Effect of speed and water depth on limb and back kinematics in Thoroughbred horses walking on a water treadmill.

Water treadmill (WT) exercise may induce limb and back kinematics that meet specific training and rehabilitation goals. The study aimed to investigate the effects of walk speed, at different water depths (WDs), on limb and back kinematics of six Thoroughbreds exercising on a WT. Horses walked at 2.8/4.3/5.5/6.0 km/h (i.e. 0.8/1.2/1.5/1.7 m/s) at dry, metacarpophalangeal and carpal WD. Videography captured limb movement in the sagittal plane. Motion-capture measured thoracolumbosacral flexion-extension (FE), and lateral bend (LB) ranges of movement (ROM) using skin surface markers on the sixth, tenth, thirteenth, eighteenth thoracic, third and fifth lumbar, and third sacral spinous processes. Inertial-motion-sensors measured poll, withers and pelvic displacements. Following preliminary univariable analyses, multivariable mixed-effects linear-regression analyses were used to examine the relationship between speed, WD and each outcome variable (P < 0.05). Peak metacarpophalangeal, carpal and tarsal joint flexion increased with speed (P ≤ 0.002) and depth combined (P 0.001) while peak metatarsophalangeal flexion increased with WD only (P 0.001). Thoracolumbar FE-ROM between T10 and L3 and hindlimb retraction was increased by speed and WD combined (P 0.001). Hindlimb protraction was increased by speed (P 0.001) while hindlimb retraction was increased by speed and WD combined (P 0.001). Dorsoventral poll displacement was increased by speed (P 0.001) and carpal WD (P = 0.013), craniocaudal poll displacement was increased by speed and WD combined (P 0.001). Pelvic (tubera coxae and sacrum) dorsoventral displacements increased with speed and WD combined (P 0.001). Understanding the effects of speed and WD on limb, back and pelvic kinematics will improve decision making relating to dry and WT exercise within training.

Water depth modifies back kinematics of horses during water treadmill exercise.

REASONS FOR PERFORMING STUDY: Water treadmill exercise can be incorporated into the rehabilitation programmes of horses recovering from back pathology, yet little is known about the effect of this type of exercise on thoracolumbar movement ranges. OBJECTIVES: To measure the flexion-extension range of motion (FE ROM) of the thoracolumbar spine and pelvic vertical displacement during water treadmill walking at 3 water depths and compare these with the control condition. STUDY DESIGN: Within-subject trial using a crossover design in healthy horses. METHODS: A total of 14 horses walked at 0.8 m/s on a water treadmill for 3 min at each of the following depths; hoof (control), metatarsophalangeal joint (low), tarsal joint (medium) and femoropatellar joint (high). Skin surface markers on T6, T10, T13, T18, L3, L5 and S3 were used to obtain FE ROM and the minimum and maximum angular motion pattern values (AMPmin and AMPmax) for T10, T13, T18, L3 and L5. Markers placed on left and right tuber coxae were used to obtain pelvic vertical displacement. Friedman's tests and post hoc Wilcoxon's signed ranks tests were used to determine the effects of water depth on measured variables. RESULTS: The FE ROM of T10 (8.4°), T13 (8.1°), T18 (6.9°) and L3 (6.4°) when walking at high depth was significantly greater than control (5.5, 5.7, 5.1 and 5.1°, respectively; P<0.008); T13 AMPmin was significantly lower in high water (-3.0°) than control (0.1°, P = 0.001) and L3 AMPmax significantly greater in high water (-1.9°) than control (-4.8°, P = 0.001). There was no significant association between pelvic vertical displacement and water depth. CONCLUSIONS: Walking in high water causes cranial thoracic extension and thoracolumbar flexion when compared with walking in water at hoof depth. This postural change should be considered when designing rehabilitation programmes for horses with back and/or hindlimb pathology.

Investigation of the incidence and type of injuries associated with high-speed treadmill exercise testing.

REASONS FOR PERFORMING STUDY: During the past 20 years, treadmill exercise testing has played an important role in both the study of equine exercise physiology and the investigation of poor athletic performance. However, it has been suggested that some trainers and veterinarians may be reluctant to refer horses for treadmill exercise testing because of fears that horses may be at increased risk of musculoskeletal injury during treadmill exercise. OBJECTIVE: To investigate the incidence and types of injuries sustained by horses undergoing treadmill exercise. METHODS: Data were collated from 9 centres in the UK, France and Belgium, and the prevalence and types of injury were established. RESULTS: A total of 2305 records were reviewed, with 2258 horses performing treadmill exercise. There was an overall injury rate of 5.4%. However, the majority of injuries sustained were minor in nature (4.7%). Only 13 horses (0.6%) sustained major injuries in association with treadmill exercise. These included 5 cases of severe exercise-induced myopathy, 4 fractures (of which 1 was catastrophic), 2 tendon injuries, 1 case with undiagnosed severe lameness and 1 with marked exacerbation of a previously diagnosed lameness. Two other major incidents were reported but were not directly associated with treadmill exercise (one had iliac thrombosis and one collapsed and died as a result of a pulmonary embolism). CONCLUSIONS: This study confirms that the majority of horses undergo treadmill exercise without incident. The majority of injuries that did occur were minor in nature and the incidence of major injuries was similar to that reported during competition elsewhere. POTENTIAL RELEVANCE: Treadmill exercise is a safe procedure and does not appear to pose an increased risk of injury in comparison with overground exercise.

Heart rate responses during acclimation of horses to water treadmill exercise.

REASONS FOR PERFORMING STUDY: The use of water treadmill exercise in horses is popular, although little is known about the physiological responses to this form of exercise. No information exists regarding the time taken to acclimate to water treadmill exercise compared to that of high-speed treadmill exercise, for both physiological and biomechanical parameters. OBJECTIVE: To determine heart rate responses during acclimation to water treadmill exercise with and without sedation on first time exposure. METHODS: All horses were exercised on a water treadmill at the walk for 15 min once a day for 4 days. Fourteen horses (mean +/- s.d. age 9 +/- 3.2 years) were assigned randomly to Group A (sedated) and Group B (nonsedated). Group A were given 20-30 microg/kg bwt romifidine within 10-15 min prior to the start of the first acclimating run. Acclimation was determined by the time taken to reach a threshold heart rate value. RESULTS: Group A and B reached threshold heart rate values by the 6th minute of the 4th run (72.8 beats/min) and the 6th min of the 3rd run (78.7 beats/min), respectively. No significant difference was found (P>0.05) between Group A and B in the time taken to reach threshold heart rate values. Acclimation to water treadmill exercise requires a minimum of 2 x 15 min nonsedated acclimating runs. Sedation can be used to prevent horses panicking during the first exposure but thereafter does not affect the time taken to acclimate. POTENTIAL RELEVANCE: Previous experience of water treadmill exercise should be taken into consideration prior to collecting physiological and biomechanical data. Further studies detailing the physiological and biomechanical responses are required prior to making recommendations for the incorporation of this mode of exercise into rehabilitation programmes.