Skeletal muscle adaptations and muscle genomics of performance horses.
Authors: Rivero José-Luis L, Hill Emmeline W
Journal: Veterinary journal (London, England : 1997)
Summary
Equine skeletal muscle possesses distinctive structural and metabolic adaptations—elevated mitochondrial volume, substantial intramuscular glycogen stores, high lactate buffering capacity, and favourable fibre-type composition with rapid shortening velocities—that collectively underpin the species' exceptional aerobic capacity and locomotor efficiency, many of which respond favourably to training stimulus. Rivero and Hill synthesise current knowledge of equine muscle physiology alongside genomic findings since the 2009 publication of the equine genome sequence, identifying candidate genes involved in muscle growth, contraction mechanics and metabolic pathways as functionally relevant markers for early performance prediction in elite horses. The authors emphasise that whilst these adaptive capacities can be improved through appropriate conditioning, performance-limiting conditions remain common in the horse population and are frequently heritable, suggesting that genetic predisposition interacts significantly with training response and injury susceptibility. Understanding the molecular basis of muscle adaptation—particularly how exercise regulates structural and metabolic gene expression—enables more targeted evaluation of individual athletic potential and informs evidence-based training and conditioning protocols. For practitioners, this framework supports the use of genetic screening as a complementary tool in early career assessment, whilst highlighting that genomic potential remains contingent on appropriate training stimulus, nutrition and injury prevention strategies throughout an athlete's competing life.
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Practical Takeaways
- •Understanding that horses have naturally superior muscle efficiency and aerobic capacity can guide realistic training expectations and help identify when poor performance may indicate pathology rather than conditioning limitations
- •Genetic testing for performance-relevant genes may help identify elite athletic potential early, but must be combined with proper training, nutrition, and management since many performance-limiting conditions are genetically influenced
- •Training effectively targets trainable adaptations including muscle mass, mitochondrial development, and metabolic substrate stores—consistent conditioning programs should focus on progressive aerobic work and appropriate intensity intervals
Key Findings
- •Equine skeletal muscles have intrinsic shortening velocities greater than predicted for body size due to specific fiber-type composition and muscle-tendon architectural design
- •High mitochondrial volume in equine muscle permits greater whole animal aerobic capacity compared to similarly-sized animals
- •The equine genome sequence (published 2009) has identified multiple genes associated with elite physical performance in muscle growth, contraction, and metabolic pathways
- •Many muscle adaptations including increased mass, aerobic capacity, and energy substrate stores are trainable and can improve with conditioning