Author(s): TANABE, Y., HEDIN, E.E., MÜLLER, A.H., VAN DEN BERG, M., SEYNNES, O., RAASTAD, T., Institution: THE UNIVERSITY OF TOKYO, Country: JAPAN, Abstract-ID: 2722

INTRODUCTION:
Curcumin possesses anti-inflammatory and antioxidant properties and has been reported to attenuate exercise-induced muscle damage. Despite these potential benefits, its influence on resistance training-induced muscle adaptations remains unclear. In addition to chronic adaptations such as muscle hypertrophy and strength development, curcumin may also modulate acute exercise-induced changes in muscle function and cellular stress responses.
Therefore, this study investigated the effects of curcumin supplementation on both training adaptations and acute exercise responses, with a focus on muscle hypertrophy, muscle strength, and markers of muscle fiber stress and damage.
METHODS:
Twenty-nine untrained healthy males and females (29 ± 5 years) were assigned to a curcumin (n = 16) or placebo (n = 13) supplementation group and completed 12 weeks of a traditional whole-body strength-training program (seven exercises, at 70–85% 1RM, 3 sessions/week). After the training period, participants performed an additional exercise bout to evaluate the effects of curcumin supplementation on acute post-exercise skeletal muscle responses.
Markers of muscle hypertrophy, strength, and physiological stress were assessed, and muscle biopsy samples were collected from the vastus lateralis before and after the training intervention as well as after the acute exercise bout. Lower-limb lean mass and muscle fiber cross-sectional area (CSA) were evaluated as indices of muscle hypertrophy. Leg press one-repetition maximum (1RM), knee extension isokinetic peak torque, and isometric maximal voluntary contraction (MVC) were assessed as indices of muscle strength. The staining intensity of αB-crystallin was used as a marker of exercise-induced muscle stress and damage.
RESULTS:
Both groups increased lower-limb muscle mass (2.0 vs. 2.7%) and the CSA of type II fibers (30 vs. 34%, Curcumin and placebo, respectively, p < 0.05). In addition, leg press 1RM (30 vs. 31%), knee extension isokinetic peak torque (18 vs. 12%), and isometric MVC (14 vs. 19%) increased significantly in curcumin and placebo, respectively (p < 0.05), with no differences between groups.
In the acute experiment, isokinetic peak torque for knee extension decreased more in the placebo group than in the curcumin group immediately post-exercise (-15 vs. -7%, respectively, p < 0.05). The staining intensity of αB-crystallin increased after exercise in both groups and across both fiber types, and the curcumin group exhibited a smaller elevation in αB-crystallin at 2 hours post-exercise compared with the placebo group (23 vs. 49%, respectively, p < 0.05).
CONCLUSION:
Curcumin supplementation did not enhance training-induced muscle hypertrophy or strength gains. However, curcumin may attenuate, and potentially protect against, acute exercise-induced fatigue and cellular stress responses. These findings suggest potential practical implications for optimizing supplement timing across different training phases.