What does a hoarse or 'horse‑voice' after exercise indicate in a normally trained adult horse, and when is veterinary evaluation required?

Hoarse Voice After Exercise in Horses

A hoarse voice or abnormal respiratory noise after exercise in horses most commonly indicates dynamic upper airway obstruction, particularly laryngeal dysfunction or pharyngeal instability, and veterinary evaluation with exercising endoscopy is required when the noise is associated with performance decline or occurs consistently during work. 1, 2, 3

Understanding Exercise-Induced Respiratory Noise

The key distinction is that many upper airway abnormalities in horses are dynamic—they only manifest during exercise and cannot be detected at rest. 1, 2

• Laryngeal dysfunction (including left-sided laryngeal paralysis) was evident only after exercise in 64% of affected horses, with normal arytenoid movement at rest. 1
• Resting endoscopy alone provided a complete and correct diagnosis in only 25% of horses with exercise-related respiratory noise. 2
• In horses referred for abnormal respiratory noise, dynamic upper airway obstruction was diagnosed in 91% of cases, but required exercising evaluation for identification in 89% of these. 2, 3

Common Causes of Exercise-Related Hoarseness

Laryngeal disorders are the most frequent cause:

• Arytenoid cartilage collapse (grades 3-5 laryngeal dysfunction) produces characteristic inspiratory stridor with a broad-band high frequency spectral component (1.1-2.7 kHz). 2, 4
• Vocal fold collapse often accompanies arytenoid dysfunction. 2, 3

Pharyngeal instability is increasingly recognized, particularly in sport horses:

• Dorsal displacement of the soft palate produces a narrow low-frequency (20-80 Hz) peak during expiration. 2, 4
• Pharyngeal collapse and palatopharyngeal arch deviation occur during exercise. 2, 3

Complex abnormalities are common:

• 62% of competition draught horses had multiple concurrent upper airway abnormalities. 3
• Head flexion and rider intervention can exacerbate upper airway instability and promote complex obstructions. 5

When Veterinary Evaluation Is Required

Immediate evaluation is warranted when:

• Abnormal respiratory noise is consistently present during exercise and associated with performance decline. 2, 3
• The horse demonstrates exercise intolerance or stops/slows during work. 2, 3
• The noise is progressive or worsening over time. 3

Important clinical context:

• An abnormal inspiratory noise was detectable in only 79% of horses with confirmed laryngeal hemiplegia, meaning absence of noise does not exclude pathology. 1
• Conversely, 9 horses produced abnormal inspiratory noise but did not have laryngeal hemiplegia, indicating noise alone is not diagnostic. 1
• Asynchronous arytenoid movement at rest was observed in 56% of horses but 91% of these were normal after exercise, demonstrating that resting findings can be misleading. 1

Diagnostic Approach

Exercising videoendoscopy is the gold standard:

• Overground endoscopy during ridden exercise is preferred for sport horses, as it allows evaluation under conditions that replicate the show ring environment where abnormalities are most prominent. 3, 5
• High-speed treadmill endoscopy is appropriate when overground evaluation is not practical. 2, 4
• Simultaneous recording of audio signal, airflow, and videoendoscopic images allows spectral analysis to characterize specific obstructions. 4

Resting endoscopy has limited value:

• Only 53% of horses with exercise-related noise had detectable abnormalities at rest, and the resting diagnosis matched the exercising diagnosis in only 48% of these cases. 2
• However, resting endoscopy should still be performed as a baseline before exercising evaluation. 2, 3

Critical Pitfalls to Avoid

• Do not rely on resting endoscopy alone to exclude upper airway pathology in horses with exercise-related respiratory noise, as dynamic obstructions are frequently missed. 1, 2
• Do not assume synchronous arytenoid movement at rest indicates normal laryngeal function, as 43% of horses with laryngeal hemiplegia had synchronous movement when at rest. 1
• Do not dismiss horses without audible noise, as 21% of horses with confirmed laryngeal dysfunction did not produce an abnormal inspiratory noise during exercise. 1
• Consider the effect of riding technique and head position, as poll flexion and rider intervention significantly exacerbate upper airway instability in sport horses. 5

Additional Considerations

Airway inflammation influences upper airway stability:

• Both lower airway inflammation and pharyngeal lymphoid hyperplasia are associated with pharyngeal instability during exercise. 5
• Addressing underlying inflammatory conditions may improve upper airway function. 5

Discipline-specific patterns exist:

• Dressage horses and showjumpers demonstrate different patterns of upper airway obstruction, likely related to differences in head carriage and work demands. 5