MUSCLE ENERGY OF TENNIS-STOPS WITH DIFFERENT MOVEMENT PATTERNS
Keywords: tennis, muscles, energy, inverse dynamics, stops
AbstractINTRODUCTION: Fast runs starting with high accelerations and ending with abrupt stops are essential elements of tennis. While acceleration is achieved in a unique way without sliding, stops are performed in various ways. Depending on the surface, shoes and anthropometry, the stopping motion may or may not sliding. Stopping without sliding is a motion in which muscles are shortened or stretched while contracting. During sliding stops, muscles also contract, but almost no shortening or stretching of the muscles is involved. This has a major influence on energy consumption. Muscle energy becomes a limiting factor for the speed and quality of performance during prolonged matches or tournaments. The purpose of this study was to approximate the relative differences in the energy consumption of tennis stops with different stopping patterns. METHOD: Five male tennis players participated in this study. All played at either the state or national level. Their ages were between 23 and 28 years (24.2±1.9). For each subject, 38 anthropometric measurements were taken. Reflective markers were placed on 17 landmarks. Each participant performed three stops in the university gymnasium (almost no sliding) and three stops on an indoor tennis court with a floor of loose rubber granulate designed to permit sliding. Movements were filmed using three 50 Hz digital cameras with a shutter speed of 1/3500 sec. Digitizing was done using an automatic WinAnalyze system. The resulting marker coordinates and 38 anthropometric measurements per athlete were the input for the SDS-98 simulation system. SDS-98 created the Hanavan model and calculated the inverse dynamics in accordance with the filmed movements. Muscle energies were computed for the joints (neck, shoulder, elbow, hip, knee, ankle, spine) using the equation: [formula], which is the integral of the absolute of the scalar product between the relative angular velocity and the torque of the joint. The efficiency 0 of a stop was calculated as the quotient of muscle energy divided by the total mechanical energy change from the beginning of the movement to the stop. RESULTS AND DISCUSSION: Significant differences were found for muscle energy/efficiency between stopping motions with and without sliding (0stop/0slide between 1.3 and 4.0). CONCLUSIONS: Deviations between real world data and research calculations can occur. They may be caused by the simplicity of the body model, by digitizing errors, and by uncertainty in calculating the center of pressure for the feet during ground contact. However, the results show quantitatively that sliding stops are favorable for players with low endurance.
Modelling / Simulation
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