Exercise began at approximately 1200 h. A target heart
rate (HR) of 150 to 160 beats per minute (bpm) was
achieved and maintained during phase II. Subcutaneous
scrotal temperatures (SQST), intramuscular neck temperatures
(IMNT), and rectal temperatures (RCT) were digitally
recorded before exercise, immediately after phase II,
immediately after phase III, and at 60 and 120 min postexercise.
Ambient temperatures were recorded hourly via
iButton temperature loggers (Maxim DS1923 iButton,
Maxim Integrated Products, Inc., Sunnyvale, CA) located
in the shaded stall area (where pre- and post-exercise temperatures
were measured) and in the sun near the motorized
equine exerciser (where phase II and III temperatures
were measured). Hourly humidity (HUM) percentages
were obtained later from NOAA (2010). Non-exercised
stallions were tied in the sun while EX stallions were being
exercised in an attempt to subject both groups to consistent
ambient temperatures.