A comparison of protraction-retraction of the distal limb during treadmill and water treadmill walking in horses

The amount of protraction-retraction of the limbs during water treadmill walking has implications for postural and muscular development of horses undertaking this exercise for training and rehabilitation purposes. The objective of this study was to compare protraction-retraction of both forelimbs (FL) and hind limbs (HL) during dry treadmill (DT) and water treadmill (WT) exercise at the typical walking speed of each as used in practice. Inertial motion sensors attached to the metacarpal/metatarsal bones were used to compare maximal protraction (PROMAX), retraction (RETMAX) and total protraction-retraction range of movement (ROM) across five walking conditions: DT at 1.6 m/s; and WT at 0.8 m/s at four water depths, hoof depth (WTHOOF), fetlock depth (WTFET), hock depth (WTHOCK) and stifle depth (WTSTIFLE). FL ROM was lowest at WTSTIFLE and significantly lower than DT (P<0.001). HL ROM was highest at WTSTIFLE and significantly greater than DT (P<0.001). FL PROMAX was significantly lower at WTHOCK (P=0.001) and WTSTIFLE (P<0.001) than DT. HL RETMAX was higher at WTHOCK (P=0.001) than on DT and was significantly greater at WTSTIFLE and WTHOCK than WTFET (P<0.001 and P=0.001 respectively).Walking slowly (0.8 m/s) on a water treadmill reduces forelimb protraction-retraction ROM and increases hind limb protraction-retraction ROM when compared with walking at normal speed (1.6 m/s) on a dry treadmill. The potential for forelimb protraction to be decreased and hind limb retraction to be increased should be taken into account when designing training and rehabilitation programmes using this exercise modality.