Are isokinetic leg torques and kick velocity reliable predictors for competitive success in taekwondo athletes?

Abstract

27The aim of the study was to analyzed the relationship between isokinetic knee 28 and hip peak torques and Roundhouse-kick velocities and expertise level (Elite vs. 29 Subelite) of Taekwondo athletes. Seven elite and seven sub-elite athletes were tested for 30 kick kinematic, power of impact and for isokinetic peak torque (PT) at slow (60 o /s) and 31 high (240 o /s) concentric mode. PTs were compared between groups and correlated with 32 the data of kick performance. It was found inter-group differences in hip flexors and 33 extensors PT at the isokinetic fast speed. The hip flexion PT at 60 o /s and 240 o /s were 34 negatively correlated with the kick time (R = -0.46, and R = -0.62, respectively). Hip 35 flexion torque at 60 o /s was also positively correlated (R = 0.52) with the peak of linear 36 velocity of the foot (LVF) and the power of impact (R = 0.51). Peak torque of hip 37 extension at 60 o /s and hip abduction at 240 o /s were correlated with the LVF (R= 0.56 38 and R = 0.46). Discriminant analysis presented an accuracy of 85.7% in predicting 39 expertise level based on fast torques of hip flexion and extension and on the knee 40 extension velocity during the kick. This study demonstrated that hip muscles strength is 41 probably the dominant muscular factor for determining kick performance. Knee angular 42 velocity combined with hip torques are the best discriminators for the competitive level 43 in taekwondo athletes.44 45 Introduction 52The most popular technique in Taekwondo (TKD) combats is the Roundhouse 53 Kick, or Bandal Chagui [1][2][3]. Defined as a multiplanar and multi-joint action[2-6] , is 54 described as a proximo-distal sequence, wherein structures nearest the center of the 55 body (proximal segments) develop first in temporal order of joints movement, while 56 distal segments lag behind, and are thereafter followed by its relative distal segment 57 acceleration while proximal segments decelerate [7][8][9]. 58According to this principle, the largest possible velocity of the proximal segment, linked 59 by the interaction with the following segments, determines the terminal velocity or 60 impact magnitude [3][4][5]7,[9][10][11][12][13]. Angular acceleration of a segment is caused by muscle 61 torques that control the proximal joint [6,7,15] and by the angular momentum 62 transmitted to the next (distal) segment [7,15,16]. The resultant torque produced during 63 the kick depends on the athlete's coordinative capacity to maximize the agonist and 64 minimize the antagonist torque [7,17,18] . 65During a kick, torques are generated at either low or high angular velocities [7,19], 66 which can be reasonably reproduced by isokinetic dynamometers [20][21][22]. Such 67 instruments present high reliability [23], validity [22], and control of speed and range of 68 motion [22,23]. Previous researchers [6,24] demonstrated that elite athletes of combat 69 sports presented improved capacities to produce torque compared with sub-elite athletes 70 or non-athletes, in isokinetic velocities from 30 ...

Principal Component Analysis can Be Used to Discriminate Between Elite and Sub-Elite Kicking Performance

“…PC1 explained more of the variance in kinematics for the elite subjects than for the sub-elite subjects across all conditions (Table 3). This indicates that the movement of hip and knee is more closely coordinated for the elite subjectsthe hip being a relatively more important driver of the movement, which is in line with previous research suggesting that hip muscle strength is probably the dominant muscular factor for determining kick performance (Moreira et al, 2020).…”

Correlation of bilateral and ipsilateral strength ratios with balance in female taekwondo athletes

“…A high level of kick combination and a good balance is necessary to hit the right spot and win the game in TKD (Kim et al, 2011). Since it is known that the most active muscles during kick strokes are the gastrocnemius, Q and H muscles (Sorensen et al, 1996), knee extensor and flexor strengths are of great importance (Moreira et al, 2020). Kim et al (2015) did not observe any significant difference between Ex and Flx values of the angular velocities of 60°/s and 180°/s, as well as the balances evaluated by the flamingo balance test, in the measurements performed on female TKD practitioners following 1-year regular TKD training.…”

“…Seo et al (2015) observed an increase in isokinetic knee strength and anaerobic capacity at an angular velocity of 60°/s with the 8-week training they applied to university-age male and female TKD practitioners. Moreira et al (2020) examined the relationship between the isokinetic strengths of the knee and kinematic data of TKD practitioners, and reported that the angular velocity of 60°/s revealed higher and significant correlations compared to 240°/s in parameters such as preparation time of kick and kick time. This is also a clear indication that the Q and H muscles, which show slow but strong contraction during the pre-kick preparation period and the kick, can also be associated with success in TKD.…”