Effects of grape juice consumption on muscle fatigue and oxidative stress in judo athletes: a randomized clinical trial
Goulart MJVC, Pisamiglio DS, MÖller GB, Dani C, Alves FD, Bock PM, Schneider CD. An Acad Bras Cienc. 2020 Nov 20;92(4):e20191551. doi: 10.1590/0001-3765202020191551. PMID: 33237140.
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Among judo athletes, 14-days of grape juice supplementation can improve the antioxidant profile; however, grape juice fails to improve fatigue after a combat simulation among judo athletes.
Strenuous exercise causes oxidative damage, which can result in cellular damage and may impair muscular strength. Antioxidants help prevent oxidative damage by scavenging free radicals produced during exercise. Grape juice is a source of the antioxidant polyphenol. We know little about the effect grape juice supplementation has on our response to exercise.
Goulart and colleagues completed a randomized controlled trial with a crossover design to evaluate the effects of grape juice supplementation on oxidative stress and muscle fatigue in judo athletes.
The researchers recruited 20 (9 men, 11 women) judo athletes between 17 and 21 years. The authors then randomly assigned participants to either a treatment (grape juice supplementation) or a control (placebo). Participants in the treatment group consumed 400 mL of reconstituted grape juice or placebo for 14 days before exercise. The placebo was designed to have the same flavor and color as grape juice. After the exercise session, the participants avoided the grape juice or placebo for 14 days. Next, the participants that initially received the grape juice got the placebo supplement. Meanwhile, participants that received the placebo switched to the grape juice supplementation for 14 days. The participants then completed another exercise bout. Each bout of exercise consisted of 3 rounds of 7-minute judo combats. Before and after each exercise bout, the researchers measured fatigue (e.g., Kimono Grip Strength Test, Horizontal Countermovement Jump, handgrip strength) and antioxidant profile (e.g., antioxidant capacity, DNA damage) assessed via blood samples. The athletes and the research team involved in data collection and analyses did not know when someone received grape juice versus placebo.
Overall, grape juice supplementation never affected fatigue. However, grape juice improved antioxidant profiles (e.g., lipid damage, DNA damage, antioxidant capacity) before the exercise bout compared to participants taking a placebo. Furthermore, grape juice improved total antioxidant capacity after exercise.
The authors demonstrated that while grape juice supplementation can improve the antioxidant profile, it fails to improve fatigue after a combat simulation among judo athletes. The improved antioxidant profile may offer other health benefits for this population. However, this should be studied further among athletes that consume grape juice for more than 14 days.
While grape juice may have some health benefits, we should educate athletes that grape juice is unlikely to reduce fatigue after exercise nor prevent exercise-related damage to DNA, protein, and lipids.
Questions for Discussion
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Written by: Kyle Harris
Reviewed by: Jeffrey Driban