Gender Comparisons of Mechanomyographic Amplitude and Mean Power Frequency versus Isometric Torque Relationships

A Pilot Study on Developed Shoes That Enhance Gait Parameters Without Increasing Muscle Activity

This pilot study investigated the potential of a newly developed shoe design to improve gait parameters without altering muscle activity in healthy women. The shoe design features a V-shaped heel and a high-elasticity midsole, which are intended to enhance stability during heel contact and promote efficient load transfer throughout the gait cycle. Ten study participants underwent a randomized crossover design, wearing developed and general shoes during the trials. Spatiotemporal gait data and muscle activity were measured to assess the impact of the shoe design developed on gait efficiency. Significant improvements in gait speed, step and stride length, and swing time were observed with the developed shoes, indicating improved gait efficiency. Importantly, these improvements were achieved without significant changes in muscle activity, suggesting that the developed shoe design improves gait efficiency without increasing muscle workload. Considering the limitations of the small sample size and the exploratory nature of this pilot study, further research with a larger cohort is necessary to validate these preliminary findings. Trial Registration: Clinical Trial Registry identifier: UMIN000054260.

Differences in Electromyographic Activities and Spatiotemporal Gait Parameters between General and Developed Insoles with a Toe-Grip Bar

The present study was aimed at comparing the muscle activities and gait parameters between the toe-grip bar insoles and general insoles during walking using randomized crossover design. Twelve healthy men participated in this study. Temporal and spatial gait parameters and electromyography (EMG) results were concurrently collected while the subjects walked along an 8 m walkway with the developed and general insoles. Developed insoles provide a three-dimensional mesh structure at the toe portion and a convex bulging structure (toe-grip bar) near the center of the proximal phalanx of the first to fifth toe. The linear mixed model was used to estimate the toe-grip bar insole effect. The results showed that there were no sequence or period effects for any of the examined parameters. During the stance phase, those wearing the developed insoles had significantly higher %IEMG for the TA, GM, and GL than those wearing the general insoles (TA: 5.03%IEMG, p = 0.005; GM: 4.65%IEMG, p = 0.046; and GL: 6.50%IEMG, p = 0.008). During the swing phase, those wearing the developed insoles had significantly higher activity for only the TA compared to those wearing the general insoles (5.54%IEMG, p = 0.011). With respect to gait parameters, those wearing the developed insoles had greater step length (2.81 cm, p = 0.038), longer stance time (0.03 s, p = 0.001), and shorter swing time (−0.02 s, p = 0.003) compared to those wearing the general insoles. The results suggest that walking with toe-grip bar insoles contributes to increased crural muscle activity and step length.

INFLUENCE OF AN ACUTE BOUT OF SELF-MYOFASCIAL RELEASE ON KNEE EXTENSION FORCE OUTPUT AND ELECTRO-MECHANICAL ACTIVATION OF THE QUADRICEPS

Background

In contrast to static stretching (SS), previous research has demonstrated increases in flexibility after an acute bout of self-myofascial release (SMR) without any subsequent decreases in force output. Previous research has utilized measures of surface electromyography (sEMG) and mechanomyography (MMG) to examine the influence of SS on the electrical and mechanical processes of muscle activation, respectively. However, there is a lack of research examining the potential changes in electro-mechanical muscle activation post-SMR.

Purpose

To examine the influence of SMR, via an acute bout of foam rolling (FR) to the vastus lateralis (VL), on the expression of knee extension force output and the inter-muscular electro-mechanical activation of the quadriceps musculature.

Study Design

Randomized crossover trial.

Methods

Twenty (10 males, 10 females) recreationally-active participants with prior FR experience completed both SMR and control (CON) testing protocols during separate testing sessions that were conducted in a randomized order 48 hours apart. During the SMR protocol, participants performed 3 sets of 60 seconds of FR over the VL portion of their quadriceps musculature, with 60 seconds of rest between sets. During the CON protocol, participants quietly sat upright for 10 minutes. Peak knee extension force output -(Force_peak) data, as well as sEMG and MMG data from the VL and the rectus femoris (RF) were collected during maximal voluntary isometric contractions (MVICs) before and after both testing protocols. Root mean square sEMG and MMG amplitudes were calculated to represent electro-mechanical muscle activation of the VL (VL-sEMG_RMS, VL-MMG_RMS) and RF (RF-sEMG_RMS, RF-MMG_RMS) musculature.

