The modulatory role of fermented Rooibos on oxidative stress and its impact on submaximal exercise performance in adult males

Abstract

Excessive production and accumulation of reactive oxygen and nitrogen species during exercise may cause oxidative stress and impact exercise performance. Rooibos with polyphenolic constituents may modulate the effects of oxidative stress during physical activities. This blinded randomised, cross-over placebo-controlled study included 30 adult males who consumed 375 ml of standardised fermented rooibos herbal extract or placebo beverage before completing a sub-maximal exercise, followed by 10 sprint bouts on a Wattbike. Rooibos appears to enhance the endogenous antioxidant defence system with increased levels of circulatory total and reduced glutathione in the participants and decreased levels in serum markers of muscle damage, creatinine kinase and aspartate aminotransferase. Mean submaximal trials (effort=75%–80% of maximum heart rate and/or 13 RPE Borg Scale) indicated after consuming rooibos, participants cycled for longer (291.83 s vs. 253.50 s: difference=14.05%), further (2790.30 m vs. 2434.93 m: difference=13.60%); produced 3.65% more power (W) and 2.42% more force (N). Mean cardiovascular responses during rooibos were modest when compared with the increased time and distance achieved, (134.55 bpm vs. 131.26 bpm: difference=2.40%) and relative oxygen uptake (27.32 ml/min/kg vs. 25.84 ml/min/kg: difference=5.53%). This suggests that rooibos may benefit metabolic responses during submaximal exercise, demonstrating its potential as an ergogenic aid.