37 Short-term effects of a single pulsed electromagnetic field therapy session on lameness, gait quality, and stress in moderately exercising horses

Abstract

Pulsed electromagnetic field (PEMF) therapy is applied to equids for a variety of preexisting conditions; however, research with its usage to enhance performance in the horse is limited. To test the hypothesis that a single PEMF therapy session improved stress, performance, and lameness parameters, 14 horses (11 ± 4.1 years) underwent a single 30-min whole body PEMF therapy session at 5 Hz and a single sham therapy session where horses were randomly assigned to a treatment order. A 2-week washout period was given between treatments. Resting heart rate, salivary cortisol, stride length, quality of movement, and lameness evaluation (fore limb vector sum, hip height difference, forehand stride rate, hind stride rate) on crushed gravel and loose sand surfaces were evaluated at 8 different time points: immediately before and after treatment, and at 2, 4, 8, 24, 48, and 72 h post treatment. Videos were assessed for stride length and were assessed by 3 blinded, carded judges for quality of movement. Mixed model analysis for crossover design with repeated measures was used to determine the effect of treatment, time, period, and all interactions. At 7.5 h post treatment, horses were subjected to a 30 min lunge to simulate a moderate exercise session. Post hoc multiple comparisons were performed with Tukey's adjustment (mean ± SE).Heart rate was lowered immediately following PEMF treatment (29 ± 1 BPM, P < 0.0001) when compared with all other sampling time points. For quality of movement (1 = poor, 10 = excellent), judges found walk quality to decrease immediately following PEMF treatment (5.68 ± 0.18) and at 4 h post (5.59 ± 0.16) when compared with 2 h sham (5.98 ± 0.1, P = 0.006) while trot quality did not differ. Walk stride length was affected by time but not treatment, increasing at 8 h (2.49 ± 0.03 m) post treatment when compared with pre-treatment sampling (2.43 ± 0.04 m, P = 0.03) but not the trot. Salivary cortisol concentration was unaffected by treatment but did have an effect of time (P < 0.0001) varying depending on the time of day of the sample. Forehand and hind stride rate were affected by surface (P = 0.004, P = 0.004) with sand having a slower rate than gravel and time (P < 0.0001, P < 0.0001) slowing stride rate as the day progressed. No differences were observed with fore limb vector sum and hip height difference. This study shows PEMF therapy has a relaxing effect evidenced by lowered heart rate immediately following treatment; however, more work is needed to determine the full effects of PEMF in performance horses.