Effects of intensified training with insufficient recovery on joint level and single muscle fibre mechanical function: the role of myofibrillar Ca 2+ sensitivity.

Autor:	Roussel OP; Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada., Pignanelli C; Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada., Hubbard EF; Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada., Coates AM; Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada., Cheng AJ; Muscle Health Research Centre, School of Kinesiology and Health Science, Faculty of Health, York University, Toronto, ON M3J 1P3, Canada., Burr JF; Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada., Power GA; Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada.
Jazyk:	angličtina
Zdroj:	Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme [Appl Physiol Nutr Metab] 2024 Dec 01; Vol. 49 (12), pp. 1646-1657. Date of Electronic Publication: 2024 Aug 09.
DOI:	10.1139/apnm-2024-0189
Abstrakt:	Intense exercise training with insufficient recovery time is associated with reductions in neuromuscular performance. However, it is unclear how single muscle fibre mechanical function and myofibrillar Ca ²⁺ sensitivity contribute to these impairments. We investigated the effects of overload training on joint-level neuromuscular performance and cellular-level mechanical function. Fourteen athletes (4 female and 10 male) underwent a 3-week intensified training protocol consisting of up to 150% of their regular training hours with three additional high-intensity training sessions per week. Neuromuscular performance of the knee extensors was assessed via maximal voluntary contraction (MVC) force, electrically evoked twitch contractions, and a force-frequency relationship. Muscle biopsies were taken from the vastus lateralis to assess single fibre mechanical function. Neither MVC force nor twitch parameters were altered following training (all p > 0.05 ), but a rightward shift in the force-frequency curve was observed with average reduction in force of 6%-27% across frequencies 5-20 Hz (all p < 0.05). In single fibres, maximal force output was not reduced following training, but there was a rightward shift in the force-pCa curve driven by a 6% reduction in Ca ²⁺ sensitivity ( p < 0.05 ). These data indicate intensified training leads to impaired Ca ²⁺ sensitivity at the single fibre level, which in part explains impaired neuromuscular function at the joint level during lower frequencies of activation. This is an important consideration for athletes, as performance is often assessed at maximal levels of activation, and these underlying impairments in force generation may be less obvious. Competing Interests: No conflicts of interest, financial or otherwise, are declared by the authors.
Databáze:	MEDLINE
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