Author(s): BOZGEYIK BAGDATLI, S., CELEBI, E., BAZANCIR APAYDIN, Z., APAYDIN, H., GUREL, M., OZCADIRCI, A., COSKUN, G., Institution: HACETTEPE UNIVERSITY, Country: TURKEY, Abstract-ID: 2632

INTRODUCTION:
Ultra-trail running is an endurance discipline characterized by prolonged and repetitive mechanical loading, which may induce structural adaptations in the muscle–tendon unit and knee joint cartilage. However, the extent to which chronic high-volume running influences quadriceps muscle thickness, patellar tendon thickness, and femoral articular cartilage thickness remains unclear. Therefore, the aim of this study was to compare ultrasonographic measurements of these structures between ultra-trail runners and sedentary controls.


METHODS:
A total of 38 participants were included in the study, consisting of 21 ultra-trail runners (mean age 41.75±7.05 years; mean BMI (body mass index) 24.19±1.75 kg/m²) and 17 sedentary controls (mean age 42.82±6.95 years; mean BMI 25.32±3.15 kg/m²). The mean weekly training volume of the ultra-trail runners was 47.90±19.76 km. Quadriceps muscle thickness, including the rectus femoris and vastus lateralis components, patellar tendon thickness, and tibiofemoral articular cartilage thickness were evaluated using ultrasonography. All ultrasound images were analyzed with ImageJ software (National Institutes of Health, USA) to quantify muscle, tendon, and cartilage thickness. Measurements were performed bilaterally on both the dominant and non-dominant lower extremities.
RESULTS:
There were no significant differences between the groups in terms of age (p=0.606) or BMI (p=0.113). Significant differences in patellar tendon thickness were observed in both the dominant (p<0.001) and non-dominant (p<0.001) limbs, favoring the control group. However, no significant between-group differences were found in rectus femoris thickness (p=0.333, p=0.207), vastus lateralis thickness (p=0.091, p=0.219), or tibiofemoral articular cartilage thickness (p=0.106, p=0.107)in either the dominant or non-dominant limbs.
CONCLUSION:
Ultra-trail runners demonstrated significantly lower patellar tendon thickness in both limbs compared with sedentary controls, whereas quadriceps muscle thickness and tibiofemoral articular cartilage thickness were preserved. These findings indicate that chronic high-volume endurance running may induce tendon-specific structural adaptations without detectable alterations in muscle morphology or knee cartilage thickness, suggesting a tissue-specific response to long-term mechanical loading.