Effects of hurdle height on lower limb joint kinematics and kinetics of male trainee sprinters during hurdle jumps

Hurdle jumps are frequently practiced in the field of sports training. The present study aimed to clarify the effect of hurdle heights on jumping height and joint kinematics, and kinetics during hurdle jumps. Ten male Japanese trainee sprinters performed at three heights (0.76, 0.91 and 1.06 m) of hurdle jumps and maximum countermovement jump (CMJ). Sagittal plane kinematics and ground reaction force were measured. Jump height significantly increased with hurdle heights (ηp2 = 0.65), but the difference in jump heights was small as compared to the difference in the hurdle heights. The contact time and mechanical work of the lower limb joints did not differ between different hurdle heights. The minimal angles of the knee (ηp2  = 0.47) and hip (ηp2  = 0.70) joints during the flight phase significantly decreased with higher hurdle heights. The load characteristics of the lower limb joint with higher hurdle heights would be similar to those with lower hurdle heights. In higher hurdle heights, since the increase in jump height was smaller than the increase in hurdle height, the legs were more flexed to clear the hurdle. Therefore, the hurdle height which is similar to the maximum CMJ height would be appropriate as a training load.

Plyometric Training Practices of Brazilian Olympic Sprint and Jump Coaches: Toward a Deeper Understanding of Their Choices and Insights

Plyometric training is extensively used by coaches to enhance neuromuscular performance in a wide variety of sports. Due to the high demands of sprint speed and power output in elite sprinters and jumpers, sprint and jump coaches are likely to have great knowledge on this topic. Undoubtedly, this expertise is even more pronounced for Olympic coaches, who work with some of the fastest and most powerful athletes in the world, and who are required to continually maintain these athletes at optimal performance levels. Describing and discussing the practices commonly adopted by these coaches in detail and extrapolating this experience to other sport coaching contexts and disciplines may be extremely relevant. The current article presents, explores, and illustrates the plyometric training practices of Brazilian Olympic sprint and jump coaches, with a special focus on training programming and exercise selection.

Countermovement, Hurdle, and Box Jumps: Data-Driven Exercise Selection

Apart from squat jumps, countermovement jumps (CMJ), and drop jumps, differences among other jump variations are not as well researched, making data-driven exercise selection difficult. To address this gap, this study compared selected concentric and eccentric jump parameters of maximal effort CMJ, hurdle jumps over 50 cm hurdle (HJ), and box jumps onto a 50 cm box (BJ). Twenty recreationally trained men (25.2 ± 3.5 years) performed 3 repetitions of CMJs, HJs, and BJs, each on separate days. The data were collected using force platforms and a linear position transducer. The mean of 3 trials of each jump variation was analyzed using repeated measures ANOVA and Cohen's d. Countermovement depth was significantly greater (p ≤ 0.05) and peak horizontal force significantly lower during CMJ compared to HJ and BJ. However, there were no differences in peak velocity, peak vertical and resultant force, and total impulsion time. Finally, BJ significantly decreased peak impact force by ~51% compared to CMJ and HJ. Therefore, the propulsive parameters of HJ and BJ seem to be similar to CMJ, despite CMJ having a greater countermovement depth. Furthermore, overall training load can be decreased dramatically by using BJ, which reduced peak impact force by approximately half.

Effects of Combined Horizontal Plyometric and Change of Direction Training on Anaerobic Parameters in Youth Soccer Players

The aim of this study is to investigate whether the combination of soccer training, plyometric training (PT), and change of direction (COD) exercises would enhance anaerobic performance to a greater extent than training on its own in youth U17 soccer players. Twenty youth players participated in this study. Players were randomly separated into two groups: the control group (CG, n = 9) and the intervention group (EX), which performed extra PT and COD exercises (EX, n = 11). The duration of the training program was six weeks. Sprint 10 m, 30 m, countermovement jump (CMJ), single leg countermovement jump (CMJ right and left), squat jump (SJ), 505 test, and Illinois agility test were measured pre and post of the training program. The performance in the 505 test improved for the EX group (right leg: p = 0.031, left leg: p = 0.004). In addition, Illinois test performance increased in the EX group (2.9%, p = 0.019). The performances of the two groups differed significantly in the Illinois agility test (p = 0.001). This study supports that a short-term combined program of PT and COD exercises can improve change of direction ability in youth U17 soccer players. The lack of effect of the intervention program on sprint and jump performance may be due to the type and volume of plyometric exercises used. The results reflect the training principle of specialization of stimulus. The improvement in performance was presented in tests that had similar characteristics to training stimuli.

