Adjustments in the force–frequency relationship during passive and exercise‐induced hyperthermia. Issue 5 (24th September 2014)

• Record Type: Journal Article
• Authors: Périard, Julien D.; Racinais, Sebastien; Thompson, Martin W.
• Is Part Of: Muscle & nerve. Volume 50:Issue 5(2014:Nov.)
• Page Start: 822
• Page End: 829
• Publication Date: 2014-09-24
• Subjects: Neuromuscular diseases -- Periodicals; Muscles -- Periodicals; Nerves -- Periodicals; 616.74
• DOI: 10.1002/mus.24228
• Languages: English
• ISSNs: 0148-639X

Abstract

<abstract abstract-type="main"> <title>ABSTRACT</title> <p> <italic>Introduction</italic>: We examined the extent to which fatiguing cycling exercise in the heat influences contractile function in modulating the force–frequency relationship. <italic>Methods</italic>: Before (∽37.0°C) and after (∽38.5°C) exercise (ExH) and passive (PaH) hyperthermia, an 8‐s train of stimulation at 10, 20, 50, and 100 H<sc>z</sc> (2 s per frequency) and a potentiated twitch were evoked on the relaxed knee extensors using percutaneous stimulation. <italic>Results</italic>: ExH and PaH produced a decrease in the 20:50 H<sc>z</sc> force ratio, indicative of low‐frequency fatigue (<italic>P</italic> &lt; 0.01). This adjustment was more pronounced after ExH than PaH (<italic>P</italic> &lt; 0.01). A rightward displacement in the force–frequency relationship occurred after ExH and PaH (<italic>P</italic> &lt; 0.05) and was exacerbated by ExH (<italic>P</italic> &lt; 0.05). Peak twitch force also decreased after ExH (<italic>P</italic> &lt; 0.05). <italic>Conclusions</italic>: ExH reduces force summation due to development of skeletal muscle fatigue, exacerbating the shift in force–frequency to the right relative to PaH. <italic>Muscle Nerve</italic><bold>50</bold>: 822–829, 2014</p> </abstract>