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The effect of sprint training on running performance and vertical jumping in pre-adolescent boys
Abstract
The purpose of this study was to investigate the effect of sprint training upon the running velocity of pre-pubescent boys. Fifteen boys (11.1±0.5yrs old) followed a specific sprint programme for ten weeks (SPR group) and another group of fifteen boys (10.9±0.7yrs old) followed the normal physical education programme and thus acted as the control group (CONT group). Running distances of 0-30m, 0-10m, 10-20m and 20-30m and squat jumps were selected as testing variables to evaluate the training programme. The sprint training programme consisted of short sprints from 5-30m with a resting interval of 3min between repetitions and 5min between sets. The total running distance was initially 150m and gradually increased to 300m. After the ten week sprint programme, the running velocity and the height of squat jumps in the SPR group increased significantly. This programme had a specific effect on the intermediary phases of the running performance; the velocity was increased for the distances 0-10m and 10-20m, but not for the distance 20-30m. The CONT group did not increase any of the tested parameters. These results indicate that the applied sprint training could increase the velocity of the acceleration phase, but not the phase of maximal velocity. The increased height observed in squat jumps in the SPR group could probably be attributed to the stretch-shortening cycle performance, which occurs during running and would have caused the appropriate adaptations to the muscle tendon unit.
... Edición Web: 1988-2041 Ferrete, 2015; Sánchez-Sixto & Floría, 2016). En el caso del voleibol, ha sido reconocido como deporte de velocidad, explosivo, de alta precisión técnica (G Battaglia, A Paoli, M Bellafiore, A Bianco, 2014; Kotzamanidis, 2003;Martinez, Mira, & Cuestas, 2017), que requiere de entrenamientos que optimicen la función fisiológica para movimientos de alta potencia a diferentes velocidades (Pereira, Costa, Santos, Figueiredo, & João, 2015;Sánchez-Moreno et al., 2018), siendo varios los investigadores que han reportado estas características en jugadores de esta especialidad (Kabacinski et al., 2016;Kipp, Kiely, & Geiser, 2016;Vilela, G;Da Silva, 2017). ...
... Respecto al entrenamiento pliométrico en niño y jóvenes, siempre debe ser destacado es la importancia de conocer la madurez de jóvenes, ya que la misma puede representar un mejor rendimiento físico/fisiológico, ya que las condiciones hormonales y neuronales van interferir en esas respuestas(Beltran-Valls, Adelantado-Renau, Segura-Ayala, Toledo-Bonifás, & Moliner-Urdiales, 2019). Investigaciones ya aportan efectos positivos en la salud, postura y rendimiento, enfatizando en la responsabilidad y supervisión de la aplicación de estos programas en sujetos jóvenes (Anis Zribi, Mohamed Zouch, Hamada Chaari, Elyes Bouajina, Hela Ben Nasr, Monia Zaouali, 2014;Chaouachi et al., 2012;Johnson et al., 2011;Kotzamanidis, 2003). A pesar de ello, las investigaciones respecto a los efectos de este tipo de entrenamiento en jóvenes que practican voleibol son de escases en la literatura, más aún, aquellos que estudien los efectos a partir de la maduración biológica, por ello, el objetivo para los investigadores fue estudiar los efectos del entrenamiento pliométrico en la fuerza explosiva de niños en estado de desarrollo puberal. ...
... D) Teníamos 3 ayudantes más el investigador principal en un ratio serian 1/12 diferencias pre y post entrenamiento no sean significativas, contrario a lo reportado (Pereira et al., 2015;Sattler et al., 2018), en jugadoras de voleibol durante 8 y 12 semanas de entrenamiento pliométrico, concluyendo los investigadores que periodos de descanso podrían generar efectos significativos en las mejoras de la fuerza explosiva. En este sentido, el presente estudios pese a utilizar mismos intervalos no evidencia resultados similares, pudiendo ser condicionada por la edad y sexo, sin embargo, en otros estudios (Branislav, Milivoj, Abella, Deval, & Siniša, 2013;Kabacinski et al., 2016;Kotzamanidis, 2003;Marques, M.A.C.;Ganzález-Badillo, 2006;Poulos et al., 2018;Sattler et al., 2018), que comparan los efectos en función del sexo, se registraron efectos significativos para ambos grupos, concluyendo los investigadores que las adaptaciones al entrenamiento polimétrico no difieren entre hombres y mujeres (Martínez-rodríguez et al., 2017), además de poner en evidencia de planear las transferencias del entrenamiento pliométrico hasta la evaluación del salto vertical (Frayne, Zettel, Beach, & Brown, 2020;Moran et al., 2020). ...