Results

Repeated measures analyses of variance (RM ANOVAs) identified a significant (p < 0.05) increase in Force_peak within the SMR protocol among males, but no change among females. No statistically significant changes in any electro-mechanical muscle activation measures were identified pre-to-post-SMR within either sex.

Conclusion

In contrast to the SS literature body, these results suggest that SMR does not influence the electro-mechanical aspects of muscle activation during MVICs. These results provide support for the absence of decreases in force output post-SMR, but further examination regarding the potential muscle mass influence of SMR on electro-mechanical muscle function remains warranted.

Level of Evidence

2c.

The effect of wearing insoles with a toe-grip bar on occupational leg swelling and lower limb muscle activity: A randomized cross-over study

OBJECTIVE

Sitting or standing for hours decreases the blood flow in the legs and results in increased pressure on the veins, leading to the development of chronic venous disease. This study aimed to investigate the effects of insoles with a toe-grip bar on occupational leg swelling and lower limb muscle activity.

METHODS

This randomized cross-over study enrolled 12 healthy men who work in a sitting or standing position. They were randomly divided into groups A (wore shoes with insoles with a toe-grip bar for 8 hours each) and B (wore shoes with regular insoles for 8 hours each). After 1 week, groups A and B wore shoes with regular insoles and shoes with insoles with a toe-grip bar, respectively, for 8 hours each. Lower leg volume was measured before and after each intervention, and lower limb muscle activity was measured at the start of each intervention.

RESULTS

Occupational leg swelling was significantly smaller in men wearing insoles with a toe-grip bar (P < .05). Moreover, the integrated electromyogram value of the tibialis anterior muscle and medial and lateral gastrocnemius muscles during the stance phase of walking, and tibialis anterior muscle during the swing phase of walking was significantly greater in men wearing insoles with a toe-grip bar (all P < .05).

CONCLUSION

Insoles with a toe-grip bar contribute to increased lower limb muscle activity, attenuating occupational leg swelling.

Mechanomyographic responses during recruitment curves in the soleus muscle

INTRODUCTION

In this study we examined relationships among mechanomyographic (MMG), electromyographic (EMG), and peak twitch torque (PTT) responses as well as test-retest reliability when recorded during recruitment curves in the soleus muscle.

METHODS

PTT, EMG (M-wave, H-reflex), and MMG responses were recorded during recruitment curves in 16 subjects (age 24 ± 2 years) on 2 separate days. The sum of the M-wave and H-reflex (M+H) was calculated. Correlations among variables and test-retest reliability were determined.

RESULTS

MMG was correlated with PTT (mean r = 0.93, range r = 0.59-0.99), the M-wave (0.95, 0.04-0.98), and M+H (0.91, 0.42-0.97), but was unrelated to the H-reflex (-0.06, -0.56 to 0.47). Reliability was consistently high among most variables, but normalizing to the maximum value improved MMG reliability and the minimum detectable change.

CONCLUSION

MMG responses predicted 86%-90% of the variability in PTT, M-wave, and M+H; thus, MMG may be a useful alternative for estimating twitch torque and maximal activation. Muscle Nerve 56: 107-116, 2017.

Spectral properties of electromyographic and mechanomyographic signals during isometric ramp and step contractions in biceps brachii

The purposes of this study were: (1) to apply wavelet and principal component analysis to quantify the spectral properties of the surface EMG and MMG signals from biceps brachii during isometric ramp and step muscle contractions when the motor units are recruited in an orderly manner, and (2) to compare the recruitment patterns of motor unit during isometric ramp and step muscle contractions. Twenty healthy participants (age = 34 ± 10.7 years) performed step and ramped isometric contractions. Surface EMG and MMG were recorded from biceps brachii. The EMGs and MMGs were decomposed into their intensities in time-frequency space using a wavelet technique. The EMG and MMG spectra were then compared using principal component analysis (PCA) and ANCOVA. Wavelet combined PCA offers a quantitative measure of the contribution of high and low frequency content within the EMG and MMG. The ANCOVA indicated that there was no significant difference in EMG total intensity, EMG(MPF), first and second principal component loading scores (PCI and PCII) between ramp and step contractions, whereas the MMG(MPF) and MMG PCI loading scores were significantly higher during ramp contractions than during step contractions. These findings suggested that EMG and MMG may offer complimentary information regarding the interactions between motor unit recruitment and firing rate that control muscle force production. In addition, our results support the hypothesis that different motor unit recruitment strategy was used by the muscle when contracting under different conditions.

