title: Homogeneity of fascicle architecture following repeated contractions in the human gastrocnemius medialis.
abstract: This investigation sought to determine the effects of fatigue on fascicle architecture across the length of the human gastrocnemius medialis (GM). With institutional ethical approval, fifteen healthy males performed repeated isometric plantar flexion maximal voluntary contractions (MVC) until peak force fell 30% below baseline. Brightness-mode ultrasound was used to determine fascicle length and pennation angle at rest and during MVC prior to and following the fatiguing contractions. The results show a significant increase in fascicle length during MVC in the distal (2.8 mm, 8.1%) middle, (4.9 mm, 14.1%), and proximal (5.2 mm, 14.7%) regions post-fatigue compared to pre-fatigue (p < 0.05). There was also a significant decrease of pennation angle during MVC in the distal (3.3°, 8.8%), middle (3.9°, 9.4%), and proximal (2.9°, 6.9%) regions post-fatigue compared to pre-fatigue (p < 0.05). These changes, however, were not region specific. These are the first results to show that fascicle shortening within the GM remains homogeneous following fatigue, suggesting that the fascicles were fatigued in a similar pattern throughout the muscle. The significant reduction of fascicle shortening may reflect an additional strategy to maintain an optimal force output in fatigued conditions, although future work is needed to confirm this notion.
authors.affiliation: Human Performance Laboratory, Faculty of Health and Science, Department of Medical and Sports Sciences, University of Cumbria, Lancaster LA1 3JD, UK. Electronic address: neil.thomas@cumbria.ac.uk.
authors.forename: Neil M
authors.initials: NM
authors.lastname: Thomas
authors.affiliation: Human Performance Laboratory, Faculty of Health and Science, Department of Medical and Sports Sciences, University of Cumbria, Lancaster LA1 3JD, UK.
authors.forename: Susan
authors.initials: S
authors.lastname: Dewhurst
authors.affiliation: Human Performance Laboratory, Faculty of Health and Science, Department of Medical and Sports Sciences, University of Cumbria, Lancaster LA1 3JD, UK.
authors.forename: Theodoros M
authors.initials: TM
authors.lastname: Bampouras
mesh_terms: D000328:Adult; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000502:physiology*; D014463:Ultrasonography
keywords: Fascicle length; Fatigue; Maximal voluntary contraction; Muscle; Pennation angle; Ultrasound