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Maximal exercise transiently disrupts hormonal secretory patterns in Standardbred geldings

1999; Wiley; Volume: 31; Issue: S30 Linguagem: Inglês

10.1111/j.2042-3306.1999.tb05288.x

2042-3306

Lorraine C. Golland, D. L. Evans, GM Stone, Catherine McGowan, David Hodgson, R. J. ROSE,

Veterinary Equine Medical Research

Summary Basal concentrations of cortisol (CORT), beta‐endorphin (ßEP), growth hormone (GH) and testosterone (T) and their disruption during 32 h of recovery after treadmill exercise were investigated in 4 geldings. Blood samples were collected from resting horses every 20 min between 0600–1000 and 1500–1900 h, and hourly between 1000–1500 h on 3 consecutive days. Treadmill exercise tests comprising 2 min intervals at 30, 50, and 70% V̇O 2max then to fatigue at 100% V̇O 2max were conducted between 1020–1130 h on Day 2. Blood was collected before, during and 15, 30, 60 and 90 min after exercise. Mean (C av ), peak (C max ) and total (i.e. integrated) (C tot ) concentrations were calculated for CORT, βEP and GH during the 20 min sampling sessions, and for CORT, βEP, GH and T between 1000–1300 h on Days 1–3 (incorporating the samples during exercise on Day 2) and 1300–1900 h on Days 1–3. C av , C max and C tot for CORT, βEP, GH and T were greater during exercise and recovery than in the same period on Day 1. C av and C tot values for plasma T during the 1300–1900 h period were significantly elevated on Day 2 and compared to Day 1 (P<.05), but there were no differences between Days 1 and 3 values for these variables. We concluded that plasma T concentration increases in response to maximal exercise in geldings, as does plasma CORT, βEP and GH. Furthermore, maximal exercise disrupts basal plasma concentrations of CORT, βEP and GH for up to 24 h and T for 26–32 h post exercise in geldings, therefore reflecting the minimum recovery periods required before evaluating normal, resting levels of these hormones in horses undergoing training.