Summary

EMG activity of lead ECU was higher in the trail arm in backswing and follow through, however EMG activity of trail arm was greater than the lead arm in downswing

Abstract

Background

Wrist injuries are the most common upper limb injuries in sub-elite and elite golfers. The left wrist accounts for 67% of all wrist injuries, of which 52% are associated with overuse, extensor carpi ulnaris (ECU) pathology. Injuries suffered by this tendon in golfers lead to an average of 3 missed tournaments. Despite ECU being the most frequently injured structure in the wrist/forearm of elite and sub-elite golfers, no study have captured its activity during the golf swing. It is unknown when ECU is most active in the golf swing and whether it is more active in the lead or trail wrist. The purpose of this study was to assess the timing and magnitude of muscle activity in the ECU muscle in the lead and trail forearms tri-planar angular velocity of the lead and trail hands during the golf swing in sub-elite golfers.

Methods

Fifteen sub-elite right-handed golfers were recruited for this study. Data was collected utilising an indoor swing studio with a simulator. Trials were conducted by hitting five pitching wedges, five seven irons and 5 drivers. To assess muscle activity, two wireless EMG sensors (Delsys TrignoTM Mini Sensors, MA, USA) were fixed using double-sided tape directly over the mid point of the muscle belly of the ECU on the left and right forearm with the sensor electrodes aligned perpendicular to the muscle fibre direction. Maximal voluntary contraction from the highest driver value was used as a reference for each player. Performance variable which were collected for analysis were, angle of attack (degrees), swing direction (degrees) and swing speed (miles per hour). Following the completion of the swings, the highest peak half-second EMG signal during the driver swings was used as the normalizing value (100%). Swing phases were divided into backswing, downswing and follow through using the interia measurement units (IMU) sensors placed on each distal forearm and dorsum of the hands. Statistical parametric analysis was used to compared the 303 data points for the lead and trail arms throughout the swing.

Results

The mean handicap of the players was 1 (SD 2). Left ECU activity in the backswing and follow-through was significantly higher than the right for all clubs (p<0.001 and p=0.024 respectively). Right ECU activity in the downswing was significantly higher than left for all clubs (p<0.001)(Figure 1-3). During the downswing, ECU activity of the lead side progressively increased towards impact, however in the trail side, ECU activity sharply peaked and then began to decline until impact. The driver had significantly higher ECU recruitment than the 7 iron and pitching wedge (p<0.001). There was no association between EMG activity in either arm and performance characteristics.

Conclusion

Despite lead sided injuries being more common, it would appear that the trail side has greater peak activity during the downswing and therefore the peak velocity of the golf swing. Knowledge surrounding the nature of tendon contraction and wrist kinematics during the downswing would be beneficial in further explaining the asymmetric nature of injuries to this tendon.