Effective recognition of human lower limb jump locomotion phases based on multi-sensor information fusion and machine learning

Jump locomotion is the basic movement of human. However, no thorough research on the recognition of jump sub-phases has been carried so far. This paper aims to use multi-sensor information fusion and machine learning to recognize the human jump phase, which is crucial to the development of exoskeleton that assists jumping. The method of information fusion for sensors including sEMG, IMU, and footswitch sensor is studied. The footswitch signals are filtered by median filter. A processing method of synthesizing Euler angles into phase angle is proposed, which is beneficial to data integration. The jump locomotion is creatively segmented into five phases. The onset and offset of active segment are detected by sample entropy of sEMG and standard deviation of acceleration signal. The features are extracted from analysis windows using multi-sensor information fusion, and the dimension of feature matrix is selected. By comparing the performances of state-of-the-art machine learning classifiers, feature subsets of sEMG, IMU, and footswitch signals are selected from time domain features in a series of analysis window parameters. The average recognition accuracy of sEMG and IMU is 91.76% and 97.68%, respectively. When using the combination of sEMG, IMU, and footswitch signals, the average accuracy is 98.70%, which outperforms the combination of sEMG and IMU (97.97%, p < 0.01). Graphical Abstract The sub-phases of human locomotion are recognized based on multi-sensor information fusion and machine learning method. The feature data of the sub-phases is visualized in 3-dimensional space. The predicted states and the true states in a complete jump are compared along the time axis.

Methodological characteristics and future directions for plyometric jump training research: A scoping review update

The aim of this scoping review was a) to update a previous review on the main methodological characteristics and shortcomings in the plyometric jump training (PJT) literature, and b) to recommend, in light of the identified methodological gaps, future research perspectives. We searched four electronic databases. From 6128 potentially relevant articles, 420 were considered eligible for inclusion. As an update of a previous review, this represents an increase of ~200 articles, illustrating that this field of research is growing fast. However, the relative "quality" or shortcomings were similar when compared to the preceding scoping review. In the current article, the main identified shortcomings were an insufficient number of studies conducted with females, individual sports, and high-level athletes (~22%, ~7%, and ~14% of overall studies, respectively); insufficient description of training prescription (~54% of studies); and studies missing an active/passive control group and a randomized group allocation process (~37% and ~24% of overall studies, respectively). Furthermore, PJT was often combined with other training methods and added to the participants' regular training routines (~50% and ~35% of overall studies, respectively). The main outcomes of this scoping review urge researchers to conduct PJT studies of high methodological quality (eg, randomized controlled trials) to get trustworthy evidence-based knowledge. In addition, owing to the limited research conducted with females, individual sports, and high-level athletes, more studies are needed to substantiate the available findings. Finally, the identification of cohort-specific PJT dose-response relations which elicit optimal training effects still needs to be identified, particularly in the long term.

Effects of flexibility combined with plyometric exercises vs isolated plyometric or flexibility mode in adolescent male hurdlers

BACKGROUND

This study aims to determine the effect of flexibility exercises combined with plyometrics in hurdles race, on physical fitness, motor skills (MS) and hip range of motion.

METHODS

Thirty-four male hurdlers, (age=15.7±0.7 years, body mass=59.7±2.3 kg, height=170.8±2.4 cm) were randomly assigned to four independent groups. The (Gflex+plyo), the (Gplyo), the (Gflex) and a control group (Gcon). All participants performed different tests: a test of right and left hip flexion (RHF, LHF) and extension (RHE, LHE), squat jump (SJ), countermovement jump (CMJ), stiffness jump (STFJ) and three (MS) exercises (running, hopping and leaping). A 60-m sprint on the hurdles was also performed.

