Evaluation of Shoulder and Knee Isokinetic Strength Profile Among Elite Adolescent Badminton Players

CONTEXT: Badminton continues to be a highly competitive sport where training is introduced at an early age and load has intensified. This exposes players to a greater risk of injuries, in particular when assessing related training outcomes such as strength, agonist-antagonist ratio, and bilateral deficit among adolescents where age- and sex-associated growth and development should be considered. OBJECTIVE: To evaluate strength profile of the upper and lower limbs among adolescent elite Malaysian badminton players. DESIGN: Cross-sectional study. SETTING: Laboratory. PARTICIPANTS: Forty-eight asymptomatic athletes (24 males and 24 females) were grouped into early and late adolescence (13-14 y old and 15-17 y old, respectively). MAIN OUTCOME MEASURE(S): Strength (absolute and normalized) of the external/internal rotators of the shoulder and flexor/extensor of the knee and strength derivatives, conventional strength ratio (CSR), dynamic control ratio (DCR), and bilateral deficits were measured. RESULTS: Males showed greater strength in all strength indices (P < .05). The older group had greater strength compared to younger for most of the upper and lower limb indices (P < .05); these effects diminished when using normalized data. For females, there was no age group effect in the shoulder and knee strength. All players displayed lower shoulder and knee normative values for CSR and DCR. Dominant and non-dominant knee strength were comparable between sex and age groups. CONCLUSIONS: For males, growth and maturation had a greater contribution to strength gained compared to training, whereas for females, growth, maturation, and training did not improve strength. The normalized data indicated that training did not improve all indices measured apart from external rotator strength in females. All players also displayed lower normative values of CSR and DCR. These results suggest that training in elite adolescent Malaysian badminton players lacks consideration of strength gain and injury risk factors.