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

Objective Overview

• This study explored how acupuncture affects the stride, running speed, and heart rate variability in Thoroughbred racehorses during their training period.
• The aim was to understand whether acupuncture could improve performance or influence cardiac autonomic regulation, potentially impacting injury prevention and recovery.

Study Background and Rationale

• Thoroughbred racehorses are prone to musculoskeletal injuries due to the high-intensity workloads involved in race preparation and trials.
• Improving health outcomes and preventing injuries are important for animal welfare in racing industries.
• Acupuncture has been used in veterinary medicine but its effects on performance parameters and heart rate variability (HRV) in racehorses had not been well studied.
• HRV is an indicator of cardiac autonomic regulation and can reflect changes in parasympathetic nervous system (vagal) activity, which relates to recovery and stress.

Study Design and Participants

• Type of study: Prospective, randomized, parallel-group controlled trial.
• Participants: 30 Thoroughbred racehorses aged about 3 years, all in full racing training and at similar career stages.
• Conditions: All horses were kept under consistent nutritional, training, and environmental conditions to minimize external variables.
• Groups: Horses were split into two groups — one received acupuncture treatments and the other served as a control without acupuncture.

Intervention Details

• The treatment group received three acupuncture sessions spread over a three-week span.
• The control group underwent no acupuncture treatment during this time period.

Measures and Outcomes

• Main parameters evaluated:
• Stride parameters (SP): Measured during an 800-meter gallop, including stride count.
• Speed: Although mentioned in the title and objective, specific speed changes were not highlighted as significant in findings.
• Heart rate variability (HRV): Metrics related to parasympathetic (vagal) activity including:
• Root mean square of successive differences (RMSSD)
• High frequency components (HF)
• Standard deviation of short-term variability (SD1)
• Pre- and post-intervention measurements were taken for both groups to calculate changes (deltas, Δ).
• Data analysis used non-parametric Mann-Whitney U tests to compare groups.

Key Findings

• The acupuncture group showed non-significant decreases in parasympathetic HRV indicators (ΔRMSSD, ΔHF, ΔSD1), suggesting reduced vagal tone after treatment.
• The control group had a significant increase in maximum stride count (Max SC), indicating improved stride performance over the same period.
• The treatment group experienced decreased stride count and vagal activity, suggesting a possible need for a recovery period following acupuncture treatment before performance improves.

Interpretation and Implications

• Decreased parasympathetic activity (vagal tone) post-acupuncture might imply that acupuncture initially induces a short-term autonomic stress or adjustment period.
• The reduced stride count in treated horses suggests performance parameters may temporarily decline immediately after acupuncture.
• Conversely, horses without acupuncture improved stride performance during the period, which may reflect usual training adaptation without intervention.
• These findings suggest that acupuncture’s benefits (if any) might occur after a recovery phase rather than immediately, highlighting the timing of acupuncture treatments as important.
• More research is needed to determine long-term effects, mechanisms involved, and optimal treatment schedules for acupuncture in equine athletes.

Conclusion

• This study provides initial evidence that acupuncture influences cardiac autonomic regulation and stride parameters in Thoroughbred racehorses but may require a recovery period before positive effects manifest.
• The findings highlight cautious interpretation of acupuncture treatments in racehorses during intense training, emphasizing further research to optimize protocols for injury prevention and performance enhancement.