Effect of acupuncture on heart rate variability at rest and on stride length and frequency at gallop in thoroughbred racehorses

Methodology

Ethical approval (REC185-19) was obtained from the Animal Ethics Committee of the University of Pretoria. This study was a quantitative randomised control trial during field conditions. The racing trainer selected 30 horses that qualified for the study. The mean (±SD) age of Group A was 4 ± 0.8 years. In Group A there were five fillies, three colts and eight geldings. In this group one horse was eliminated due to injury. The control group had a mean (±SD) age of 3 ± 0 years and consisted of seven geldings and eight colts with no fillies. All participants were kept in uniform conditions within one stable yard, received identical nutrition and training. The researcher randomly allocated these horses into an acupuncture treatment group (A) and a control or non-treatment group (B), with 15 horses in each group. All individuals involved in the study, except the researcher, were blinded to which group was the control or treatment group.

The researcher performed a clinical health examination on each horse participating in the project and the horses were habituated to the equipment. The HRV and SP were measured pre-treatment and post-treatment, i.e., after the treatment group received three dry needle acupuncture treatments spaced evenly over a three-week period.

The dry needle acupuncture technique was performed by inserting acupuncture needles into pre-selected acupuncture points (GB21, ST36, LI10, Bai Hui, Shen Shu, Shen Peng, Shen Jiao, Yan Chi, BL40, GB27, LU1, BL54 and SI9). Needles were inserted for 20 minutes and stimulated in a clockwise direction every five minutes. The non-treatment group was haltered and kept in the stable for the same period.

Heart Rate Variability

The Televet100 echocardiogram (ECG) device was used to record, digitally on a laptop 15 minutes of echocardiogram data. It was attached with gel on the skin surface by four ECG electrodes (Trachsel et al., 2010), and secured with a surcingle. The data were recorded pre- and post-treatment at the stables midmorning on a Sunday when the horses were rested, one hour after feeding.

The data was downloaded from the recording monitor using the Televet100 software, then transferred to the HRV Analysis Software 2.1 for Windows or Kubios. The RR-intervals were quantified (determining the various HRV parameters) using the Kubios software. The frequency band widths in Kubios were set at 0.01- 0.06 Hz for low frequency and 0.07-0.6 Hz for high frequency. A five-minute segment (within the 15 minutes recording) with the least number of artefacts (visually) was chosen. This five-minute segment was then analysed using no correction, very low, low correction, medium- and high-correction factors (CF) for each of the horses pre- and post-treatment. The lowest CF that corrected the data without affecting the variability was then chosen on an individual basis as recommended by the Kubios website. Where the tachogram quality was extremely poor the results were excluded from the analysis.

Using Kubios software, the variability of the beat-to-beat (RR) intervals was quantified with the aid of time domain, frequency domain and Poincaré plot analyses. The following HRV indicators (SDNN, RMSSD, LF, HF, LF/HF, LF nu, HF, SD2) and heart rate measures (mean RR, mean HR) were determined and statistically analysed.

Stride parameters

A GPS girth-mounted device EquinITy™ was used to measure stride parameters and running performance in a gallop over 600m. The following was recorded by the EquinITy™ software: maximum stride length (SL Max), average stride length (SL Avg), maximum stride frequency (SF Max), average stride count (SC Avg), maximum stride count (SC Max), maximum speed (Max Speed), stride count at maximum speed (SC Max Speed), stride length at maximum speed (SL Max Speed) and average speed (Avg Speed). Once the EquinITy™ data was downloaded from the device at the end of the training session it was processed by the EquinITy™ Technology website per horse and work session.