Effect of Rapid Weight Loss on Hydration Status and Performance in Elite Judo Athletes

Reference Values for Hydration Biomarkers: Optimizing Athletic Performance and Recovery

The negative effects of dehydration or overhydration on exercise performance and health are widely recognized. However, the interindividual variability of fluid imbalances among athletes and across various sports is large, due to the complex interactions of physiological, environmental, and sport-specific factors. Such complexity not only makes it difficult to predict fluid needs prior to competition or training sessions, but also supports the creation of an individualized hydration plan (IHP) for each athlete. Measurements of valid, field-expedient biomarkers such as body mass change, urine concentration, and thirst enable ongoing monitoring of an athlete's hydration state and are integral components of an IHP. Unfortunately, no extensive repository of sport-relevant hydration biomarker data exists. Therefore, this narrative review presents a novel inventory of pre- and post-exercise reference values for body mass change, urine specific gravity, and subjective rating of thirst. These reference values were identified via electronic database searches that discovered field studies of competitive events, weight category sports, training sessions, and routine daily activities. We propose that comparing an athlete's real-time body mass change, urine specific gravity, and thirst rating to previously published reference values will clarify the extent of dehydration or overhydration, guide rehydration efforts, and optimize subsequent exercise performance, recovery, and health.

Post-training breakdown: acute effects of different training types on body hydration status and performance

Objective

Wrestling is a complex sport that requires a combination of strength, endurance, and wrestling-specific technical training. Endurance activities, such as running, are commonly performed for rapid weight reduction before competition. However, these activities can severely disrupt recovery and lead to significant declines in performance. This study aimed to examine the acute effects of endurance, strength, and wrestling training sessions on hydration status and performance parameters in young wrestlers, providing insights to guide more effective hydration and recovery strategies.

Method

A total of 14 experienced young wrestlers participated in a crossover design, completing endurance, strength, and wrestling training sessions on separate days. The hydration status was assessed through urine specific gravity (USG) before and after each session. The performance measures included hand grip strength, back and leg strength tests, anaerobic power (vertical and horizontal jumps), respiratory muscle strength (maximal inspiratory pressure, MIP), and reaction time assessments.

Results

The endurance training caused the most significant acute reductions in the hydration (USG increase: 0.016 ± 0.005 g/cm3, p < 0.05) and body mass (BM; -1.89 ± 0.4%, p < 0.05), along with immediate performance decrements in the back strength (-7.02 ± 1.2%, p < 0.001), right-hand grip strength (-8.79 ± 2.1%, p < 0.001), jump height (-7.26 ± 1.8%, p < 0.001), and MIP (-9.01 ± 2.3%, p < 0.001). The hydration levels in the endurance group did not fully recover by the next day (USG post-training vs. before the next day's training: p < 0.05). In contrast, the strength training improved the reaction time before the next day's session (+5.6 ± 1.3%, p < 0.05), while the attention remained unaffected across all training types.

Conclusion

Endurance training-commonly used for rapid weight loss-can acutely compromise hydration and reduce key performance measures, with recovery taking more time compared to strength or wrestling sessions. Given these findings, endurance sessions should be strategically scheduled before rest days or low-intensity technical training to minimize their negative effects on subsequent performance. Implementing enhanced hydration strategies during endurance-focused sessions may also help mitigate these acute impacts and optimize recovery and performance in young wrestlers.

A scoping review of rapid weight loss in judo athletes: prevalence, magnitude, effects on performance, risks, and recommendations

PURPOSE

Combat sports, such as judo, are weight categorized. Weight control was established to promote fair disputes among individuals. However, combat sports athletes adopt rapid weight loss (RWL) to obtain an advantage over smaller and lighter opponents. This scoping review article presents the prevalence, magnitude, and methods of RWL and its effects on physical and competitive performance, health risks, and psychological effects. Specific recommendations for attenuating the effects of RWL are also presented.

METHODS

Studies were retrieved from Web of Science, PubMed, and Scopus databases. Four hundred and forty-six articles were identified, of which fifty-three were considered eligible for this review.

RESULTS

The results showed that the prevalence of RWL was between 40% and 92.9% and that athletes reduced their body mass by approximately 5%. Although the literature suggests that RWL impairs the performance and psychological well-being of athletes, these results were obtained when recovery time was not provided.

CONCLUSION

No negative effects on performance were observed when the recovery time was >4 h. However, health risks due to RWL practices should be considered, and RWL should be avoided.

The Cognitive Function and Taekwondo-Specific Kick Performance of Taekwondo Athletes at Different Hydration Statuses

PURPOSE

Successful participation in taekwondo (TKD) requires athletes to possess quick decision-making abilities and demonstrate technical proficiency during competition. Dehydration, occurring during both training and competition, is widely recognized to have various negative effects.

