Abstract:
TO THE EDITOR: We are struck by the remarkable results contained in the article by Zhang et al. (5). Put bluntly, if these results are independently verified, then a fundamental reappraisal of over four decades of muscle energetics will be required. This is because Zhang et al. (5) infer from their data that, under conditions of submaximal stimulation (at 30°C), ∼80% of the metabolic cost of contraction of isolated, fast-twitch, skeletal muscle [mouse extensor digitorum longus (EDL)] is attributable to Ca2+ pumping by the sarcoplasmic reticulum (SR), leaving only 20% to cross-bridge cycling. These values are roughly the converse of what is conventionally considered to be the economics of energy expenditure by active striated muscle. We are rather skeptical, for the following reasons.
