The Effect of Beetroot Juice Supplementation on Muscle Performance During Isokinetic Knee Extensions in Male Taekwondo Athletes; [L'effet De La Supplementation De Jus De Betterave Sur La Performance De Muscle Pendant Des Prolongations Isokinetic De Genou Dans Les Athletes Masculins De Taekwondo] Publisher



Khosravi S¹ ; Ahmadizad S² ; Yekaninejad MS³ ; Karami MR⁴ ; Djafarian K⁵ Show Affiliations
Source: Science and Sports Published:2021

Abstract

Objectives: Little information is available regarding the effects of beetroot juice (BRJ) on muscle performance and contractions during resistance exercise. The muscle strength and power of the lower extremity is an important attribute in Taekwondo, therefore, present study examines the effects of 6 days of BRJ supplementations on muscle performance during isokinetic contractions of knee muscle in male Taekwondo athletes. Equipments and methods: Twelve male Taekwondo athletes (age, 19.2 ± 1.6 yrs) were volunteered to take part in this double-blind, placebo-controlled, randomized crossover design. Participants consumed either 140 mL nitrate-rich concentrated BRJ (∼12.8 mmol NO3−) or placebo (blackcurrant juice) for six consecutive days. On the last day of supplementation, the knee extensions were performed on a Biodex isokinetic dynamometer. Treatment periods were separated by a 10-day washout periods. Results: Knee extensor peak torque increased significantly (P < 0.05) following BRJ supplementation from 2.45 ± 0.19 to 2.60 ± 0.23 and from 1.89 ± 0.12 to 2.01 ± 0.18 Nm/kg at angular velocities of 180 and 360°/s, respectively in the dominant leg and it increased significantly (P < 0.05, from 2.04 ± 0.15 to 2.07 ± 0.24 Nm/kg) at 360°/s in the non-dominant. An increase in peak torque was also detected during 50 maximal knee extensions at 180°/s. Responses of blood pressure supplementation and placebo were not significantly different. It is concluded that short-term BRJ supplementation enhances bilateral muscle strength during highest velocities of isokinetic contractions and reduces fatigue during muscular contractions of knee extensor in male Taekwondo athletes. © 2021 Elsevier Masson SAS