Electromyographic analysis of the rider's muscles at trot

Research PaperAbstractThe aim of this study was to investigate rider muscle activity in relation to horse movement. Electromyographic(EMG) activity of 12 upper-body muscles was recorded simultaneously with the horse’s footfall timing for sixriders, riding the same horse at trot. Data for five strides were analysed for each rider. Rectus abdominis,upper trapezius, middle trapezius, flexor carpi radialis, biceps brachii, triceps brachii and middle deltoidmuscles had constant patterns with two peaks occurring in the same phase of the stride in all riders. PeakEMG values in the upper trapezius and middle trapezius occurred in early stance, and were considered to stabilizethe rider’s neck and scapula during impact of the diagonal limbs. The rectus abdominis showed peak EMGactivity in mid-stance to stabilize the trunk and enable the rider to follow the horse’s movement by swingingthe pelvis forward as the horse’s body reversed direction from downward to upward motion. The triceps brachii,which was active during late stance, and the biceps brachii, which was activated early in stance, stabilized therider’s hands and maintained contact with the bit. Teres major, extensor carpi ulnaris and serratus anteriormuscles had a small range of activity (33, 26 and 37%, respectively), consistent with tonic activation or were inac-tive, suggesting that their function may be related to general postural control.Keywords: equestrian sport; electromyography; EMG; horseback ridingIntroductionEquestrian sports involve two athletes, one equine andone human. The motion of the horse’s limbs and trunkvaries according to the gait being performed. The ridershould follow the motion of the horse’s body in a har-monious manner, which implies having the ability toadapt to the motion patterns that are characteristicof the different gaits. In the trot, each stride consistsof two diagonal stance phases alternating with twoflight phases. The horse’s trunk ascends from mid-stance until the middle of the flight phase, then des-cends during the second half of the flight phase andearly stance. Thus, the direction of the horse’s bodymovement reverses in mid-stance and in mid-swing.Co-ordinated contractions of the rider’s musclesare used to stabilize the rider’s position, to followthe motion of the horse’s body and to influence thehorse’s performance. It would be expected that whenmuscles act to stabilize the rider or to follow thehorse’s movement, their activity patterns would beco-ordinated with the rhythm of the stride, givingeach gait a characteristic, cyclic pattern of muscle acti-vation. Use of the rider’s muscles to influence thehorse’s performance is likely to show a more variablepattern of muscle activation.Electromyography (EMG) offers a simple techniquefor detecting muscle activation and co-ordination pat-terns. Its applications in equestrian sports have beenlimited, and have focused on function of the backmuscles. For instance, it has been shown that, at thesitting trot, novice riders used their adductormagnus muscle to maintain their posture because oflack of co-ordination between the rectus abdominisand erector spinae