Skeletal muscle ATP turnover by 31P magnetic resonance spectroscopy during moderate and heavy bilateral knee-extension

Cannon, Daniel T and Bimson, William E and Hampson, Sophie A and Bowen, Scott T and Murgatroyd, Scott R and Marwood, Simon and Kemp, Graham J. and Rossiter, Harry B (2014) Skeletal muscle ATP turnover by 31P magnetic resonance spectroscopy during moderate and heavy bilateral knee-extension. Journal of Physiology, 592. pp. 5287-5300. ISSN 1469-7793

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Abstract

During constant-power high-intensity exercise, the expected increase in oxygen uptake (V̇O2) is supplemented by a V̇O2 slow component (V̇O2 sc ), reflecting reduced work efficiency, predominantly within the locomotor muscles. The intracellular source of inefficiency is postulated to be an increase in the ATP cost of power production (an increase in P/W). To test this hypothesis, we measured intramuscular ATP turnover with (31)P magnetic resonance spectroscopy (MRS) and whole-body V̇O2 during moderate (MOD) and heavy (HVY) bilateral knee-extension exercise in healthy participants (n = 14). Unlocalized (31)P spectra were collected from the quadriceps throughout using a dual-tuned ((1)H and (31)P) surface coil with a simple pulse-and-acquire sequence. Total ATP turnover rate (ATPtot) was estimated at exercise cessation from direct measurements of the dynamics of phosphocreatine (PCr) and proton handling. Between 3 and 8 min during MOD, there was no discernable V̇O2 sc (mean ± SD, 0.06 ± 0.12 l min(-1)) or change in [PCr] (30 ± 8 vs. 32 ± 7 mm) or ATPtot (24 ± 14 vs. 17 ± 14 mm min(-1); each P = n.s.). During HVY, the V̇O2 sc was 0.37 ± 0.16 l min(-1) (22 ± 8%), [PCr] decreased (19 ± 7 vs. 18 ± 7 mm, or 12 ± 15%; P < 0.05) and ATPtot increased (38 ± 16 vs. 44 ± 14 mm min(-1), or 26 ± 30%; P < 0.05) between 3 and 8 min. However, the increase in ATPtot (ΔATPtot) was not correlated with the V̇O2 sc during HVY (r(2) = 0.06; P = n.s.). This lack of relationship between ΔATPtot and V̇O2 sc , together with a steepening of the [PCr]-V̇O2 relationship in HVY, suggests that reduced work efficiency during heavy exercise arises from both contractile (P/W) and mitochondrial sources (the O2 cost of ATP resynthesis; P/O).

Item Type: Article
Additional Information and Comments: This is the peer reviewed version of the following article: Cannon, D. T., Bimson, W. E., Hampson, S. A., Bowen, T. S., Murgatroyd, S. R., Marwood, S., Kemp, G. J. and Rossiter, H. B. (2014), Skeletal muscle ATP turnover by P magnetic resonance spectroscopy during moderate and heavy bilateral knee extension. J Physiol, 592: 5287–5300. doi:10.1113/jphysiol.2014.279174, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1113/jphysiol.2014.279174/full. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."
Keywords: 2014.279174
Faculty / Department: Faculty of Science > School of Health Sciences
Depositing User: Karen Foxton
Date Deposited: 22 Mar 2016 09:39
Last Modified: 22 Mar 2016 09:39
URI: http://hira.hope.ac.uk/id/eprint/784

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