The horse has a phenomenal capacity for strength and endurance
One of the major components in athletic performance is the respiratory system
Optimising oxygen intake and removal of carbon dioxide is crucial to basic function as well as performance and recovery
Here are some interesting facts about the equine respiratory system during exercise:
Horses have a resting respiratory rate of ~8-12 breaths per min (bpm)
During exercise this can reach a max of ~180bpm. For comparison, humans have a resting rate of ~12-18bpm with a max of ~40bpm
Conditioning will have some improvement to the efficacy of the respiratory system. Improved blood supply to alveoli, increased surface area for gaseous exchange and improved fitness of the muscles responsible for breathing all contribute to increased exercise tolerance.
The oxygen uptake of a horse under exercise can increase by ~40 x their oxygen uptake at rest. Elite human male athletes can increase their oxygen uptake by ~8 x resting rate
VO2max - the optimum rate the heart, lungs and muscle can effectively use oxygen during exercise (or max aerobic capacity) is used as an indicator of endurance and cardio-respiratory fitness
A thoroughbred horse has a VO2max of around 200ml per kg of body weight per min of exercise. Elite human male endurance athletes have a VO2max of ~85ml per kg per min
The horses’ capacity for oxygen consumption exceeds the hearts capacity for delivery. Skeletal muscle has a huge oxygen demand which outstrips cardiovascular physiology - VO2max can increase until heart rate peaks
The phenomenal success of the race horse Secretariat who famously won the Belmont Stakes by 31 lengths was partly attributed to his enlarged heart. An autopsy revealed his heart to be approx 21lbs. Compare this to the average horse heart size ~9lbs and you can start to appreciate how much of a physiological advantage he had before taking conformation and training into account!