To date there exists no scientific studies and/or simple mathematical equations that determine what is — or isn’t — too heavy for a ridden horse to comfortably carry.
Current research would seem to suggest that once the combined weight of a rider and tack falls into the range of 15 to 20 per cent of the horse’s body weight, the rider needs to increase their awareness, sensibility and sensitivity towards equine welfare.
These suggestions mirror previously noted traditional guidelines rooted in early-century military trials of the U.S. Cavalry. The trials showed that long-term health deteriorated when the horse carried loads i.e. rider and tack over 20 per cent.
A horse that is “overburdened” by the weight of the rider will begin to show signs of discomfort like hollowing of the back, heaviness of the forehand, elevated head position, gait and limb kinematic abnormalities i.e. tense and uneven stride, a reluctance to willingly go forward, sensitivity over the back, temporary lamenesses, and undesirable behaviours.
If the weight carried continues to be “too much” for the horse then the short-term effects turn into long-term consequences to the health of the horse. This is especially true for the immature skeleton of the young horse. The growth plates of the lower neck and vertebral column do not fully mature and close in the horse until five years of age, even later in certain breeds. As a result the young horse’s back is particularly vulnerable to the ill effects associated with overburdening,
Improper loading of the horse’s back interferes with and prevents the proper use and lightness of the horse’s forehand and engagement of the hindquarters. This is critical to the long-term soundness of a ridden horse.
Whenever the elastic networks of the horse’s musculoskeletal system are excessively strained or fatigued the horse is unable to physically benefit from their elastic recoil. A similar outcome occurs when a children’s pogo stick is overloaded with an adult — no bounce or spring. As a result the horse’s gait will lack lightness in stride. In an attempt to stabilize and balance the load the horse compensates by overweighting its forehand. The extra weight encumbers and greatly disadvantages the horse’s own abilities to carry its body in proper carriage,
As the musculoskeletal structures of the horse are overloaded and fatigued the horse is placed at a greater risk for injury along both acute and chronic timelines. Therefore it is in the best interest of the horse, especially when considering the young horse to give it the benefit of the doubt whenever it comes to large loads.
The appropriateness of saddle fit has traditionally been focused upon relative to its fit for the horse, however, as both the weight and height of modern riders have increased it is apparent that the saddle must fit both the backside of the horse and the backside of the rider.
Proper saddle fit is essential with any horse-rider combination and is important not only to the rider’s balance and comfort but to their safety as well. With both the larger and the very tall rider the saddle mismatch often imposes physical limitations upon the rider’s abilities to hold a balanced seat with proper alignment between the shoulders, hips and heels. The resulting rearward distribution of weight onto the cantle and forward running of the rider’s thighs and heels distributes abnormal forces onto the horse’s back and grossly interferes with the ability of the muscular structures of the back to function properly. The English saddle tends to be less forgiving of rider-saddle mismatch than the western or stock saddle.
The moments when a heavy rider mounts or dismounts can be particularly troublesome to the horse as undue twisting and torquing forces are transferred onto the withers and spinal column. These harmful distractive forces can be mitigated by the use of a mounting block.
If a mounted rider visibly appears to be “too big” for a horse or if the rider is unable to achieve a proper riding position in the saddle then it would be beneficial to both horse and rider to make adjustments in the horse-rider combination or saddle fit.
Whenever addressing the horse-rider suitability it is of value to be considerate of factors specific to the individual horse. These include but are not limited to — the horse’s age, breed, conformation, fitness level, body condition, level of preparation to carry a rider, strength, injury history, type of riding to be undertaken and for how long, condition of the feet, the duration and intensity of the work and the terrain on which the work is taking place. The weaknesses, sensitivities and vulnerabilities of individual horses become readily apparent as the burden of the load increases.
A suitable horse-rider partnership is more complicated than a math equation and therefore justification for or debate regarding upper limits is rarely in the best interest or comfort of either the rider or the horse. However, agreements can certainly be made that ideal body weights for both the rider and the horse are of benefit to the partnership.