collection: Gravitational biology and space medicine

“…Investigations of the human stance during PF maneuvers compared to 1 g- conditions revealed the similarity of postural recovery responses in 1 g -, hypo- and hyper-gravity conditions 17 . These results showed that muscle synergies and segmental strategies acquired on Earth are robust and persistent across variable acute changes in gravitation 17 .…”

“…The Guest Edited Collection ‘ Gravitational biology and space medicine ’ includes publications reporting on health concerns for astronauts and cosmonauts 14–16 during space missions, and physiological changes caused by short-term µ g 17 . Several studies investigating the impact of µ g on the behaviour and health of mice on the ISS were published in this Collection 18–23 , in addition to investigations at the cellular level in space 24 and in short-term µ g provided by PF maneuvers 25 .…”