Abstract:
Background. The lower limbs play a key role to develop the linear momentum for
hitting power in effective boxing. The knee extensor and flexor strength guarantees the
dynamic stability of boxers. The insufficient extensor strength of the lower extremities
causes compensation during flexion resulting in movement errors or damage to knee
joint muscles. This study was conducted to explore the isokinetic concentric strength
of the knee flexor and extensor and the relationship between isokinetic knee extensors
strength and countermovement jump (CMJ) performance in elite boxers.
Methods. Thirteen elite male boxers (Age: 25.15 ± 3.98 years, height 1.72 ± 0.04 m,
weight 61.82 ± 10.46 kg, training years = 11.56 ± 2.67 years) performed the CMJ, and
the isokinetic knee test was performed using the Biodex dynamometer.
Results. The maximal isokinetic peak torque of the knee extensor and flexor muscles
was recorded at three angular velocities (60◦
/s, 180◦
/s, and 240◦
/s) on both sides of the
legs. The relative peak value of torque in the knee extensors decreased significantly with
increasing angular velocity. A difference in relative peak torque (RPT) was only seen at
60◦
/s in knee flexors. However, the H/Q ratio increased as the velocity increased from
60◦
/s to 240◦
/s (P < 0.05). The highest peak torque was found in the knee extensors
at a velocity of 240◦
/s (r = 0.73, P < 0.001). The correlation between RPT and vertical
jump height was the strongest at 240◦
/s. The strongest relationship was found between
the height of the CMJ and the RPT of the deficit of knee extensors.
Conclusions. We suggest that explosive force training of the isokinetic muscles should
be optimally carried out at a speed of 240◦
/s. The results of this study provide a reference
for boxers to improve their jump height and lower-limb explosive strength through
isokinetic strength training of the knee flexor and extensor.