RESULTS

The two-way analyses of covariance for repeated measures showed that Gflex+plyo increased significantly: the CMJ, performance on 60-m and showed higher performance in the between groups' comparison. The Gflex+plyo and Gflex showed the higher percentages of changes in flexibility (RHF: 3.2±1.3% and 3.0±2.1%; RHE: 6.4±2.4% and 9.4±4.1%, LHE: 8.4±3.4% and 7.8±4.3%, respectively). Gplyo increased significantly the LHF (3.9±1.4%) more than the other groups. In the between groups' comparison, Gplyo showed the higher percentage of change in STFJ (6.4±1.8%) and the Gflex+plyo showed the higher values in running and hopping (10.7±4.6% and 13.3±2.1%, respectively).

CONCLUSIONS

Specific stretching exercises combined with plyometrics may be more beneficial than other training strategies in young sprint-hurdlers. This may better improve physical fitness, hip range of motion and may increase different level of skills which may better improve performance in hurdles race.

Effect of Jump Direction on Joint Kinetics of Take-Off Legs in Double-Leg Rebound Jumps

Vertical (VDJ) and horizontal (HDJ) double-leg rebound jumps are used as plyometric exercises in direction-specific training regimens for various sports. We investigated the effects of jump direction on joint kinetics of the take-off legs in double-leg rebound jumps. Twelve Japanese male track and field athletes performed VDJ, 100% HDJ, 50% HDJ (50% of 100% HDJ distance), and 75% HDJ (75% of 100% HDJ distance). Kinematic and kinetic data in the sagittal plane were calculated using a force platform and high-speed video camera. Hip negative power during the eccentric phase decreased from VDJ to 50% HDJ (VDJ, -4.40 ± 4.25 W/kg; 50% HDJ, -0.83 ± 2.10; 75% HDJ, -0.33 ± 0.83; 100% HDJ, 0 ± 0), while hip positive power increased from VDJ to 100% HDJ (VDJ, 4.19 ± 2.73 W/kg; 50% HDJ, 9.37 ± 2.89; 75% HDJ, 11.15 ± 3.91; 100% HDJ, 18.51 ± 9.83). Knee negative power increased from VDJ to 75% HDJ (VDJ, -14.48 ± 7.67 W/kg; 50% HDJ, -18.98 ± 7.13; 75% HDJ, -21.57 ± 8.54; 100% HDJ, -23.34 ± 12.13), while knee positive power decreased from VDJ to 75% HDJ (VDJ, 23.18 ± 9.01 W/kg; 50% HDJ, 18.83 ± 5.49; 75% HDJ, 18.10 ± 5.77; 100% HDJ, 16.27 ± 6.22). Ankle joint kinetics remained unchanged. Differences in hip and knee joint kinetics between VDJ and HDJ were associated with direction control, becoming more pronounced as jump distance increased.

Kinetic Analysis of Horizontal Plyometric Exercise Intensity

Kossow, AJ, DeChiara, TG, Neahous, SM, and Ebben, WP. Kinetic analysis of horizontal plyometric exercise intensity. J Strength Cond Res 32(5): 1222-1229, 2018-Plyometric exercises are frequently performed as part of a strength and conditioning program. Most studies assessed the kinetics of plyometric exercises primarily performed in the vertical plane. The purpose of this study was to evaluate the multiplanar kinetic characteristics of a variety of plyometric exercises, which have a significant horizontal component. This study also sought to assess sex differences in the intensity progression of these exercises. Ten men and 10 women served as subjects. The subjects performed a variety of plyometric exercises including the double-leg hop, standing long jump, single-leg standing long jump, bounding, skipping, power skipping, cone hops, and 45.72-cm hurdle hops. Subjects also performed the countermovement jump for comparison. All plyometric exercises were evaluated using a force platform. Dependent variables included the landing rate of force development and landing ground reaction forces for each exercise in the vertical, frontal, and sagittal planes. A 2-way mixed analysis of variance with repeated-measures for plyometric exercise type demonstrated main effects for exercise type for all dependent variables (p ≤ 0.001). There was no significant interaction between plyometric exercise type and sex for any of the variable assessed. Bonferroni-adjusted pairwise comparisons identified a number of differences between the plyometric exercises for the dependent variables assessed (p ≤ 0.05). These findings should be used to guide practitioners in the progression of plyometric exercise intensity, and thus program design, for those who require significant horizontal power in their sport.

