EVALUATING MUSCLE TENSION SCORES AS AN INDICATOR OF STRESS IN RIDING HORSES

Correlations between muscle tone and pain are limited in equine research, lagging behind human studies. Muscle dysfunction can lead to poor performance and reduced welfare in horses. Previous studies done in humans involving tension type headaches and increased muscle tension (MT) post exercise have correlated muscle hardness with soreness. Periods of increased stress levels in horses are associated with elevated cortisol concentrations. The described physiologic stress markers enable equine researchers an opportunity to find correlations involving less evaluated indicators of stress, like muscle tension. Therefore, the purpose of this study was to evaluate correlations between serum cortisol concentrations, and muscle tension in nonverbal equids with the intent of determining whether or not it would be possible to create a universal MT scoring system. It was hypothesized that increased muscle tension would correlate with increased cortisol, an indicator of stress. Two experiments were conducted: experiment one studied 17 therapeutic riding horses over two eight-week long riding session, and experiment two studied 25 horses enrolled in a beginner level riding course. Serum cortisol was collected and manual muscle testing evaluated on a scale between 1.5 and 2.5, was based on previously published research (Chen et al., 2017). Serum cortisol levels declined from Pre to Post 30 minutes post exercise, but increased in both experiments as the semester progressed. Changes in MT was observed in riding horses for the following muscles: facial, quadriceps femoris, and semitendinosus. Quadriceps femoris and triceps tended to be tenser on the left versus right side. Interestingly, the longissimus dorsi and trapezius did not change in experiement two over time