Downhill backwards walking causes repeated, cyclical loading of the muscle-tendon unit. The effect this type of repeated loading has on the mechanical behaviour of the Achilles tendon is presently unknown. This study aimed to investigate the biomechanical response of the Achilles tendon aponeurosis complex following a downhill backwards walking protocol. Twenty active males (age: 22.3 +/- 3.0years; mass: 74.7 +/- 5.6kg; height: 1.8 +/- 0.7m) performed 60min of downhill (8.5 degrees), backwards walking on a treadmill at -0.67m center dot s(-1). Data were collected before, immediately post, and 24-, 48- and 168-h post-downhill backwards walking. Achilles tendon aponeurosis elongation, strain and stiffness were measured using ultrasonography. Muscle force decreased immediately post-downhill backward walking (P=0.019). There were increases in Achilles tendon aponeurosis stiffness at 24-h post-downhill backward walking (307 +/- 179.6N center dot mm(-1), P=0.004), and decreases in Achilles tendon aponeurosis strain during maximum voluntary contraction at 24 (3.8 +/- 1.7%, P=0.008) and 48h (3.9 +/- 1.8%, P=0.002) post. Repeated cyclical loading of downhill backwards walking affects the behaviour of the muscle-tendon unit, most likely by altering muscle compliance, and these changes result in tendon stiffness increases.
Tendinopathy is frequently associated with structural disorganization within the tendon. As such, the clinical use of ultrasound and magnetic resonance imaging for tendinopathy has been the focus of numerous academic studies and clinical discussions. However, similar to other musculoskeletal conditions (osteoarthritis and intervertebral disc degeneration), there is no direct link between tendon structural disorganization and clinical symptoms, with findings on imaging potentially creating a confusing clinical picture. While imaging shows the presence and extent of structural changes within the tendon, the clinical interpretation of the images requires context in regard to the features of pain and the aggravating loads. This review will critically evaluate studies that have investigated the accuracy and sensitivity of imaging in the detection of clinical tendinopathy and the methodological issues associated with these studies (subject selection, lack of a robust gold standard, reliance on subjective measures). The advent of new imaging modalities allowing for the quantification of tendon structure or mechanical properties has allowed new critical insight into tendon pathology. A strength of these novel modalities is the ability to quantify properties of the tendon. Research utilizing ultrasound tissue characterization and sonoelastography will be discussed. This narrative review will also attempt to synthesize current research on whether imaging can predict the onset of pain or clinical outcome, the role of monitoring tendon structure during rehabilitation (ie, does tendon structure need to improve to get a positive clinical outcome?), and future directions for research, and to propose the clinical role of imaging in tendinopathy.