Effectiveness of Traditional Strength vs. Power Training on Muscle Strength, Power and Speed with Youth: A Systematic Review and Meta-Analysis

Numerous national associations and multiple reviews have documented the safety and efficacy of strength training for children and adolescents. The literature highlights the significant training-induced increases in strength associated with youth strength training. However, the effectiveness of youth strength training programs to improve power measures is not as clear. This discrepancy may be related to training and testing specificity. Most prior youth strength training programs emphasized lower intensity resistance with relatively slow movements. Since power activities typically involve higher intensity, explosive-like contractions with higher angular velocities (e.g., plyometrics), there is a conflict between the training medium and testing measures. This meta-analysis compared strength (e.g., training with resistance or body mass) and power training programs (e.g., plyometric training) on proxies of muscle strength, power, and speed. A systematic literature search using a Boolean Search Strategy was conducted in the electronic databases PubMed, SPORT Discus, Web of Science, and Google Scholar and revealed 652 hits. After perusal of title, abstract, and full text, 107 studies were eligible for inclusion in this systematic review and meta-analysis. The meta-analysis showed small to moderate magnitude changes for training specificity with jump measures. In other words, power training was more effective than strength training for improving youth jump height. For sprint measures, strength training was more effective than power training with youth. Furthermore, strength training exhibited consistently large magnitude changes to lower body strength measures, which contrasted with the generally trivial, small and moderate magnitude training improvements of power training upon lower body strength, sprint and jump measures, respectively. Maturity related inadequacies in eccentric strength and balance might influence the lack of training specificity with the unilateral landings and propulsions associated with sprinting. Based on this meta-analysis, strength training should be incorporated prior to power training in order to establish an adequate foundation of strength for power training activities.

Effect of unilateral, bilateral, and combined plyometric training on explosive and endurance performance of young soccer players

The aim of the study was to compare the effects of bilateral, unilateral, or combined bilateral and unilateral plyometric training (PT) on muscle power output, endurance, and balance performance adaptations in young soccer players. Four groups of young soccer players (age 11.4 ± 2.2 years) were divided into control group (CG; n = 14), bilateral group (BG; n = 12), unilateral group (UG; n = 16), and bilateral + unilateral group (B + UG; n = 12). Players were measured in unilateral and bilateral countermovement jump with arms, 5 multiple bounds test, 20-cm drop jump reactive strength index, maximal kicking velocity, sprint and agility test time, endurance, and balance performance. The PT was applied during 6 weeks, 2 sessions per week, for a total of 2,160 jumps. After intervention, all PT groups showed a statistically significant (p ≤ 0.05) change in all performance measures, with no statistically significant differences between treatments. Among the 21 performance measures, the B + UG showed a significantly (p ≤ 0.05) higher performance change in 13 of them vs. the CG, whereas the UG and BG showed only 6 and 3, respectively. The current study showed that bilateral, unilateral, and combined bilateral and unilateral PT ensured significant improvement in several muscular power and endurance performance measures in young soccer players. However, the combination of unilateral and bilateral drills seems more advantageous to induce superior performance improvements.

Neuromuscular characteristics of drop and hurdle jumps with different types of landings

The objective of this study was to compare drop (DJ) and hurdle jumps using a preferred, flat foot (FLAT) and forefoot (FORE) landing technique. Countermovement jump height was used to establish the hurdle and the DJ heights. The subjects performed forward hurdles and vertical DJs on a force plate. Measures included vertical ground reaction force (VGRF), contact time, leg stiffness, and rate of force development (RFD). Electromyographic (EMG) activity was measured in the rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius during 3 phases: preactivity, eccentric phase, and concentric phase. All the kinetic variables favored hurdles over DJs. Specifically, hurdle-preferred technique and FORE exhibited the shortest contact time and DJ FLAT the longest. The VGRF was higher in hurdle preferred and FORE than in DJ preferred, FLAT, and FORE. For stiffness and RFD, hurdle preferred and FORE were higher than DJ preferred and FLAT. Hurdle jumps showed higher rectus femoris EMG activity than DJ did during preactivity and eccentric phases but lower activity during the concentric phase. Considering the type of landing, FLAT generally demonstrated the greatest EMG activity. During the concentric phase, DJ exhibited higher rectus femoris EMG activity. Biceps femoris activity was higher with hurdles in all the phases. Gastrocnemius showed the highest EMG activity during the concentric phase, and during the eccentric phase, hurdle preferred and FORE showed the highest results. In conclusion, the hurdle FORE technique was the most powerful type of jump.