Related Experiment Video
Updated: May 13, 2026

Muscle Imbalances: Testing and Training Functional Eccentric Hamstring Strength in Athletic Populations
Published on: May 1, 2018
Upper limb muscle-bone asymmetries and bone adaptation in elite youth tennis players
Alex Ireland1, Thomas Maden-Wilkinson, Jamie McPhee
1Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, Manchester, UK.
Introduction:
The study of tennis players allows the nonracket arm to act as an internal control for the exercising racket arm. In addition, the study of the upper limbs removes the influence of gravitational loading, allowing the examination of the influence of muscular force on bone adaptation.
Methods:
The role of muscular action on bone, strength parameters of the radius, ulna (both at 4% and 60% distal-proximal ulnar length), and humerus (at 35% distal-proximal humerus length) as well as muscle size in both arms of 50 elite junior tennis players (mean ± SD age = 13.5 ± 1.9 yr) were measured with peripheral quantitative computed tomography (pQCT).
Results:
Strong relationships were found between muscle size and bone size in both arms (all correlations, P < 0.001, R = 0.73-0.86). However, the muscle-bone ratio was significantly lower (P < 0.001) in the upper arm on the racket side (compared with the contralateral arm). In addition, material eccentricity analysis revealed that bone strength in bending and torsion increased more than strength in compression as the moment arms for these actions (bone length and width, respectively) increased (in all cases, P > 0.001, R = 0.06-0.7) with relationships being stronger in torsion than in bending. Large side differences were found in bone strength parameters and muscle size in all investigated sites, with differences in distal radius total BMC (+37% ± 21%) and humerus cortical cross-sectional area (+40% ± 12%) being most pronounced (both P < 0.001).
Conclusions:
These results support a strong influence of muscular action on bone adaptation; however, interarm muscle-bone asymmetries suggest factors other than local muscle size that determine bone strength. The results also suggest that torsional loads provide the greatest stress experienced by the bone during a tennis stroke.
Related Concept Videos
Bones of the Upper Limb: Humerus
Changes in the Appendicular Skeleton with Age
Initially, the limb buds consist of a core of mesenchyme covered by a layer of ectoderm. The ectoderm at the end of the limb bud thickens to form a narrow crest called the apical ectodermal ridge. This ridge stimulates the underlying...
Bones of the Upper Limb: Ulna
Bones of the Upper Limb: Radius
The radius has a nail-shaped head, and a short...
Bones of the Lower Limb: Femur and Patella
Development of the Limb Synovial Joints
The mesenchymal stem cells differentiate into chondrocytes that form the hyaline cartilage, and later the cartilaginous model of the bone. This model further transforms into a bone. This process is known as endochondral ossification.
During development, the limbs...

