Do Muscle Activities of M. Splenius and M. Brachiocephalicus Decrease Because of Exercise-Induced Fatigue in Thoroughbred Horses?
Authors: Takahashi Yuji, Mukai Kazutaka, Ohmura Hajime, Takahashi Toshiyuki
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Fatigue-Induced Changes in Head and Neck Muscle Activity during Exercise Understanding how fatigue affects muscle performance beyond the obvious hindlimb musculature is crucial for trainers and veterinarians managing exercise tolerance and recovery in racehorses. Takahashi and colleagues used surface electromyography to measure activity patterns in the splenius and brachiocephalicus muscles (head and neck region) alongside shoulder muscles in nine Thoroughbreds during high-intensity treadmill galloping at 3% incline until fatigue, with comparison trotting bouts before and after. Both the splenius and brachiocephalicus showed significant reductions in integrated electromyographic activity following fatigue (P < 0.05) during galloping and in subsequent trotting, whilst shoulder muscles (infraspinatus and deltoid) remained unaffected; notably, stride frequency declined substantially during the fatigued gallop (P < 0.001) but not during trotting. The findings suggest these cervical muscles are functionally linked to stride frequency and locomotor speed, implying that fatigue-related decrements in head and neck stability may compromise proprioceptive feedback and postural control—factors particularly relevant for injury prevention and performance optimisation in racing and athletic contexts. For practitioners, monitoring changes in neck muscle function during recovery protocols could provide practical biomarkers of residual fatigue that merit further investigation.
Read the full abstract on PubMed
Practical Takeaways
- •Surface electromyography of neck muscles (splenius and brachiocephalicus) may serve as practical indicators of fatigue during exercise in Thoroughbred horses
- •Fatigue-induced changes in head and neck muscle activity are associated with decreased stride frequency, suggesting these muscles play a key role in maintaining locomotor mechanics during tiring work
- •Shoulder muscles (infraspinatus and deltoid) do not show consistent fatigue responses, indicating regional variation in muscle fatigue patterns that should be considered in conditioning and rehabilitation protocols
Key Findings
- •Integrated electromyographic values of splenius and brachiocephalicus muscles significantly decreased with fatigue during gallop exercise in both lead and trailing limbs (P < 0.05)
- •Stride frequency significantly decreased at the end of gallop exercise (P < 0.001) but did not change during trotting
- •Infraspinatus and deltoid muscle activities showed no significant changes with fatigue at either gallop or trot
- •Median frequency of muscle discharge showed no changes in any muscles with fatigue