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

Abstract

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 following fatigue; however observations have not been contextualised by concurrent physiological measures. Objective: The aim of the present investigation was to measure peripheral fatigue-induced alterations in mechanical and contractile properties of the plantar flexor muscles through non-invasive TMG concurrently with maximal voluntary contraction (MVC) and passive muscle tension (PMT) in order to validate TMG as a gauge of peripheral fatigue. Design: Pre- and post-test intervention with control. Setting: University laboratory. Participants: Twenty-one healthy male volunteers. Interventions: Subjects plantar flexors were tested for TMG parameters, along with MVC and PMT, before and after either a 5 minute rest period (control) or a 5 minute 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 vs, p=0.031), while contraction velocity remained unaltered. Additionally, MVC significantly declined by 122.6 ± 104 N (p<0.001) following stimulation (fatigue). PMT was significantly increased following fatigue (139.8 ± 54.3 vs. 111.3 ± 44.6 N, p=0.007).  Conclusion: TMG successfully detected fatigue, evident from reduced MVC, by displaying impaired muscle displacement, accompanied by elevated PMT. TMG could be useful in establishing fatigue status of skeletal muscle without exacerbating the functional decrement of the muscle.