Athanasia Smirniotou

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

Abstract Paradisis, GP, Pappas, PT, Theodorou, AS, Zacharogiannis, EG, Skordilis, EK, and Smirniotou, AS. Effects of static and dynamic stretching on sprint and jump performance in boys and girls. J Strength Cond Res 28(1): 154–160, 2014—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.

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), Cronbachs 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.

Acute Effects of Stretching on Flexibility, Power and Sport Specific Performance in Fencers

Acute Effects of Stretching on Flexibility, Power and Sport Specific Performance in Fencers Elite athletes are eager to perform to the best of their ability, regardless of different warm-up stretching techniques used before training or competition which actually help or hinder specific performance variables. The aim of this study was to investigate the acute effects of static or ballistic stretching on flexibility and leg power characteristics of fencing performance in fencers of both genders. Ten male and ten female international level fencers participated in this study. Each subject performed static or ballistic stretching (3 sets of 20 sec) on three muscles of the lower limbs on separate days. Flexibility, squat jump, countermovement jump, drop jump, time and power of lunge and shuttle run test were measured before and after different stretching interventions. Neither static nor ballistic stretching exercises affected flexibility, jumping ability and leg functional fencing performance tests. Moreover, stretching conditions did not affect differently. The results of this study suggest that static or ballistic stretching in the later stages of a general warm-up normally used before training or competition does not hinder specific performance in fencing. Consequently, fencers can continue performing any type of stretching before training or competition at their preference.

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

Abstract 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.

The acute effects of different training loads of whole body vibration on flexibility and explosive strength of lower limbs in divers

The purpose of this study was to examine the acute effects of different vibration loads (frequency and amplitude) of whole-body vibration (WBV) on flexibility and explosive strength of lower limbs in springboard divers. Eighteen male and female divers, aged 19 ± 2 years, volunteered to perform 3 different WBV protocols in the present study. To assess the vibration effect, flexibility and explosive strength of lower limbs were measured before (Pre), immediately after (Post 1) and 15 min after the end of vibration exposure (Post 15). Three protocols with different frequencies and amplitudes were used in the present study: a) low vibration frequency and amplitude (30 Hz/2 mm); b) high vibration frequency and amplitude (50 Hz/4 mm); c) a control protocol (no vibration). WBV protocols were performed on a Power Plate platform, whereas the no vibration divers performed the same protocol but with the vibration platform turned off. A two-way ANOVA 3 x 3 (protocol × time) with repeated measures on both factors was used. The level of significance was set at p < 0.05. Univariate analyses with simple contrasts across time were selected as post hoc tests. Intraclass coefficients (ICC) were used to assess the reliability across time. The results indicated that flexibility and explosive strength of lower limbs were significantly higher in both WBV protocols compared to the no vibration group (NVG). The greatest improvement in flexibility and explosive strength, which occurred immediately after vibration treatment, was maintained 15 min later in both WBV protocols, whereas NVG revealed a significant decrease 15 min later, in all examined strength parameters. In conclusion, a bout of WBV significantly increased flexibility and explosive strength in competitive divers compared with the NVG. Therefore, it is recommended to incorporate WBV as a method to increase flexibility and vertical jump height in sports where these parameters play an important role in the success outcome of these sports.

Acute effects of stretching on leg and vertical stiffness during treadmill running

Abstract 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−1, 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

ABSTRACT 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.

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

ABSTRACT 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.

Acute effects of specific actions after the "On your Marks" command

Improved temporal sequencing of high – intensity muscle contractions prior to the sprint start may maximize motoneuron excitability and may enhance fast twitch fiber recruitment and sprint start effectiveness. The aim of the study was to assess a) the electromyographic activity of the gastrocnemius lateralis, biceps femoris and vastus femoris muscles under exposure to specific voluntary, dynamic actions (quick skipping or tuck jumps that sometimes sprinters perform after the “on your marks” command) and to an external involuntary stimulus (WBV-whole body vibration) and b) the effectiveness of the above stimuli applied on the activation level of lower limb muscles in order to produce neuromuscular activation the very last moment just behind the blocks, as this is measured by the RT and time in 1.5m and 3m after the sprint start.Ten male sprinters executed sprint starts under 4 experimental conditions after the “on your marks command”: 1st condition – without performing any action, 2nd performing tuck jumps, 3rd performing quick skipping and 4th after being exposed to vibration stimuli. No significant difference in average muscle activity was observed after evaluation of the EMG raw data for the tuck jumps and quick skipping actions. No significant differences were, also, observed for RT and time in 1.5m and 3m in conditions 2 to 4.