Effects of Rider Weight and Pony Age on Epaxial Muscle Pain Sensitivity and Heart Rate Variability in Exmoor Ponies: A Preliminary Study

Jenna  Payne; Nikki  Routledge; Sally  Charlton; Adrian  Hunnisett

doi:10.64292/ijes.229

Authors

Jenna Payne McTimoney Animal Association/Private Practice, St Day, Redruth, United Kingdom https://orcid.org/0009-0004-6136-1384
Nikki Routledge McTimoney College of Chiropractic, Abingdon, OX14 1BZ, United Kingdom https://orcid.org/0009-0003-0325-8373
Sally Charlton McTimoney College of Chiropractic, Abingdon, OX14 1BZ, United Kingdom https://orcid.org/0009-0007-0380-6500
Adrian Hunnisett McTimoney College of Chiropractic, Abingdon, OX14 1BZ, United Kingdom https://orcid.org/0000-0002-6112-0896

DOI:

https://doi.org/10.64292/ijes.229

Keywords:

Equine, back pain, thoracolumbar, rider weight, pony age, epaxial muscles, welfare

Abstract

Welfare concerns surrounding rider–horse weight ratios are central to equestrianism's Social Licence to Operate. This crossover study investigated the effects of rider weight and pony age on epaxial mechanical nociceptive thresholds (MNTs) and heart rate variability (HRV) in trekking Exmoor ponies. Ten ponies (18 ± 4 years; 345 ± 26 kg) completed a 4.28 km ride on three consecutive days under lightweight (LW), middleweight (MW), and heavyweight (HW) riders (9.7%–23.1% of body weight). MNTs were measured using pressure algometry, and HRV was recorded pre-ride, immediately post-ride, and after two hours of rest. Across all ponies, compared with pre-ride values, MNTs significantly increased immediately post-ride for HW (P < 0.001) riders, indicating reduced epaxial muscle sensitivity. MNTs significantly decreased after two hours of rest for all rider categories (LW, P = 0.005; MW, P < 0.001; HW, P = 0.015). Immediately post-ride, MNTs in older ponies (≥18 years) significantly increased for all rider weights: LW (P = 0.002), MW (P = 0.014), and HW (P < 0.001), whereas in younger ponies (≤17 years), MNTs significantly increased only for HW riders (P = 0.003). After two hours of rest, MNTs significantly decreased compared with pre-ride values only in younger ponies for the LW and MW rider weights (LW, P = 0.001; MW, P < 0.001). This suggests age-related differences in short-term recovery. There were no significant effects on HRV across time points for each rider weight or age group, except for a significant increase during the two-hour rest period for the LW rider condition (P = 0.007). Rider weight and pony age influence short-term changes in epaxial muscle sensitivity following ridden exercise, particularly in the mid-thoracic and lumborum regions. HRV responses indicated no sustained physiological stress. Further research using larger and more diverse cohorts is warranted.

References

Challinor CL, Randle H, Williams JM. Understanding rider:horse bodyweight ratio trends, weight management practices and rider weight perceptions within leisure and amateur riders in the UK. Comparative Exercise Physiology 2021;17:403–20. https://doi.org/10.3920/cep200082.

Mothershead M, Sukovaty L, Webb S, Webb G, Boyer W, McClain W. Effect of weight carried and time ridden on back pain in horses ridden in an equestrian program as determined by pressure algometry. Journal of Equine Veterinary Science 2017;52:65–6. https://doi.org/10.1016/j.jevs.2017.03.072.

Quiney LE, Ellis A, Dyson SJ. The influence of rider weight on exercise-induced changes in thoracolumbar dimensions and epaxial muscle tension and pain. Equine Veterinary Journal 2018;50:16–16. https://doi.org/10.1111/evj.24_13008.

Roberts A, Dyson S, Harris P, Ellis A, Hemmings A. The influence of rider bodyweight on salivary cortisol concentrations and spontaneous blink rate for horses performing a standardised exercise test. Equine Veterinary Journal 2018;50:16–7. https://doi.org/10.1111/evj.25_13008.

Powell DM, Bennett-Wimbush K, Peeples A, Duthie M. Evaluation of indicators of weight-carrying ability of light riding horses. Journal of Equine Veterinary Science 2008;28:28–33. https://doi.org/10.1016/j.jevs.2007.11.008.

