Introduction: The purpose of this research was to evaluate the mechanical characteristics of the patellar tendon (PT) in elite level jumping athletes. Patellar tendon (PT) mechanical properties including strain, stiffness, stress, elastic modulus, cross-sectional area (CSA) and mechanical work done were measured a mean of 344 days, range 254-512, apart. Methods: Real-time ultrasound imaging of the PT and maximal voluntary isometric contraction (MVIC) force of the knee extensors, were synchronously recorded for the left and right sides of 13 athletes (17.9 years of age, range 16-24, 201 cm in height, range 196-209 and 91 kg in weight, range 81-108) participating in volleyball or basketball on a full-time basis at the Australian Institute of Sport. All participants volunteered providing written and informed consent. Four of the 13 participants had patellar tendinopathy at the time of testing and were not included in the analysis. A repeated 2 × 2 ANOVA was used to compare PT mechanical properties before and after a competitive season and between sides. For each side, a 2-way ANOVA was used to compare the PT CSA between the proximal, mid and distal sites along the PT and before and after the competitive season. Results: The main findings were that PT elastic modulus at near maximal effort (70-80% MVIC) was significantly lower during session 2 (p = 0.03) and there was a significantly greater percentage of mechanical work done in session 2 compared to session 1 from mid-range to maximal efforts (50-100% MVIC) (p < 0.02). Patellar tendon elastic modulus and stiffness were significantly greater on the right compared to left side at mid-range MVIC efforts (40-50% MVIC) (p < 0.05). Conclusions: The PT may adapt its ability to withstand tensile load at mid-range to near-maximal knee extensor isometric efforts. These contraction efforts are similar to those used during training and competition in jumping activities such as volleyball and basketball. These findings are similar to those of strengthening programs targeted at treating patellar tendinopathy. Thus, the loading history of the PT may influence its ability to withstand tensile load especially as there was no change in mechanical characteristics (stiffness or strain), PT force or CSA. This is the first study that examined the mechanical characteristics of the PT prospectively over one year of training and competition in elite level athletes. The findings indicate that any observed change in mechanical properties must be specific to the sample being tested rather than generalised to a broader population.
© Copyright 2011 Journal of Science and Medicine in Sport. Elsevier. All rights reserved.