Motor control of landing from a countermovement jump in simulated microgravity

2016 ◽  
Vol 120 (10) ◽  
pp. 1230-1240 ◽  
Author(s):  
C. N. Gambelli ◽  
D. Theisen ◽  
P. A. Willems ◽  
B. Schepens
Keyword(s):  
Motor Control ◽  
Lower Limb ◽  
Muscular Activity ◽  
Damping Coefficient ◽  
Gravity Level ◽  
Countermovement Jump ◽  
Lower Limb Muscles ◽  
Limb Muscles ◽  
Stiffness And Damping Coefficient ◽  
Stiffness And Damping

Landing from a jump implies proper positioning of the lower limb segments and the generation of an adequate muscular force to cope with the imminent collision with the ground. This study assesses how a hypogravitational environment affects the control of landing after a countermovement jump (CMJ). Eight participants performed submaximal CMJs on Earth (1- g condition) and in a weightlessness environment with simulated gravity conditions generated by a pull-down force (1-, 0.6-, 0.4-, and 0.2- g0 conditions). External forces applied to the body, movements of the lower limb segments, and muscular activity of six lower limb muscles were recorded. 1) All subjects were able to jump and stabilize their landing in all experimental conditions, except one subject in 0.2- g0 condition. 2) The mechanical behavior of lower limb muscles switches during landing from a stiff spring to a compliant spring associated with a damper. This is true whatever the environment, on Earth as well as in environments where sensory inputs are altered. 3) The motor control of landing in simulated 1 g0 reveals an increased “safety margin” strategy, illustrated by increased stiffness and damping coefficient compared with landing on Earth. 4) The motor command is adjusted to the task constraints: muscular activity of lower limb extensors and flexors, stiffness and damping coefficient decrease according to the decreased gravity level. Our results show that even if in daily living gravity can be perceived as a constant factor, subjects can cope with altered sensory signals, taking advantage of the remaining information (visual and/or decreased proprioceptive inputs).

scholarly journals Exoskeleton for Gait Rehabilitation: Effects of Assistance, Mechanical Structure, and Walking Aids on Muscle Activations

2019 ◽  
Vol 9 (14) ◽  
pp. 2868 ◽  
Author(s):  
Alice De Luca ◽  
Amy Bellitto ◽  
Sergio Mandraccia ◽  
Giorgia Marchesi ◽  
Laura Pellegrino ◽  
...  
Keyword(s):  
Lower Limb ◽  
Statistical Parametric Mapping ◽  
Muscular Activity ◽  
Gait Training ◽  
Motor Deficits ◽  
Gait Rehabilitation ◽  
Mechanical Structure ◽  
Lower Limb Muscles ◽  
Limb Muscles ◽  
Muscle Activations

Several exoskeletons have been developed and increasingly used in clinical settings for training and assisting locomotion. These devices allow people with severe motor deficits to regain mobility and sustain intense and repetitive gait training. However, three factors might affect normal muscle activations during walking: the assistive forces that are provided during walking, the crutches or walker that are always used in combination with the device, and the mechanical structure of the device itself. To investigate these effects, we evaluated eight healthy volunteers walking with the Ekso, which is a battery-powered, wearable exoskeleton. They walked supported by either crutches or a walker under five different assistance modalities: bilateral maximum assistance, no assistance, bilateral adaptive assistance, and unilateral adaptive assistance on each leg. Participants also walked overground without the exoskeleton. Surface electromyography was recorded bilaterally, and the statistical parametric mapping approach and muscle synergies analysis were used to investigate differences in muscular activity across different walking conditions. The lower limb muscle activations while walking with the Ekso were not influenced by the use of crutches or walker aids. Compared to normal walking without robotic assistance, the Ekso reduced the amplitude of activation for the distal lower limb muscles while changing the timing for the others. This depended mainly on the structure of the device, and not on the type or level of assistance. In fact, the presence of assistance did not change the timing of the muscle activations, but instead mainly had the effect of increasing the level of activation of the proximal lower limb muscles. Surprisingly, we found no significant changes in the adaptive control with respect to a maximal fixed assistance that did not account for subjects’ performance. These are important effects to take into careful considerations in clinics where these devices are used for gait rehabilitation in people with neurological diseases.

Human motor control of landing from a drop in simulated microgravity

2016 ◽  
Vol 121 (3) ◽  
pp. 760-770 ◽  
Author(s):  
C. N. Gambelli ◽  
D. Theisen ◽  
P. A. Willems ◽  
B. Schepens
Keyword(s):  
Motor Control ◽  
Lower Limb ◽  
Sensory Information ◽  
Muscular Activity ◽  
The Body ◽  
Experimental Conditions ◽  
Human Motor Control ◽  
Lower Limb Muscles ◽  
Human Motor ◽  
Drop Landings

Landing on the ground on one's feet implies that the energy gained during the fall be dissipated. The aim of this study is to assess human motor control of landing in different conditions of fall initiation, simulated gravity, and sensory neural input. Six participants performed drop landings using a trapdoor system and landings from self-initiated counter-movement jumps in microgravity conditions simulated in a weightlessness environment by different pull-down forces of 1-, 0.6-, 0.4-, and 0.2 g. External forces applied to the body, orientation of the lower limb segments, and muscular activity of 6 lower limb muscles were recorded synchronously. Our results show that 1) subjects are able to land and stabilize in all experimental conditions; 2) prelanding muscular activity is always present, emphasizing the capacity of the central nervous system to approximate the instant of touchdown; 3) the kinetics and muscular activity are adjusted to the amount of energy gained during the fall; 4) the control of landing seems less finely controlled in drop landings as suggested by higher impact forces and loading rates, plus lower mechanical work done during landing for a given amount of energy to be dissipated. In conclusion, humans seem able to adapt the control of landing according to the amount of energy to be dissipated in an environment where sensory information is altered, even under conditions of non-self-initiated falls.

