A Hurdle-Based Learning Design Effect on Locomotion Pattern and Hurdle Clearance Kinematic Reorganization.

The study assessed the manifestation of a regulated locomotion pattern while clearing the first two hurdles during running. In addition, the effect of a hurdles' learning design, using specific activities and manipulated task constraints, on regulation strategies and kinematic reorganization was examined. Pre- and posttests were conducted. Twenty-four young athletes were randomly assigned into an experimental and a control group, and performed 18 training sessions, consisting of a hurdle-based intervention for experimental participants and a more generalized athletics training for control participants. Different footfall variability curves were recorded, suggesting that young athletes regulated locomotion pattern to clear the hurdles according to their needs. Task-specific training contributed to lower values of variability for the entire approach run and to functional movement reorganization, affording learners to take-off further from the hurdle with a higher horizontal velocity, leading to a more flat hurdle clearance stride and to a significant hurdle running performance improvement.

Target Constraints Influence Locomotion Pattern to the First Hurdle.

The study examined to what extent the manipulation of hurdle height (0.76-m hurdle, low hurdle 0.50 m, and white stripe) would affect visual regulation strategies and kinematic reorganization when approaching the first hurdle. In addition, the impact of constraints as a training tool in terms of creating movement patterns functional for and representative of competitive movement models was assessed. The approach phase to the first hurdle of 13 physical education students with no previous experience in hurdling was video recorded and analyzed. Emergence of different footfall variability curves and movement coordination patterns suggests that participants interact differently with features of the performance context. Contrary to the white stripe, the hurdle height required participants to initiate regulation and distribute adjustments over a larger number of steps, and afforded the preparation for takeoff in order to clear the hurdle. In task design, manipulation of task constraints should offer valuable information regarding the dynamics of movement.

Sprinting and dribbling differences in young soccer players: a kinematic approach.

Sprinting and dribbling a ball are considered essential for success in team sports, such as soccer. The purpose of the present study was to examine straight line (SL) and changes of direction (COD) sprinting and dribbling abilities after a standing and a flying starting position. Twelve amateur U12 male soccer players participated in the study. The participants were tested in four different sprinting conditions. The first consisted of 15 m SL sprinting and dribbling test by standing position; the second consisted of 15 m SL sprinting and dribbling test by flying start. The third condition consisted of 15 m COD sprinting and dribbling test by standing position, and the fourth condition consisted of 15 m COD sprinting and dribbling test by flying start. T-tests analysis indicated significant differences between SL sprinting and dribbling sprinting tests (P < 0.05) and between standing and flying start positions (P < 0.05). Step frequency was higher for sprinting tests (P < 0.05). Moreover, the results showed that step length was longer when players had a standing position (P < 0.05). These findings emphasize the importance for trainers to add parts without ball, focused on the development of certain fitness and running components.

Anthropometric and Leg Power Factors Affect Offensive Kinetic Patterns in Fencing.

This study aimed to identify potential factors that may influence specific fencing offensive kinetic patterns in a large group of well-trained fencers having different ages, gender level, and training specialization. One-hundred-thirty fencers (males: n = 72) and (females: n = 58), participating in three different fencing weapons (epee, foil, and sabre), having considerable experience of national and international competitions. All members of seven national fencing teams were measured for basic anthropometric parameters, leg power performance and velocity values for three specific kinetic offensive patterns during an International Fencing camp. A multivariate analysis of variance (MANOVA) revealed a significant velocity multivariate effect in age competitive categories (Wilks Λ = 0.129, F = 2.112, p <0.01, n 2 = 0.060) gender (Wilks Λ = 0.103, F = 3.743, p < 0.05, n 2 = 0.103), competition levels (Wilks Λ = 0.863, F = 5.198, p <0.01, n 2 = 0.137) and discipline practiced (Wilks Λ = 0.239, F = 4.305, p < 0.001, n 2 = 0.119) respectively. Significant correlations were observed between lunge and step lunge velocity and long jump (LJ), countermovement jump (CMJ), drop jump (DJ), and reaction strength index (RSI). Age, gender, level of participants, and the choice of the weapon practiced, influenced fencing performance. Different leg power abilities could be decisive factors in training schedules design and monitoring training adaptations.