Dyson S, Ellis AD, Mackechnie-Guire R, Douglas J, Bondi A, Harris P. The influence of rider:horse bodyweight ratio and rider-horse-saddle fit on equine gait and behaviour: A pilot study. Equine Veterinary Education 2019;32:527–39. https://doi.org/10.1111/eve.13085.

Von Borell E, Langbein J, Després G, Hansen S, Leterrier C, Marchant J, et al. Heart rate variability as a measure of autonomic regulation of cardiac activity for assessing stress and welfare in farm animals — A review. Physiology & Behavior 2007;92:293–316. https://doi.org/10.1016/j.physbeh.2007.01.007.

Haussler KK. Pressure algometry for the detection of mechanical nociceptive thresholds in horses. Animals 2020;10:2195. https://doi.org/10.3390/ani10122195.

Baker S. Survival of the fittest. Dulverton: Exmoor Books; 1993.

Stefánsdóttir GJ, Gunnarsson V, Roepstorff L, Ragnarsson S, Jansson A. The effect of rider weight and additional weight in Icelandic horses in tölt: part I. Physiological responses. Animal 2017;11:1558–66. https://doi.org/10.1017/s1751731117000556.

Rendle D, McGregor Argo C, Bowen M, Carslake H, German A, Harris P, et al. Equine obesity: current perspectives. UK-Vet Equine 2018;2:1–19. https://doi.org/10.12968/ukve.2018.2.s2.3.

Cravana C, Fazio E, Ferlazzo A, Medica P. Therapeutic riding horses: Using a hypothalamic-pituitary-adrenal axis measure to assess the physiological stress response to different riders. Journal of Veterinary Behavior 2021;46:18–23. https://doi.org/10.1016/j.jveb.2021.07.013.

Carroll CL, Huntington PJ. Body condition scoring and weight estimation of horses. Equine Veterinary Journal 1988;20:41–5. https://doi.org/10.1111/j.2042-3306.1988.tb01451.x.

Clark L, Bradley EJ, Mackechnie-Guire R, Taylor A, Ling J. Trunk kinematics of experienced riders and novice riders during rising trot on a riding simulator. Journal of Equine Veterinary Science 2022;119:104163. https://doi.org/10.1016/j.jevs.2022.104163.

Dyson S, Berger J, Ellis AD, Mullard J. Development of an ethogram for a pain scoring system in ridden horses and its application to determine the presence of musculoskeletal pain. Journal of Veterinary Behavior 2018;23:47–57. https://doi.org/10.1016/j.jveb.2017.10.008.

Sullivan KA, Hill AE, Haussler KK. The effects of chiropractic, massage and phenylbutazone on spinal mechanical nociceptive thresholds in horses without clinical signs. Equine Veterinary Journal 2008;40:14–20. https://doi.org/10.2746/042516407x240456.

Greve L, Murray R, Dyson S. Subjective analysis of exercise-induced changes in back dimensions of the horse: The influence of saddle-fit, rider skill and work quality. The Veterinary Journal 2015;206:39–46. https://doi.org/10.1016/j.tvjl.2015.06.009.

Roost L, Ellis AD, Morris C, Bondi A, Gandy EA, Harris P, et al. The effects of rider size and saddle fit for horse and rider on forces and pressure distribution under saddles: A pilot study. Equine Veterinary Education 2019;32:151–61. https://doi.org/10.1111/eve.13102.

Jindal SK. Veterinary physiology. New Delhi: Nipa Genx Electronic Resources & Solutions P. Ltd; 2023.

Grevendonk L, Connell NJ, McCrum C, Fealy CE, Bilet L, Bruls YMH, et al. Impact of aging and exercise on skeletal muscle mitochondrial capacity, energy metabolism, and physical function. Nature Communications 2021;12:4773. https://doi.org/10.1038/s41467-021-24956-2.

Li C, White SH, Warren LK, Wohlgemuth SE. Effects of aging on mitochondrial function in skeletal muscle of American American Quarter Horses. Journal of Applied Physiology 2016;121:299–311. https://doi.org/10.1152/japplphysiol.01077.2015.