scholarly journals Neuromechanics of Dynamic Balance Tasks in the Presence of Perturbations

2021 ◽  
Vol 14 ◽  
Author(s):  
Victor Munoz-Martel ◽  
Alessandro Santuz ◽  
Sebastian Bohm ◽  
Adamantios Arampatzis
Keyword(s):  
Motor Control ◽  
Mechanical Loading ◽  
Lower Limb ◽  
The Body ◽  
Muscle Synergy ◽  
Emg Activity ◽  
Modular Organization ◽  
Joint Moments ◽  
Lower Limb Muscles ◽  
Limb Muscles

Understanding the neuromechanical responses to perturbations in humans may help to explain the reported improvements in stability performance and muscle strength after perturbation-based training. In this study, we investigated the effects of perturbations, induced by unstable surfaces, on the mechanical loading and the modular organization of motor control in the lower limb muscles during lunging forward and backward. Fifteen healthy adults performed 50 forward and 50 backward lunges on stable and unstable ground. Ground reaction forces, joint kinematics, and the electromyogram (EMG) of 13 lower limb muscles were recorded. We calculated the resultant joint moments and extracted muscle synergies from the stepping limb. We found sparse alterations in the resultant joint moments and EMG activity, indicating a little if any effect of perturbations on muscle mechanical loading. The time-dependent structure of the muscle synergy responsible for the stabilization of the body was modified in the perturbed lunges by a shift in the center of activity (later in the forward and earlier in the backward lunge) and a widening (in the backward lunge). Moreover, in the perturbed backward lunge, the synergy related to the body weight acceptance was not present. The found modulation of the modular organization of motor control in the unstable condition and related minor alteration in joint kinetics indicates increased control robustness that allowed the participants to maintain functionality in postural challenging settings. Triggering specific modulations in motor control to regulate robustness in the presence of perturbations may be associated with the reported benefits of perturbation-based training.

scholarly journals Muscular activity of lower limb muscles associated with working on inclined surfaces

Ergonomics ◽  
2014 ◽  
Vol 58 (2) ◽  
pp. 278-290 ◽  
Author(s):  
Ming-Lun Lu ◽  
Laurel Kincl ◽  
Brian Lowe ◽  
Paul Succop ◽  
Amit Bhattacharya
Keyword(s):  
Lower Limb ◽  
Muscular Activity ◽  
Lower Limb Muscles ◽  
Inclined Surfaces ◽  
Limb Muscles

scholarly journals Vibration Attenuation Via Mean of Lower Limb Muscles Occurs During Whole Body Vibrations And Differs Across Frequencies And Postures

2021 ◽  
Author(s):  
Isotta Rigoni ◽  
Tecla Bonci ◽  
Paolo Bifulco ◽  
Antonio Fratini
Keyword(s):  
Muscle Contraction ◽  
Lower Limb ◽  
Soft Tissues ◽  
Muscular Activity ◽  
Whole Body ◽  
Tonic Vibration Reflex ◽  
Leg Muscles ◽  
Lower Limb Muscles ◽  
Limb Muscles ◽  
Whole Body Vibrations

Abstract Lower limb muscles actively contribute to maintain body posture but also act to attenuate soft tissues oscillations that occur during everyday life. This elicited activity can be exploited as a mean of neuromuscular training or rehabilitation. In this study, Whole Body Vibrations (WBV) at different frequencies were delivered to healthy subjects while holding static postures to test the transient muscles mechanical responses. Twenty-five participants underwent WBV at 15, 20, 25 and 30 Hz while holding either a static ‘hack squat’ or ‘fore feet’ posture. Soft tissue accelerations and surface electromyography (sEMG) were recorded from Gastrocnemius Lateralis (GL), Soleus (SOL) and Tibialis Anterior (TA) muscles. Estimated displacement at muscle bellies revealed a resonant pattern, different across frequencies and postures (p<.001). Specifically, a peak in the displacement was measured after the onset of the stimulation, followed by a drop and a further plateau (only after few seconds after the peak) suggesting a delayed neuromuscular activation. Although oscillation dampening was correlated to an increased muscular activity, only specific WBV settings were promoting a significant muscle contraction. For example, SOL and GL induced activation was maximal for subject in forefeet and while exposed to higher frequencies (p<.05). The non-immediate response of leg muscles to a vibratory stimulation confirms the tonic nature of the vibration induced muscle contraction (the tonic vibration reflex) and its strong influence on postural tonic muscles (GL and SOL). This may have significant impact on training or rehabilitation protocols aiming towards postural and balance improvement or recovery.

Measurement and reproducibility of strength and voluntary activation of lower-limb muscles

2004 ◽  
Vol 29 (6) ◽  
pp. 834-842 ◽  
Author(s):  
Gabrielle Todd ◽  
Robert B. Gorman ◽  
Simon C. Gandevia
Keyword(s):  
Lower Limb ◽  
Voluntary Activation ◽  
Lower Limb Muscles ◽  
Limb Muscles
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