Achieving the maximum possible impact force of the front kick can be related to the isokinetic lower limb muscle strength. Therefore, we aimed to determine the regression model between kicking performance and the isokinetic peak net moment of hip rotators, flexors, and hip extensors and flexors at various speeds of contraction. Twenty-five male soldiers (27.7 ± 7.2 yrs, 83.8 ± 6.1 kg, 180.5 ± 6.5 cm) performed six barefoot front kicks, where impact forces (N) and kick velocity (m∙s-1) were measured. The 3D kinematics and isokinetic dynamometry were used to estimate the kick velocity, isokinetic moment of kicking lower limb hip flexors and extensors (60, 120, 240, 300°∙s-1), and stance lower limb hip internal and external rotators (30, 90°∙s-1). Multiple regression showed that a separate component of the peak moment concentric hip flexion and extension of the kicking lower limb at 90°∙s-1 can explain 54% of the peak kicking impact force variance (R2 = 0.54; p < 0.001). When adding the other 3 components of eccentric and concentric hip internal and external rotations at 30°∙s-1, the internal and external hip rotation ratios at 30°∙s-1 on the stance limb and the concentric ratio of kicking limb flexion and extension at 300°∙s-1 that explained the variance of impact force were 75% (p = 0.003). The explosive strength of kicking limb hip flexors and extensors is the main condition constraint for kicking performance. The maximum strength of stance limb internal and external rotators and speed strength of kicking limb hip flexors and extensors are important constraints of kicking performance that should be considered to improve the front kick efficiency.

Introduction The efficiency of front kick is related to the kicking technique. Thus, the aim of this study was to find the kinematic determinants of front kick dynamics across different performance and loading levels (no load to 45-kg load). Materials and Methods Twenty-four elite and sub-elite professional military personnel (26.8 ± 10.1 years, 84.2 ± 5.4 kg, 181.1 ± 6.4 cm) performed six front kicks into a force plate across five different loading conditions. Three-dimensional kinematics of the kicks was quantified and included velocity of the hip (Vhip), velocity of the knee (Vknee), velocity of the shoulder (Vshoulder), velocity of the foot (Vfoot), angular velocity of the knee (AVknee), and angular velocity of the hip (AVhip). Results The main kinematic differences between the two groups were that the sub-elite group had an increased kick time for all loading conditions (P &lt; .001) and a lower Vfoot (P = .05) and a decreased Vhip and Vshoulder (P &lt; .05) in the highest load condition. Vhip and AVhip were the best predictors (up to R2 = 0.58; P = .020) of peak force and impact force during no-load or loaded kicking at the elite level. Typical predictors of impulse in the elite group were AVhip, Vhip, and Vshoulder and those in the sub-elite group were AVknee and Vfoot. Conclusions The kinematic variables provide good predictions of kicking dynamics; however, the best predictor varies with the loading conditions and performance levels. Hip motion is the main differentiating factor.

Front kicks are often used in combat activities that involve the use of kicks and punches, including close combat military training. To mimic real-life combative environments where soldiers execute forceful front kicks while wearing military boots, it is logical to wear these boots during close combat training. However, the effect of military footwear on front kick forces remain unknown. Therefore, the aim of this study was to compare the effects of military boots on front kick dynamics. Six male soldiers (23.3 ± 1.7 yr, 74.3 ± 6.2 kg, 175.5 ± 4.5 cm) performed eight individual front kicks with no military boots, in bare feet (NB) and with military boots (MB). Peak force (N), impulse (N.s) and time to reach peak force (ms), were measured during each kick. Data were analyzed using paired sample t-tests or nonparametric Wilcoxon pair test and Cohen's d. Results. Neither peak force (3180 ± 647 N) nor impulse (367 ± 40 N.s) of MB were different than NB (3157 ± 291 N and 360 ± 48 N.s, respectively) (p = 0.85; d = 0.04 and p = 0.36; d = 0.12, respectively). Peak force was reached in a significantly shorter time during MB (39 ± 16 ms) compared to NB (56 ± 8 ms; d = −0.88). Conclusion. Peak force was reached in a shorter time using MB compared to barefoot (NB) front kicks. The use of military boots changes the time course of peak force during the front kick.

Kicking is an essential skill for combat athletes and military personnel. Therefore, the aim of this article is to present evidence-based training principles to achieve beneficial changes in technique and performance through functional training. The profile of subelite and elite kickers is presented and is used as a foundation for exercise prescription in both populations. The article emphasizes the importance of combining both functional training with a core emphasis and traditional general strength preparation to improve all aspects of front push kick performance. Example training programs for both subelite and elite kickers are presented that are based on a block periodization approach.

Since the flat serve (FS) minimizes the ball spin and kick serve (KS) combined topspin and sidespin, this systematic review aimed to explore the ball impact location (BI) within the FS and KS at the professional men, junior men, and women tennis players. The PRISMA guideline was used, and the original articles were searched in Scopus, Web of Science, and PubMed. The means and standard deviations computed from the distance of BI from the origin within the FS and KS on the x, y, and z axes (global coordinate system) were normalized by the participants’ height and weighted by the number of participants in one-way ANOVA. Ten articles with a pooled sample of 133 males and 51 females aged 11–25 were included. The professional men had more stable BI on the x-axis within the FS by 56% (p < 0.001), within the KS by 58% (p < 0.001), and on the y-axis within the KS by 90% (p < 0.001) than junior men. The professional and junior men had the BI more leftwards from the origin on the x-axis within the KS by 188% (p < 0.001) and 88% (p < 0.001), respectively than within the FS.

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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.

Review question / Objective: To summarize the sprint reference acceleration and speed values for different sprint distances and suggest optimal unification of ice-hockey straight sprint testing. Eligibility criteria: The title and abstract screening was done by two researchers (PS and RR) who selected a set of articles for full text screening, where the inclusion criteria were: 1) male or female ice-hockey players; 2) any cross-sectional or intervention study; 3) tests of ice-hockey sprinting over any distance or any battery of conditioning tests that included straight-line sprints; and, 4) results reported straight-line sprint distance, speed, time, or acceleration. In the case of disagreement between the evaluating authors, the final decision was made by a third author (MV).The full text screening exclusion criteria were: 1) if the article was not in English; 2) the testing did not include straight-line sprinting; 3) the reported values did not include data distribution; 4) the study reported only maximum speed without skating time or average speed; 5) the end of the sprint was defined by the point the player stopped sprinting; 6) the measurement was made with a stopwatch; and, 7) the study had high bias estimation. The maximum speed test was not included due to the uncertain velocity conditions at beginning of testing distance. The bias estimation was performed using the JBI (Joanna Briggs Institute) Critical Appraisal Checklist for Analytical Cross Sectional Studies (supplementary material 1).