El objetivo del estudio fue evaluar los efectos de un programa de entrenamiento pliométrico en la potencia muscular de niñas practicantes de voleibol (n=78; edad = 12,18±1,27 años). Las participantes fueron divididas subdividas de acuerdo con el grado de maduración en: grupo control (GC=48 con grado de maduración 2=11; 3=19; 4=19) y grupo de trabajo (GT=30 con grado de maduración 2=10; 3=10; 4=10). Ambos grupos realizaron 3 sesiones semanales de entrenamiento de voleibol, adicionando 3 sesiones de ejercicios pliométricos a GT que incluyeron salto en zigzag, lineales y profundidad. Para la evaluación pre y post entrenamiento se utilizó test Squat Jump, Saltos Movimiento, Drop Jump y Abalakov. La estadística prueba t student para significancia pre y post entrenamiento (p < 0,05) y también el análisis de la magnitud del efecto. Los resultados no reportaron diferencias significativas post entrenamiento a pesar de registrar pequeños y moderadas magnitudes de efecto. Se concluye que el entrenamiento polimétrico no genero efectos positivos en la saltabilidad de niñas púberes que practican voleibol. Abstract. The aim of this study was to evaluate the effects of plyometric training (PT) on muscle power (PR) of the lower limbs in girls volleyball players aged ( n=78; 12.18 ± 1.27years). Participants were divided according to the degree of maturation into control group (GC = 48 with maturity level 2 = 11; 3 = 19; 4 = 19) and working group (GT = 30 with maturity degree 2 = 10; 3 = 10; 4 = 10). held three sessions per week of volleyball and experimental group - EG n = 24, which held in addition of 3 weekly sessions of volleyball, more 3 weekly sessions of PT that comprised the multi jump, jump over hurdle and drop jumps. For pre- and post-training evaluation test was used Squat Jump, Counter Moviment Jump and Jump Drop Abalakov. The statistical student t test for significance Pre-post (p <0.05) and the analysis of the magnitude of the effect. The results reported no significant differences training post despite posting small to moderate effect sizes. It is concluded that the polymetric training did not generate positive effects on the saltability of pubertal girls who practice volleyball.
... The main difference between adult and young individuals in terms of sprint speed, apart from the lower maximum speed achieved by prepubescents, lies in the duration and total distance of the acceleration phase. Research revealed a difference regarding the secondary acceleration phase [45], which is very short in prepubescents and is completed between 20 and 30 m [46,47]. Furthermore, children achieve their maximum velocity around 30 m, they present a very short steady period [15,46], and a decrease afterward [46]. ...
... The test was a 50-m all-out sprinting task for groups AM and AF and a 40-m full-effort sprint for groups PPB and PPG. The shorter distance for PPB and PPG was selected since it has been found that secondary acceleration in kids concludes at 20-30 m [47,59]. Furthermore, previous findings suggest that children cannot maintain their maximum RV after the 40-m mark of a maximal sprinting test [60]. ...
The purpose of this study was to compare the step parameters, the Body Center of Mass (BCM) kinematics, as well as the angular and linear kinematics of the lower extremities’ joints of prepubescent and adult sprinters of both sexes. A total of forty-two athletes were examined, including adult men (AM) and women (AF) as well as preadolescent boys (PPB) and girls (PPG). A 2D-DLT analysis was conducted on video recordings (sampling frequency: 100 fps) of the participants’ maximum effort trial while in their maximum sprinting velocity phase. A 2 (age) × 2 (sex) ANOVA revealed significant (p < 0.05) effects of the factors age and sex, and an interaction of age × sex in the sprint running velocity. It was also found that the spatiotemporal structure of the step parameters was significantly (p < 0.05) different between AM and AF but not between PPB and PPG. Also, a significant (p < 0.05) main effect of age was evident mainly for the ankle joint of both legs, as well as for the angular kinematics of the swing leg’s knee joint. In conclusion, apart from the possible disparities in training experience, differences due to age and sex exist in the step parameters and the kinematics of the sprinting technique due to differences in the technical elements related to coordination, strength application capability, and stiffness.
