Isokinetic Knee Strength, Bilateral Muscle Balance, and Anaerobic Performance in Adolescent Athletes

Lower-limb strength and anaerobic power are important parts of the physical profile of adolescent athletes in high-intensity sports such as wrestling. Isokinetic dynamometry allows knee extensor (quadriceps) and flexor (hamstring) strength and the balance between these muscle groups to be measured objectively, while the 30-second Wingate Anaerobic Test (WAnT) is a widely used laboratory test of anaerobic performance. Evidence on how these measures relate to each other in adolescent athletes is limited.

This is a cross-sectional, correlational observational study. Twenty-one male adolescent athletes aged 15-16 years will be recruited in Malatya, Turkey. Written informed consent will be obtained from parents or legal guardians, and assent from participants. Testing will take place on two separate days to limit fatigue. Participants will avoid heavy exercise for 48 hours and caffeine for 12 hours before testing.

Day 1: Height and body mass are measured and body mass index is calculated. Concentric knee extension and flexion are then tested bilaterally on a HUMAC NORM isokinetic dynamometer at 60, 120 and 180 degrees per second (three practice repetitions followed by five maximal repetitions at each speed; 45 seconds of rest between speeds and 10 minutes between limbs). Peak torque is recorded for the quadriceps and hamstrings of each limb, and the conventional hamstring-to-quadriceps (H/Q) ratio is calculated.

Day 2: Participants complete a 30-second WAnT on a mechanically braked cycle ergometer (Monark 874E) with a braking load of 0.075 kg per kg of body mass, after a standardized warm-up. Peak power, mean power and fatigue index are recorded.

Differences between the right and left limbs will be examined with paired-samples t-tests (with 95% confidence intervals and Cohen's dz). Associations between isokinetic variables and WAnT outcomes will be examined with Pearson correlation. The sample size (minimum 19) was calculated with G\*Power for a correlation of r = 0.60 (alpha = 0.05, power = 0.80); 21 participants are planned to allow for possible data loss.

Male adolescent athletes aged 15-16 years who regularly train and compete. All participants complete anthropometric measurements, bilateral isokinetic knee strength testing, and the Wingate Anaerobic Test on separate days.

Diagnostic Test: Isokinetic Knee Strength Testing · Diagnostic Test: Wingate Anaerobic Test

Bilateral concentric knee extension and flexion tested on an isokinetic dynamometer at 60, 120, and 180 degrees per second. Peak torque and the conventional hamstring-to-quadriceps ratio are recorded.

A 30-second all-out cycling test on a mechanically braked cycle ergometer with a braking load of 0.075 kg per kg of body mass. Peak power, mean power, and fatigue index are recorded.

Plazo: Day 1 of testing (single measurement session)

Peak torque (N·m) of the quadriceps and hamstrings, measured separately for the right and left limbs at 60, 120, and 180 degrees per second on an isokinetic dynamometer (highest value across five maximal concentric repetitions). Right-to-left differences and associations with Wingate Anaerobic Test outcomes are analyzed.

Plazo: Day 2 of testing (single measurement session)

Highest power output (W) achieved during the 30-second Wingate Anaerobic Test performed on a mechanically braked cycle ergometer with a braking load of 0.075 kg per kg of body mass.

Plazo: Day 1 of testing

Concentric hamstring peak torque divided by quadriceps peak torque, multiplied by 100 (%), calculated for each limb at 60, 120, and 180 degrees per second.

Plazo: Day 2 of testing

Average power output (W) maintained across the 30-second Wingate Anaerobic Test.

Plazo: Day 2 of testing

Percentage decline from peak power to the lowest power output during the test: \[(peak power - minimum power) / peak power\] × 100.

Relationship of Isokinetic Knee Strength and Bilateral Muscle Balance With Anaerobic Performance in Adolescent Athletes