The effect of acute beetroot supplementation on the muscular endurance of university level hockey players during resistance exercise

Abstract

It has been suggested that supplementation of inorganic nitrate (NO3) through consumption of beetroot juice may decrease the oxygen cost of exercise, and also increase tolerance and endurance to high intensity exercise. Improvements in power output during cycling exercise protocols have also been observed, however, a lack of research into the effects of inorganic nitrate upon resistance exercise has been highlighted. This study therefore investigated the effect of acute NO3 supplementation on performance during a muscular endurance exercise protocol. Ten male hockey players (Mean ± SD; age 20.8 ± 0.75 years, stature 180 ± 6.2 cm, body mass 82.6 ± 8.6 kg) were assigned to a single-blind, randomised, placebo-controlled, repeated measures design. Participants ingested nitrate rich beetroot juice (70 ml, ~4.2 mmol NO3) or a blackcurrant cordial placebo (70 ml, ~0.01 mmol NO3) 2.5 – 3 hours before completing as many repetitions as possible of 60% of their respective one repetition maximum (1RM). Results showed that bench press total load volume (TLV) was significantly higher when ingesting beetroot juice in comparison to the blackcurrant cordial placebo (1112.7 ± 172.2 vs. 900 ± 158.5 TLV; P = 0.0001). However, there was no significant difference found in leg press total load volume when ingesting beetroot juice in comparison to the placebo (6514 ± 1814.4 vs. 5336.6 ± 1799.3 TLV; P = 2.9). In conclusion, acute dosage of concentrated beetroot juice increased the muscular endurance and mean TLV for the bench press exercise.