Acute Effects of Stretching on Leg and Vertical Stiffness During Treadmill Running.

Pappas, PT, Paradisis, GP, Exell, TA, Smirniotou, AS, Tsolakis, CK, and Arampatzis, A. Acute effects of stretching on leg and vertical stiffness during treadmill running. J Strength Cond Res 31(12): 3417-3424, 2017-The implementation of static (SS) and dynamic (DS) stretching during warm-up routines produces significant changes in biological and functional properties of the human musculoskeletal system. These properties could affect the leg and vertical stiffness characteristics that are considered important factors for the success of athletic activities. The aim of this study was to investigate the influence of SS and DS on selected kinematic variables, and leg and vertical stiffness during treadmill running. Fourteen men (age: 22.58 ± 1.05 years, height: 1.77 ± 0.05 m, body mass: 72.74 ± 10.04 kg) performed 30-second running bouts at 4.44 m·s, under 3 different stretching conditions (SS, DS, and no stretching). The total duration in each stretching condition was 6 minutes, and each of the 4 muscle groups was stretched for 40 seconds. Leg and vertical stiffness values were calculated using the "sine wave" method, with no significant differences in stiffness found between stretching conditions. After DS, vertical ground reaction force increased by 1.7% (p < 0.05), which resulted in significant (p < 0.05) increases in flight time (5.8%), step length (2.2%), and vertical displacement of the center of mass (4.5%) and a decrease in step rate (2.2%). Practical durations of SS and DS stretching did not influence leg or vertical stiffness during treadmill running. However, DS seems to result in a small increase in lower-limb force production which may influence running mechanics.

Step characteristic interaction and asymmetry during the approach phase in long jump.

The aim of this study was to investigate the relative influence of step length (SL) and step frequency (SF) on step velocity (SV) during the approach run of high-level long jumpers and to quantify the asymmetry of these step characteristics. Spatiotemporal data of the approach run were collected during national competition from 10 long jumpers (age 26.2 ± 4.1 years, height 1.84 ± 0.06 m, mass 72.77 ± 3.23 kg, personal best performance 7.96 ± 0.30 m). Analyses were conducted for total approach, early approach and late approach. For the total approach 4/10 athletes were SF reliant and 6/10 athletes favoured neither characteristic. At the early approach, 3/10 athletes were SF reliant and 7/10 athletes favoured neither. During late approach 2/10 athletes demonstrated SL reliance, 7/10 athletes were SF reliant and 1/10 athletes favoured neither. Four athletes displayed significant asymmetry for SL and three for SF. However, no athletes demonstrated significant asymmetry for SV indicating that the asymmetrical demands of take-off do not have a marked influence on step characteristic asymmetry, probably due to the constraints of the event. Consideration should be given to the potentially conflicting demands between limbs for individual athletes.

Static and dynamic balance deficiencies in chronic low back pain.

BACKGROUND: According to previously conducted studies, people with Low Back Pain (LBP) present with static balance deficiencies. OBJECTIVE: The aim of the present study was to compare static, as well as dynamic balance ability between Chronic Low Back Pain (CLBP) and healthy subjects. METHODS: The CLBP group comprised 17 subjects and the control group of 16 subjects, matched for age, BMI and gender. The protocol applied compared the balance ability when performing the Star Excursion Balance Test (SEBT) and the static 1-leg stance position. The innovation introduced in the protocol was that the participants performed not only the static 1-leg stance, but also the dynamic SEBT on a force plate which recorded the target sway (TS), i.e. the Center of Pressure (CoP) excursion. RESULTS: The CLBP group had significantly reduced performance in SEBT, coupled with greater static and dynamic TS values. Age and especially BMI also bear a significant effect on SEBT execution. The inclusion of SEBT and TS derived scores in a stepwise logistic regression equation lead to the correct classification of 85% of the subjects. CONCLUSIONS: Dynamic and static balance ability provide supplementary information for the identification of the presence of CLBP, with dynamic balance being more instrumental.