... Upon closer examination of the studies included in the review, major methodological and statistical limitations are evident. Of the 7 studies that used timing gates to assess overground sprinting reliability in youth, 4 relied solely on Pearson's correlation coefficient (r), reporting values between 0.90 and 0.97 for the assessment of test-retest reliability (34)(35)(36)(37). While Pearson's r is a widely accepted statistical tool for measuring the strength of a linear relationship between 2 variables (6,7), its application in this specific context fails to address critical aspects of reliability, such as nonlinear relationships, sensitivity to systematic changes, influence of outliers, individual variability versus group consistency, assumption of homoscedasticity, and lack of absolute agreement assessment (6,7). ...
Wannouch, YJ, Leahey, SR, Whitworth-Turner, CM, Oliver, JL, YH, KC, Laffer, JC, and Leicht, AS. A comprehensive analysis of 10-yard sprint reliability in male and female youth athletes. J Strength Cond Res XX(X): 000-000, 2024-This study investigates the inter-week test-retest reliability of 10-yard sprint times in youth athletes. Although essential for assessing athletic ability and training efficacy, the critical and comprehensive examination of both relative and absolute reliability indices for short-distance sprints has been insufficient in youth contexts. One hundred ninety-eight youth athletes (128 males and 70 females) underwent 2 sprint attempts across 2 separate trials 24 hours apart and within 7 days of each other. The sprints were measured using dual-beam timing gates to capture split times for 0-5, 5-10, and 0-10 yards. The minimal mean difference between the best sprint times across trials was 0.02 6 0.13 seconds for males and 0.003 6 0.14 seconds for females. No significant mean differences were found between trials for either gender (males: p 5 0.0875; females: p 5 0.8752), suggesting no systematic bias in sprint times. The SEM was 0.092 seconds for males and 0.099 seconds for females, with a corresponding SEM CV% of 4.6 and 4.8%. The overall coefficient of variation was 9.8% for males and 8.9% for females. Intraclass correlation coefficient values suggested that the sprint times across trials were reliable (males: 0.80; females: 0.76). The minimal detectable change was 0.25 seconds for males, 0.27 seconds for females. Cohen's d indicated trivial effects (,0.2) for males (0.154) and females (0.021). Minimal mean differences, a low SEM, and consistent ICC values demonstrate that the 0-10-yard sprint is a reliable assessment in youth athletes.
... Like any research of a transversal character that aims to prove the relationships, impact, dependence between different anthropological characteristics, skills and conditions, even this research is based on proving the influence of one anthropological field with the other in order to increase the information in favor of identifying the factors that are of particular importance in increasing the motor skills of anaerobic character speed. [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. ...
The knowledge of morphological development and their impact on motor skills in short-distance athletes should be one of the main concerns of athletics coaches, because any scientific research in the field of physical culture and sports is about proving the development and evaluation of anthropological characteristics which are responsible for achieving success in athletics. The purpose of this paper is to confirm the impact of some anthropometric characteristics in the execution of running speeds on short distances, specifically in running at 100, 200 and 400 meters to students aged 18 ± 6 years of the Faculty of Physical Education and Sports in Prishtina. The sample of this research has included a total of 60 students aged 18 years of the Faculty of Physical Education and Sports in Prishtina. The measurements were executed during September in the hall of the Faculty, while the 100, 200, and 400 meter runs in the stadium "Fadil Vokrri" Prishtina. The only condition that was used during the determination of the sample was: that the students are involved in regular physical education classes (and on the day of the measurement be healthy, without the flu, cold or other symptoms). The variables which are applied in this research have been 8 anthropometric variables and 3 motor-specific variables. The results obtained after their processing indicate that the impact of anthropometric variables is higher in running at 100, 200 and 400 meters. Short distance running and long distance running reduces the impact of anthropometric parameters whereas the influence of metabolic factors of energy production is increased. These results were also confirmed using regression analysis, so that groups of predictors of anthropometric characteristics, specific motor skills that statistically significantly influenced each variable of individual criteria. The world records below the 10-second limit, in the 100 m, near the 9-meter limit, show not only the high level of sports, but also the strong impact on the growth, especially of strength indicators, speed-strength, explosive force, as main and applied motor skills in sports and athlete’s everyday life.
