Morphofunctional upper limb asymmetries in young tennis players: the role of maturity status

The aim of this study was to check for upper limb volume asymmetry and strength ratio of shoulder muscle rotators in young tennis players. A total of 21 young male tennis players took part in the study. Subjects’ maturity status was determined using predicted age at peak height velocity (PHV); thus, the sample was divided into two groups: negative maturity offset values (PRE_PHV; n = 9) and positive values, including 0 (POST_PHV; n = 12). Upper limb volumes were estimated using the truncated cone method. Concentric peak torque in the external and internal shoulder rotations was determined using an isokinetic dynamometer at 60^o.s⁻¹. The external to internal rotation ratio was also calculated. There was morphological upper limb asymmetry in both groups (p < 0.05), with no difference between the groups. However, only the POST_PHV group presented shoulder strength asymmetry. External to internal rotation ratios were 76% and 89% for dominant and nondominant arms, respectively, in the POST_PHV group. PHV seems to be a critical period for functional asymmetry in young tennis players, particularly the internal rotation strength and conventional ratio of shoulder rotation. Thus, an assessment of shoulder rotator strength is required to monitor its progression and avoid the risk of injury in the dominant rotator cuff.