Mitochondrial enzymes increase in muscle in response to 7-10 days of cycle exercise

Abstract

Endurance exercise training induces a significant increase in the respiratory capacity of skeletal muscle. This is reflected by a training-induced increase in mitochondrial enzyme activity. One consequence of this adaptation is that there is a decreased reliance on carbohydrate utilization with a concomitant increase in fat utilization, resulting in an improvement in endurance capacity. Recently it has been reported that 7-14 days of cycle ergometer exercise training does not induce an increase in mitochondrial enzyme levels in skeletal muscle but, nevertheless, results in smaller decreases in phosphocreatine and glycogen and smaller increases in Pi and lactate in muscle in response to the same exercise after compared with before training. However, previous studies in rats have shown that an adaptive increase in mitochondrial enzymes is already evident after only 2 days of exercise training. In view of this discrepency, the present study was performed to reevaluate the effect of short-term training (7-10 days) on mitochondrial enzymes in skeletal muscle of humans. Twelve subjects [6 men and 6 women, 27 +/- 5 (SE) yr old] underwent 7 (n = 5) or 10 days (n = 7) of cycle ergometer exercise for 2h/day at 60-70% of peak O2 consumption. Peak O2 consumption was increased by 9% (from 2.97 +/- 0.16 to 3.24 +/- 0.17 l/min) in response to training. Blood lactate levels were lower at the same absolute work rates after than before training. The activities of citrate synthase, beta-hydroxyacyl-CoA dehydrogenase, mitochondrial thiolase, and carnitine acetyltransferase were increased by approximately 30% in response to training. The results of the present study provide evidence that in humans, as in rats, the adaptive increase in mitochondrial enzymes in skeletal muscle occurs fairly rapidly in response to exercise training. They provide no support for the claim that this adaptive response is delayed for > 2 wk after the onset of training.

Effects of intrinsic aerobic capacity, aging and voluntary running on skeletal muscle sirtuins and heat shock proteins

“…However, aforementioned studies show that even modest endurance training increases VO2max to some extent. Furthermore, other studies have also shown a 5 to 10% improvement in VO2max and increases in mitochondrial enzyme level with only a short-term endurance training program (Mier et al 1997;Hickson 1981;Spina et al 1996). Recently very low volume high-intensity interval training (all-out exercise efforts above 100% of peak workload) has been proposed as a novel, time-effective exercise regime for improving VO2max (Saanijoki et al 2015;Burgomaster et al 2007).…”

Slow component of V̇O2 kinetics: the effect of training status, fibre type, UCP3 mRNA and citrate synthase activity

“…11 CS activity correlates highly with in vitro measurements of skeletal muscle mitochondrial oxidative capacity 26 and has been commonly used as a marker of muscle oxidative capacity. 27,28 Histochemical staining Serial cross-sections 10 mm thick were cut from the mounted muscle sample in a cryostat maintained at 7 20 C. The sections for fibre typing were preincubated at pH 4.30 and 4.54, and were classified as either type I, IIa or IIx according to the acid lability of different isoforms of myosin adenosine triphosphatase. 25 For each subject, a mean ( AE s.d.)…”

“…However, linear stepwise regression revealed that the magnitude of the relative SC of the Tr group was best explained by CS activity alone, with CS explaining 77% of the variance of the magnitude of the relative SC. CS activity is a marker of muscle oxidative capacity 27,28 and these correlations imply that the greater the CS activity, the smaller will be the size of the relative SC for endurance trained subjects. Although these findings do not indicate a causal link, it is reasonable to speculate that the lower SC is in response to an increase in the oxidative capacity of the contracting muscle.…”

Citrate synthase expression and enzyme activity after endurance training in cardiac and skeletal muscles

“…It has been extensively used as a metabolic marker in assessing oxidative and respiratory capacity (22). More than 30 years ago, Holloszy and his colleagues (8) reported that endurance exercise training increases the oxidative enzyme activities in skeletal muscle.…”

“…More than 30 years ago, Holloszy and his colleagues (8) reported that endurance exercise training increases the oxidative enzyme activities in skeletal muscle. After that, numerous studies were conducted to examine the effect of exercise training on muscle oxidative capacity and metabolic characteristics (7,15,20,22,29). It is generally recognized that the skeletal muscle oxidative capacity and the activities of mitochondrial enzymes are elevated by endurance exercise training.…”