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Publication Open Access Stress cortisol and muscle stiffness in horses used for equine-assisted therapy(2017) Nuttawut Nuchprayoon; Nlin Arya; Pattama Ritruechai; Mahidol University. Faculty of Veterinary ScienceEquine-assisted therapy uses horseback riding to improve the patient's health and wellbeing. However, the possible stress and damage of this therapy on the back horse muscle (longissimus dorsi) are understudied. We studied the stress cortisol... and muscle stiffness of two ponies and a horse used for equine-assisted therapy on a child with autism. Salivary cortisol levels and heart rate were used as indicators of physiologic stress and a muscle indenter was employed to estimate the back musclePublication Open Access Comparison of the longissimus dorsi muscle tone in Thoroughbred racehorses before and after training(2016) Pichet Jewmongkonchai; Arunothai Muangma; Pattama Ritruechai; Mahidol University. Faculty of Veterinary Science. Department of Clinical Science and Public HealthThe longissimus dorsi is the largest back muscle of the horse and has the potential to contribute movement to the horse's back. Damage to the longissimus dorsi is very common to cause back injuries, which is also a major cause of poor performance and gait abnormalities in horses. The muscle indenter is a tool that allows measuring the stiffness of the back muscles. We hypothesized that the longissimus dorsi muscle tone after training would be stiffer than at rest. One sound mare and three gelding Thoroughbred racehorses were used in this study. The muscle tone was measured using a muscle indenter along both sides of the T14, T16, T18 and L2 longissimus dorsi muscle. Blood sample were collected to measure the blood lactate concentration before and after training. Heart rate was measured at rest and at 0, 5, 10, 15 and 20 minutes after training. We found a significant increase in muscle tone after training at T14, T16 and T18. The blood lactate concentration of studied horses significantly increased after training, although the values were still within the normal range. The recovery heart rates for all horses are tended to decrease (< 70 bpm) after 5 minutes of stopping exercise. We confirmed that the longissimus dorsi is a key muscle in horse movement that can be sensitive to relatively small training sessions; that is why this muscle is prone to get injured. Generally, the muscle intender was a successful tool of objectively measuring this muscle tone.Publication Open Access A review on the functions of the horse back and longissimus dorsi muscle(2015) Pattama Ritruechai; Mahidol University. Faculty of Veterinary Science. Department of Clinical Science and Public HealthThe function of a muscle is to permit movement and maintain posture. Such a key role depends on the interplay between its anatomical structure and the way is used during movement. From a mechanical sense, a muscle changes its length to generate force. If it generates force while shortening (concentric), it will generate mechanical power, and if it generates force whilst it is being stretched (eccentric), it will absorb mechanical power. The longissimus dorsi, the largest muscle of the horse's back, is of considerable importance for its key functions on the athletic ability and performance of the animal. In this review, I summarized the anatomy, functions, biomechanics, and disorders of the horse back. The biomechanics of the horse's back depend on the interaction between the spinal column and the spinal musculature. Especially, longissimus dorsi muscle performs different functions both along its length and different regions across each segment. Several studies have reported muscular disorders in the horse's back such as stiffness and limitation of motion range, as also by electromyography records on the muscle activity (albeit at single recording sites during locomotion). These reports are typically isolated observations and no study has yet integrated muscle activity patterns with the cycles of flexion-extension in any detail, neither a study has linked these factors to the muscle fascicle strains in the longissimus dorsi. Such studies will be fundamental to fully understand the mechanical role of the longissimus dorsi, particularly during locomotion, and will develop new treatment techniques for horse veterinarians. In addition, 3D anatomical measures of the structure in vivo integrated with measures of function back motion and longissimus dorsi muscle activity would be ideal to understand in further detail the function of the horse's back.