Study finds beetroot supplementation of benefit in resistance training

The new research was published in the journal Nutrients​.  It was the work of researchers associated with several Spanish universities.

The researchers noted that beetroot juice and beet extract products have long been associated with better performance in endurance exercise.  This has been linked to the botanical’s ability to stimulate nitric oxide (NO) production.  NO is a powerful vasodilator, which works to bring more oxygen to working muscles.

Is there a benefit for strength training?

There is less information on how beetroot products might affect outcomes in resistance training, however.  One of the unknowns in athletic training is why individual athletes will respond differently to identical workloads, or why the same athlete might respond differently over time.  A certain amount of weight in the deadlift might feel easy one day and overly hard the next, for example.

To quantify these differences, researchers and trainers have come up with the concept of ‘internal load,’ which can equate to the perceived rate of exertion.  While the latter might be viewed as overly subjective benchmark, researchers have started to put some more precisely measurable parameters around the former.  Finding ways to better assess and manage internal load could presumably lead to better training outcomes and help athletes more easily avoid overtraining or overuse injuries.

Heart rate variability provides clue to internal load

Measuring the variability in an athlete’s heart rate has recently come to be seen as a useful marker in assessing internal load. 

Among the statistical techniques used to parse this data is something called the root mean square successive difference (RMSSD) in heart period series, a time domain measure of heart period variability. The RMSSD is sensitive to high-frequency heart period fluctuations in the respiratory frequency range and has been used as an index of vagal cardiac control.

The researchers applied RMSSD technique to data generated from a small cohort of subjects participating in a resistance training protocol.  The goal was to see if the cardioprotective effects of higher NO levels could benefit strength athletes to see if training sessions could be made more efficient.

As a study population the researchers recruited 11 men between the ages of 18 and 30 for the test, 10 of whom completed the study. They were familiarized with the back squat and bench press exercises.  Other inclusion criteria were that they were to refrain from other supplements for a three month period prior to the test, and were instructed not to brush their teeth or use mouthwash for 24 hours prior to the test.  Beetroot juice boosts NO levels via a multi-step pathway that includes interactions with the oral microbiome and subsequent ingestion of saliva.  Excluding toothpaste and mouthwash from the picture presumably was a way to eliminate a potential confounding factor.

The researchers selected the Beet It juice product manufactured by UK brand holder Beet It Sport.  A dosage of 70 ml was selected, with a black currant juice drink chosen as a placebo.  Each drink was ingested two hours before the research visits.

Seeking effects following one repetition max lifts

After ingestion the beetroot juice or placebo, the study participants did a warm up routine and then did a one repetition maximum lift in both the back squat and bench press exercises.  The group was blindly randomized 50-50 between the intervention and placebo for each of the two visits.

Blood pressure was measured prior to the test and after.  Heart rate was monitored continuously via a wearable device.

The researchers found no effect on blood pressure between the two groups.  However, they did find a difference when applying the RMSSD technique to the heart rate data, finding a clear benefit for the beetroot juice group.

“Specifically, a decrease in RMSSD during exercise was observed with BJ (beetroot juice) consumption. . . . Therefore, we conclude that BJ is a useful supplementation tool increasing the parasympathetic regulation in RT and thus decreasing the internal load,”​ the researchers concluded.

The study was funded by an internal research grant from the University of Córdoba.

Source: Nutrients​​​
2022​,14​,5119. https://doi.org/ 10.3390/nu14235119
Beetroot Juice Produces Changes in Heart Rate Variability and Reduces Internal Load during Resistance Training in Men: A Randomized Double-Blind Crossover​
Authors: Jurado-Castro JM, et al.