... Maćkala et al. [11] state that some research studies have found SL as the most significant parameter for the development of maximal running speed, whereas other research studies state SF as the most significant factor. An application of vertical and horizontal types of jumping exercises could contribute to longer SL [11,59,60]. However,Čoh et al. [61] claim that CT is the most important kinematic parameter in sprint running that distinguishes better and weaker sprinters. ...
In sports practice, motor tests are commonly used to predict success in specific segments of sprint running, as well as post-injury tests in rehabilitation. The purpose of this analytical cross-sectional study was to determine the prognostic validity of the unilateral horizontal cyclic jumps for a 20 m (UHCJ20m) test on sprint running success. A sample of 118 kinesiology students aged 20.5 ± 1.2 years with an average height of 179.7 ± 6.4 cm and a body mass of 75.6 ± 7.3 kg was used to determine the correlation between the results of the UHCJ20m test and the results of the 20 m sprint start run (MRLS20m), the 20 m sprint flying start run (MRFS20m), and the 100 m run (M100m). The results showed a moderate correlation in all tests (MRLS20m (R = 0.49), MRFS20m (R = 0.53), and M100m (R = 0.38)) with UHCJ20m. In addition to the final result, the multiple regression analysis showed a significant moderate correlation between the kinematic parameters of the UHCJ20m test and the results in the MRLS20m (R = 0.38), MRFS20m (R = 0.49), and M100m (R = 0.37) tests. The stride length (SL) and the contact time (CT) of the UHCJ20m test were statistically significant predictors for the 100 m sprint, the number of steps for MRLS20m, and the SL and the CT for MRFS20m sprint success. Unilateral horizontal cyclic jumps are a significant predictor of success in sprint running, especially for the maximal speed running segment.
... Our research strengthens the findings of previous studies. Kotzamanidis [26] in a study found that the 10-week sprint training program was successful in increasing vertical jump height significantly. Similar to our results, Kotzamanidou et al. [27] reported that vertical jumps increased after five weeks of training for sprinting. ...
The aim of this study was to investigate the effect of the 60-m sprint training program on the vertical jump height of female youth volleyball players. In this quasi-experimental study, a one-group pretest/posttest design was utilized. Participants were 10 female youth volleyball players (aged 12-15) who were registered in a 12-session sprint training program at a junior sports organization in Yogyakarta, Indonesia. The training program was carried out on a 100-m flat track at the Athletic Field, Faculty of Sport Sciences of Yogyakarta State University. The stand and reach method was used to measure the vertical jump height. To compare the pretest and posttest scores, a paired samples t-test was used. The results indicated that there was a significant increase in vertical jump height from pretest to posttest with a high effect size. Thus, it can be concluded that a 4-week sprint training program can effectively increase the vertical jump height of young volleyball players. It is recommended that volleyball coaches and trainers implement a sprint training program as a step towards developing the vertical jump of their young athletes.
... Our findings are in accordance with much of the prior reported literature. Kotzamanidis et al. (2013) 33 and Venturelli et al. (2008) 34 examined pre-PHV subjects and observed a significant improvement in sprint performances (10, 20 and 30 m sprint time) following 12 weeks of linear sprint training. Two recent reviews 24,35 reported a significant improvement in sprint velocity (ES ¼ À0.71 to À0.92 and ES ¼ 0.43 to 1.59, respectively) with a moderate heterogeneity between maturity-groups. ...
