Adaptation of tendon tissue to exercise load in children

Submission note: A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Physiotherapy to the Department of Physiotherapy, Faculty of Health Sciences, La Trobe University, Bundoora.

Tendon forms an anatomical link between muscle and bone, transmitting mechanical load from muscle to the bone surface. How tendon adapts to mechanical load associated with exercise during childhood growth and whether this is influenced by gender and pubertal status is unknown. Little is also known about the relationship between tendon, muscle and bone growth in children. The aims of this study were to determine (i) differences in tendon size between dominant and non-dominant arms of children who play tennis, (ii) if tendon size is influenced by gender and pubertal status, and (iii) the relation of tendon size to muscle and bone size during childhood growth. The triceps brachii tendon size was measured from MRI scans of both arms in 104 children (58 boys, 46 girls). Data were analysed with multiple regression analyses. Results found that physical loading from exercise affects tendon size. There was a significant difference in tendon size between dominant and non-dominant arms in children who played tennis and children who did not play tennis, and this was influenced by pubertal status. The non-dominant arm triceps brachii tendon was significantly smaller (p equals 0.01 for boys and p equals 0.05 for girls) than the dominant side. Gender did not influence tendon size. However between pubertal groups, there was a difference in the dominant arm triceps brachii tendon size (F(2, 99) equals 8.2, p equals 0.001), and non-dominant arms (F(2, 99) equals 3.8, p equals 0.03). There was a significant relation between tendon, muscle and bone size during growth in children. Tendon size during growth was moderately related to muscle size (t equals 2.52, p equals 0.01) and strongly related to cortical bone size (t equals 2.78, p equals 0.007). This study highlights the importance of physical exercise during childhood on tendon growth and indicates a method for addressing long term tendon health.