Time and frequency domain responses of the mechanomyogram and electromyogram during isometric ramp contractions: A comparison of the short-time Fourier and continuous wavelet transforms

The purposes of this study were to examine the mechanomyographic (MMG) and electromyographic (EMG) time and frequency domain responses of the vastus lateralis (VL) and rectus femoris (RF) muscles during isometric ramp contractions and compare the time-frequency of the MMG and EMG signals generated by the short-time Fourier transform (STFT) and continuous wavelet transform (CWT). Nineteen healthy subjects (mean+/-SD age=24+/-4 years) performed two isometric maximal voluntary contractions (MVCs) before and after completing 2-3, 6-s isometric ramp contractions from 5% to 100% MVC with the right leg extensors. MMG and surface EMG signals were recorded from the VL and RF muscles. Time domains were represented as root mean squared amplitude values, and time-frequency representations were generated using the STFT and CWT. Polynomial regression analyses indicated cubic increases in MMG amplitude, MMG frequency, and EMG frequency, whereas EMG amplitude increased quadratically. From 5% to 24-28% MVC, MMG amplitude remained stable while MMG frequency increased. From 24-28% to 76-78% MVC, MMG amplitude increased rapidly while MMG frequency plateaued. From 76-78% to 100% MVC, MMG amplitude plateaued (VL) or decreased (RF) while MMG frequency increased. EMG amplitude increased while EMG frequency changed only marginally across the force spectrum with no clear deflection points. Overall, these findings suggested that MMG may offer more unique information regarding the interactions between motor unit recruitment and firing rate that control muscle force production during ramp contractions than traditional surface EMG. In addition, although the STFT frequency patterns were more pronounced than the CWT, both algorithms produced similar time-frequency representations for tracking changes in MMG or EMG frequency.

Inter-individual variability in the torque-related patterns of responses for mechanomyographic amplitude and mean power frequency

The purpose of this study was to examine the inter-individual variability for the patterns of responses for mechanomyographic (MMG) amplitude and mean power frequency (MPF) versus isometric torque in lower-strength (LS) and higher-strength (HS) individuals. Twelve participants (mean +/- S.D. age = 25 + 4 years) performed two isometric maximal voluntary contractions (MVCs) before and after completing nine submaximal step muscle actions (15%, 25%, 35%, 45%, 55%, 65%, 75%, 85%, and 95% MVC) of the right leg extensors. MMG signals were recorded from the vastus lateralis muscle, and MMG amplitude and MPF values were computed for each corresponding percentage of the MVC. Polynomial regression analyses indicated that the composite MMG amplitude versus isometric torque relationship was best fit with a linear model (r(2) = 0.980) for the LS group and a cubic model (r(2) = 0.994) for the HS group. The composite MMG MPF versus isometric torque relationships were best fit with linear models for both the LS (r(2) = 0.529) and HS (r(2)=0.591) groups. However, only 66% of the individuals exhibited the same linear MMG amplitude patterns as the composite relationship for the LS group, whereas only 33% of the individual relationships were cubic for the HS group. Only one subject exhibited a positive linear (r(2) = 0.681) relationship for the MMG(MPF) versus isometric torque relationship for either the LS or HS groups. These findings suggested that strength differences do not affect the patterns of responses for MMG amplitude or MPF. The lack of consistency between the individual and composite patterns of responses suggested some degree of inter-individual variability. Therefore, future studies should examine the individual patterns of response to draw conclusions about motor control strategies.

Mechanomyographic and electromyographic responses to eccentric muscle contractions

Little is known regarding the modulation of torque during eccentric muscle actions. Mechanomyographic (MMG) and electromyographic (EMG) signals have been used to examine motor control strategies. The purpose of this study was to examine the MMG and EMG amplitude and frequency in relation to torque during eccentric muscle contractions. Eight women performed eccentric leg extension muscle contractions at 10-100% of peak torque (PT). A piezoelectric crystal contact sensor and bipolar surface electrodes were placed on the vastus medialis to detect the MMG and EMG signals. Polynomial regression analyses indicated that EMG amplitude (r(2)=0.994) and MMG wavelet center frequency (CF) (r(2)=0.846) increased linearly to 100% eccentric PT, whereas there were no significant relationships for EMG wavelet CF or MMG amplitude and eccentric torque. These results suggested that eccentric torque is primarily modulated through changes in motor unit firing rate.