Objective The aim of this study was to examine the effects of two different sprint-training regimes on sprint and jump performances according to age in elite young male soccer players over the course of one soccer season. Methods Players were randomly assigned to two training groups. Group 1 performed systematic change-of-direction sprints (CODST, U19 [n = 9], U17 [n = 9], U15 [n = 10]) while group 2 conducted systematic linear sprints (LST, U19 [n = 9], U17 [n = 9], U15 [n = 9]). Training volumes were similar between groups (40 sprints per week x 30 weeks = 1200 sprints per season). Pre and post training, all players performed tests for the assessment of linear and slalom sprint speed (5-m and 10-m), countermovement jump, and maximal aerobic speed performance. Results For all physical fitness measures, the baseline-adjusted means data (ANCOVA) across the age groups showed no significant differences between LST and CODST at post (0.061 < p < 0.995; 0.0017 < d < 1.01). The analyses of baseline-adjusted means for all physical fitness measures for U15, U17, and U19 (LST vs. CODST) revealed no significant differences between LST and CODST for U15 (0.213 < p < 0.917; 0.001 < d < 0.087), U17 (0.132 < p < 0.976; 0.001 < d < 0.310), and U19 (0.300 < p < 0.999; 0.001 < d < 0.049) at post. Conclusions The results from this study showed that both, LST and CODST induced significant changes in the sprint, lower limbs power, and aerobic performances in young elite soccer players. Since no significant differences were observed between LST and CODST, the observed changes are most likely due to training and/or maturation. Therefore, more research is needed to elucidate whether CODST, LST or a combination of both is beneficial for youth soccer athletes’ performance development.
Athletics disciplines are characterized by motor movements that can be successfully applied during the educational process or through other forms of exercise, which significantly affect the development of general psychophysical abilities of individuals. Each of the disciplines of athletics acts on the development of individual abilities, but also on the general psychophysical status of man and for this reason athletics is called the "queen of sports". Athletic activities have a characteristic of participant inclusion.The values of the paper will be based on the purpose of anthropometric, basic motor and specific motor characteristics of students aged 21 years ± 6 months.A total of 70 male students, 7 anthropometric variables, 7 motor variables and 1 specific motor variable that were tested during the period of May, of the academic year, 2020/2021 were included in the research.In the basic parameters students, based on the results achieved in this anthropometric variable, are presented as a moderately homogeneous group.Although it is seen that the acquired flexibility and convexity (Skewness and Kurtosis) have a pronounced asymmetry, in the vast majority of anthropometric variables. Although it is seen that the acquired flexibility and convexity (Skewness and Kurtosis) have a pronounced asymmetry, in the vast majority of motor and criterion variables. Thus the statistically significant coefficients of the variables with the highest degree of statistical inference (p <0.01) are denoted by two asterisks. With easier statistical conclusion criterion (p <0.05) correlation coefficients. All variables have statistically significant correlation to all anthropometric, basic and criterion motor variables.
The aim of this paper was to prove the relationship between motor skills and anthropometric characteristics as a predictive system with effectiveness and results in running the discipline at 400 meters as situational-motor variables of the criteria system. The research was done by testing 60 samples of men 18 years old, ± 6 months, of the Faculty of Physical Education and Sports in Prishtina. Regarding the anthropometric variable, bigger correlation has been shown by the
variable dermal tipple of the arm (AMTP) which correlate positively with running in 400 meter, from which we can conclude that the fullest in the upper limbs are students, the more slowly realize running in the 400 meters and conversely. The measurements were executed during
September in the hall of the Faculty, in 400 meter runs in the stadium "Fadil Vokrri" Prishtina. The only condition that was used during the determination of the sample was: that the students are involved in regular physical education classes (and on the day of the measurement be healthy, without the flu, cold or other symptoms). The variables which are applied in this research have
been 8 anthropometric variables and 1 motor-specific variables. The results obtained after their processing indicate that the impact of anthropometric variables is higher in running 400 meters. Short distance running and long distance running reduces the impact of anthropometric parameters whereas the influence of metabolic factors of energy production is increased. These results were also confirmed using regression analysis, so that groups of predictors of
anthropometric characteristics, specific motor skills that statistically significantly influenced each variable of individual criteria. The results obtained from regression analysis indicate that in the variable 400 m running from low start (MV400MU) does not affect any anthropometric variables applied.We can emphasize that the test (F-test) is more valuable if the multiple correlation is greater, in the concrete case of this paper is significant (Sig = 0.645), because the
value of the F-test is = 0.753.
