Temporal and kinetic analysis of unilateral jumping in the vertical, horizontal, and lateral directions.
ABSTRACT The aims of this study were to: (1) assess the reliability of various kinetic and temporal variables for unilateral vertical, horizontal, and lateral countermovement jumps; (2) determine whether there are differences in vertical ground reaction force production between the three types of jumps; (3) quantify the magnitude of asymmetry between limbs for variables that were established as reliable in a healthy population and whether asymmetries were consistent across jumps of different direction; and (4) establish the best kinetic predictor(s) of jump performance in the vertical, horizontal, and lateral planes of motion. Thirty team sport athletes performed three trials of the various countermovement jumps on both legs on two separate occasions. Eccentric and concentric peak force and concentric peak power were the only variables with acceptable reliability (coefficient of variation = 3.3-15.1%; intra-class correlation coefficient = 0.70-0.96). Eccentric and concentric peak vertical ground reaction force (14-16%) and concentric peak power (45-51%) were significantly (P < 0.01) greater in the vertical countermovement jump than in the horizontal countermovement jump and lateral countermovement jump, but no significant difference was found between the latter two jumps. No significant leg asymmetries (-2.1% to 9.3%) were found in any of the kinetic variables but significant differences were observed in jump height and distance. The best single predictors of vertical countermovement jump, horizontal countermovement jump, and lateral countermovement jump performance were concentric peak vertical power/body weight (79%), horizontal concentric peak power/body weight (42.6%), and eccentric peak vertical ground reaction force/body weight (14.9%) respectively. These findings are discussed in relation to monitoring and developing direction-specific jump performance.
- Physiotherapy Theory and Practice 01/1985; 1(2):71-76.
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ABSTRACT: 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.Sports Medicine 07/1992; 13(6):376-92. · 5.24 Impact Factor
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ABSTRACT: Hamstring muscle strain is the most prevalent injury in Australian Rules Football, accounting for 16% of playing time missed as a result of injury. Thirty-seven professional footballers from an Australian Football League team had preseason measurements of hamstring and quadriceps muscle concentric peak torque at 60, 180, and 300 deg/sec measured on a Cybex 340 dynamometer. Players were studied prospectively throughout the 1995 season. During that time, six players sustained clinically diagnosed hamstring muscle injuries that caused them to miss match-playing time. The injured hamstring muscles were all weaker than in the opposite leg in absolute values and hamstring-to-quadriceps muscle ratios. According to our t-test results, hamstring muscle injury was significantly associated with a low hamstring-to-quadriceps muscle peak torque ratio at 60 deg/sec on the injured side and a low hamstring muscle side-to-side peak torque ratio at 60 deg/sec. Flexibility (as measured by the sit-and-reach test) did not correlate with injury. Discriminant-function analysis using the two significant ratio variables resulted in a canonical correlation with injury of 0.4594 and correctly classified legs into injury groups with 77.4% success. These results indicate that preseason isokinetic testing of professional Australian Rules footballers can identify players at risk of developing hamstring muscle strains.The American Journal of Sports Medicine 01/1997; 25(1):81-5. · 4.44 Impact Factor