Variations in Muscle Activity of Vastus Lateralis and Gastrocnemius Lateralis with Increasing Draft Load

Abstract

IntroductionMinimal research has examined the effect of draft loading on equine muscle activity. It is hypothesised that increases in draft load of 10 and 20% body mass (BM) will increase EMG intensity and duration of vastus lateralis (VL) and gastrocnemius lateralis (GL) during walk.MethodsData were collected from six Irish Cob geldings (11 ± 4 years; height: 1.47 ± 0.05 m; BM: 490 ± 65 kg) all trained to draft‐load. A modified lorry tyre was used as a loading platform. Surface EMG electrodes were positioned over VL and GL. An accelerometer placed on the left hind hoof collected kinematic data. EMG and accelerometer data at a draft load equivalent to 0 (zero load), 10 and 20% BM were recorded as the horses were led at walk in a 20 m straight line. A stopwatch determined mean speed over 20 m. Mean kinematic and EMG values were determined for 10 consecutive strides. EMG intensities were normalised to each horse. Kolmogorov‐Smirnov test explored data normality. Friedman test (P<0.05) compared between conditions. A pair‐wise Wilcoxon signed ranks test identified where the differences lay.ResultsData for one horse was excluded because of poor accelerometer data. The remaining horses (n = 5) maintained a constant velocity (1.10 ± 0.02 m/s {SD}) between conditions (P>0.7). VL and GL increased their muscular activity in terms of EMG intensity and duration of contraction with increasing draft load from 0 to 10% and 10 to 20% BM (P = 0.04; n = 5).ConclusionsDraft loading can be utilised for strength training following injury or to improve athletic performance.Ethical Animal ResearchThe study was approved by the Royal Veterinary College Ethics Committee. Sources of funding: Royal Veterinary College. Competing interests: none.