The knowledge of morphological development and their impact on motor skills in short-distance athletes should be one of the main concerns of athletics coaches, because any scientific research in the field of physical culture and sports is about proving the development and evaluation of anthropological characteristics which are responsible for achieving success in athletics. The purpose of this paper is to confirm the impact of some anthropometric characteristics in the execution of running speeds on short distances, specifically in running at 100 meters to students aged 18 ± 6 years of the Faculty of Physical Education and Sports in Prishtina. The sample of this research has included a total of 60 students aged 18 years of the Faculty of Physical Education and Sports in Prishtina. The measurements were executed during September in the hall of the Faculty, while the 100 meter runs in the stadium "Fadil Vokrri" Prishtina. The only condition that was used during the determination of the sample was: that the students are involved in regular physical education classes (and on the day of the measurement be healthy, without the flu, cold or other symptoms). The variables which are applied in this research have been 8 anthropometric variables and 1 motor-specific variables. The results obtained after their processing indicate that the impact of anthropometric variables is higher in running at 100 meters. Short distance running and long distance running reduces the impact of anthropometric parameters whereas the influence of metabolic factors of energy production is increased. These 107 results were also confirmed using regression analysis, so that groups of predictors of anthropometric characteristics, specific motor skills that statistically significantly influenced each variable of individual criteria. The world records below the 10-second limit, in the 100 m, near the 9-meter limit, show not only the high level of sports, but also the strong impact on the growth, especially of strength indicators, speed-strength, explosive force, as main and applied motor skills in sports and athlete's everyday life.
Training effect on the anaerobic performance of children as measured by the Wingate Anaerobic Test
Understanding of biomechanical factors in sprint running is useful because of their critical value to performance. Some variables measured in distance running are also important in sprint running. Significant factors include: reaction time, technique, electromyographic (EMG) activity, force production, neural factors and muscle structure. Although various methodologies have been used, results are clear and conclusions can be made.
The reaction time of good athletes is short, but it does not correlate with performance levels. Sprint technique has been well analysed during acceleration, constant velocity and deceleration of the velocity curve. At the beginning of the sprint run, it is important to produce great force/ power and generate high velocity in the block and acceleration phases. During the constant-speed phase, the events immediately before and during the braking phase are important in increasing explosive force/power and efficiency of movement in the propulsion phase. There are no research results available regarding force production in the sprint-deceleration phase. The EMG activity pattern of the main sprint muscles is described in the literature, but there is a need for research with highly skilled sprinters to better understand the simultaneous operation of many muscles. Skeletal muscle fibre characteristics are related to the selection of talent and the training-induced effects in sprint running.
Efficient sprint running requires an optimal combination between the examined biomechanical variables and external factors such as footwear, ground and air resistance. Further research work is needed especially in the area of nervous system, muscles and force and power production during sprint running. Combining these with the measurements of sprinting economy and efficiency more knowledge can be achieved in the near future.
The purpose of the present study was to investigate the effects of 8 months of a specific and controlled sprint training programme on three groups of young athletes (two groups of males and one of females). Biopsies of vastus lateralis were taken before and after the period of training. The type percentage and diameter of the fibres, as well as the glycogen content and the activities of the enzymes of glycogen metabolism (glycogen synthase and glycogen phosphorylase), glycolysis (phosphofructokinase, pyruvate kinase, aldolase and lactate dehydrogenase), oxidative metabolism (succinate dehydrogenase) and creatine kinase and aminotransferases were studied. The results show an increase in the percentage of type I fibres and an increase in the diameter of both fibre types. A significant increase was also observed in glycogen content, and in the activities of glycogen synthase, glycogen phosphorylase, phosphofructokinase, pyruvate kinase, succinate dehydrogenase, aspartate aminotransferase and alanine aminotransferase. We conclude that a long period of sprint training induces a biochemical muscle adaptation to anaerobic exercise. This metabolic adaptation is followed by a morphological adaptation, although this is probably not as specific as the biochemical one.
