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Alterations in step frequency and muscle activities using body weight support influence the ventilatory response to sinusoidal walking in humans.

ABSTRACT: The use of body weight support (BWS) can reveal important insights into the relationship between lower-limb muscle activities and the ventilatory response during sinusoidal walking. Here, healthy participants (n = 15) walked on a treadmill while 0%, 30%, and 50% of their body weight was supported with BWS. The walking speed was varied sinusoidally between 3 and 6 km h^-1, and three different frequencies, and periods ranging from 2 to 10 min were used. Breath-by-breath ventilation ([Formula: see text]) and CO₂ output ([Formula: see text]) were measured. The tibialis anterior (TA) muscle activity was measured by electromyography throughout the walking. The amplitude (Amp), normalized Amp [Amp ratio (%)], and phase shift (PS) of the sinusoidal variations in measurement variables were calculated using a Fourier analysis. The results revealed that the Amp ratio in [Formula: see text] increased with the increase in BWS. A steeper slope of the [Formula: see text]-[Formula: see text] relationship and greater [Formula: see text]/[Formula: see text] values were observed under reduced body weight conditions. The Amp ratio in TA muscle was significantly positively associated with the Amp ratio in the [Formula: see text] (p < 0.001). These findings indicate that the greater amplitude in the TA muscle under BWS may have been a potent stimulus for the greater response of ventilation during sinusoidal walking.

SUBMITTER: Fujita M

PROVIDER: S-EPMC10509255 | biostudies-literature | 2023 Sep

REPOSITORIES: biostudies-literature

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Alterations in step frequency and muscle activities using body weight support influence the ventilatory response to sinusoidal walking in humans.

Fujita Mako M Kamibayashi Kiyotaka K Horiuchi Masahiro M Ebine Naoyuki N Fukuoka Yoshiyuki Y

Scientific reports 20230919 1

The use of body weight support (BWS) can reveal important insights into the relationship between lower-limb muscle activities and the ventilatory response during sinusoidal walking. Here, healthy participants (n = 15) walked on a treadmill while 0%, 30%, and 50% of their body weight was supported with BWS. The walking speed was varied sinusoidally between 3 and 6 km h<sup>-1</sup>, and three different frequencies, and periods ranging from 2 to 10 min were used. Breath-by-breath ventilation ([For ...[more]

PMID: 37726511

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Project description:It is widely accepted that humans and animals minimize energetic cost while walking. While such principles predict average behavior, they do not explain the variability observed in walking. For robust performance, walking movements must adapt at each step, not just on average. Here, we propose an analytical framework that reconciles issues of optimality, redundancy, and stochasticity. For human treadmill walking, we defined a goal function to formulate a precise mathematical definition of one possible control strategy: maintain constant speed at each stride. We recorded stride times and stride lengths from healthy subjects walking at five speeds. The specified goal function yielded a decomposition of stride-to-stride variations into new gait variables explicitly related to achieving the hypothesized strategy. Subjects exhibited greatly decreased variability for goal-relevant gait fluctuations directly related to achieving this strategy, but far greater variability for goal-irrelevant fluctuations. More importantly, humans immediately corrected goal-relevant deviations at each successive stride, while allowing goal-irrelevant deviations to persist across multiple strides. To demonstrate that this was not the only strategy people could have used to successfully accomplish the task, we created three surrogate data sets. Each tested a specific alternative hypothesis that subjects used a different strategy that made no reference to the hypothesized goal function. Humans did not adopt any of these viable alternative strategies. Finally, we developed a sequence of stochastic control models of stride-to-stride variability for walking, based on the Minimum Intervention Principle. We demonstrate that healthy humans are not precisely "optimal," but instead consistently slightly over-correct small deviations in walking speed at each stride. Our results reveal a new governing principle for regulating stride-to-stride fluctuations in human walking that acts independently of, but in parallel with, minimizing energetic cost. Thus, humans exploit task redundancies to achieve robust control while minimizing effort and allowing potentially beneficial motor variability.

Dataset Information

Alterations in step frequency and muscle activities using body weight support influence the ventilatory response to sinusoidal walking in humans.

Publications

Alterations in step frequency and muscle activities using body weight support influence the ventilatory response to sinusoidal walking in humans.

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