A simple method for measuring power, force, velocity properties, and mechanical effectiveness in sprint running.

This study aimed to validate a simple field method for determining force- and power-velocity relationships and mechanical effectiveness of force application during sprint running. The proposed method, based on an inverse dynamic approach applied to the body center of mass, estimates the step-averaged ground reaction forces in runner's sagittal plane of motion during overground sprint acceleration from only anthropometric and spatiotemporal data. Force- and power-velocity relationships, the associated variables, and mechanical effectiveness were determined (a) on nine sprinters using both the proposed method and force plate measurements and (b) on six other sprinters using the proposed method during several consecutive trials to assess the inter-trial reliability. The low bias (<5%) and narrow limits of agreement between both methods for maximal horizontal force (638 ± 84 N), velocity (10.5 ± 0.74 m/s), and power output (1680 ± 280 W); for the slope of the force-velocity relationships; and for the mechanical effectiveness of force application showed high concurrent validity of the proposed method. The low standard errors of measurements between trials (<5%) highlighted the high reliability of the method. These findings support the validity of the proposed simple method, convenient for field use, to determine power, force, velocity properties, and mechanical effectiveness in sprint running.

Sprint mechanics in world-class athletes: a new insight into the limits of human locomotion.

The objective of this study was to characterize the mechanics of maximal running sprint acceleration in high-level athletes. Four elite (100-m best time 9.95-10.29 s) and five sub-elite (10.40-10.60 s) sprinters performed seven sprints in overground conditions. A single virtual 40-m sprint was reconstructed and kinetics parameters were calculated for each step using a force platform system and video analyses. Anteroposterior force (FY), power (PY), and the ratio of the horizontal force component to the resultant (total) force (RF, which reflects the orientation of the resultant ground reaction force for each support phase) were computed as a function of velocity (V). FY-V, RF-V, and PY-V relationships were well described by significant linear (mean R(2) of 0.892 ± 0.049 and 0.950 ± 0.023) and quadratic (mean R(2) = 0.732 ± 0.114) models, respectively. The current study allows a better understanding of the mechanics of the sprint acceleration notably by modeling the relationships between the forward velocity and the main mechanical key variables of the sprint. As these findings partly concern world-class sprinters tested in overground conditions, they give new insights into some aspects of the biomechanical limits of human locomotion.

Match-play activity profile in professional soccer players during official games and the relationship between external and internal load.

AIM: The aim was to quantify for the first time the physical and physiological profile of professional soccer players in official games using GPS and heart rate (HR) response. METHODS: Thirty professional soccer players were investigated during a half in competitive club level matches (N.=348) using GPS devices. RESULTS: The relative total distance was 118.9±10.7 m∙min(-1) and player's Work-To-Rest Ratio was 2.1:1. Defenders covered the lowest total distance, while Second-Strikers (2(nd)S) and Wide-Midfielders (W-MD) traveled the greatest total distance. Defenders presented the lowest Work-To-Rest Ratio values. Playing position also impacted on all sprinting performance results, except in average sprint distance and time of sprint. The number of sprints and repeated-sprint sequences recorded by the W-MD and Strikers (S) were significantly greater than any other group. The average HR recorded was 87.1%HRmax and the relationship between the external and internal load value (Effindex) was 1.4 with significant differences in both between playing positions. W-MD recorded a significantly smaller average HR than any other group and Centre-Backs showed a significantly smaller Effindex value than any other group. Conversely, W-MD showed a significantly greater Effindex value than any other group, except the 2(nd)S. CONCLUSION: This study has verified a number of statistically significant differences between the different playing positions. Coaches should be focused on the specific physical and physiological requirements of the playing positions to optimize the training prescription in soccer. The relationships between external and internal load measures among position-specific indicates that players with less overall running performance during match-play were the worst in Effindex.

Effect of plyometric training on chair-rise, jumping and sprinting performance in three age groups of women.

