Abstract
In order to characterize the physiological adjustments within the neuromuscular system that contribute to task failure, this study examined the surface mechanomyographic (MMG) response during maximal and submaximal isometric force tasks of the elbow flexors sustained to failure. The time and frequency components of the MMG signal have shown to be influenced by motor unit activation patterns as well as tetanus. Therefore, it was hypothesized that the rate of change for the MMG response would associate with failure times and would be reduced to a similar degree between the two tasks. The isometric force tasks were performed by the dominant elbow flexors of twenty healthy males (age: 25 ± 4 years) and MMG was collected from the biceps brachii. Regression analyses were used to model the relationships between the rates of change for MMG versus failure times. There were high levels of interindividual variability in the response patterns, yet the models demonstrated significant negative associations between the rate of change for the MMG responses and failure times during both tasks (R 2 = 0.41–0.72, P < 0.05). Similarly, the mean MMG amplitude and frequency values were reduced to comparable levels at the failure point of the two tasks. The results of this study demonstrated that force failure is associated with the rate of diminution in the properties of the muscle force twitch.
Highlights
The mechanomyographic (MMG) signal is composed of the low-frequency lateral oscillations that resonant from the unfused, active muscle fibers within the frequency range of ~2–120 Hz (Barry and Cole 1990; Orizio 1993; Beck et al 2008)
The MMG signal is generated by dimensional changes in muscle fiber diameter that occur in response to motor unit activation (Frangioni et al 1987; Orizio 1993)
Bivariate regression showed that the rate of change within the composite models for the MMG mean frequency (MNF) (R2 = 0.461, n = 10, P = 0.031; Fig. 2A) and amplitude (R2 = 0.416, n = 11, P = 0.032; Fig. 2B) responses during the maximal task were associated with failure times
Summary
The mechanomyographic (MMG) signal is composed of the low-frequency lateral oscillations that resonant from the unfused, active muscle fibers within the frequency range of ~2–120 Hz (Barry and Cole 1990; Orizio 1993; Beck et al 2008). The MMG signal is generated by dimensional changes in muscle fiber diameter that occur in response to motor unit activation (Frangioni et al 1987; Orizio 1993). It is believed (Gordon and Holbourn 1948; Orizio et al 2003; Beck et al 2007a) the signal reflects the mechanical properties of muscle contraction and contains information regarding motor control patterns (i.e., the relative contribution of motor unit recruitment and firing rate). This places a premium on examining the fatigue-based MMG response patterns in order to examine the contractile state of the muscle and infer upon adaptive patterns of motor control
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
