Muscle Tuning During Running

NewsBot · Dec 14, 2006

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Muscle Tuning During Running: Implications of an Un-tuned Landing.
J Biomech Eng. 2006 Dec;128(6):815-22
Boyer KA, Nigg BM

Background: The impact force in heel-toe running is an input signal into the body that initiates vibrations of the soft tissue compartments of the leg. These vibrations are heavily damped and the paradigm of muscle tuning suggests the body adapts to different input signals to minimize these vibrations. The objectives of the present study were to investigate the implications of not tuning a muscle properly for a landing with a frequency close to the resonance frequency of a soft tissue compartment and to look at the effect of an unexpected surface change on the subsequent step of running.

Method: Thirteen male runners were recruited and performed heel-toe running over two surface conditions. The peak accelerations and biodynamic responses of the soft tissue compartments of the leg along with the EMG activity of related muscles were determined for expected soft, unexpected hard and expected hard landings.

Results and Conclusions: For the unexpected hard landing there was a change in the input frequency of the impact force, shifting it closer to the resonance frequency of the soft tissue compartments. For the unexpected landing there was no muscle adaptation, as subjects did not know the running surface was going to change. In support of the muscle-tuning concept an increase in the soft tissue acceleration did occur. This increase was greater when the proximity of the input signal frequency was closer to the resonance frequency of the soft tissue compartment. Following the unexpected change in the input signal a change in pre-contact muscle activity to minimize soft tissue compartment vibrations was not found. This suggests if muscle tuning does occur it is not a continuous feedback response that occurs with every small change in the landing surface properties. In previous studies with significant adaptation periods to new input signals significant correlations between the changes in the input signal frequency and the EMG intensity have been shown, however, changes in soft tissue accelerations have not been found. The results of the present study showed that changes in these soft tissue accelerations can occur in response to a resonance frequency input signal when a muscle reaction has not happened
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NewsBot · Jan 6, 2019

Modeling the central nervous system functionality in controlling the calf muscle activity during running with sport shoes
Peyman Jalali, Mohammad-Reza Sayyed Noorani, Reza Hassannejad, ...
Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine January 1, 2019

Biological findings show that the activity of the calf muscle group is controlled by the central nervous system during running. The central nervous system tries to retain the peak values of the ground reaction force at constant levels as well as to minimize the vibration amplitude of soft tissues of the lower leg. Furthermore, these objectives are functions of stiffness and damping (compliance properties) of the calf muscle-tendon unit, especially gastrocnemius-Achilles. In this article, a new model for the calf muscle-tendon unit activity is presented in which the coefficients of stiffness and damping are exponential functions of the force produced at the Achilles tendon in the duration of stance phase, that is, they are time variant instead of having constant values. Then, the central nervous system functionality to control the activity of the muscle-tendon unit is formulated through definition of an optimization problem. This problem is solved by additionally considering the hardness of sport shoes. The muscle activity is indeed controlled via optimally adjusting two tuning parameters of the muscle-tendon unit model in terms of the hardness of shoes. This idea is examined separately for two running speeds. The results show the following: (1) The hardness of shoes affects the muscle activity. We find safe areas of the hardness parameters to design sport shoes. (2) When hard shoes are worn, the running speed has negligible effects on the tuning parameters, while with soft shoes the tuning parameters significantly change the muscle activity and the ground reaction force depended on running speed. (3) The ability of muscle in changing its compliance properties (specified by bound limits over the muscle-tendon unit tuning parameters) has the most influence in the safe area. (4) Rising running speed leads to a decrease in the safe area of shoes’ parameters.
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NewsBot · Aug 18, 2021

Soft-tissue vibration and damping response to footwear changes across a wide range of anthropometrics in running
Anja-Verena Behling ,Marlene Giandolini,Vinzenz von Tscharner,Benno Maurus Nigg
PLOSOne: August 17, 2021

Different factors were shown to alter the vibration characteristics of soft-tissue compartments during running. Changing pre-heel strike muscle activation or changing footwear conditions represents two possibilities to influence the vibration response via frequency shift or altered damping. Associated with the study of muscle pre-tuning is the difficulty in quantifying clean experimental data for the acceleration of soft-tissue compartments and muscle activities in heterogeneous populations. The purpose of this study was to determine the vibration and pre-tuning response to footwear across a wide range of participants during running and establish and describe groups formed according to the damping coefficient. 32 subjects were used for further analysis. The subjects ran at a self-selected speed (5 min) on a treadmill in two different shoes (soft & hard), while soft-tissue accelerations and muscle activation at the gastrocnemius medialis were quantified. Damping coefficients, total muscle intensity and dominant vibration frequencies were determined. Anthropometrics and skinfold measurements of the lower limbs were obtained. According to the damping coefficient response to the footwear intervention, three groups were formed, with most runners (n = 20) showing less damping in the hard shoe. Total muscle intensity, anthropometrics, and dominant vibration frequency across footwear were not different for these three groups. Most runners (84.4%) used the strategy of adjusting the damping coefficients significantly when switching footwear. Despite damping being the preferred adjustment to changes in footwear, muscle pre-tuning might not be the only mechanism to influence damping as previously suggested. Future studies should focus on the subject-specific composition of soft-tissue compartments to elucidate their contribution to vibrations.
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