AIM: The main purpose of this study was to investigate the influence of 8-wk periodized plyometric training (PT) on chair-rise, jumping and sprinting performance in three groups of women of different age (40-50; 50-60; 60-70 years). METHODS: This study involved a group of 55 women between the ages of 40 and 70 with no PT experience participating in a gymnastic program and recreational activity that did not involve jumping and who had participated since five years. All tests to determine the values of strength endurance, vertical jumping performance (VJP) and velocity were carried out before (PRE), after (POST) and following 8 weeks of rest (DETRAINING) of the 8 weeks of PT. The performance tests were completed in 3 days. RESULTS: The primary finding of this investigation indicates that low impact PT using moderate volume of jumps produced similar enhancements in the three age groups of women in jumping and chair-rise performance (30 CST) (ranging 15-24 %). There were no enhancements in 10 m-sprint time in any of the age groups. In addition, 8 weeks of detraining following an 8 week PT program resulted in similar decreases in chair-rise and jumping performance in all training groups, whereas no further changes were observed in 10-m sprint time. CONCLUSION: The low impact PT proposed appears to be an optimal stimulus for improving VJP and 30 CST during short-term training periods in untrained middle-aged and elderly women.

Relación entre fuerza máxima, potencia y velocidad en jugadores de waterpolo / Relationship between maximal strength, power and speed in water polo players

Propósito: Los propósitos del presente estudiofueron evaluar la potencia de salto en el agua dejugadores de Waterpolo y determinar la fuerza explosivay potencia de su tren inferior.Métodos: 12 jugadores de Waterpolo de la selecciónde Costa Rica ejecutaron los test. Comopruebas de potencia se realizaron el test de saltoSargent (adaptado para el agua), el test de Wingatey el test de salto vertical. Como test de fuerzaexplosiva se realizó el test de press de pierna ytambién se realizó un test de velocidad de 10 y 20m lisos. El coeficiente de correlación de Pearsonse utilizó para determinar las relaciones.Resultados: Entre el test de Sargent y el test deWingate se registró una correlación media pero noestadísticamente significativa (r = -0,510). El testde salto vertical se correlacionó significativamentecon las dos pruebas de velocidad 0-10 m y 0-20 m(r = -0,910; r = -0,932). Hubo correlación significativaentre el test de Press de pierna y la potenciade salto vertical (r = 0,654), así como entre el testde Wingate y el salto vertical (r = 0,558).Discusión: La baja correlación presentada entrela prueba de salto Sargent en el agua y el restode los test indica la gran importancia de medir acada atleta en su medio específico, ya que es sumamenteimportante el gesto técnico que se realizay no solamente la musculatura implicada en esegesto o la potencia de cada sujeto. La relación estadísticamentesignificativa entre la fuerza explosivay la potencia de salto remarca la importanciade tener altos niveles de fuerza explosiva para obtenerbuenos rendimientos en el salto, ya que sonacciones relativamente rápidas y explosivas

Aim: The aims of this research were to test thejump power in the water of Waterpolo players andto determine leg strength and power.Methods: Twelve Waterpolo players from theCosta Rica national team carried out the tesst. Forpower the “Sargent jump test” (adapted for water),the Wingate test and the vertical jump wereperformed. For explosive strength the “leg presstest” and were performed a speed test 10-20 m.The Pearson correlation coefficient was used todetermine the relations.Results: Between the Sargent and Wingate testsan average correlation recorded but not statisticallysignificant (r = -0.510). The vertical jumpwas significantly correlated with two speed proofs(0-10 m and 0-20 m) (r = -0.910; r = -0.932). Therewas a significant correlation between the leg press test and the vertical jump power (r = 0.654),as well as between the Wingate test and the verticaljump (r = 0.558).Discussion: The low correlation between theSargent jump test in water and the other testsshows the great importance of measuring each athletein his specific environment. The technical gesturecarried out and not only the muscles impliedin that gesture or the power of each character areof great concern. The statistically significant relationbetween the explosive force and the jump powerremarks the importance of having high levelsof explosive force to achieve a good performancein the jump, as they are relatively fast and explosiveactions