Quadriceps Muscle Atrophy

A large amount of patients with COPD suffer from muscle dysfunction characterized by losses of muscle mass and strength. Studies have shown an association between a loss of quadriceps muscle mass and premature death. This study aims to investigate the clinimetric properties of a simple quadriceps perimetry and ShearWave elastography to improve the monitoring of skeletal muscle function in patients with COPD.

While there are a number studies that have reported on the use of blood flow restriction training (BFRT) in the adult population, there is limited information about the use of BFRT in the adolescent population. This study aims to evaluate the use of BFRT in conjunction with traditional anterior ligament reconstruction (ACLR) rehabilitation in adolescents. The purpose of this study is to compare the addition of a BFRT based exercise protocol to a standard ACL rehabilitation protocol in adolescents. Does the addition of BFRT-based exercise improve strength, hypertrophy, and patient reported outcomes after ACLR in the adolescent population?

The goal of this randomized clinical trial is to evaluate the effects of vibration on factors related to the risks of post-traumatic knee osteoarthritis and secondary anterior cruciate ligament (ACL) injury in individuals who have undergone anterior cruciate ligament reconstruction surgery (ACLR). The main objectives are to compare the effects of Standard rehabilitation vs. rehabilitation that includes whole body vibration (WBV) or local muscle vibration (LMV) on: * Quadriceps muscle function * Gait biomechanics linked to post-traumatic knee osteoarthritis development * Patient self-report outcomes * MRI indicators of knee joint health and muscle quality * Landing biomechanics linked to secondary ACL injury risk * Evidence-based return-to-physical-activity criteria Participants will be assigned to 1 of 3 groups (standard rehabilitation, standard rehabilitation + WBV, or standard rehabilitation + LMV) and will complete assessments of quadriceps function, gait biomechanics, landing biomechanics, functional ability, patient-report outcomes, and MRI 1, 6, and 12 months after ACLR. Researchers will compare the groups to see if vibration embedded in ACLR rehabilitation improves joint health outcomes.

Quadriceps muscle strength is one of the key determinants for patients to fulfill the Return-to-Play (RTP) criteria after an anterior cruciate ligament reconstruction (ACLR), in which the muscle size is directly linked to muscle strength. Quadriceps muscle atrophy is unavoidable after ACLR, but the rehabilitation program should increase quadriceps muscle mass. However, despite good rehabilitation compliance, some patient's progress is sub-par and fail to regain muscle mass. Quadriceps muscle atrophy can persist beyond the completion of the rehabilitation program in almost half the patients and the reason behind this is still unknown. This represents an area that requires significant investigation, as quadriceps muscle atrophy and weakness have been shown to be determinants of poor knee function, decreased performance in sports and increased risk of reinjury. Quadriceps muscle atrophy after ACLR is well documented. This can be due to a decreased ability to regain muscle mass with rehabilitation. Athletes are one of the high-risk groups for vitamin D insufficiencies. Vitamin D deficiency can potentially result in decreased hypertrophy when exercising the muscle, leading to a poorer outcome in rehabilitation. Vitamin D has long been recognized for its effect on musculoskeletal health. It can have a direct effect on muscle hypertrophy by acting on specific vitamin D receptors (VDRs) on myocytes, and sufficient or increased levels of vitamin D in patients have been found to correlate with an increase in the size, number, and strength of muscle fibres. Quadriceps muscle hypertrophy after ACLR is triggered by exercise training, facilitated by diet and a number of intrinsic factors. As the rehabilitation programs and diets are similar in patients with varying extents of quadriceps muscle atrophy, individual responses (intrinsic factors) to exercise training may account for the resulting persistent quadriceps muscle atrophy. In this study, the investigators hypothesize that the deficiency of vitamin D may contribute to persistent quadriceps atrophy and weakness. With a stringent double-blinded randomized-controlled-trial (RCT) research design, our proposal will then address the research questions: 'Does vitamin D supplements improve the vitamin D deficiency status in patients after ACL reconstruction?', and 'Does vitamin D supplements improve quadriceps muscle strength for patients after ACLR?'