Effects of a sand running surface on the kinematics of sprinting at maximum velocity

Performing sprints on a sand surface is a common training method for improving sprint-specific strength. For maximum specificity of training the athlete’s movement patterns during the training exercise should closely resemble those used when performing the sport. The aim of this study was to compare the kinematics of sprinting at maximum velocity on a dry sand surface to the kinematics of sprinting on an athletics track. Five men and five women participated in the study, and flying sprints over 30 m were recorded by video and digitized using biomechanical analysis software. We found that sprinting on a sand surface was substantially different to sprinting on an athletics track. When sprinting on sand the athletes tended to ‘sit’ during the ground contact phase of the stride. This action was characterized by a lower center of mass, a greater forward lean in the trunk, and an incomplete extension of the hip joint at take-off. We conclude that sprinting on a dry sand surface may not be an appropriate method for training the maximum velocity phase in sprinting. Although this training method exerts a substantial overload on the athlete, as indicated by reductions in running velocity and stride length, it also induces detrimental changes to the athlete’s running technique which may transfer to competition sprinting

Efectos de un programa de estiramientos FNP sobre el salto y la flexibilidad en jugadores profesionales de fútbol sala

The purpose of this study was to examine the effects of a stretching program with the contraction-relaxation-agonist-contraction technique (CRAC) on jumping performance (JP) and range of motion (ROM). A total of 21 elite futsal players participated in the present study. Participants were assigned to a control group (CG) and an experimental group (EG) according to their jumping ability. Before and after the intervention, the JP and ROM of hip flexion with the extended knee (FCRE) and dorsi-flexion of the ankle (DFTRE) were measured. For the measurement of the JP and the ROM, a contact platform and an ISOMED inclinometer were used, respectively. The EG performed a stretching program in the hamstrings and triceps sural for 4 weeks with a weekly frequency of 5 days. The players significantly increased the FCRE ROM (p = 0.02) with strong effect (hp2 = 0.730) and ROM DFTRE (p = 0.01) with moderate effect (hp2 = 0.546), of the values ​​of CMJ (p = 0.03) with strong effect (hp2 = 0.650) and of the values ​​of index of utilization of the elastic capacity [IACE] (p = 0.04) with strong effect (hp2 = 0,742) in the EG after the stretching. The CG players significantly increased the performance in the CMJ ​​(p = 0.02) with moderate effect (hp2 = 0.519) and IACE (p = 0.04) with moderate effect (hp2 = 0.548); in addition, significant differences were observed in the values ​​of IACE (p = 0.02) between both groups. The results of this study allow us to conclude that a training period with the CRAC technique improves ROM and JP in professional futsal players.El objetivo de este estudio fue comprobar los efectos de un programa de estiramiento con la técnica contracción-relajación-agonista-contracción (CRAC) sobre la capacidad de salto (CS) y el rango de movimiento (ROM). Un total de 21 jugadores de élite de fútbol sala participaron en el presente trabajo. Los participantes fueron asignados a un grupo control (GC) y a un grupo experimental (GE) según su CS. Antes y después de la intervención se midió la CS y el ROM de flexión de cadera con la rodilla extendida (FCRE) y dorsi-flexión de tobillo (DFTRE). Para la medición del CS y del ROM se utilizó una plataforma de contacto y un inclinómetro ISOMED, respectivamente. El GE realizó un programa de estiramientos en los isquiosurales y tríceps sural durante 4 semanas con una frecuencia semanal de 5 días. Los jugadores aumento significativamente el ROM FCRE (p = 0,02) con efecto fuerte (hp2 = 0,730) y ROM DFTRE (p = 0,01) con efecto moderado (hp2 = 0,546), de los valores de CMJ (p = 0,03) con efecto fuerte (hp2 = 0,650) y de los valores de índice de aprovechamiento de la capacidad elástica [IACE] (p = 0,04) con efecto fuerte (hp2 = 0,742) en el GE después de los estiramientos. Los jugadores del GC aumentaron significativamente el rendimiento en el CMJ (p = 0,02) con efecto moderado (hp2 = 0,519) e IACE (p = 0,04) con efecto moderado (hp2 = 0,548); además, se observaron diferencias significativas en los valores de IACE (p = 0,02) entre ambos grupos. Los resultados de este estudio permiten concluir que un periodo de entrenamiento con el método CRAC mejora el ROM y la CS en jugadores profesionales de fútbol sala