Fatiguing high‑intensity intermittent exercise depresses maximal Na+‑K+‑ATPase activity in human skeletal muscle assessed using a novel NADH‑coupled assay

Jeppe F. Vigh‑Larsen, Sara M. Frangos, Kristian Overgaard, Graham P. Holloway, Magni Mohr

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Abstract

The Na+-K+-ATPase is a critical regulator of ion homeostasis during contraction, buffering interstitial K+ accumulation, which is linked to muscle fatigue during intense exercise. Within this context, we adopted a recently reported methodol
ogy to examine exercise-induced alterations in maximal Na+-K+-ATPase activity. Eighteen trained healthy young males completed a repeated high-intensity cycling protocol consisting of three periods (EX1-EX3) of intermittent exercise.
Each period comprised 10 × 45-s cycling at ~ 105% Wmax and a repeated sprint test. Muscle biopsies were sampled at baseline and after EX3 for determination of maximal in vitro Na+-K+-ATPase activity. Blood was drawn after each
period and in association with a 2-min cycling test at a standardized high intensity (~ 90% Wmax) performed before and after the session to assess plasma K+ accumulation. Further, a 5-h recovery period with the ingestion of carbohydrate or placebo supplementation was implemented to explore potential effects of carbohydrate availability before sampling a final biopsy and repeating all tests. A ~ 12% reduction in maximal Na+-K+-ATPase activity was emonstrated following EX3 compared to baseline (25.2 ± 3.9 vs. 22.4 ± 4.8 μmol·min−1·g−1 protein, P = 0.039), which was sustained at the recovery time point (~ 15% decrease compared to baseline to 21.6 ± 5.9 μmol·min−1·g−1 protein, P = 0.008). No significant effect of carbohydrate supplementation was observed on maximal Na+-K+-ATPase activity after recovery (P = 0.078). In conclusion, we demonstrate an exercise-induced depression of maximal Na+-K+-ATPase activity follow
ing high-intensity intermittent exercise, which was sustained during a 5-h recovery period and unrelated to carbohydrate availability under the present experimental conditions. This was shown using a novel NADH coupled assay and confirms previous findings using other methodological approaches.
Original languageEnglish
Number of pages14
JournalPflügers Archiv: European Journal of Physiology
DOIs
Publication statusPublished - 14 Nov 2024

Keywords

  • excitability
  • excitation-contraction coupling
  • potassium
  • fatigue
  • glycogen
  • carbohydrate

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