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Biomechanics

Biomechanics - Poster Session C

Poster E4 - Instrumented Tennis Racket to Train Proper Grip in Novice Tennis Players

Friday, October 25, 2024
10:00 AM - 11:00 AM EST
Location: Exhibit Hall E, F & G

Introduction:  With the safety of the player in mind, this instrumented tennis racket is made to teach new players proper grip strength so they do not over-exert their muscles and develop “tennis elbow.” Tennis elbow is caused by repeatedly gripping the racket too hard which strains the muscles causing tears and inflammation. The long-term goals were to embed force sensors into the racket grip, measure the grip strength of the player, and provide real-time haptic feedback to the player so they can adjust their grip strength during training sessions. The racket used during these training sessions would be connected to an app that measures and reports the grip for the swing the user is practicing and reinforces skill development and proper grip strength while learning each hit. The work presented here describes the development and proof of concept testing of a prototype racket.

Materials and

Methods:  Eight to ten miniature 12 mm motors were placed in the base of a Wilson tennis racket. When the player grips the racket too hard, a small vibration is generated from inside the racket, alerting them to loosen their grip. These specifications were determined by calibrating the sensors to measure the player’s maximum grip strength. A code implemented in the controller sets a threshold for a maximum healthy grip strength at half of the player’s maximum measured strength. From then on, the haptics were activated whenever the player’s grip strength exceeded that threshold. Three force sensor strips were applied along the most common grip location bevels of the racket (bevels 2, 3, 4 for a right-handed player). These strips detected the player’s grip level and sent the information to an Arduino Nano 33 IoT microcontroller, which determines whether or not to turn on the motors. The Arduino also controlled a buzzer that confirmed whether the phone had successfully Bluetooth connected to the racket. It beeped twice when Bluetooth disconnected.
A pilot test was conducted with one participant. The participant gripped the racket in each of the three different grip positions. For this device, bevels 2, 3, and 4 were selected to represent continental, eastern, and semi-western grip, respectively. The maximum and average force values for all grips were determined and the average forces were normalized to maximum grip strength.

Results, Conclusions, and Discussions: We found out that in the eastern grip, the average force was 9%, for continental 29%, and for semi-western 31%. An observation found through this testing was that the eastern grip which is monitored on bevel 3 is a much looser grip than the other two. Bevel 3 is wider than bevels 2 and 4. Also, bevel 3 is flatter with less contact with the player’s hand compared to bevels 2 and 4 which are gripped at an angle. Therefore, this lower average grip for bevel 3 is reasonable and aligns with the other observations from the racket and locations. Although the participant pool for this proof of concept testing was limited, these results are very encouraging. Additional testing is needed to determine whether this trend is common, especially amongst novice players.
In a future semester, this device will be tested with participants from a beginners tennis class at Hope College. The current focus of this device is on swings in the dominant hand of the player: the serve, forehand, and volley. Future work may explore a two-handed backhand swing. In conclusion, this work demonstrates that an instrumented tennis racket can measure grip forces applied at three different bevels on a tennis racket. The device may be beneficial for teaching novice tennis players how to properly grip the racket and prevent the risk of injury.

Acknowledgements (Optional):  This work was funded by the Clare Booth Luce Foundation and Hope College's Jacob E. Nyenhuis Faculty Development Grant. The authors thank Chris Laubach and Mackenzie Niswonger for their work on the application associated with the device.