Reduced Radial Displacement of the Gastrocnemius Medialis Muscle After Electrically Elicited Fatigue

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Lewis J. Macgregor
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Massimiliano Ditroilo
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Iain J. Smith
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Malcolm M. Fairweather
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Angus M. Hunter
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Context:

Assessments of skeletal-muscle functional capacity often necessitate maximal contractile effort, which exacerbates muscle fatigue or injury. Tensiomyography (TMG) has been investigated as a means to assess muscle contractile function after fatigue; however, observations have not been contextualized by concurrent physiological measures.

Objective:

To measure peripheral-fatigue-induced alterations in mechanical and contractile properties of the plantar-flexor muscles through noninvasive TMG concurrently with maximal voluntary contraction (MVC) and passive muscle tension (PMT) to validate TMG as a gauge of peripheral fatigue.

Design:

Pre- and posttest intervention with control.

Setting:

University laboratory.

Participants:

21 healthy male volunteers.

Interventions:

Subjects’ plantar flexors were tested for TMG parameters, along with MVC and PMT, before and after either a 5-min rest period (control) or a 5-min electrical-stimulation intervention (fatigue).

Main Outcome Measures:

Temporal (contraction velocity) and spatial (radial displacement) contractile parameters of the gastrocnemius medialis were recorded through TMG. MVC was measured as an indicator of muscle fatigue, and PMT was measured to assess muscle stiffness.

Results:

Radial displacement demonstrated a fatigue-associated reduction (3.3 ± 1.2 vs 4.0 ± 1.4 mm, P = .031), while contraction velocity remained unaltered. In addition, MVC significantly declined by 122.6 ± 104 N (P < .001) after stimulation (fatigue). PMT was significantly increased after fatigue (139.8 ± 54.3 vs 111.3 ± 44.6 N, P = .007).

Conclusions:

TMG successfully detected fatigue, evident from reduced MVC, by displaying impaired muscle displacement accompanied by elevated PMT. TMG could be useful in establishing skeletalmuscle fatigue status without exacerbating the functional decrement of the muscle.

Macgregor, Smith, and Hunter are with the Health and Exercise Sciences Research Group, University of Stirling, Scotland. Ditroilo is with the Dept of Sport, Health & Exercise Science, University of Hull, England. Fairweather is with the Sportscotland Institute of Sport, Stirling, Scotland.

Address author correspondence to Lewis Macgregor at l.j.macgregor1@stir.ac.uk.
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