Performance environment and nested task constraints influence long jump approach run: a preliminary study.

The purpose of the study was to investigate possible changes at step pattern and technical performance of the long jump approach run in seven young long jumpers by modifying the performance environment (long jump runway versus track lane) and the nested actions (run-through with take-off versus complete long jump). Our findings suggest that the step pattern and technical aspects of the approach run are affected by environmental context and nested task constraints. In terms of environmental context, it appears that practising the training routine of run-through followed by take-off on the long jump runway allows athletes to simulate competition conditions in terms of step regulation and technical efficacy. The task of run-through followed by take-off on the track lane failed to initiate visual perception, step regulation and technical efficiency at the steps preceding the instant of take-off. In terms of nested task constraints, when run-ups were followed by jump for distance instead of only a take-off, a higher level of consistency was achieved and step regulation was based on perception-action coupling. Practising long jump run-up accuracy at a setting not containing the informational elements of the performance environment fails to develop the key elements of the skill.

Reliabilities of leg and vertical stiffness during treadmill running.

The aim of this study was to determine the intra-participant variabilities (i.e. intra-day and inter-day reliabilities) in leg and vertical stiffness, as well as related kinematic parameters, during treadmill running using the sine-wave method. Twenty-two healthy men ran on a treadmill at 4.44 m/s, and the flight and contact times were measured with a high-speed video camera. Three 30-s running bouts with 2-min inter-bout rests were performed to examine the intra-day reliability, and single 30-s running bouts on three separate days with 24- to 48-h inter-bout intervals were performed to examine the inter-day reliability. The reliability statistics included repeated-measure analyses of variance, average inter-trial correlations, intra-class correlation coefficients (ICCs), Cronbach's α reliability coefficient, and the coefficient of variation. Both leg and vertical stiffness produced high ICCs within 0.972 and 0.982, respectively, and between 0.922 and 0.873 days, respectively. High values were also observed for all of the reliability coefficients. Similar results were found regarding contact time, flight time, step length, and step rate. It was concluded that the measurements of leg and vertical stiffness, as well as related kinematic parameters, obtained using the sine-wave method during treadmill running at 4.44 m/s, were highly reliable, both within and across days.

Effects of static and dynamic stretching on sprint and jump performance in boys and girls.

The aim of this study was to investigate the acute effects of static (SS) and dynamic stretching (DS) on explosive power, flexibility, and sprinting ability of adolescent boys and girls and to report possible gender interactions. Forty-seven active adolescent boys and girls were randomly tested after SS and DS of 40 seconds on quadriceps, hamstrings, hip extensors, and plantar flexors; no stretching was performed at the control condition. Pretreatment and posttreatment tests examined the effects of stretching on 20-m sprint run (20 m), countermovement jump (CMJ) height, and sit and reach flexibility test. In terms of performance, SS hindered 20 m and CMJ in boys and girls by 2.5 and 6.3%, respectively. Dynamic stretching had no effect on 20 m in boys and girls but impaired CMJ by 2.2%. In terms of flexibility, both SS and DS improved performance with SS being more beneficial (12.1%) compared with DS (6.5%). No gender interaction was found. It can therefore be concluded that SS significantly negates sprinting performance and explosive power in adolescent boys and girls, whereas DS deteriorates explosive power and has no effect on sprinting performance. This diversity of effects denotes that the mode of stretching used in adolescent boys and girls should be task specific.

Locomotor control in the long jump approach run in young novice athletes.

We examine the presence of visually regulated control in young, novice long jumpers as they approach the takeoff board. The approach run of 27 novice jumpers (age 12-13 years) practising jump training for a short period was video-recorded during competition. Findings revealed that young, novice participants adjust the length of the final steps of their approach run, suggesting the presence of visual control. Step regulation commenced on the fifth and fourth step from the board for boys and girls respectively. Their pattern of footfall variability was found to be comparable to that of skilled long jumpers, although young, novice participants presented slightly higher variability. It appears that even a limited period of jump training may contribute to a more consistent run-up as well as to smaller takeoff error, offsetting the limitations imposed by the partially developed cognitive abilities and perceptual awareness of young athletes.