Jacobs 2013 J Appl Physiol

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Jacobs R, Flück D, Bonne TC, Bürgi S, Christensen PM, Toigo M, Lundby C (2013) Improvements in exercise performance 1 with high-intensity interval training 2 coincide with an increase in skeletal muscle mitochondrial content and function. J Appl Physiol 115:785-93.

» PMID: 23788574 Open Access

Jacobs R, Flueck D, Bonne TC, Buergi S, Christensen PM, Toigo M, Lundby C (2013) J Appl Physiol

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 six sessions of HIT to determine the mechanisms explaining improvements in exercise performance. Sixteen untrained (43 ± 6 ml·kg(-1)·min(-1)) subjects completed six 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-wk 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 six HIT sessions may facilitate improvements in respiratory capacity and oxygen extraction, and ultimately are responsible for the improvements in maximal whole body exercise capacity and endurance performance in previously untrained individuals.

Keywords: HIT, Interval training, Mitochondria, Oxygen extraction, Sprint training

O2k-Network Lab: CH Zurich Lundby C, US CO Colorado Springs Jacobs RA

Labels: MiParea: Respiration, mt-Biogenesis;mt-density, Exercise physiology;nutrition;life style 

Organism: Human  Tissue;cell: Skeletal muscle  Preparation: Permeabilized tissue 

Coupling state: LEAK, OXPHOS, ET  Pathway: F, N, S, CIV, NS, ROX  HRR: Oxygraph-2k 

MiR05, MitoEAGLE muscle buffer