Original ResearchInvestigation of Myofascial Trigger Points in Equine Pectoral Muscles and Girth-Aversion Behavior

- Myofascial trigger points (MTrPs) are common in the transverse and posterior pectoral muscles.
- Horses with an owner-reported history of girth-aversion behavior had more reactive MTrPs on palpation.
- Knowledge of the presence and location of MTrPs will assist in the development of prevention and management strategies.

Horses displaying aversion to fastening of the girth may be expressing pain from myofascial trigger points (MTrPs). The location of MTrPs in the pectoral region of horses has not been previously described. The objectives of this study were as follows: (1) to locate and map MTrPs in the transverse and ascending pectoral muscles; (2) to score the severity of the MTrPs by behavioral reaction to palpation; and (3) to look for associations between these findings and girth-aversion behavior. Thirty-eight horses were recruited in a cross-sectional clinical study. Taut bands were identified on palpation of horses undergoing physiotherapy assessment and then scored for behavioral reaction to palpation as normal (0), mild (1), moderate (2), or severe (3) and mapped. Owner-reported history of girth-aversion behavior was compared with the severity score using chi-squared analysis. Myofascial trigger points were identified in all horses (average severity: mild n = 6, moderate n = 24, and severe n = 8) with the most common regions of ascending pectoral muscles being the axillary and along the region usually covered by the girth. Horses with an owner-reported history of girth-aversion behavior (n = 13) had higher severity scores than horses without a history of girth-aversion behavior (n = 25; P = .014). Knowledge of the presence and location of MTrPs could assist in the development of prevention and management strategies to improve comfort, optimize performance, and reduce girth-aversion behavior.