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 methodology to examine exercise-induced alterations in maximal Na + -K + -ATPase activity. Eighteen trained healthy young males completed a repeated high-intensity cycling protocol consisting o...

This historical review traces key discoveries regarding K + and Na + ions in skeletal muscle at rest and with exercise, including contents and concentrations, Na + ,K + -ATPase (NKA) and exercise effects on plasma [K + ] in humans. Following initial measures in 1896 of muscle contents in various species, including humans, electrical stimulation of animal muscle showed K + loss and gains in Na + , Cl − and H 2 0, then subsequen...

Perturbations in K + have long been considered a key factor in skeletal muscle fatigue. However, the exercise-induced changes in K + intra-to-extracellular gradient is by itself insufficiently large to be a major cause for the force decrease during fatigue unless combined to other ion gradient changes such as for Na + . Whilst several studies described K + -induced force depression at high extracellular [K + ] ([K + ] e ), oth...