METHODS

This study investigated the impact of different levels of dehydration on cognitive function, as measured by the Vienna Test System, and the specific performance of kicking techniques among TKD athletes. Using a randomized crossover design, 12 participants were involved in the study. Before and after 1 hour of training at 80% of maximal heart rate, participants were weighed and provided urine samples. All participants were randomly assigned to 3 different hydration conditions: the euhydrated (EUH) group had unrestricted access to fluid consumption, while the hypohydrated (HYP) and severely HYP (S-HYP) groups experienced reductions of 2.0% and 4.0% of their initial body weight, respectively.

RESULTS

The EUH group exhibited better reaction speed in reaction-time test-form S1 than the HYP and S-HYP groups. Notably, the EUH group demonstrated a significantly higher success rate in the front-side kick (EUH 98%, HYP 90%, S-HYP 88%; P < .05). However, the success rates of back roundhouse kick and free head kick were similar among the 3 statuses. Furthermore, postexercise heart rates were found to be significantly higher in the HYP and S-HYP groups compared with the EUH group.

CONCLUSIONS

This study provides insight into the negative effects of dehydration on cognitive function and TKD-specific performance. It is recommended that TKD athletes maintain optimal hydration levels during training and competition to ensure optimal performance.

Evidence of weight loss in junior female judo athletes affects their development

Purpose

The facile manipulation of body weight in junior athletes has the potential to pose significant risks to their lifelong health. In judo, which is a weight class sport, pre-competition weight loss is widespread even among juniors, but information on the current situation is scarce, especially for female athletes, for whom it is important to provide adequate nutrition and enhance bone mass during the growth period, and the details of the current situation are not clear. Therefore, the purpose of this study was to determine the actual weight loss during the growth period in junior female judo athletes and its subsequent impact on their health.

Methods

The survey was a cross-sectional survey of junior female judo athletes in Japan using a questionnaire. Participants were asked to respond via an online questionnaire about their weight, height, weight loss experience, menstruation, competition results, and other lifestyle.

Results

51.8% of subjects experienced weight loss for competition during their junior high school years (ages 12-15). Those who experienced weight loss during secondary sexual characteristics were found to be significantly shorter in current height than those who did not (p < 0.05). Weight loss during secondary sexual characteristics did not affect current menstrual cycle. There was no significant difference in competition results due to the experience of weight loss during junior high school (χ 2 = 4.485, df = 3, n.s.).

Conclusions

These findings suggest that weight loss during the growth spurt phase may adversely impact normal development. It also suggested that weight loss during the junior high school years may not be a strategy to bring about better competition results. These observations indicate the need for education on appropriate class selection and weight control for junior athletes in weight class competitions.

Which Performance Tests Best Define the Special Judo Fitness Test Classification in Elite Judo Athletes?

The normative values of the Special Judo Fitness Test (SJFT) are used to evaluate judo athletes, and the question arises of which performance tests from crucial motor abilities best define the SJFT classification in elite judo athletes. This study aimed to investigate the relationship between elite judo athletes’ physical performance and the evaluation using SJFT index norms. Nineteen judo athletes (11 females) (22.8 ± 2.5 years old) from the senior judo national team voluntarily participated in this study. Body composition, reaction time, balance, flexibility, agility, hand grip strength, 20 m sprint, vertical jump, SJFT, and Wingate tests were performed by athletes on four separate days at one-day intervals. Athletes were classified as regular and above (≥regular) or poor and below (≤poor) according to their SJFT index scores. Simple logistic regression analysis was used to evaluate this classification’s consistency with performance test results. Odds ratios (OR) and 95% confidence intervals related to each possible factor and Wald test statistics were calculated. The SJFT index classification was associated with Wingate peak and mean power, vertical jump, and sprint performance results (p < 0.05), whereas it was not associated with body fat percentage, agility, reaction time, hand grip strength, flexibility, and balance performances (p > 0.05). SJFT index classificatory norms are mainly related to athletes’ anaerobic power. Higher anaerobic power increases athletes’ possibility of being classified as ≥regular.

Acute Dehydration Impairs Performance and Physiological Responses in Highly Trained Judo Athletes

Background: The present study investigated highly trained male judo athletes and how a 5% body mass dehydration affects their judo-specific performance and physiological responses. Methods: Nine highly trained international-level male judo athletes who are weight-cyclers voluntarily participated in the study. The study had a controlled crossover design in nature. Athletes completed three sessions, including a familiarisation session and two experimental sessions (dehydration (DEHY) and control (CON)) with judo-specific tests, including maximal handgrip strength test (HGS), judogi grip strength tests (JGST), and the Special Judo Fitness Test (SJFT). Results: Intergroup analysis revealed a significant increase in urine specific gravity (USG) and decreased body mass following DEHY condition compared to CON. Furthermore, significant decreases were determined in HGS, JGSTs, and a number of throws in the first and third series of SJFTs, as well as higher heart rate (HR) responses in the second and third series of SJFT and worse SJFT index in DEHY condition (p < 0.05). Conclusions: We concluded that 5% dehydration of body mass led to impairment in dynamic and isometric strength in upper limbs and in judo-specific performance, as well as elevated HR during the SJFT.