Training the equine respiratory muscles: Ultrasonographic measurement of muscle size.
Authors: Fitzharris Laura E, Hezzell Melanie J, McConnell Alison K, Allen Kate J
Journal: Equine veterinary journal
Summary
# Training the equine respiratory muscles: Ultrasonographic measurement of muscle size Limited research has characterised how respiratory muscles adapt to exercise training in racehorses, despite the obvious relevance to performance and airway function. Fitzharris and colleagues used ultrasonography to track changes in upper airway, diaphragmatic, accessory respiratory and locomotor muscles across three timepoints: initial unfitness, after 12 weeks of conventional training, and at race fitness following a further 10–12 weeks; horses at one yard additionally completed inspiratory muscle training (IMT) randomised to high-load or low-load protocols between the latter two timepoints. Upper airway muscles consistently enlarged with conventional training, whilst the diaphragm expanded during the initial 12-week conditioning phase but responded differently to IMT—maintaining or increasing size with high-load IMT but declining with low-load or no IMT. Interestingly, gluteal muscle thickness was significantly greater in horses without prior airway surgery, suggesting previous surgical intervention may have systemic training effects. These findings demonstrate that respiratory muscles are trainable adaptations, distinct from locomotor conditioning, with high-load inspiratory training capable of preserving diaphragmatic size during intensive competition phases—potentially valuable information for optimising respiratory capacity in performance horses, though larger IMT cohorts would strengthen these recommendations.
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Practical Takeaways
- •Conventional race training effectively develops both respiratory and locomotor muscles; consider inspiratory muscle training as an adjunct to enhance diaphragm conditioning in competition horses
- •High-load inspiratory muscle training protocols appear necessary to maintain diaphragm gains; low-load protocols do not provide additional benefit over standard training alone
- •Previous airway surgery may impact locomotor muscle development; monitor gluteal muscle development carefully in horses with surgical history
Key Findings
- •Upper airway muscle size increased significantly in response to conventional race training between timepoints A-C and B-C
- •Diaphragm size increased between initial unfitness (A) and after 12 weeks conventional training (B)
- •High-load inspiratory muscle training maintained or increased diaphragm size between timepoints B-C, while low-load IMT and no IMT resulted in diaphragm size decrease
- •Horses without previous airway surgery showed greater gluteal muscle thickness (left 3.9%, right 4.5%) compared to those with prior surgery