Comparison of a standalone consumer grade smartphone with a specialist inertial measurement unit for quantification of movement symmetry in the trotting horse.

This study compares the use of consumer-grade smartphones to a custom-built inertial measurement unit (IMU) in measuring movement symmetry and range of motion in trotting horses. The study concluded that smartphones provided valuable data and exhibited similar results to the custom-built IMU, although they were more sensitive to the alignment of the sensors.

Objectives and Methodology

• The main objective of this study was to compare a specialist IMU system with a consumer-grade smartphone for quantification of movement symmetry and range of motion of pelvic movement in trotting horses. This was achieved by establishing the limits of agreement between the two systems.
• The study involved 20 horses equipped with both the specialist IMU and a consumer-grade smartphone (Apple iPhone6) attached in the midline over the sacrum. The horses were made to trot in-hand and on ropes in a soft-arena exercise condition.
• The study aimed to determine the effect of the medial-lateral positioning of the sensors on the athletic performance of horses, and for this purpose, data collection was repeated in 6 horses.

Results

• The data from 17 horses produced limits of agreement values for three critical metrics – MinDiff (difference between left and right hind mid-stance), MaxDiff (difference between left and right hind propulsion), and ROM across horses and exercises.
• The study found that the limits of agreement were narrower for straight-line exercise and that the negative bias reduced significantly when the smartphone was moved to the right of the midline.

Conclusions

• The study concluded that the consumer-grade smartphone provided useful gait data in quantifying movement symmetry and range of motion in trotting horses. The limits of agreement, particularly for in-hand exercise and mediolateral positioning, were similar to published asymmetry thresholds.
• The study pointed out that due to the sensitivity to medial-lateral positioning, precision needs to be exercised while placing the IMU over the midline of the horse.