Abstract

Introduction Heavy slow resistance (HSR) training is currently regarded as the treatment of choice for the conservative treatment of patellar tendinopathy (Malliarias et al. 2013). However, the efficacy of this type of intervention in reducing pain and restoring tendon structure and function has never been assessed against a wait-and-see tendinopathic control group. In this prospective study, we compare the effects of HSR training in patients with patellar tendinopathy to the changes measured without intervention in equally affected controls. Methods Patients with chronic (>3 months), untreated patellar tendinopathy were randomized to 3 months of wait-and-see (WaS; 29±5 yrs; male=12; female=1) or HSR (27±6 yrs; male=11; female=3). Pre- and post-intervention testing comprised evaluations of neovascularization, tendon degeneration (hypo-echoic area and/ or anterior-posterior thickening), pain (VAS), functional limitations (VISA-P), ultrasound-based determination of mechanical and material properties and MRI-based measurement of patellar tendon cross-sectional area in vivo. Results At baseline, anthropometric and tendon parameters did not differ between groups. During the course of the study, mean HSR training compliance was 80%. Significant group x time interactions for the VISA-P (p=.005, ηp2=.36) and VAS scores (p=.002, ηp2=.25) proved clinically improvement for the HSR group only (+24±15pts; -38±26pts). However, training did not affect indicators of tendon degeneration and neovascularization. Similarly, isometric quadriceps strength (+7%; p=.223; ηp2=.06), patellar tendon stiffness (-7%; p=.411; ηp2=.03) and Young’s modulus (-4%; p=.850 ηp2<.01) were unaffected by HSR training, although a site-specific decrease in patellar tendon cross-sectional area (medial site: -5%; p=.018; ηp2=.21) was observed in this group. Discussion The meaningful improvements in patellar tendon pain and function after HSR training were comparable to recent findings (Kongsgaard et al. 2010). Interestingly, the efficacy of HSR on this primary outcome was not reflected in features typically used in the diagnosis of tendinopathy (tendon degeneration and neovascularization) or in measurements of tendon mechanical and material properties. Additionally, the reasons why isometric knee extension torque did not increase with training or the decrease in patellar tendon cross-sectional area remain elusive. In summary, this study confirmed the efficacy of HSR to treat tendinopathy in a design including WaS patients but further research is needed to uncover the mechanisms associated with clinical improvements. References Kongsgaard et al., Am J Sports Med 2010. Malliaras et al., Sports Med, 2013.