The main objective of this study is to evaluate quadriceps thigh muscle activity during active straight leg raise (ASLR) with a knee brace.

An additional aim of the study is to evaluate quadriceps activity during straight leg raise with a knee brace in a variable command and manner of task performance. The study will be conducted on a group of healthy individuals aged 18 - 35 years. Height and weight were measured using a scale and centimetre tape. Then, according to the study protocol, specific measurements will be taken of the rectus femoris, medial vastus and lateral vastus muscles using surface EMG of a non-invasive nature.

Study participants will undergo the following measurements:

1. Measurement of the MVIC (maximum voluntary isometric contraction) of the quadriceps of the thigh, in a sitting position with the lower leg flexed to 90 degrees and in knee extended (0 degrees).
2. Measurement of muscle activity during elevation of the straightened lower limb in a supine position without an orthosis.
3. Measurement of muscle activity during straight leg raise in supine position with knee brace (default and different commends).

The study will be conducted on a group of healthy individuals aged 18 - 35 years. After an interview confirming that the subject does not have exclusion criteria and inclusion criteria apply. Written consent to participate in the study and next anthropometric measurements will be taken using a scale and tape measure. The subjects will be informed in detail about the procedure and the form of the measurements, the way in which they are to be taken, and will be familiarized with the measuring instruments and their principles of operation. Then, in accordance with the study protocol, specific measurements will be taken of the rectus femoris, medial vastus and lateral vastus muscles using surface EMG of a non-invasive nature.

Study participants will undergo the following measurements:

1. Measurement of the MVIC (maximum voluntary isometric contraction) of the quadriceps femoris, in a sitting position with the lower leg flexed to 90 degrees, next MVIC of the quadriceps femoris in supine with knee fully extended (0 degrees).
2. Measurement of muscle activity during elevation of the straightened lower limb (ASLR) in supine without knee brace.
3. Measurement of muscle activity during ASLR in supine position with knee brace. Ad.a. Measurement of quadriceps maximum electric signal of the dominant lower limb using surface EMG in a seated position with the trunk stabilized with hands behind the pelvis and the lower leg flexed to 90 degrees, stabilized in the distal part (without taking the foot) against a stationary object (belt) to execute maximal volitional isometric quadriceps muscle contraction. Next MVIC in supine position, with knee fully extended, pushing back of the knee into hand of an examiner without lifting heel.

Ad.b. Measurement of quadriceps excitability using surface EMG in supine position without orthosis. The subject raises the tested limb (dominant) by touching the anterior surface of the tibia to a pole set at 30 cm at first sound of metronome set at 60 BMP, then hold the leg for the next beat, and next lowers the limb at the next metronome sound. This action is repeated three times in a row without any brake.

Ad.c. Measurement of quadriceps excitability of the dominant lower limb using surface EMG in supine position with knee extension brace on. Measurement performed in three variants:

1. The subject raises the test limb (dominant) by touching the anterior surface of the tibia to a pole set at 30 cm at first sound of metronome set at 60 BMP, then hold the leg for the next beat, and next lowers the limb at the next metronome sound. This action is repeated three times in a row without any brake.
2. The test subject is asked to apply maximum tension to the quadriceps then maintaining the tension he/she raises the limb touching the front surface of the tibia to the pole placed at the height of 30 cm at first sound of metronome set at 60 BMP, then hold the leg for the next beat, and next lowers the limb at the next metronome sound. This action is repeated three times.
3. Before the test, the test subject is verbally instructed to 'Try, despite the orthosis holding your knee straight, to bend the knee and raise the leg so that the quadriceps do not tense'. Then, lift the limb touching the front surface of the tibia to the pole placed at the height of 30 cm at first sound of metronome set at 60 BMP, then hold the leg for the next beat, and next lowers the limb at the next metronome sound. This activity is repeated three times.

Between MVICs and test trial it was 30s brake. MVICs were hold for 3 seconds. The time for the full test is approximately 15-20 minutes per participant. Statistical analysis will be performed using Statistica and/or JASP software. The study will be carried out with a minimum of 20 adults aged 18 - 35 years. The exact number of participants in the study, will be determined after performing an a-priori sample size estimation after collecting data from the first 10 people examined. Eligibility of subjects will include a subject and physical examination by a physiotherapist.

Inclusion criteria: age between 18-35 years, no contraindications to physical exercise, ability to perform the required commands without pain or discomfort, full range of motion of the knee joint.

Exclusion criteria: those with a history of knee and/or hip surgery, damage to ligamentous structures of the knee joint in the past treated conservatively or meniscus treated conservatively, muscle and tendon injury of the knee joint area in the past 3 months.

Inclusion Criteria:

• age between 18-35 years
• no contraindications to exercise
• ability to perform the required commands without pain or discomfort
• full range of motion of the knee joint.

Exclusion Criteria:

• those with a history of knee and/or hip surgery
• damage to ligamentous structures of the knee joint in the past treated conservatively or meniscus treated conservatively.
• muscle and tendon injury of the knee joint area in the past 3 months.

young healthy people 18-35 years old

Individual participant data (IPD), including raw EMG data from electrodes and processed data normalized as %MVIC for statistical analysis, will be available upon reasonable request after primary results publication. Data will be anonymized to protect participant confidentiality and shared following ethical guidelines. Requests may be submitted to the corresponding author for up to 5 years post-publication.

Raw EMG data are available on reasonable request. We request investigators to contact us directly to discuss data sharing. On reasonable request statistical protocol and code for R or Python are available.