Objective: To study the effect of two damper shapes on tennis racket on the peak force and damping time at the grip area for a centre or off-axis locations of the ball-impact.
Materials and Methods: The peak force and damping time were tested on tennis rackets grips with 3 different settings: use of damper: no damper, button damper, or worm damper. Tennis balls were served using a tennis strike-simulating machine using 30 m/s racket speed. The peak force and damping time were recorded from a force transducer attached to the grip and were compared when the ball-strokes were at four locations: centre, above centre, below centre, and off-axis.
Results: Both types of dampers did not reduce the impact force at the grip regardless of the location. However, the worm
damper yielded a 15% decrease in damping time of an off-axis impact: 230.2+3.1 ms to 196.1+13.8 ms (p = 0.002). Neither damper reduced the damping time with the on-axis impacts.
Conclusion: Worm damper reduced the racket’s damping time when the ball impacts in an off-axis position but does not
affect the impact force transmitted to the other locations of the grip.

Keywords: Damping time, Peak force, Impact locations, Damper, Vibration