Taekwondo is a predominantly aerobic combat sport modality (58-66%) in which high-intensity actions are performed with the contribution of the anaerobic alactic system (26-30%) followed by the contribution of the anaerobic lactic metabolism (4-5%). High-intensity actions are performed repeatedly with muscular power and short duration. Thus, seeking to understand the relationship between the variables that represent maximum muscle strength, and the aerobic capacity of taekwondo athletes is relevant for a better understanding of the modality.

The aim of this study was to determine whether the 10-second Frequency Speed of Kick Test (FSKT10s) correlates with maximal muscle strength in black belt taekwondo athletes.

Nine male athletes (age: 20.3 ± 5.2 years; height: 177 ± 7.2 cm; body mass: 71.8 ± 15.3 kg and practice time: 9.6 ± 7.2 years) who competed at the state level or more prominently (international: 73%; national: 9%; state: 18%) participated in the study. All were free of any lower limb injury and had no neuromuscular disorder. Maximum muscle strength was achieved in the half-squat exercise, as previously described in the literature. FSKT10s is 10s long, alternating semi-circle kicks between right and left segments on a dummy using a simple torso protector, as often seen in taekwondo matches. Each participant was instructed to read and sign the Informed Consent Form with information about the procedures and risks associated with the study. The Kolmogorov-Smirnov test was used to assess data normality. Pearson's correlation was used to determine the relationship between selected variables. Correlations were classified as follows: 0.0 – 0.1 (trivial), >0.1 – 0.3 (minor), >0.3 – 0.5 (moderate), >0.5 – 0.7 (large), >0.7 – 0.9 (very large), and >0.9 – 1.0 (perfect). For all analyzes an α = 5% was adopted.

The athletes reached 133±33 kg (95% CI: 108 – 158) during the maximal strength test performed in the half-squat exercise. Values are expressed in relation to the body mass value (1RM/Body mass: 1.9±0.3, 95% CI: 1.6 – 2.1) and allometric scale (1RM/(body mass)0.67 : 7.6±1.4, 95% CI: 6.5 – 8.7). Pearson's correlation showed a statistically significant correlation between the maximum muscle strength test and the FSKT10s. The correlation between 1RM/body mass was r = 0.72 (p=0.014). The correlation between 1RM/ (body mass)0.67 was r = 0.84 (p=0.004). Both correlations were classified as 'very large'.

There is a strong correlation between maximal muscle strength and FSKT10s.

The strong correlation between the variables studied indicates that athletes with muscular strength developed at optimum levels also improve the frequency of blows applied in a short period of time. Thus, coaches and strength and conditioning coaches will be able to help taekwondo athletes to improve their performance by applying means and training methods aimed at developing maximum muscle strength at optimal levels.