Lower-Limb Connective Tissue Morphologic Characteristics in Runners. How Do They Relate with Running Biomechanics and Tendon Pathology? A Systematic Review

Abstract

Although the role of connective tissue in running injuries and biomechanics has been widely investigated, systematic reviews on this issue were rarely reported. The aim of this study is to systematically review the current literature regarding the morphological characteristics (i.e., cross-sectional area and thickness) of the main connective tissue of the lower limb in runners and its relationship with running biomechanics and tendon pathology. The main keywords used were: Achilles and patellar tendons, plantar fascia, ultrasound, thickness, cross-sectional area and running. Observational design English-written studies published between January 2000 and September 2020 were included. After exclusion criteria were applied, 34 studies remained. 16 studies analysed connective tissue related to sample characteristics where mainly the differences between runners and controls were studied along other factors such as gender, weight and nationality. Regarding running biomechanics, 10 studies assessed connective tissue on running biomechanics with focusing on foot strike pattern and footwear characteristics. Regarding tendon pathology, 8 studies analysed the connective tissue assessing, mainly, whether the pathological tendons are thicker. Runners show higher tendons, in terms of thickness and CSA, than control subjects and athletes from other disciplines whose tendons are subjected to lighter loads. Adaptation to load leads to better performance, what seems to explain these morphological differences. Study registration. None.

Epidemiology of Shoulder Arthroplasty in a Southern-Italy Region: A Three-Year Registry Study

“…Our study also showed wider cross-section area (CSA) of running rats compared to control group. As mentioned in previous systematic review published at 2022 (21), tendon connective tissue involvement plays important role in Achilles tendinopathy pathogenesis. Wider CSA is formed as an adaptation towards repetitive overload.…”

“…Normally repetitive overload induced increasing tenocyte and collagen fiber of tendon. But if the repetitive overload was excessive, collagen fiber formation would not be unable to keep up with tenocyte production and producing stiffer and wider tendon (21). Running the rats on the treadmill as an attempt to induce Achilles tendinopathy also increases several inflammatory markers.…”

Does Lower-Limb Tendon Structure Influence Walking Gait?

“…No comparison with pathological (i.e., gait pathologies) or sport (i.e., runners) populations has been carried out here. Long-distance runners tend to show larger dimensions in terms of CSA and thickness in the PT, AT and PF given the amount of load supported by these tendons [28]. As it seems that a thicker PT significantly correlates with a longer R1, we might hypothesize that long-distance runners would exhibit longer R1 duration.…”