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Beetroot Juice Increases Human Muscle Force without Changing Ca2+-Handling Proteins.

Jamie Whitfield1, Daniel Gamu, George J F Heigenhauser

  • 11Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, CANADA; 2Department of Kinesiology, University of Waterloo, Waterloo, ON, CANADA; 3Department of Medicine, McMaster University, Hamilton, Ontario, CANADA; and 4Department of Human Movement Sciences, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University, Maastricht, THE NETHERLANDS.

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Dietary inorganic nitrate from beetroot juice enhances skeletal muscle force at low frequencies. This improvement in muscle function in humans is not linked to changes in cellular redox state or calcium handling proteins.

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Area of Science:

  • Exercise Physiology
  • Nutritional Biochemistry

Background:

  • Dietary inorganic nitrate (NO3) supplementation is known to improve skeletal muscle (SkM) contractile efficiency.
  • Previous rodent studies suggested improved calcium handling or redox modifications as mechanisms, but these remain unconfirmed in humans.

Purpose of the Study:

  • To investigate the effects of 7-day beetroot juice (BRJ) supplementation on human SkM contractile characteristics and function.
  • To determine if BRJ supplementation alters proteins related to calcium handling or cellular redox state in human SkM.

Main Methods:

  • Recreationally active males received 7 days of BRJ supplementation (280 mL/day, ~26 mmol NO3).
  • Skeletal muscle contractile properties were assessed using transcutaneous electrical muscle stimulation.
  • Skeletal muscle biopsies were analyzed for calcium handling proteins and the glutathione redox ratio (GSH:GSSG).

Main Results:

  • BRJ supplementation did not alter maximal voluntary force or electrically induced tetanic contractions.
  • Force production at low stimulation frequencies (10 Hz) significantly increased post-supplementation.
  • Peak twitch tension and maximal rates of force development and relaxation were enhanced.

Conclusions:

  • Beetroot juice supplementation improves skeletal muscle function at lower stimulation frequencies in humans.
  • These functional improvements occur independently of changes in cellular redox state or the expression of key calcium handling proteins.