The Physiology Of The Racing Greyhound

Few people really appreciate what an amazing athlete the racing greyhound is. I certainly didn’t until, many years ago, I read an article in New Scientist on the physiology of the greyhound. Some of the physiological statistics that define the racing greyhound are truly incredible. For example, when a greyhound breaks from the traps it reaches speeds of up to 70 kilometres per hour within six strides. The only animal that is faster over distances up to two hundred metres is the cheetah. As it accelerates towards the first bend the greyhound is travelling at close to 20 metres per second. Over the standard 500 metre race distance it will race at 16–17 metres per second, slowing slightly to around 15 metres per second as it approaches the finish line. Around half the total energy that a greyhound uses in a race is expended as it accelerates towards the first bend.

For the first few seconds of a 30 second race the greyhound relies for its energy not on oxygen, but on adenosine triphosphate (ATP, a coenzyme used as an energy carrier in the cells), and creatine phosphate. Then the anaerobic system converts glycogen, stored in the muscles, to glucose in order to create energy. Thirdly, the aerobic system uses oxygen to produce ATP energy. A greyhound inhales up to 90 litres of air during a 30 second race, from which it takes 1500 millilitres of oxygen in order to metabolise the energy in its muscles. It uses twice as much oxygen during intense exercise as a human does. This is because a greyhound’s blood can carry more oxygen than that of a human, or even that of a racehorse.

A greyhound’s blood volume is around 3.4 litres, and during a 500 metre race it will circulate that volume up to five times. A greyhound has the highest blood volume of any athlete relative to its body weight.

The greyhound’s heart is uniquely adapted for the job it is required to do. Whereas a human heart weighs 0.5% of body weight, and a racehorse’s weighs between 1% and 1.3%, a greyhound’s heart comprises 1.5% of its body weight. During a race its heart will beat 300 times a minute.

A greyhound’s muscles are specialized for power and speed. Almost 100% of the muscle fibres in its legs are ‘fast twitch’ fibres, which produce energy anaerobically. So the dog can reach top speed before its circulatory system properly kicks in. Sixty per cent of a greyhound’s body mass is muscle, compared with forty per cent of most other species. A higher proportion of that muscle is around its thighs and quarters than in other breeds, allowing it to generate great thrust in its stride.

Sources

'Science goes to the dogs' (Gail Vines): New Scientist 29th October 1987

'Greyhound athlete'; article on www.greyhoundracingtoday.com

'Clinical aspects of the greyhound': Robert. L. Gillette DVM; article on www.gra-america.org

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