title: Acute passive stretching in a previously fatigued muscle: Electrical and mechanical response during tetanic stimulation.
abstract: The aim of this study was to assess the effects of acute passive stretching on the electrical and mechanical response of a previously fatigued muscle. Eleven participants underwent maximal tetanic stimulations (50 Hz) of the medial gastrocnemius, before and after a fatiguing protocol and after a bout of passive stretching of the fatigued muscle. During contraction, surface electromyography (EMG), mechanomyography (MMG), and force were recorded. The following parameters were calculated: (1) the EMG root mean square (RMS), mean frequency, and fibre conduction velocity; (2) MMG peak-to-peak and RMS; (3) the peak force, contraction time, half-relaxation time, peak rate of force development (dF/dt) and its acceleration (d(2)F/dt(2)). Fatigue reduced peak force by 18% (P < 0.05) and affected the other force, EMG, and MMG parameters. After stretching: (1) all EMG parameters recovered to pre-fatigue values; (2) MMG peak-to-peak remained depressed, while RMS recovered to pre-fatigue values; (3) the peak force, peak rate of force development and its acceleration were further reduced by 22, 18, and 51%, respectively, and half-relaxation time by 40% (P < 0.05). In conclusion, acute passive stretching, when applied to a previously fatigued muscle, further depresses the maximum force-generating capacity. Although stretching does not alter the electrical parameters of the fatigued muscle, it does affect the mechanical behaviour of the muscle-tendon unit.
authors.affiliation: Department of Sport, Nutrition and Health Sciences, University of Milan, Italy. fabio.esposito@unimi.it
authors.forename: Fabio
authors.initials: F
authors.lastname: Esposito
authors.forename: Emiliano
authors.initials: E
authors.lastname: Ce
authors.forename: Susanna
authors.initials: S
authors.lastname: Rampichini
authors.forename: Arsenio
authors.initials: A
authors.lastname: Veicsteinas
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography; D006801:Humans; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D052580:Muscle Stretching Exercises; D018482:Muscle, Skeletal / Q000502:physiology*; D013710:Tendons / Q000502:physiology; D013746:Tetany / Q000503:physiopathology*; D055815:Young Adult