Clinical Research Directory

Sex Differences in Knee Strength and Speed in Male and Female Football Players

Force-velocity (F-V) profiling is increasingly used to describe the mechanical capacities of the knee extensors and knee flexors in football, but almost all available reference data come from male players. It is not established whether male and female players differ in the parameters of the isokinetic force-velocity relationship, or whether any such differences persist once differences in body size are accounted for. This single-centre, cross-sectional observational study compared the isokinetic force-velocity profiles of the knee extensors and knee flexors between male and female competitive football players. Eligible participants were competitive players aged 18 to 35 years, training at least three times per week, free of current lower limb pain or injury and with no history of knee or hip surgery. During a single testing session, participants performed bilateral concentric isokinetic knee extension and flexion at five angular velocities (30, 60, 180, 240 and 300 degrees per second) on an isokinetic dynamometer, after a standardised warm-up, individual gravity correction and a familiarisation session. For each participant, limb and muscle group, peak torque was regressed against angular velocity to fit an individual linear torque-angular velocity relationship. The following parameters were derived: theoretical maximal torque (F0), theoretical maximal angular velocity (V0), the slope of the relationship, maximal theoretical power (Pmax), and torque and power at the extremes of the tested velocity range. The participant, defined as the mean of both limbs, was the unit of analysis. Male and female players were compared in absolute terms and after adjustment for body size, using ratio scaling to body mass, log-log allometric models and analysis of covariance with body mass and age as covariates. Secondary comparisons included the conventional hamstring-to-quadriceps ratio, inter-limb asymmetry and the orientation of the profile (F0/V0 ratio). The purpose of the study is to determine which sex differences in isokinetic force-velocity parameters are explained by body size and which persist after adjustment, in order to establish whether reference values obtained in male players can legitimately be applied to female players.

Clinical and Functional Outcomes After ACL Reconstruction Versus Primary Repair

The anterior cruciate ligament (ACL) is the primary structure responsible for controlling anterior-posterior translation and rotational stability of the knee joint. Although ACL reconstruction has long been considered the gold standard among surgical interventions following ACL injury, arthroscopic primary repair techniques have recently regained interest. With advances in minimally invasive surgical procedures, refined patient selection criteria, and improved rehabilitation strategies, the clinical effectiveness of primary repair is once again being re-evaluated. However, there remains a limited body of literature directly comparing the medium- to long-term effects of these two surgical techniques on neuromuscular performance, fatigue tolerance, and functional outcomes. The aim of this study is to comparatively investigate postoperative muscle strength and endurance, isokinetic fatigue response, muscle oxygenation, proprioception, knee stability, postural control, and patient-reported outcome measures in individuals who have undergone ACL reconstruction or primary repair. Assessments will include low- and high-velocity tests performed on the Cybex Norm isokinetic dynamometer, a 33-repetition fatigue protocol at 300°/s, muscle oxygenation analysis using Train.Red NIRS, knee laxity measurement via the GNRB arthrometer, single-leg balance and landing evaluations using the KFORCE force platform, and subjective outcome measures (IKDC, ACL-RSI). The findings of this study are expected to provide a more comprehensive understanding of how surgical technique influences physiological, biomechanical, and functional outcomes. This knowledge may contribute to the development of individualized rehabilitation approaches and evidence-based return-to-sport criteria.

Metabolic, Respiratory, and Muscle Oxygenation Responses to Sub-maximal Eccentric and Concentric Isokinetic Exercise to Exhaustion

This study aims to measure and compare the metabolic response during sub maximal eccentric and concentric isokinetic exercise performed to exhaustion. Fourteen healthy female participants in the early phase of the menstrual cycle will perform concentric exercise with one lower limb and eccentric exercise with the contralateral limb. The assignment of exercise mode to limb and the order of testing will be randomized. The exercise protocol will consist of repeated knee extensor contractions on an isokinetic dynamometer for 10 minutes at 40% of maximal torque, followed by exercise at 70% of maximal torque until exhaustion. Oxygen consumption and respiratory quotient and will be measured continuously throughout exercise using open-circuit spirometry. Muscle oxygenation will be measured also continuously using near infrared spectroscopy. Lactate and pH concentration will be measured at frequent time points during the exercise to exhaustion.

Muscle Architecture vs Alfredson Protocol in Achilles Tendinopathy

Achilles tendinopathy is a frequent overuse disorder caused by repetitive loading of the tendon, particularly observed in athletes and middle-aged men. It is typically characterized by mid-portion pain, stiffness in the morning, and functional limitations, with structural alterations such as thickening and disrupted collagen alignment. Chronic progression often compromises performance and quality of life. Eccentric training protocols, such as the Alfredson regimen, are commonly prescribed but their standardized nature does not fully address individual variability. Alternative approaches including Heavy Slow Resistance training and progressive loading models (e.g., Silbernagel protocol) have demonstrated clinical effectiveness and higher patient adherence, yet they still apply uniform loading across the triceps surae without accounting for architectural differences. Given the heterogeneous structure of the soleus and gastrocnemii, targeted loading strategies may be required to optimize tendon adaptation. To address this, the present study employs a muscle architecture-based exercise program tailored to the functional and structural properties of each muscle. Ultrasound imaging will be used to evaluate muscle-tendon morphology, while isokinetic dynamometry and functional performance tests will quantify outcomes. Pain (VAS) and functional capacity (VISA-A) will also be assessed. This randomized controlled trial aims to compare the effectiveness of an architecture-specific program with the Alfredson protocol on tendon remodeling, strength, endurance, functional performance, and symptom reduction in individuals with non-insertional Achilles tendinopathy.

Proprioceptive Fatigue Adaptation in Osteoarthritis

This study aims to investigate the effects of fatigue induced by isokinetic exercise on passive and active joint position sense in postmenopausal women diagnosed with knee osteoarthritis (gonarthrosis). A healthy control group matched for age and sex will also be included for comparative analysis. Participants will undergo proprioceptive assessments before and after an isokinetic fatigue protocol. We hypothesize that (1) fatigue will impair both passive and active joint position sense in patients with gonarthrosis, (2) active joint position sense will be more affected than passive sense, and (3) the deterioration in proprioception will be greater in the gonarthrosis group compared to healthy controls.