2017, Volume 13

Muscular strength of knee extensors and flexors and bilateral and ipsilateral ratio in elite male kickboxers

Tomas Maly¹, Lucia Mala², Frantisek Zahalka³, Mikulas Hank², Michaela Simkova<sup>2

1</sup>Sport Research Centre, Charles University in Prague, Faculty of Physical Education and Sport, Czech Republic, Praha 6, Czech Republic
²Sport Research Centre, Charles University in Prague, Faculty of Physical Education and Sport, Czech Republic, Prague, Czech Republic
³Sport Research Center, Charles University in Prague, Faculty of Physical Education and Sport, Czech Republic, Prague, Czech Republic


Author for correspondence: Tomas Maly; Sport Research Centre, Charles University in Prague, Faculty of Physical Education and Sport, Czech Republic, Praha 6, Czech Republic; email: tomimaly[at]yahoo.com

Full text

Abstract

Background and Study Aim: Kickboxing is combat sport where the form of combat are strikes, performed by hands and legs. The aim of this study was verification of the hypothesized that the non-preferred leg of elite male kickboxers would have lower knee extensor and flexor strength and there will be a higher incidence of bilateral and unilateral strength deficit.

Materials and Methods: The study involved elite kickboxing athletes (n = 17, age 23.6  ±7.1 years, body height 183.3 ±5.5 cm and body weight 80.1 ±11.8 kg). The participants’ concentric muscle contractions were tested on the isokinetic dynamometer (Cybex NORM ®, Humac, CA, USA) at angular speeds of 60, 180 and 300°·s^–1. The following variables were evaluated: maximum peak muscle torque of knee extensors (PTE) and flexors (PTF) in the preferred (PL) and non-preferred leg (NL), bilateral ratio between the exerted strength of knee extensors (Q:Q) and flexors (H:H) and unilateral ratio of muscle torque for both PL and NL (H:Q_PL and H:Q_NL, respectively).

Results: The results indicated a significant effect of angular velocity (λ = 0.27, F_4,190 = 44.01, p<0.01, η² = 0.48) and laterality (λ = 0.93, F_2,95 = 3.36, p < 0.05, η² = 0.07) on peak torque in male kickboxers. The comparison of PTE revealed an insignificant difference between both limbs (p>0.05). On the contrary, in PTF, kickboxers produced significantly greater muscular strength in the preferred limb at velocities of 60° and 180°·s^–1 (p<0.05). The effect of angular velocity on the bilateral ratio (Q:Q ratio, H:H ratio) in kickboxers was not significant (λ = 0.98, F_2,31 = 0.23, p>0.05, η² = 0.42). We revealed a significant difference in the size of the bilateral ratio between knee extensors (Q:Q ratio) and flexors (H:H ratio) (F_1,32 = 5.55, p < 0.05, η² = 0.15). A significantly higher bilateral deficit was found in knee flexors at angular velocities of 180° and 300°·s^–1 (p<0.05). A significantly higher H:Q ratio (p<0.05) was observed in favour of the preferred limb at lower angular velocities (60° or 180°·s^–1, respectively). The results revealed strength asymmetries in favour of PTF when almost 60% of athletes achieved a critical value at higher velocities. The ipsilateral ratio (H:Q) was significantly lower in the non-preferred limb, which indicates a lower preparedness of the non-preferred limb.

Conclusions: The research presents PTEs and PTFs in the preferred and non-preferred limb at different angular velocities. These data may serve comparative purposes for other researchers, as well as a base (criterion) of assessment for elite professional kickboxers or for comparison with other martial arts, respectively. In terms of practice, the results may be beneficial for athletes, coaches, physiotherapists, doctors and other clinical staff.

Key words: combat sports, isokinetic strength, strength asymmetries, maladaptation, youth athletes