I was grateful to be able to watch the replay of the Saddle Research Trust 4th International Conference, which was presented online on 11th December 2021. Here I share with you some of my learnings from the conference. Find out more about the Saddle Research Trust, and see the proceedings from previous conferences, at www.saddleresearchtrust.com.
We can think of the horses back as a bookshelf, that can sag if it is overloaded. The weight of the internal organs is around 300kg, and the weight of the rider could be 50-120 kg. Any time we add weight to the back, it will hollow the back to some degree. Hollowing of the back makes it more likely that the horse gets kissing spines. This is a good reason to train the horse to lift through his back in his ridden work from an early age.
Horses with shorter backs are less likely to hollow, but can find it more difficult to bend. Horses with a short, broad loin, and a bigger circumference to the cannon bone, are better able to carry weight without hollowing. We can use exercises to improve the strength of the horse’s back. These could include baited stretches, use of rehabilitation systems such as the Equiband system, and physiotherapy techniques to encourage muscle activation. It’s helpful to match the weight of the rider to an appropriate horse.
Dr Sue Dyson led a study where 4 riders of different weights rode 6 non-lame horses. Each horse was ridden by each rider, and the horses were assessed for lameness and ridden behaviour. The riders were categorised according to the percentage of their bodyweight in relation to the horse’s bodyweight. The test was abandoned if the horse became lame, or showed too many signs of discomfort in the ridden behaviour. All 13 tests when the horse was ridden by the heavy or very heavy rider were abandoned, 12 due to lameness and 1 due to behavioural signs. It was noted that the saddle was not fitted to the horse / rider partnership, and so this could have had an impact. All the horses trotted up sound in hand when they were reassessed an hour after the ridden test. The conclusion of this study was that a rider who is too heavy for the horse (more than 15% of the horse’s bodyweight) can cause temporary lameness, and behaviours that are symptomatic of musculoskeletal pain.
A 1997 study looked at the effect of added weight on jumping. Six horses and riders with or without 17kg of added weight jumped a simulated event course, and the landing kinematics were measured over a specific fence at the end of the course. This showed a significant increase in knee extension and fetlock extension with the added weight. These changes could increase the likelihood of soft tissue injury.
In 2020, Christensen et al studied horses doing a 5 minute dressage test carrying between 17% and 23% of bodyweight. The results showed no changes in stride frequency, behaviour or physiological variables. De Oliveira et al looked at therapeutic riding horses over 3 months of doing low intensity gymnastic training, which included baited stretches. At the end of the 3 months they were evaluated at the trot carrying 20-25% of bodyweight. Horses who completed the train program had improved regularity and symmetry of the trot, and a larger range of vertical motion. In 2017, Stefansdottir at al looked at Icelandic horses tilting. The horses heart rate increased and the back muscles became sore when the rider was around 25% of the horse’s weight. These studies perhaps suggest that horses in light to moderate work can cope with a rider of up to around 20% of their own bodyweight.
Thinking about the forces that go through the horses back in ridden work, we know that the total force on the horses back is linked to the riders weight. In walk, the total force remains approximately equal to the riders bodyweight. In the trot, the total force changes in a cyclical pattern, and the maximum total force is approximately equal to double the riders bodyweight. In the canter, the maximum force can be 2.5 – 3 times the bodyweight, and this force is exerted on the horses back once per stride. The forces are changed according to whether the rider is doing sitting trot, rising trot, or standing in the stirrups. The peak force is lower when the rider stands in the stirrups, because some of the energy is absorbed in the riders hip, knee and ankle joints. A 2009 study showed that when jockeys started the race in a crouched position (as opposed to standing up in the stirrups), the race times improved 5-7%. It’s likely that riding in a light seat could be beneficial to young horses, for waking up, for horses with back pain, and for horses rehabilitating from back injury or back surgery.
Most riders are asymmetrical, and it’s likely that this affects the horse. A 2019 study by Gunst et al found more force through the left side of the saddle from riders who are leaning to the left, and from riders who have collapsed the right hip. MacKechnie-Guire et al found that if the rider had one stirrup 5cm shorter than there other, the fetlock extension increased on the side of the longer stirrup, which suggests increased loading through that side. In truth, both the horse and the rider are likely to be asymmetrical to some degree.
Harmony between horse and rider can be more easily seen than explained. Biomechanically, we think of it as synchronicity of the movement of horse and rider. A 2021 study found that the movement of the riders’ pelvis in relation to the saddle varies between riders in terms of pitch (tipping forwards and backwards) but not in terms of roll (rolling left and right). A 2005 study showed increased synchronicity of the expert riders’ upper body and arms in relation to the horses back, compared to the novice rider. Increased synchronicity leads to greater consistency in the horse’s way of going. In 2004, researchers found that an expert rider has a greater stabilising influence on the horse compared to a novice rider.
Hobbs et al (2020) researched determinants of performance in dressage. The study found that the movements of the riders pelvis and trunk are important indicators of the influence of the rider on the horse, and that the best results came from the riders who gave minimal disruption to the horse.
In summary, the health and performance of the horse is affected by the weight and symmetry of the rider, by riding technique, and by the synchrony of movement between horse and rider. We can help to improve health and performance through selecting for good conformation, and through good training, both ridden and in hand.
Find out more about the Saddle Research Trust, and see the proceedings from previous conferences, at www.saddleresearchtrust.com.
© Sue Palmer, The Horse Physio, 2021
Treating your horse with care, connection, curiosity and compassion
