Influence of sprint interval training on skeletal muscle mitochondria as determined by high‐resolution respirometry

Abstract

Short‐term sprint interval training (SIT) improves skeletal muscle mitochondrial function, as reflected by increased maximal activity of several oxidative enzymes. To date, no studies have determined directly the influence of SIT on mitochondrial respiration. 6 sedentary, but healthy adults (3 males; 25±2 years, peak oxygen uptake: 39±2 ml/kg/min (mean±SE)) completed 9 sessions of 4–8, 30‐second sprints, over 21 days. Vastus lateralis samples were obtained prior to and 48‐hours following SIT. Mitochondrial respiratory function was determined in saponin permeabilized fibers using high‐resolution respirometry, combined with a variety of substrate, uncoupler and inhibitor combinations. Measures of maximal complex‐I+II (all substrates) supported mitochondrial respiration revealed 9–13% increases in respiratory efficiency following SIT (P<0.05). Total respiratory chain capacity per mg of muscle was unaltered, as was oxidative phosphorylation (OXPHOS) capacity and efficiency with palmitoylcarnitine + malate (fatty acid) as substrate. Conversely, OXPHOS capacity and efficiency were increased by 16–25% when pyruvate + malate (carbohydrate) was used as substrate, either in the presence or absence of fatty acid (P<0.05). These preliminary data indicate that 3 weeks of SIT selectively improves the efficiency of muscle carbohydrate oxidation, with no appreciable effect on fatty acid oxidation or total muscle respiratory capacity.