VET NEWS
By John Konkhe
Reprinted courtesy Greyhound Star
Some people are fascinated by the horsepower, cornering dynamics and top speed of a fast car, the climb speed and maneuverability of a fighter plane, or endless records broken at last year’s Olympic Games.
But is there a limit to athletic performance?
Having been a greyhound vet and admirer for 20 or more years, I am awed by the specialised running machine and athlete we call a racing greyhound. So, in this article, I thought I would gather a few statistics on the greyhound as an athletic and physiological marvel for those who are equally fascinated by this lovable, elite breed of dog.
Over the past 20 years, starting with Dr Ross Staaden in Perth who ran greyhounds on a high speed treadmill to measure their energy and oxygen use, heart rates and other physiological parameters, until today with Dr Robert Gillette of Alabama University in the USA, measuring stride lengths, galloping patterns and weight forces, we have gained an insight into how a
greyhound functions as a finely tuned and well adapted canine athlete.
The statistics below illustrate the adaptation of the greyhound to the high speed chase.
The figures are based on the average 30kg greyhound, at the peak of fitness and obviously injury free.
Energy Use
In the first 7.5 seconds of a 30-second race, a greyhound metabolises high energy creatine and glycogen stores in its muscles without the need for oxygen.
It uses the creatine energy base during the first 3.5 seconds acceleration phase to the first bend of a standard circle track.
In fact, a greyhound expends half of its total energy used in a race for this acceleration stage.
However, surprisingly greyhounds and even racing sprint horses performing for less than one minute expend in a race only about 6% of their total energy intake required each day to meet the exercise needs in training.
Acceleration Speed
At maximum acceleration, a greyhound reaches a full speed of 70 kmh within 30 metres or six strides from the boxes, traveling at almost 20 metres per second for the first 250 metres of a race.
The only other animal that can accelerate faster over a short distance is a cheetah that can reach speeds of 109 kmh over 3-4 strides from a standing start.
The greyhound can maintain an average speed of 16.45 metres per second over a 500 metre race, decreasing to around 14.6 metres per second as it crosses the finish line.
A thoroughbred racehorse can achieve a maximum speed of around 49 kmh or 13.6 metres per second.
An elite human sprinter can reach 40kmh in a 10 second sprint race at an all out speed of 11 metres per second.
The muscles of a greyhound generate 75-80% of their power from anaerobic metabolic pathways during a 30 second race.
In distance races, or coursing trials in excess of 40 seconds duration, 80% of the total energy in the final half of the race or gallop is metabolised using oxygen.
The Heart
In a racing greyhound, the heart output increases from about 200mL per kg body weight per minute at rest to over 1000mL per kg at the full gallop. A greyhound circulates up to 15 litres of blood around its body, or half its own body weight in a 30 second-race.
A racing greyhound circulates its entire blood volume between 4-5 times during a 30 second gallop.
These figures equate to a greyhound pumping its entire blood volume of around 3.4 litres up to 4-5 times around its body during a 30 second gallop. A greyhound’s heart weight ranges from 1.18 to 1.73% of body weight, or 270 grams to 519 grams for a 30kg greyhound, which is higher than an elite racehorse at 1.0-1.3% of its body weight.
Other breeds of dogs have a heart weight equal to 0.77% of their body weight, compared to 0.5% for humans.
An average 70kg human athlete has a heart size similar to a 30kg greyhound, but the greyhound’s heart delivers blood at almost twice the rate, beating at 310-340 beats/minute at the gallop, compared to humans at 170.210 beats/minute.
Blood Volume
A fit greyhound has the highest blood volume of any athlete, relative to its body size, with blood contributing 11.4%, compared to 10.5% for a racehorse, 9.5% for a human sprint athlete and 7.2% for a normal pet dog.
A greyhound has around 35 x 1012 red blood cells in its body, producing around 5 million replacement red cells per second in its bone marrow and spleen.
A fit greyhound has about 3 litres of blood consisting of around 2 litres red cells, or about 6.6% of its body weight or a PCV of 60% of blood volume. A racehorse has a blood volume of around 55 litres, but a PCV of around 40% when fit, or 4.4% of its body weight.
Track Contact
At a gallop, a racing greyhound is only touching the track surface for 25% of its stride distance, and during the remainder of the stride, it is suspended above the ground until the next limb hits the ground.
Up the straight, a greyhound carries 2.26 times its body weight on the weight bearing front limb at each stride, increasing to 5 times (or roughly 150kg) in downward weight force on its left inside front limb when leaning over around a sharp bend on the track.
A greyhound has a stride length of around 5 metres making 4 strides per second as it accelerates from the traps, decreasing to 3.25 strides per second up the home straight, with each limb touching the ground for about 0.11 seconds.
The forelimbs have a flight distance (off the ground) of 1.23 metres, and the rear legs 2.45 metres or double the distance.
Wrist/Bone Joints
The wrist joint bones on the front limbs sustain pressure of 500psi or 20,000 newtons per square cm when cornering at the gallop.
The wrist and lower limb structures withstand up to 150kg of downward pressure when galloping around a corner, which is created by the centrifugal force in proportion to the speed of the greyhound and the radius of the track circle.
This sideways force is imposed on the greyhound’s front limb on the second stride into the corner and if the track surface is unstable or shears, the outward flinging force causes increased sideways pressure on the joint, which can result in injury to the wrist.
Respiratory & Blood Pressure Dynamics
A greyhound draws in 60-90 litres of air in 50-90 breaths in a 30-second gallop, extracting 1500 mLs of oxygen from the air to metabolise the energy in its muscles.
During the gallop, the blood pressure in the lung arteries increases from 7 mm mercury pressure units at rest, to 40 units at the gallop, similar to the pressure peak in a human athlete, but only one third of the maximum pressure in a racehorse’s lung artery, which reaches 120 mm mercury pressure, or roughly 2.1 psi of pressure.
A greyhound produces around 100Kcals or 100,000 watts of waste heat energy during a 30 second race, sufficient to bring 600mL of tap water to the boil in around 2 minutes.
After a race, the gut function is restored over a 30 minute period to digest food, but the immune system is depressed for 30-120 minutes after a hard gallop.
Loading stress placed on the limb bones is repaired over a 7-10 day period after a race.
What a dog !!!!!!!!
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