Serum hormones and physical performance capacity in boy athletes (AG;n = 19) were investigated during a 1-year training period (between the ages of 11.6 and 12.6 years). Six young untrained boys served as the control group (CG). The mean serum testosterone concentration increased significantly in AG (P<0.05) following the training period from 2.92 nmoll–1, SD 1.04 to 5.81 nmoll–1, SD 1.33. Significant differences were not observed in the cortisol, sex hormone binding globulin and growth hormone levels during the follow-up period. The AG clearly increased speed (P<0.001), speed-strength (P<0.01-P<0.001) and anaerobic capacity (P<0.001) whereas CG had only slight increases (NS) in physical performance capacity during a 1-year period. During the last 6-month training period significant positive correlations (r=0.490–0.58;P<0.05 -P<0.01) were observed in AG between the relative changes in testosterone, testosterone: cortisol ratio and growth hormone and the relative performance change in speed, maximal isometric force and endurance, respectively. At the end of the period significant positive correlations were observed in all subjects between the level of testosterone and speed-strength (r=0.52–0.64;P<0.01 -P<0.001) and anaerobic capacity (r=0.49;P<0.05). It was concluded that an increase in anabolic activity with the synchronous training already has positive effects on trainability and physical performance capacity at an early stage in puberty.
The relationships between ground reaction forces, electromyographic activity (EMG), elasticity and running velocity were investigated
at five speeds from submaximal to supramaximal levels in 11 male and 8 female sprinters. Supramaximal running was performed
by a towing system. Reaction forces were measured on a force platform. EMGs were recorded telemetrically with surface electrodes
from the vastus lateralis and gastrocnemius muscles, and elasticity of the contact leg was evaluated with spring constant
values measured by film analysis. Data showed increases in most of the parameters studied with increasing running speed. At
supramaximal velocity (10.36±0.31 m×s−1; 108.4±3.8%) the relative increase in running velocity correlated significantly (P<0.01) with the relative increase in stride rate of all subjects. In male subjects the relative change in stride rate correlated
with the relative change of IEMG in the eccentric phase (P<0.05) between maximal and supramaximal runs. Running with the towing system caused a decrease in elasticity during the impact
phase but this was significant (P<0.05) only in the female sprinters. The average net resultant force in the eccentric and concentric phases correlated significantly
(P<0.05−0.001) with running velocity and stride length in the maximal run. It is concluded that (1) increased neural activation
in supramaximal effort positively affects stride rate and that (2) average net resultant force as a specific force indicator
is primarily related to stride length and that (3) the values in this indicator may explain the difference in running velocity
between men and women.
To investigate the influence of skeletal muscle fiber composition on the mechanical performance of human skeletal muscle under dynamic conditions, 34 physical education students with differing muscle fiber composition (M. vastus lateralis) were used as subjects to perform maximal vertical jumps on the force-platform. Two kinds of jumps were performed: one from a static starting position (SJ), the other with a preliminary counter-movement (CMJ). The calculated mechanical parameters included height of rise of center of gravity (h), average force (F), net impulse (NI) and average mechanical power (W). It was observed that the percentage of fast twitch fibers was significantly related (p< 0.05-0.01) to these variables in SJ condition and also to h and NI of the positive work phase in CMJ. It is concluded that skeletal muscle fiber composition also determines performance in a multijoint movement. The result is explainable through the differences in the mechanical characteristics of the motor units and their respective muscle fibers.
This study attempted to assess and compare the amount of cocontraction present in thigh and leg muscles in three groups of children during treadmill walking and running. Thirty children, aged 7-8 (n = 10), 10-12 (n = 10) and 15-16 (n = 10) years, performed 4-min bouts of submaximal treadmill exercise at two walking and four running speeds, assigned in a randomized order. Three seconds of EMG data were collected during the final minute of each bout from the vastus lateralis (VL), hamstrings (H), tibialis anterior (TA) and soleus (S). The processed linear envelopes of VL and H, and likewise of TA and S, were overlapped and a cocontraction index calculated (area of overlap divided by the number of data points) for thigh and leg segments, respectively. Cocontraction was highest for the youngest children and lowest for the oldest, for both thigh and leg, whether expressed in terms of absolute speed or as a percentage of each child's VO(2 max). Larger amounts of cocontraction may help to explain the higher metabolic cost of locomotion for younger children, when compared with adolescents and adults.
