A Sub-Maximal Eccentric Training Coupling with Eurycoma Longifolia Jack Supplementation Induced Quadriceps Muscular Strength and Thickness in Young Elite Rugby Players

Eurycoma longifolia Jack (ElJ) contains a useful organic compound proprietary for various medical purposes and was reported to able to stimulate the androgen hormones such as testosterone. However, its use for enhancing training and sports performance was unclear. Therefore, this study aimed to examine the effects of consuming ElJ supplementation when implementing submaximal eccentric training on quadriceps muscular strength and muscle thickness in elite athletes. Sixteen young elite rugby sevens players (21.5±1.5years; 1.74±0.06m; 80. 0±10.kg) were randomly assigned to one of two groups that supplemented with either ElJ (400mg per day) or similar taste and appearance placebo (PLA). They performed a submaximal eccentric training 3 times a week for 6 weeks in which the load increased from 75% to 100% of concentric 1RM (5% increase/week). Dependent variables of one repetition maximum (1RM) concentric and eccentric strength during leg press; concentric and eccentric peak torque at speeds of 60°/s and 180°/s during isokinetic knee extension and flexion, respectively; isometric peak torque and muscle thickness (vastus medialis, vastus lateralis, and rectus femoris) were collected within a week prior to, and after the 6-week training period, and then analysed accordingly. Mixed ANOVA indicated a significant interaction was evidenced for concentric 1RM (p = 0.018). Significant changes (p < 0.05) for pre and post-test were detected for concentric and eccentric 1RM, peak torque at 60°/s and 180°/s (with the exception for concentric peak torque at 180°/s), isometric peak torque, and muscle thickness of the vastus medialis, vastus lateralis, and rectus femoris; however, no between-group differences were found. The results indicated that combined ElJ supplementation and eccentric submaximal training induced significant improvement of quadriceps strength and quadriceps muscle thickness in young elite rugby players