High‐intensity interval training alters ATP pathway flux during maximal muscle contractions in humans

Abstract

Aim High-intensity interval training (HIT) results in potent metabolic adaptations in skeletal muscle, however little is known about the influence of these adaptations on energetics in vivo. We used magnetic resonance spectroscopy to examine the effects of HIT on ATP synthesis from net PCr breakdown (ATPCK), oxidative phosphorylation (ATPOX) and non-oxidative glycolysis (ATPGLY) in vivo in vastus lateralis during a 24-s maximal voluntary contraction (MVC). Methods Eight young men performed 6 sessions of repeated, 30-s “all-out” sprints on a cycle ergometer; measures of muscle energetics were obtained at baseline, and after the first and sixth sessions. Results Training increased peak oxygen consumption (35.8±1.4 to 39.3±1.6 ml·min−1·kg−1, p=0.01) and exercise capacity (217.0±11.0 to 230.5±11.7 W, p=0.04) on the ergometer, with no effects on total ATP production or force-time integral during the MVC. While ATP production by each pathway was unchanged after the first session, 6 sessions increased the relative contribution of ATPOX (from 31±2 to 39±2% of total ATP turnover, p<0.001), and lowered the relative contribution from both ATPCK (49±2 to 44±1%, p=0.004) and ATPGLY (20±2 to 17±1%, p=0.03). Conclusion These alterations to muscle ATP production in vivo indicate that brief, maximal contractions are performed with increased support of oxidative ATP synthesis, and relatively less contribution from anaerobic ATP production following training. These results extend previous reports of molecular and cellular adaptations to HIT and show that 6 training sessions are sufficient to alter in vivo muscle energetics, which likely contributes to increased exercise capacity after short-term HIT.

Skeletal muscle ATP synthesis and cellular H+ handling measured by localized 31P-MRS during exercise and recovery

“…14), as the VO 2 method is a more direct quantification of Q . Other 31 P MRS studies1923 also show similar relations at end of exercise, and as they calculate Q equally or similar to Q ADP (cf. Eq.…”

Anaerobic exercise affects the saliva antioxidant/oxidant balance in high-performance pentathlon athletes

“…In an intermittent high-intensity test such as the RAST, major sources for ATP replacement are initially phosphocreatine hydrolysis and glycolysis, but a shift toward oxidative metabolism to replenish ATP has been demonstrated for later trials in a sequence of sprints [21]. We observed a high correlation between VO 2max and anaerobic power, consistent with a role for aerobic power in anaerobic performance, and suggesting the importance of such a shift during the RAST, as observed for other anaerobically trained athletes, for example, judo players performing an anaerobic judo test that lasted 60 s [22].…”

Training: functional improvements of skeletal muscle oxidative metabolism can occur earlier than the enhancement of mitochondrial biogenesis

“…Interestingly, in the study by Larsen et al . (), the reported greater rates of oxidative ATP production after training were accompanied by unchanged [ADP free ] during exercise. Although Larsen et al .…”

“…It was reported by these authors that six sessions of repeated 30 s ‘all‐out’ sprints performed on a cycle ergometer within a 2 week period of training led to an increase, in quadriceps muscles during maximal voluntary contraction lasting 24 s, in the absolute and relative contributions of ATP production via oxidative phosphorylation, in presence of a relative reduction in ATP supply from creatine kinase and anaerobic glycolysis (Larsen et al . ). No substantial changes in their study were observed after only one training session.…”

“…A recent study by Larsen et al . () suggest that to a certain extent a similar scenario could also occur after the widely used ‘high‐intensity training’ (HIT). It was reported by these authors that six sessions of repeated 30 s ‘all‐out’ sprints performed on a cycle ergometer within a 2 week period of training led to an increase, in quadriceps muscles during maximal voluntary contraction lasting 24 s, in the absolute and relative contributions of ATP production via oxidative phosphorylation, in presence of a relative reduction in ATP supply from creatine kinase and anaerobic glycolysis (Larsen et al .…”