• horse;
  • respiratory rate;
  • airflow;
  • accelerometer;
  • stride frequency;
  • ventilation-locomotor coupling


Two durable, inexpensive and non-invasive sensors for detecting airflow direction and footfall in exercising horses were developed. The airflow sensor measured temperature of the gas at the nostrils using a copper/constantan thermocouple. The response time of the thermocouple unit, the time for the signal to change from 10% to 90% of its final value, was 260 ms in forced air. The tip of the thermocouple was held just inside the false nostril by a small wire frame. The sensor did not interfere with placement of face masks and the addition of the mounting frame slightly decreased response time of the sensor to 208 ms. The footfall sensor was a simple accelerometer, using the contact arm of an electrical relay as a spring/mass unit. Bending of the metal strip was recorded using a strain gauge. The response of the accelerometer was highly under-damped when attached to a rigid surface (resonant frequency 117 Hz, quality factor (Q) 171) but attaching it to the hoof with adhesive foam increased the damping considerably. Both sensors were used in a study of Standardbred horses exercising maximally on a treadmill. Air temperature at the nostril changed from ambient on inspiration to about 35°C on expiration and each leading hoof strike produced a burst of signal from the accelerometer. The sensors may be useful in studies that examine respiration, stride rate and respiratory-locomotor coupling in exercising horses.