Despite the known beneficial effects of creatine in treating exercise-induced muscle damage (EIMD), its effectiveness remains unclear. This study investigates the recovery effect of creatine monohydrate (CrM) on EIMD. Twenty healthy men (21–36 years) were subjected to stratified, randomized, double-blind assignments. The creatine (CRE) and placebo (PLA) groups ingested creatine and crystalline cellulose, respectively, for 28 days. They subsequently performed dumbbell exercises while emphasizing eccentric contraction of the elbow flexors. The EIMD was evaluated before and after exercise. The range of motion was significantly higher in the CRE group than in the PLA group 24 h (h) post exercise. A similar difference was detected in maximum voluntary contraction at 0, 48, 96, and 168 h post exercise (p = 0.017–0.047). The upper arm circumference was significantly lower in the CRE group than in the PLA group at 48, 72, 96, and 168 h post exercise (p = 0.002–0.030). Similar variation was observed in the shear modulus of the biceps brachii muscle at 96 and 168 h post exercise (p = 0.003–0.021) and in muscle fatigue at 0 and 168 h post exercise (p = 0.012–0.032). These findings demonstrate CrM-mediated accelerated recovery from EIMD, suggesting that CrM is an effective supplement for EIMD recovery.

This study aimed to investigate the relationship between the muscle shear modulus of the biceps brachii, urinary titin N-terminal fragment (UTF), and other damage markers after eccentric exercise. Seventeen healthy males performed five sets of ten eccentric exercises with dumbbells weighing 50% of the maximum voluntary contraction (MVC) at the elbow joint. Muscle shear modulus with range of interest set to only biceps brachii muscle measured by ultrasound shear wave elastography, UTF, MVC, range of motion (ROM), and soreness (SOR) were recorded before, immediately after, and 1, 24, 48, 72, 96, and 168 h after eccentric exercise. Each marker changed in a time course pattern, as found in previous studies. The peak shear modulus showed a moderate negative correlation with peak MVC (r = –0.531, P < 0.05) and a strong positive correlation with peak UTF (r = 0.707, P < 0.01). Our study results revealed a significant relationship between muscle strength, shear modulus measured by ultrasound SWE, and titin measured by UTF, as a non-invasive damage marker after eccentric exercise to track changes in EIMD.

Eccentric exercise induces muscle damage and inflammation, resulting in a state of reduced physical activity with muscle dysfunction and a feeling of tiredness after exercise. Creatine is known to act as an energy buffer, but it has also been suggested to exert inhibitory effects on muscle damage and peripheral inflammation. The purpose of this study was to test the hypothesis that creatine supplementation alleviates fatigue after eccentric exercise and to explore the mechanism of this effect. C57BL/6J mice were fed an AIN-93G-formulated control diet or a creatine-containing diet for 6 days and were then subjected to downhill running, a model of eccentric exercise, to assess the effects on the total creatine concentrations in skeletal muscle and brain tissue, spontaneous activity, the urine concentration of titin N-fragment, and inflammatory gene expression. The results showed that creatine supplementation significantly increased the total creatine concentrations in skeletal muscle and brain tissue. Furthermore, spontaneous activity significantly decreased after downhill running and creatine supplementation maintained a significantly higher level of spontaneous activity. In addition, creatine supplementation significantly suppressed the downhill-running-induced increase in the mRNA expression of genes encoding ICAM-1, E-selectin, CD18, and BKB1R in the soleus muscle and IL-1β in the hypothalamus. On the other hand, creatine supplementation did not clearly influence the urine concentration of titin N-fragment. These results indicate that creatine supplementation may alleviate fatigue after eccentric exercise by partially suppressing inflammation in slow-twitch skeletal muscle and brain tissue.

Background/Objectives: In this study, we aimed to examine the effect of creatine monohydrate (CrM) supplementation on recovery from eccentric exercise-induced muscle damage (EIMD) in diverse populations, including different sexes and age groups. EIMD decreases maximal voluntary contraction (MVC), restricts the range of motion (ROM), and increases muscle stiffness and delayed-onset muscle soreness, all of which negatively impact athletic performance. Therefore, developing effective recovery strategies is essential. Methods: A double-blind, randomized, placebo-controlled trial was conducted with 40 healthy male and female participants. After 33 days of supplementation with either CrM or placebo (crystalline cellulose), the participants performed eccentric exercises. Recovery indices, including MVC, muscle stiffness, subjective muscle extensive soreness, fatigue, and upper arm circumference, were measured at baseline, immediately after exercise, 48 h post-exercise, and 96 h post-exercise. Results: The creatine supplementation group (CRE) demonstrated a significantly quicker recovery of MVC than the placebo group (PLA). Furthermore, reductions in shear modulus and muscle fatigue were observed in the CRE group. Notably, females in the CRE group exhibited a significant suppression of post-exercise edema, suggesting a sex-specific response. Conclusions: These findings indicate that CrM supplementation may enhance recovery from EIMD, contributing to the maintenance of muscle function and the reduction of discomfort after exercise. CrM has the potential to serve as a practical nutritional strategy to promote recovery, not only for athletes, but also for a broader population.

Ice slurry ingestion enhances exercise performance by lowering the core body temperature. However, an operational issue related to this ingestion is the requirement for a high intake of 7.5 g·kg^-1 to produce the desired effects. We investigated the effects of the intake of low amounts of ice slurry at −2°C on the tympanic temperature and exercise performance during repeated high-intensity intermittent exercises in a hot environment. This study was a randomized, crossover study, with a 6-day washout period. Twelve university rugby union players performed two 30-min sessions of high-intensity intermittent exercises separated by a 15-min half-time break on a cycle ergometer in a hot environment (28.8°C ± 0.1°C, 49.5% ± 0.6% relative humidity). The participants ingested 450 g of −2°C-ice slurry (ICE), or a 30°C-beverage (CON) having the same composition as ICE, or 30°C-water (WAT) during the half-time break. The tympanic temperature and skin temperature were measured as the physiological data, and the peak power and mean power as the exercise performance data. The tympanic temperature at the half-time break and beginning of the 2^nd session was significantly lower in the ICE group as compared with the CON and WAT groups. The skin temperature at the half-time break was significantly lower in the ICE group as compared with the WAT group. While the peak power and mean power during the 2^nd session were significantly greater in the ICE group as compared with the CON and WAT groups. Our findings suggest that even the intake of lower amounts, as compared with those used in previous studies, of low-temperature ice slurry can reduce the body temperature and improve the peak power. These results suggest that intake of low-temperature ice slurry as a strategy for internal body cooling is useful for improving endurance exercise performance in hot environments.

Relationships between Changes in Muscle Shear Modulus, Urinary Titin N- Terminal Fragment, and Maximum Voluntary Contraction Torque after Eccentric Exercise of the Elbow Flexors