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Improvements in exercise performance with high-intensity interval training coincide with an increase in skeletal muscle mitochondrial content and function


Jacobs, Robert A; Flück, Daniela; Bonne, Thomas Christian; Bürgi, Simon; Christensen, Peter M; Toigo, Marco; Lundby, Carsten (2013). Improvements in exercise performance with high-intensity interval training coincide with an increase in skeletal muscle mitochondrial content and function. Journal of Applied Physiology, 115(6):785-793.

Abstract

Six sessions of high-intensity interval training (HIT) are sufficient to improve exercise capacity. The mechanisms explaining such improvements are unclear. Accordingly, the aim of this study was to perform a comprehensive evaluation of physiologically relevant adaptations occurring after 6 sessions of HIT to determine the mechanisms explaining improvements in exercise performance. Sixteen untrained (43 ± 6 ml kg(-1) min(-1)) subjects completed 6 sessions of repeated (8-12) 60 s intervals of high-intensity cycling (100% peak power output elicited during incremental maximal exercise test) intermixed with 75 s of recovery cycling at a low intensity (30 W) over a 2-week period. Potential training-induced alterations in skeletal muscle respiratory capacity, mitochondrial content, skeletal muscle oxygenation, cardiac capacity, blood volumes, and peripheral fatigue resistance were all assessed prior to and again following training. Maximal measures of oxygen uptake (VO2peak; ~8%; p = 0.026) and cycling time to complete a set amount of work (~5%; p = 0.008) improved. Skeletal muscle respiratory capacities increased, most likely as a result of an expansion of skeletal muscle mitochondria (~20%, p = 0.026), as assessed by cytochrome c oxidase activity. Skeletal muscle deoxygenation also increased while maximal cardiac output, total hemoglobin, plasma volume, total blood volume, and relative measures of peripheral fatigue resistance were all unaltered with training. These results suggest that increases in mitochondrial content following 6 HIT sessions may facilitate improvements in respiratory capacity, oxygen extraction, and ultimately are responsible for the improvements in maximal whole-body exercise capacity and endurance performance in previously untrained individuals.

Abstract

Six sessions of high-intensity interval training (HIT) are sufficient to improve exercise capacity. The mechanisms explaining such improvements are unclear. Accordingly, the aim of this study was to perform a comprehensive evaluation of physiologically relevant adaptations occurring after 6 sessions of HIT to determine the mechanisms explaining improvements in exercise performance. Sixteen untrained (43 ± 6 ml kg(-1) min(-1)) subjects completed 6 sessions of repeated (8-12) 60 s intervals of high-intensity cycling (100% peak power output elicited during incremental maximal exercise test) intermixed with 75 s of recovery cycling at a low intensity (30 W) over a 2-week period. Potential training-induced alterations in skeletal muscle respiratory capacity, mitochondrial content, skeletal muscle oxygenation, cardiac capacity, blood volumes, and peripheral fatigue resistance were all assessed prior to and again following training. Maximal measures of oxygen uptake (VO2peak; ~8%; p = 0.026) and cycling time to complete a set amount of work (~5%; p = 0.008) improved. Skeletal muscle respiratory capacities increased, most likely as a result of an expansion of skeletal muscle mitochondria (~20%, p = 0.026), as assessed by cytochrome c oxidase activity. Skeletal muscle deoxygenation also increased while maximal cardiac output, total hemoglobin, plasma volume, total blood volume, and relative measures of peripheral fatigue resistance were all unaltered with training. These results suggest that increases in mitochondrial content following 6 HIT sessions may facilitate improvements in respiratory capacity, oxygen extraction, and ultimately are responsible for the improvements in maximal whole-body exercise capacity and endurance performance in previously untrained individuals.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Physiology
07 Faculty of Science > Institute of Physiology

04 Faculty of Medicine > Center for Integrative Human Physiology
05 Vetsuisse Faculty > Institute of Veterinary Physiology
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:2013
Deposited On:23 Aug 2013 06:18
Last Modified:05 Apr 2016 16:55
Publisher:American Physiological Society
ISSN:0161-7567
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1152/japplphysiol.00445.2013
PubMed ID:23788574

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