Does exercise change the shape of your horse’s back?

Sue Dyson & Line Greve

Recommendations concerning saddle-fit are empirical and based on anecdotal information. We know that the saddle needs to fit the horse in motion, but there has been no investigation of whether the thoracolumbar region changes in shape in association with exercise or how improper saddle-fit may influence potential changes.

The aims of the study were to investigate exercise-induced changes in back-dimension in sports horses of variable age, from a range of work disciplines, working at different levels. The objectives were to quantify changes in back-dimension that occur subsequent to ridden exercise

  1. determine the influence of work-quality
  2. determine the influence of saddle-fit
  3. determine the influence of rider skill-level.

We hypothesized that:

  1. changes in back-dimension immediately after exercise were quantifiable;
  2. horses working ‘on the bit’ would have larger changes than horses not working ‘on the bit’; and
  3. an ill-fitting saddle before work would diminish any transient enlargement of the back muscles with work.

Sixty-three sports horses in normal work were assessed prospectively. Thoracolumbar shape/symmetry was measured at predetermined sites before and immediately after a 30 minute exercise period; width ratios for two levels at each site were calculated. The work quality and rider-skill were graded; the presence of lameness and saddle-fit were recorded. Descriptive statistics, univariable and multivariable mixed-effect linear regression were performed to assess the relationship between horse-saddle-rider factors and changes in back dimensions.

The mean back-shape ratio immediately after ridden exercise was greater compared with before work for all sites. Mean changes in back-shape were greater in horses working correctly versus not working correctly, and in horses with correctly-fitting versus ill-fitting saddles at each site. Mean changes were greater in horses ridden by good > moderately > poorly-skilled riders. Mean changes were less in lame horses compared with sound horses.

Exercise-induced back-dimension changes varied among predetermined sites. In the saddle region, the degree and direction of changes are mainly determined by the saddle-fit, whereas outside the saddle region the work-quality is the most influential factor. A uniformly-flocked saddle, fitted with even contact and fitted in balance, was associated with larger dimension changes in the middle third of the saddle region compared with other saddles. The balance of the saddle was the most influential factor for changes in back width in the cranial third of the saddle region. A saddle tipping back or forward has uneven contact, causing focal areas of increased pressure, which may restrict the normal back movement. There were decreased exercise-induced width changes at the shoulder region, T8 and T18 with increased convexity (greater ratio) before exercise. This finding supports previous observations that most dramatic changes occur in young horses with a prominent spine (low ratio [concave shape]) that are worked correctly, and that well-muscled advanced horses also worked correctly exhibit less change after exercise. This is presumably related to better core strength and muscular support of the thoracolumbar spine in an older advanced horse compared with a young horse.

We recommend that saddle-fit should be checked on a regular basis both before and after exercise. Early recognition of an ill-fitting saddle may provide an opportunity for owners, trainers and veterinarians to reduce the risk of compromised back movement, development of back pain, muscle atrophy and deterioration in performance because of an ill-fitting saddle