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High‐intensity interval training alters ATP pathway flux during maximal muscle contractions in humans
Author(s) -
Larsen R. G.,
Maynard L.,
Kent J. A.
Publication year - 2014
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/apha.12275
Subject(s) - oxidative phosphorylation , anaerobic exercise , glycolysis , skeletal muscle , in vivo , high intensity interval training , medicine , atp synthase , endocrinology , energetics , chemistry , contraction (grammar) , interval training , metabolism , biology , biochemistry , physical therapy , gene , ecology , microbiology and biotechnology
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 PC r breakdown ( ATP CK ), oxidative phosphorylation (ATP OX ) and non‐oxidative glycolysis (ATP GLY ) 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 ATP OX (from 31 ± 2 to 39 ± 2% of total ATP turnover, P < 0.001) and lowered the relative contribution from both ATP CK (49 ± 2 to 44 ± 1%, P = 0.004) and ATP GLY (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.