November 20, 2019
Devin G McCarthy, PhD Student
Department of Kinesiology, McMaster University, Hamilton, ON, Canada
The KT committee is introducing a new format for Knowledge Translation articles with an emphasis on how current research may impact practitioners. This month’s article is written by Devin McCarthy. Devin is a second year PhD student at McMaster University in the Human Performance lab and supervised by Dr. Martin Gibala. Devin is a current CSEP member and has previous experience in journalism that includes 2 years with the Students Communicating Research in Biology Education (SCRIBE) program at the University of Guelph.
Beetroot Juice is a commercially-available beverage that, when consumed, increases blood levels of nitrate and nitrite (and most likely nitric oxide) and in turn affects many physiological and metabolic processes. Several well-controlled studies demonstrated that pre-exercise BRJ ingestion enhanced exercise performance in recreationally-active males; an effect partially explained through improved electrically stimulated calf muscle force production and exercise economy. Despite strong evidence for these effects in males, there are few data in females.
- Twelve young, healthy females who were currently taking oral contraceptives and exercised for about 4.5 hours per week consumed either a BRJ or placebo supplement twice-daily for 7 days, waited one week and then consumed the second course of the supplement for 7 days.
- On the first and last day of supplementation, participants cycled in the lab to assess the acute and chronic effects of BRJ, respectively.
- Before exercising, blood samples were obtained to confirm nitrate and nitrite were elevated and to quantify menstrual cycle hormones
- During 20 minutes of moderate intensity cycling the amount of oxygen used by the body was measured to estimate economy. During exercise the body uses oxygen to create energy and then movement; economy indicates how efficiently this process occurs. In terms of exercise performance, a lower exercise economy is undesirable because it means more oxygen was used to achieve the same distance covered.
- Next, a time trial where participants cycled a predetermined distance as fast as possible, was completed to measure exercise performance.
- Calf muscle force production was measured by electrically stimulating the nerve at a low frequency (a similar frequency that is used when performing a moderate effort voluntary contraction), which activated a muscle that is actively used for cycling. The calf muscle force produced was measured and a more efficient contraction meant the muscle produced more force from the same electrical stimulus.
What the researchers found
- Blood nitrate and nitrite levels were increased 2.5 hours after drinking BRJ, remained elevated throughout the exercise protocol, and were elevated throughout the 7-day BRJ supplementation.
- There was no effect of BRJ on exercise efficiency during exercise or endurance-cycling performance.
- BRJ ingestion did improve stimulated calf muscle force production at a low activation frequency.
- These findings in recreationally-active females are different than the data from comparable males, and therefore warrant additional sex-based research on the topic.
Neither acute nor chronic BRJ ingestion affected exercise efficiency during exercise and cycling performance despite improving electrically stimulated muscle force production at a low frequency. Since these trends are different than comparable male populations, future research should examine sex-based differences with BRJ ingestion.
- Ingesting beetroot juice (BRJ) before exercising improved involuntary calf muscle force production (electrically stimulated at a frequency similar to that of walking up stairs) in recreationally-active females
- However, BRJ did not affect the oxygen required to exercise at a fixed workload (exercise economy) or cycling performance.
Wickham, K. A., McCarthy, D. G., Pereira, J. M., Cervone, D. T., Verdijk, L. B., van Loon, L. J. C., Power, G. A., Spriet, L. L.. No effect of beetroot juice supplementation on exercise economy and performance in recreationally active females despite increased torque production. Physiol Rep, 7 ( 2), 2019, e13982, https://doi.org/10.14814/phy2.13982
This article is a summary of an article published in Applied Physiology, Nutrition & Metabolism. If you intend to cite any information in this article, please consult the original article and cite that source. This summary was written for the Canadian Society for Exercise Physiology and it has been reviewed by the CSEP Knowledge Translation Committee.