Abstract
This study aimed to determine the effects of a betalain-rich concentrate (BRC) of red beets, containing antioxidant and anti-inflammatory properties, on performance and exercise-related muscle damage. Thirteen (25.3 ± 5.4 years) competitive male runners completed two double-blind, cross-over, randomized trials (BRC and control) separated by seven days. Each trial was preceded by six days of supplementation with 100 mg of BRC or control. On the seventh day, exercise trials commenced 150 min after supplementation with 50 mg BRC or control and consisted of 30 min of treadmill running (77 ± 4% VO2max) followed by a 5-km time trial (TT). During exercise at the same intensity, BRC resulted in a 3% lower heart rate, a 15% lower rate of perceived exertion (RPE) and a 14% lower blood lactate concentration compared to the control (p = 0.05). Five-kilometer TT duration (23.0 ± 4.2 versus 23.6 ± 4.0 min) was faster in 10 of the 13 subjects, and RPE was lower (p < 0.05) with the BRC treatment compared to the control. Lactate dehydrogenase, a marker of muscle damage, increased less from baseline to immediately and 30 min after the 5-km TT with the BRC treatment, despite no differences in subjective measures of muscle soreness and fatigue. In summary, BRC supplementation improved 5-km performance time in male competitive runners.
Highlights
Beetroot has received much attention from competitive athletes, coaches and scientists as a natural food supplement for improving exercise performance [1,2]
The nitrate in the beetroot juice was thought to increase the production of nitric oxide through the nitrate-nitrite-nitric oxide reduction pathway induced by bacterial nitrate reductases in the oral cavity [1,2]
We found no significant differences in VO2 or respiratory exchange ratio (RER); heart rate (HR) was 2.7 ̆ 0.8%, and rate of perceived exertion (RPE)
Summary
Beetroot has received much attention from competitive athletes, coaches and scientists as a natural food supplement for improving exercise performance [1,2]. Several studies have found a correlation between nitrate-rich beetroot juice (5–9 mmol of nitrate or about 85 g of beets) and 5–16.1-km time-trial performances in competitive runners and cyclists [3,4,5,6]. Higher nitric oxide could improve muscle blood flow and oxygenation and, exercise time trial performance. Lauded for their free radical scavenging capacity [8] and protecting cell membranes from lipid peroxidation and heme decomposition [9]. This property is likely due to the phenol and cyclic amine groups in betalains, which are good electron and proton donors [9].
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