Last week (March 25th) the press was buzzing with stories of overweight British riders causing suffering, pain and lameness to their horses, sparking debate amongst horse owners, worried that they were hurting their horses. The research that these stories were based upon was published in the Journal of Veterinary Behaviour. As a therapist, these stories drew my attention and prompted me to seek out the original paper. On reading it, it was clear the press had blown it out of all proportion as usual!
The “10% criteria” as stated in the paper was being examined after an “industry practitioner” proposed that a 10% rider to horse bodyweight ratio to be optimum, 15% to be satisfactory and 20% to be a welfare issue. All riders in the study were of a healthy body mass index (BMI), a medical measure of healthy body weight, and were found to be between 14.2% and 16.6% of their horses’ bodyweight. The authors aknowledged that the 10% rule appeared to be unrealistic within the general riding population and that more research was needed. No measures of rider suitability were made, neither were any measures of lameness or pain associated with increased rider weight.
When looking further into this issue, I uncovered research published in 2008 that found horses could comfortably carry 15% or 20% of their bodyweight, while carrying 25-30% caused increased breathing, heart rate took longer to return to pre-exercise levels, and post-exercise muscle soreness and tightness were more common. Carrying over 30% of their bodyweight horses were also found to have increased blood lactate levels, a measure of how hard the muscles are working. The researchers of this study also found that increased cannon bone circumference and horses with wider loins were able to carry more weight, a scientific understanding for measuring the cannon bone when judging weight carrying capacity.
In addition to this, research carried out on japanese native ponies found that they were more than capable of carrying up to 29% of their body weight without detrimental effect.
Riders obviously need to be sensible when following the results of any research. A 500Kg cob with good conformation and no injuries would obviously be able to carry more weight than a 500Kg Thoroughbred.
Previous injury, age and conformation would all have an impact on how much weight a horse can carry. Overweight horses would need to carry less weight that a similar horse of normal weight, carrying its own excess weight plus the weight of a heavy rider would inevitably cause problems, possibly lameness or muscle damage.
Regardless of how well a horse and rider are matched, taking into account their weight ratio, conformation, previous injuries and weight of the horse, being ridden with correct technique and training, with a rider that is truely self balanced is the best way to increase performance, longevity of working life, and welfare of the horse.