Beetroot Juice Increases Human Muscle Force Without Changing Ca2+-handling Proteins.

Dietary inorganic nitrate (NO3-) supplementation improves skeletal muscle (SkM) contractile efficiency, and while rodent literature has suggested improvements in calcium handling or redox modifications as likely explanations, the direct mechanism-of-action in humans remains unknown. PURPOSE: To examine the effects of 7-d of beetroot juice (BRJ) supplementation on SkM contractile characteristics and function. METHODS: Recreationally active males (n=8) underwent transcutaneous electrical muscle stimulation of the vastus lateralis for evaluation of contractile characteristics before (pre) and after (post) 7-d of BRJ supplementation (280 mL/day, ~26 mmol NO3-). An additional group of individuals (n=8) followed the same supplementation protocol but underwent SkM biopsies pre/post supplementation for determination of proteins associated with calcium handling via Western blotting, and the ratio of reduced/oxidized glutathione (GSH:GSSG), an indicator of cellular redox state, via HPLC. RESULTS: Following supplementation, there was no change in maximal voluntary force production (602 +/- 50 vs 596 +/- 56 N), or electrically-induced tetanic contractions. In contrast, force production was increased at 10 Hz electrical stimulation (41.1 +/- 2.3 vs 37.6 +/- 2.4% of peak force, p

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