S. P. Magnusson

Purpose To investigate power Doppler (PD) activity and tendon structure (between the injured and contralateral limb) in patients with unilateral patellar tendinopathy (PT) using ultrasonography (US). Secondly, the aim was to determine the intra‐rater reliability of the PD activity and tendon structure. Methods This study analyzed US baseline data from 57 male participants with symptomatic unilateral PT who had been enrolled in one of two randomized clinical trials. Data were analyzed to examine if systematic differences existed between injured and contralateral limbs using Fiji ImageJ. Results The PD activity of the symptomatic tendon was larger 25.6 (Q1 = 14.9; Q3 = 41.6) mm 2 than the asymptomatic 0 (Q1 = 0.0; Q3 = 0.0) mm 2 ( p < 0.001). There was a significantly greater tendon thickness at the proximal (2.5 mm 95% CI [2.0; 3.0]), mid (0.8 mm 95% CI [0.5; 1.1]), and distal (0.2 mm 95% CI [0.1; 0.4]) part of the tendon for the symptomatic compared to the asymptomatic tendon. Intra‐rater reliability for PD activity and tendon structure ranged from moderate‐to‐excellent (0.74; 0.99). Conclusion These results provide mean estimates for tendon thickness of symptomatic and asymptomatic tendons, that can be used for clinicians to reliably estimate pathological tendon thickness.

Introduction Heavy‐load free‐flow resistance exercise (HL‐FFRE) is a widely used training modality. Recently, low‐load blood‐flow restricted resistance exercise (LL‐BFRRE) has gained attention in both athletic and clinical settings as an alternative when conventional HL‐FFRE is contraindicated or not tolerated. LL‐BFRRE has been shown to result in physiological adaptations in muscle and connective tissue that are comparable to those induced by HL‐FFRE. The underlying mechanisms remain unclear; however, evidence suggests that LL‐BFRRE involves elevated metabolic stress compared to conventional free‐flow resistance exercise (FFRE). Aim The aim was to evaluate the initial (<10 min post‐exercise), intermediate (10–20 min), and late (>30 min) hormonal, immune, and oxidative stress responses observed following acute sessions of LL‐BFRRE compared to FFRE in healthy adults. Methods A systematic literature search of randomized and non‐randomized studies was conducted in PubMed, Embase, Cochrane Central, CINAHL, and SPORTDiscus. The Cochrane Risk of Bias (RoB2, ROBINS‐1) and TESTEX were used to evaluate risk of bias and study quality. Data extractions were based on mean change within groups. Results A total of 12525 hits were identified, of which 29 articles were included. LL‐BFRRE demonstrated greater acute increases in growth hormone responses when compared to overall FFRE at intermediate (SMD 2.04; 95% CI 0.87, 3.22) and late (SMD 2.64; 95% CI 1.13, 4.16) post‐exercise phases. LL‐BFRRE also demonstrated greater increase in testosterone responses compared to late LL‐FFRE. Conclusion These results indicate that LL‐BFRRE can induce increased or similar hormone and immune responses compared to LL‐FFRE and HL‐FFRE along with attenuated oxidative stress responses compared to HL‐FFRE.

Background Muscle strain injuries in the human calf muscles are frequent sports injuries with high recurrence. Potential structural and functional changes in the medial head of the musculus gastrocnemius (GM) and the associated aponeurosis are not well documented. Purpose To test whether a GM muscle strain injury affects muscle fascicle length, pennation angle, and the morphology of the deep aponeurosis at rest and during muscle contraction long time after the injury. Additionally, electromyography (EMG) of the GM and the soleus muscle during a unilateral heel rise was measured in the injured and uninjured calf. Methods GM fascicle length, pennation angle, and aponeurosis thickness was analyzed on dynamic ultrasonography (US) recordings in 10 participants with a chronic calf strain. In addition, US images taken across the distal portion and mid‐belly of the GM were analyzed at three different ankle positions. EMG recordings were obtained during a unilateral heel rise. Results The pennation angle of the injured distal GM was significantly larger compared to the uninjured GM in the contracted, but not the relaxed state. Pennation angle increased more in the injured compared to the uninjured GM during contraction. Fascicle length was shorter in the most distal portion of the injured GM. Fascicles at the distal portion of the injured GM showed a pronounced curvilinear shape as the muscle contracted and the aponeurosis was enlarged in the injured compared to the uninjured GM. The ratio between GM and soleus EMG activity showed a significantly higher relative soleus activity in the injured compared to the healthy calf. Conclusion The greater change in pennation angle and curvilinear fascicle shape during contraction suggest that a long‐term consequence after a muscle strain injury is that some muscle fibers at the distal GM are not actively engaged. The significantly enlarged aponeurosis indicates a substantial and long‐lasting connective tissue involvement following strain injuries.

We investigated the impact of aging and exercise on extracellular matrix components of intramuscular connective tissue using proteomics. Middle-aged and old mice were subjected to three different levels of regular physical activity for 10 wk (high-resistance wheel running, low-resistance wheel running, or sedentary controls). We prepared extracts of extracellular matrix proteins depleted of cellular proteins. Our findings indicate that intramuscular connective tissue alters its soluble protein content with age but is unaffected by training.