Background Inspiratory muscle training applies a training stimulus directly to the inspiratory muscles and is distinct from whole‐body training. The potential benefits of inspiratory muscle training have yet to be explored in horses. Objectives The objectives were as follows: (a) to develop an equine‐specific method of testing and training inspiratory muscles; (b) to assess tolerance and feasibility in a pilot study in a commercial Thoroughbred training establishment. Study design Field study. Methods A mask was used to interface commercial human inspiratory muscle training equipment. Ten horses undertook inspiratory muscle training once daily while stood in the stable approximately 5 days/wk over a 9‐week period. Inspiratory muscle strength testing employed a continuous incremental inspiratory loading protocol alternating two loaded and two minimally loaded breaths until failure to tolerate the load occurred or the maximum 60 breaths were completed. The inspiratory muscle strength testing was undertaken twice; firstly, in 10 horses with minimal acclimatisation and secondly, in eight horses experienced with the inspiratory muscle training programme. Results The 10 horses undertook inspiratory muscle training for a median of 42 days, reaching a median peak training load of 32.5 cm H2O. One horse did not tolerate the mask with repeated snorting and was replaced. All horses completed the inspiratory muscle strength testing. The median peak value in inspiratory muscle strength testing protocol 1 was 27 cm H2O and in inspiratory muscle strength testing protocol 2 was 41 cm H2O. Two of 10 horses reached the maximum possible value in inspiratory muscle strength testing protocol 1; therefore, the test was adapted to permit a higher maximum value, despite this 3/8 horses reached the maximum possible value in inspiratory muscle strength testing protocol 2. Main limitations A small number of horses were assessed. The inspiratory muscle strength testing protocol was refined during the study and requires additional refinement. Conclusion Inspiratory muscle testing and training were feasible and tolerated in horses. Further research is required to understand whether the inspiratory muscle strength testing values obtained correlate with other physiological/performance outcomes. The potential benefits and/or adverse effects of inspiratory muscle training warrant further investigation.

Background: Limited information exists regarding changes in the size of respiratory and locomotor muscles in response to exercise training in the Thoroughbred racehorse. Objectives: To describe and compare the responses of the respiratory and locomotor muscles to conventional exercise training and inspiratory muscle training (IMT). Study design: Prospective randomised controlled trial. Methods: Thoroughbred racehorses, in training for competition in National Hunt races, were recruited from two training establishments. Ultrasonographic images were obtained for selected muscles of the upper airway, diaphragm, accessory respiratory, and locomotor systems and their sizes measured. Examinations were performed at three timepoints: (A) when unfit, (B) following 12 weeks of conventional exercise training and (C) following 10-12 weeks continued training at race fitness. In addition, horses at yard 1 performed IMT, between timepoint B and C, and were randomly assigned into high-load (treatment) or low-load (control) group. Repeated measures models were constructed to compare the change in muscle measurements over time, and to investigate the effects of yard, previous airway surgery and IMT on the change in ultrasonographic size measurements obtained. Results: Upper airway muscle size increased in response to conventional race training between timepoints A-C, and B-C. Diaphragm size increased in response to conventional exercise training between timepoints A and B. The diaphragm size of horses that undertook high-load IMT was either maintained or increased, whereas diaphragm size decreased in horses that undertook low-load IMT or no IMT between timepoints B and C. A significant interaction between gluteal muscle size and airway surgery status was observed, with greater gluteal muscle thicknesses measured in horses that had not previously undergone airway surgery (left gluteal 3.9%, p < 0.001; right 4.5%, p = 0.04). Main limitations: Low number of horses underwent IMT. Conclusions: Respiratory and locomotor muscles increase in size in response to conventional exercise training, with a further change in diaphragm size in response to inspiratory muscle training.

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Objective: To determine the proportion of horses treated by laryngoplasty prosthesis removal (LPR) for complications associated with prosthetic laryngoplasty (LP), the reason for LPR, and the outcome of horses undergoing LPR to manage iatrogenic coughing/dysphagia. Study design: Retrospective study. Sample population: Client-owned horses treated with LP (n = 1202) and LPR (n = 58). Methods: Clinical case records were reviewed to determine the number of horses treated with LP and LPR by the same surgeon. Historical, clinical, endoscopic, and surgical data were extracted for those horses undergoing LPR. Long-term outcome was assessed by questionnaire. Results: The proportion of horses treated with LP and subsequently treated with LPR by the same surgeon was 3.5% (42/1202). Coughing/dysphagia was the reason for LPR in 90% (52/58) of horses. Sufficient follow-up to determine outcome in horses undergoing LPR for coughing/dysphagia was available in 32 horses. Arytenoid abduction grade at the time of LPR did not influence clinical response (P = .416). Presenting clinical signs resolved after LPR in 21 of 32 (66%) horses, and 24 of 32 (75%) horses returned to exercise. Conclusion: Coughing/dysphagia was the most common reason for LPR. Clinical signs improved in most horses after LPR. Clinical significance: Laryngoplasty prosthesis removal can be a useful treatment option for horses affected with unmanageable coughing/dysphagia caused by LP.

Introduction During canter and gallop most horses maintain a locomotor‐respiratory coupling (LRC) ratio of one breath every stride. Occasional big respiratory cycles (BRC) are described when a single breath is taken over two strides. This is considered a transient but normal feature of ventilation. However, a change to a more persistent 2:1 LRC ratio is considered to be ‘abnormal’. It has been suggested that upper respiratory tract (URT) disorders could result in a horse adopting an abnormal breathing pattern, although current information is limited. Methods Simultaneous audio and URT endoscopy recordings from 365 horses referred for treadmill evaluation were analysed. Breathing pattern at canter and gallop was categorised at each one minute speed step: Normal: 1:1 with <2 BRC Normal: 1:1 with 2 BRC Abnormal: breathing pattern disrupted by repetitive and frequent BRC's Abnormal: alternating between periods of 2:1 and 1:1 Abnormal: 2:1 throughout Data analysis was performed using PASW 18.0. A chi‐square test was used to identify associations between breathing pattern and presence of URT obstructions. Results During the entire exercise test 30% of horses had an abnormal breathing pattern at canter or gallop, of which 23% had a 2:1 breathing pattern. The prevalence of abnormal breathing patterns was higher at low canter speeds than during strenuous exercise. There was a significant association between breathing pattern during strenuous exercise and the presence of an URT obstruction (P = 0.008). Conclusions Loss of a 1:1 LRC ratio during canter and gallop is more common than previously realised and may be associated with dynamic URT obstructions. Ethical Animal Research Retrospective analysis of case records. Sources of funding: none declared. Competing interests: none.