The primary objective of the study is to evaluate the impact of ACL injury and ACL reconstruction on voluntary activation during maximal voluntary contraction (measured by neurophysiological parameters) according to the contraction mode.

The goal is to provide elements of knowledge to clinicians about the mechanisms of the activation failure depending on contraction mode, but also the resulting adapted clinical recommendations for conducting rehabilitation, and particularly for the use of different contraction modes.

The main hypothesis is that activation failure is not equal according to the contraction mode during maximal voluntary contractions and neurophysiological parameters will be decreased in comparison with non-injured subjects.

Secondary objectives are:

• To analyze the evolution of neurophysiological parameters between sessions interspaced by several months according to the contraction mode.
• To observe this time evolution depending on the treatment strategy chosen: rehabilitation or surgery plus rehabilitation.

Inclusion Criteria:

A. ACL-injured groups (surgically or conservatively treated):

1. Age between 18 and 50 years
2. Free, informed consent signed by the participant and the investigator.
3. Session 1: Delay of 2 to 6 weeks after injury, with a quiet knee (range of motion 110- 0°, minimal effusion, maximal contraction pain ≤ 2/10)
4. Session 2: Duration of 36 to 42 weeks after injury, with a quiet knee (range of motion 110-0°, minimal effusion, maximal contraction pain ≤ 2/10)
5. Independent person (Unprotected: under guardianship, curatorship or other legal protection, deprived of liberty by judicial or administrative decision)

B. ControlGroup:

1. Age between 18 and 50 years
2. Free, informed consent signed by the participant and the investigator.
3. Sport practitioners: at least once per week practicing activities like collective sports, racket sports, combat sports, skiing, or on-loading activities with changing of directions.
4. Independent person (Unprotected: under guardianship, curatorship or other legal protection, deprived of liberty by judicial or administrative decision)

Exclusion Criteria:

• 1. Subjects fitted with an implanted electronic device such as a cardiac pacemaker 2. Professional athlete 3. Pregnant women 4. Subject with systemic pathology or treatment affecting the musculoskeletal system 5. Subject with a history of neurological pathology or traumatic pathology, or pathology that required orthopedic treatment and/or surgery of the knee, hip and/or lumbar spine 6. Contraindication to isokinetic testing: incapacitating pain, evolving pathological process, non- healed fracture, unbalanced cardiovascular pathology (angina pectoris, arterial hypertension) 7. Contralateral knee injury 8. Subject inability to follow procedures or insufficient knowledge of project language 9. Data acquisition issue or injury during testing

The study population will comprise both male and female subjects, divided into three groups. The first group will consist of 20 subjects with isolated (only ACL rupture) or non-isolated ACL rupture (rupture associated with other knee lesion), treated with rehabilitation. The second group will include 20 subjects with ACL rupture, treated with surgery and rehabilitation. A third control group will also be included.