ORIGINAL RESEARCH article
Front. Nutr.
Sec. Sport and Exercise Nutrition
Volume 12 - 2025 | doi: 10.3389/fnut.2025.1559917
This article is part of the Research TopicAdvancements in Dietary Supplements: Enhancing Sport Performance and RecoveryView all 3 articles
Individual Responses to Purple Grape Juice Consumption on Endurance, Explosive Power, and Fatigue in Young Male Elite Soccer Players
Provisionally accepted
Alireza Niknam1
Kamran Tahmasebi2
Mohammad Hemmatinafar1*
Walaa Jumah Alkasasbeh3
Mark Elisabeth Willems4
Maryam Koushkie Jahromi1
Morteza Bagheri Kalayeh5Mohammad Hadi Zare1- 1Shiraz University, Shiraz, Iran
- 2University of Isfahan, Isfahan, Iran
- 3Middle East University, Amman, Jordan
- 4University of Chichester, Chichester, United Kingdom
- 5University of Tehran, Tehran, Tehran, Iran
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Background: Purple grape juice (PGJ), a natural carbohydrate-and polyphenol-rich supplement, may enhance exercise performance. This study, incorporating individual response analysis, examined the acute effects of PGJ ingestion on endurance, explosive power, and perceived fatigue in elite male soccer players.Methodology: Twenty-two U-20 male soccer players (Age: 19.7± 0.3; height: 178 ± 4 cm; body mass: 72 ± 5 kg; body mass index [BMI]: 22.6 ± 0.9 kg/m 2 )) participated in an equally allocated, double-blind, crossover design study. Participants were allocated to one of two conditions: (1) purple grape juice (PGJ, n=11) or ( 2) placebo (PLA, n=11). The PGJ or placebo was ingested in four equal portions (10 ml/kg of body mass PGJ or PLA diluted with water) starting 4 hours before the test and continuing every hour, with the final ingestion 60 minutes before the 30-15 Intermittent Fitness Test (IFT). The placebo consisted of a calorie-free, grape-flavored liquid designed to match the taste and appearance of the PGJ. A 7-day washout period was maintained between the two conditions. Perceived fatigue and standing long jump (SLJ) performance were assessed at baseline, immediately and 5 minutes after the IFT. Maximum oxygen consumption (VO2max), time to exhaustion (TTE), and final velocity in the IFT (VIFT) were recorded during the test. The smallest worthwhile change (SWC) analysis was used to evaluate individual responses.Results: PGJ improved VIFT (P<0.001, Cohen's d=0.58), TTE (P<0.001, Cohen's d=0.69), and VO2max (P<0.001, Cohen's d=0.56) compared to PLA. No effects were found for SLJ or perceived fatigue (P>0.05), SWC analysis revealed that 77% of participants showed improvements in VIFT and VO2max, and 54% showed improvements in SLJ five minutes post-IFT.PGJ supplementation enhanced endurance performance parameters in most participants, with significant individual variability in response. These findings highlight the potential benefits of PGJ, particularly for athletes more responsive to its effects, emphasizing the need for personalized supplementation strategies.
Keywords: carbohydrate, endurance performance, Grape Juice, Jump performance, Soccer players
Received: 13 Jan 2025; Accepted: 19 May 2025.
Copyright: © 2025 Niknam, Tahmasebi, Hemmatinafar, Alkasasbeh, Willems, Koushkie Jahromi, Bagheri Kalayeh and Zare. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Mohammad Hemmatinafar, Shiraz University, Shiraz, Iran
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