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

Abstract

Contemporary descriptions of motor control suggest that variability in movement can be indicative of skilled or unskilled performance. Here we used principal component analysis to study the kicking performance of elite and sub-elite soldiers who were highly familiar with the skill in order to compare the variability in the first and second principal components. The subjects kicked a force plate under a range of loaded conditions, and their movement was recorded using optical motion capture. The first principal component explained >92% of the variability across all kinematic variables when analyzed separately for each condition, and both groups and explained more of the variation in the movement of the elite group. There was more variation in the loading coefficient of the first principal component for the sub-elite group. In contrast, for the second principal component, there was more variation in the loading coefficient for the elite group, and the relative magnitude of the variation was greater than for the first principal component for both groups. These results suggest that the first principal component represented the most fundamental movement pattern, and there was less variation in this mode for the elite group. In addition, more of the variability was explained by the hip than the knee angle entered when both variables were entered into the same PCA, which suggests that the movement is driven by the hip.

A Systematic Review of Dynamic Forces and Kinematic Indicators of Front and Roundhouse Kicks across Varied Conditions and Participant Experience

“…This is consistent with the finding that circular kicks generate greater foot velocity at impact than linear kicks due to the rotational involvement of the segments in different planes [ 62 ]. Both kicks are characterized by proximo-distal movement; however, while the FK is primarily executed through hip movement in the sagittal plane and foot velocity is largely influenced by knee velocity [ 10 , 32 , 63 ], the RK achieves comparable hip velocity in the sagittal plane. However, when combined with the transversal and frontal planes, the RK attains higher velocity [ 25 ].…”

“…For instance, they exhibited smaller angular ranges of leg movement and higher activation of the rectus femoris, vastus lateralis, biceps femoris, and gastrocnemius muscles [ 11 ]. Additionally, elite participants displayed lower variability in hip and knee joint movements [ 10 , 39 ]. In the case of the RK, the elite group reached higher angular velocities during hip and knee extension and ground reaction force [ 53 , 64 , 65 ].…”

“…These findings partially explain the results showing an increase in angular velocity of knee extension after eight weeks of training focused on explosive lower limb strength without a significant increase in hip angular velocity [ 2 ]. Nevertheless, the primary movement of the hip is cited as crucial for the overall effectiveness of both the FK and RK [ 10 , 51 ]. Therefore, training to improve the angular velocity of the hip should also focus on functional exercises with an emphasis on core training [ 2 , 61 ].…”

“…The impact force of the kick may be related to the isokinetic strength of the hip flexors and extensors and the knee angular velocity [2,51]. Therefore, fighters should focus on enhancing the impact force from a larger distance with the help of increasing their angular velocity during knee extension in the pre-contact phase [10].…”

“…Previous research has often compared kicks to punches and explored comparisons among different experience levels, genders, and fighting actions [5][6][7][8][9][10][11]. Notably, studies have examined kicks at various distances from the target, with varying types of targets, and even under various carried military loads [12][13][14][15][16][17].…”