It is widely publicised that a growing number of the human adult population are overweight or clinically obese. Although it is recognised that inappropriate rider size has welfare implications for horses1, there is a lack of reliable scientific evidence on which to base guidelines.
A recent study2 has assessed the gait and behavioural responses in typical non-elite competition riding horses undergoing a standardised exercise test, when ridden by four experienced riders of similar ability but different bodyweights. The study design mimicked the situation that occurs in many riding establishments and equestrian disciplines in which a horse or pony may be ridden in its usual saddle by riders of varying weights and body shapes.
Six non-lame horses in regular work were ridden by each of four riders: Light (L), Moderate (M), Heavy (H) and Very Heavy (VH). Saddle fit was assessed subjectively throughout the study. Each horse was ridden twice by riders L and M, and once by rider H. Rider VH rode five horses once and one twice.
Each horse‐rider combination undertook a standardised, 30‐min ‘dressage‐test' which was abandoned if lameness was observed of grade ≥ 3/8 in one limb, grade ≥ 2/8 in ≥ 2 limbs, or ≥ 10/24 behavioural markers of pain. Horses were reassessed in hand 45–60 min after any abandonment.
Mean rider bodyweights, body mass index (BMI) values and rider:horse bodyweight percentages for the L, M, H and VH riders were respectively: 60.8, 77.8, 91.0, 142.1 kg; 23.2, 28.0, 26.3, 46.9 kg/m2; 10.0–11.7%, 12.8–15.0%, 15.3–17.9%, 23.6–27.5%. All 13 H and VH rider tests (lameness, n = 12; behaviour, n = 1) and one of 12 M rider tests (lameness) were abandoned.
Lameness was confirmed using inertial measurement unit data. All horses trotted sound after test abandonment and completed the study moving well when ridden. Although saddle fit was not ideal in all horse‐rider combinations and abandonment criteria were subjective, large riders consistently induced temporary lameness and behaviours consistent with musculoskeletal pain. This may relate to rider bodyweight and/or weight distribution. Riders M and H had similar BMI but markedly different test abandonment rates, therefore bodyweight is likely to be more relevant than BMI. Further work is required to determine if horse fitness, adaptation to heavier weights and better saddle fit for heavier/taller riders can increase horses' weight‐carrying capacity.
References
1. Clayton, H., Dyson, S., Harris, P. and Bondi, A. (2015) Horses, saddles and riders: applying the science. Equine Vet. Educ. 27, 447‐452.
2. Dyson, S., Ellis, A.D., Mackechnie‐Guire, R., Douglas, J., Bondi, A. and Harris, P. (2020) The influence of rider:horse bodyweight ratio and rider‐horse‐saddle fit on equine gait and behaviour: A pilot study. Equine Vet Educ, 32: 527-539. Available HERE