Exercise-related changes in the anabolic index (testosterone to cortisol ratio) and serum amyloid A concentration in endurance and racehorses at different fitness levels.
Authors: Grzędzicka Jowita, Dąbrowska Izabela, Malin Katarzyna, Witkowska-Piłaszewicz Olga
Journal: Frontiers in veterinary science
Summary
# Editorial Summary This 2023 research investigated how testosterone, cortisol, and their ratio (T/C anabolic index)—established stress markers in human sports medicine—respond to exercise in equine athletes, alongside serum amyloid A as an acute phase inflammation indicator. Researchers compared 12 endurance and 32 racehorses across different fitness levels, collecting blood samples before and immediately after a single training session to measure hormonal and inflammatory changes. The results revealed markedly different endocrine responses between disciplines: testosterone increased 2.5-fold in experienced racehorses post-exercise but decreased in endurance horses regardless of fitness level, whilst the T/C ratio fell in inexperienced horses from both groups but rose significantly in experienced racehorses (p<0.01). The anabolic index emerged as a potentially reliable marker of fitness adaptation, particularly in racing populations, suggesting that hormone profiling could help practitioners distinguish between appropriate training adaptation and problematic overreaching before clinical signs develop. For farriers, veterinarians, and coaching teams, these findings offer a physiologically grounded framework for monitoring training tolerance and recovery status, though further validation in larger populations and across repeated training cycles would strengthen clinical application.
Read the full abstract on PubMed
Practical Takeaways
- •Monitor T/C ratio alongside training progression to identify whether horses are adapting appropriately or moving toward overtraining; a falling ratio in experienced horses may indicate inadequate recovery
- •Expect different hormonal responses to the same training stimulus based on sport type (racing vs. endurance) and fitness level—inexperienced horses show catabolic dominance while fit racehorses show anabolic response
- •Consider combining T/C ratio with SAA measurement as part of fitness assessment and overtraining detection protocols, particularly when training intensity increases
Key Findings
- •Testosterone increased 2.5-fold after race training in experienced racehorses but decreased in endurance horses regardless of fitness level (p<0.05)
- •Testosterone-to-cortisol (T/C) ratio decreased in inexperienced horses of both disciplines after exercise but increased in experienced racehorses (p<0.01)
- •T/C ratio showed potential as a biomarker for fitness status discrimination, particularly in racing horses
- •Serum amyloid A (SAA) responses differed between endurance and racehorses, supporting use of multiple acute phase markers for health monitoring