Effects of acupuncture on stride, speed, and heart rate variability in Thoroughbred racehorses

Thoroughbred racehorses are at increased risk of injury during race preparations and trials, primarily due to intensive workloads that predispose them to musculoskeletal injuries. Evaluating clinical interventions to improve health and prevent injury is essential for addressing animal welfare concerns. This study investigated the medium-term effects of acupuncture on stride, speed and cardiac autonomic regulation (assessed via heart rate variability [HRV]), in Thoroughbred flat racehorses. This prospective, randomised, parallel-group study included an intervention and a control group. Thirty Thoroughbred racehorses in full training (racing age 3 years; range 3.0-3.9), from a single professional training yard, and at the same stage of their racing careers, were maintained under similar nutritional, training, and environmental conditions. The intervention group received three acupuncture treatments, over a three-week period. HRV and 800-m gallop stride parameters (SP) were measured pre- and post-acupuncture period in both groups. Pre-post changes or delta (Δ) in each indicator were calculated for both groups and compared using non-parametric Mann-Whitney U tests. Treatment was associated with non-significant reductions in parasympathetic HRV indicators namely root mean square of successive differences in beat-to-beat RR-interval (ΔRMSSD: treatment vs control: - 2.19 vs. 1.47 ms), high frequency components (ΔHF: - 37.19 vs. 19.42 ms²), and standard deviation of short-term variability (ΔSD1: - 1.56 vs. 1.04 ms), suggesting lower vagal tone. Maximum stride count (Max SC) increased significantly in the control group (p = 0.004). Overall, the treatment group showed decreased stride count and vagal activity indicating that a short recovery period may be required after acupuncture.