The relationships between muscle fibre characteristics and the physical performance capacity of trained athletic boys (aged 11-13 years) were studied over 2 days. The subjects were divided into two groups according to muscle fibre distribution. The 'fast' group (FG) comprised 10 subjects (sprinters, weightlifters, tennis players) with more than 50% fast-twitch fibres (type II), and the 'slow' group (SG) comprised 8 subjects (endurance runners, tennis players, one weightlifter) with more than 50% slow-twitch fibres (type I) in their vastus lateralis muscle. The 'fast' group had 59.2 +/- 6.3% and the 'slow' group had 39.4 +/- 9.8% type II fibres. Other clear differences (P less than 0.05-0.01) between the groups were observed as regards reaction time, rate of force development and rise of the body's centre of gravity in the squatting jump. For these variables, the 'fast' group was superior to the 'slow' group. Muscle fibre distribution (% type II) correlated (P less than 0.05-0.01) negatively with reaction time. Muscle fibre area (% type II) correlated negatively with reaction time (P less than 0.05-0.001) and positively with chronological age (P less than 0.05) height (P less than 0.05), mass (P less than 0.001), serum testosterone (P less than 0.05), force production (P less than 0.05-0.01) and blood lactate (P less than 0.05) in the 60-s maximal anaerobic test. There were no significant correlations between muscle fibre characteristics and maximal oxygen uptake. The present study assumes that heredity partly affects the selection of sporting event. Growth, development and training are associated with muscle fibre area, which affects the physical performance capacity of the neuromuscular system in trained young boys.
Possible changes in muscle size and function due to resistance training were examined in prepubertal boys. Thirteen boys (9-11 yr) volunteered for each of the training and control groups. Progressive resistance training was performed three times weekly for 20 wk. Measurements consisted of the following: 1 repetition maximum (RM) bench press and leg press; maximal voluntary isometric and isokinetic elbow flexion and knee extension strength; evoked isometric contractile properties of the right elbow flexors and knee extensors; muscle cross-sectional area (CSA) by computerized tomography at the mid-right upper arm and thigh; and motor unit activation (MUA) by the interpolated twitch procedure. Training significantly increased 1 RM bench press (35%) and leg press (22%), isometric elbow flexion (37%) and knee extension strength (25% and 13% at 90 degrees and 120 degrees, respectively), isokinetic elbow flexion (26%) and knee extension (21%) strength, and evoked twitch torque of the elbow flexors (30%) and knee extensors (30%). There were no significant effects of training on the time-related contractile properties (time to peak torque, half-relaxation time), CSA, or %MUA of the elbow flexors or knee extensors. There was, however, a trend toward increased MUA for the elbow flexors and knee extensors in the trained group. Strength gains were independent of changes in muscle CSA, and the increases in twitch torque suggest possible adaptations in muscle excitation-contraction coupling. Improved motor skill coordination (especially during the early phase of training), a tendency toward increased MUA, and other undetermined neurological adaptations, including better coordination of the involved muscle groups, are likely the major determinants of the strength gains in this study.
The purpose of this study was to determine the role of knee torque at various joint velocities, body composition, flexibility, and age, height and weight in 30 meter sprint performance. Subjects were 14 male pubescents whose mean (±SD) age and percent fat were 11.8±.31 years and 20.6±4.9%, respectively. Maximum knee extension and knee flexion torque at 30°/sec-1 and 300°/sec-1 was assessed with a Cybex II isokinetic dynamometer system. Joint torque variables were expressed as absolute and relative values (the latter as torque per kg bodyweight), ratios and percent loss of torque from the slow (30°/sec-1) to fast (300°/sec-1) velocity. Hydrostatic weighing was used to determine body composition. None of the variables were significantly related to 30 meter sprint time (p>.05). The highest correlation with sprint time was knee extension torque at 30°/sec-1·kg bodyweight (r = -.374). Stepwise forward multiple regression analysis produced an R of .992 and included 9 variables before R was significant. It was concluded that sprint ability in these pubescent boys is not highly related to knee torque at 30° and 300°/sec, body composition, height or weight.