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The use of electromyography interference pattern analysis to determine muscle force of the deep digital flexor muscle in healthy and laminitic horses.

  • Hardeman, L C1
  • van der Meij, B R1
  • Back, W1, 2
  • van der Kolk, J H3
  • Wijnberg, I D1
  • 1 a Department of Equine Sciences , Faculty of Veterinary Medicine, Utrecht University , Yalelaan 114, 3584 CM Utrecht , The Netherlands. , (Netherlands)
  • 2 b Department of Surgery and Anaesthesiology , Faculty of Veterinary Medicine, Ghent University , Salisburylaan 133, 9820 Merelbeke , Belgium. , (Belgium)
  • 3 c Department of Clinical Veterinary Medicine , Swiss Institute for Equine Medicine, Vetsuisse Faculty, University of Bern and Agroscope , Bern , Switzerland. , (Switzerland)
Published Article
The veterinary quarterly
Publication Date
Jan 01, 2016
DOI: 10.1080/01652176.2015.1106116
PMID: 26610153


In equine laminitis, the deep digital flexor muscle (DDFM) appears to have increased muscle force, but evidence-based confirmation is lacking. The purpose of this study was to test if the DDFM of laminitic equines has an increased muscle force detectable by needle electromyography interference pattern analysis (IPA). The control group included six Royal Dutch Sport horses, three Shetland ponies and one Welsh pony [10 healthy, sound adults weighing 411 ± 217 kg (mean ± SD) and aged 10 ± 5 years]. The laminitic group included three Royal Dutch Sport horses, one Friesian, one Haflinger, one Icelandic horse, one Welsh pony, one miniature Appaloosa and six Shetland ponies (14 adults, weight 310 ± 178 kg, aged 13 ± 6 years) with acute/chronic laminitis. The electromyography IPA measurements included firing rate, turns/second (T), amplitude/turn (M) and M/T ratio. Statistical analysis used a general linear model with outcomes transformed to geometric means. The firing rate of the total laminitic group was higher than the total control group. This difference was smaller for the ponies compared to the horses; in the horses, the geometric mean difference of the laminitic group was 1.73 [geometric 95% confidence interval (CI) 1.29-2.32], and in the ponies this value was 1.09 (geometric 95% CI 0.82-1.45). In human medicine, an increased firing rate is characteristic of increased muscle force. Thus, the increased firing rate of the DDFM in the context of laminitis suggests an elevated muscle force. However, this seems to be only a partial effect as in this study, the unchanged turns/second and amplitude/turn failed to prove the recruitment of larger motor units with larger amplitude motor unit potentials in laminitic equids.

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