Age-related changes in metabolic properties of equine skeletal muscle associated with muscle plasticity.
Authors: Kim Jeong-su, Hinchcliff Kenneth W, Yamaguchi Mamoru, Beard Laurie A, Markert Chad D, Devor Steven T
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary Ageing horses undergo measurable shifts in skeletal muscle composition that favour glycolytic over oxidative metabolism, according to research examining muscle biopsies from 18 horses aged 2–30 years. Investigators analysed myosin heavy chain (MHC) isoform expression and key enzymatic markers of metabolic capacity in the semitendinosus muscle, finding that type-I MHC proportions declined significantly with age whilst type-IIA and type-IIX isoforms remained relatively stable. Citrate synthase activity—a marker of aerobic capacity—decreased substantially with advancing years, whereas lactate dehydrogenase activity increased, indicating a progressive metabolic shift towards less efficient energy production and greater reliance on anaerobic pathways. This age-related transition mirrors patterns observed in ageing humans and suggests that older horses may experience reduced stamina and faster fatigue accumulation during endurance work, with implications for training intensity, competition expectations, and recovery protocols across disciplines. For practitioners managing mature and senior horses, these findings underscore the importance of tailored conditioning programmes that account for diminished oxidative capacity and the need for extended recovery periods, whilst also highlighting potential value in nutritional and training strategies that might help preserve aerobic muscle function.
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Practical Takeaways
- •Older horses (20+ years) experience declining aerobic muscle capacity and shift toward glycolytic metabolism, which may affect endurance performance and recovery from exercise
- •Training and conditioning programs should account for age-related changes in muscle metabolic properties; older horses may require modified exercise intensity and duration
- •Nutritional support targeting oxidative metabolism and muscle preservation may be increasingly important in geriatric horses to maintain functional capacity
Key Findings
- •Type-I myosin heavy chain isoforms decreased significantly with advancing age in horses aged 2-30 years
- •Citrate synthase activity (oxidative capacity marker) decreased with age while lactate dehydrogenase activity increased, indicating a shift toward glycolytic metabolism
- •Type-IIA and type-IIX MHC proportions showed no significant correlation with age, but overall pattern suggests transition toward more glycolytic muscle phenotype with aging
- •Age-related metabolic changes in equine muscle parallel those documented in human aging and reflect muscle plasticity in response to aging