The Ultimate Endurance Machine

The Ultimate Endurance Machine

10 July 2008, 4:00PM
Anna Rolleston

The Alaskin husky is the only mammal in the world that has greater endurance capacity than humans. Our biomechanical and musculoskeletal design which promotes upright movement (walking and running) due to a leg length to body weight ratio that is the greatest among all mammals and our ability to exercise in high heat because we can sweat means that we really are built to be endurance athletes.

The Antarctic explorers of the early 1900’s – Robert Scott and Ernest Shackleton - set the limits of human endurance capacity with their expeditions across the ice continent. Early studies of energy expenditure by this group indicate that they expended close to 1million kcal over 160 consecutive days of sled-hauling through snow and ice. Consider this in comparison to modern-day endurance events where energy expenditure is significantly lower e.g. Tour de France (168,000kcal) or running across the America (340,000kcal). Considering our health status as humans compared to the early 1900’s and the abundance of food supplies it is interesting that human endurance limits may have been set in Antarctica early last century and that we possibly have not come near to the same type of capacity since.
So what is it about being human that makes us the ultimate endurance machine?
The capacity to lose heat by sweating is a mechanism that is relatively unique to the human race. Horses, camels and donkeys are the only other mammals that have a sweat mechanism that is as developed as ours. We possibly evolved this capacity by having to run long distances in the heat of the day with no access to water and this idea is supported by research at Vermont University which suggests we have a hypertrophied sweating response that has developed over time. We required sweating not to outrun predators or to chase down other animals for food but to sustain exercise in the heat of the day. An animal like an antelope can be run down by a human because their lack of sweat response means that they ultimately overheat when forced to run continuously. We probably can’t run faster than an antelope but we can run for longer, and in early human life this meant we chased them all day until they collapsed.
The musculoskeletal structure of humans allows for locomotion over long distances at moderate speed. 20 anatomical features of the human musculoskeletal system have been identified that describe various structures in our body that aid our ability to maintain exercise for prolonged periods. Other mammals do not have these structural benefits as they are, in most cases, unique to humans.
Our superior endurance capacity compared to other animals means that we may not be great sprinters, but we can run for miles. Even the fastest human sprinters can only reach speeds of about 10.2m/s for about 15 seconds compared to our mammalian cousins (e.g. horses, greyhounds, cheetahs) who can reach speeds of 15-35m/s and remain at that speed for a few minutes. So we’re not built for speed and power but we are built for endurance. This makes sense as free living animals don’t often travel vast distances apart from the husky dogs that can run for days in freezing conditions. But in hot conditions, humans would outdo the husky because the dog is limited by its lack of a sweat response and inability to rapidly lose heat.
What is your endurance limit?
Technological advances in equipment and clothing aid our ability to perform exercise so it might seem that we should be able to stretch the limits of human endurance well beyond the energy expenditures reached by the Scott and Shackleton groups. Additionally, we have the benefit of a scientific field specifically focused on performance that helps our top athletes achieve their aims by allowing them to push their body’s to ‘the limit’. Some theorists believe that despite these things the mechanisation of our world, and especially the introduction of the internal combustion engine has removed the need for humans to test the limits of their endurance capacity. In earlier times if you needed to get somewhere you ‘had’ to walk or run, now if we don’t get into our car, we at least catch a plane, train or bus. Are the wonders of the modern world de-evolving our ability to perform at our best? Are we losing some of our superior endurance capacity because the majority of our time is spent in sedentary activity – even if we are highly trained athletes? Would improving our daily physical activity, above and beyond our daily training activities, help to improve our ability to push our physiological limits? It would certainly go a long way toward helping the environment if nothing else.
Think about it. Discuss the concept with your training partners, family and friends. Are we limiting our endurance capacity, our ability to optimally adapt to training by leading otherwise sedentary lives? Our long ago forebears spent little time sitting idle (and working all day at your desk may not be idle but it’s certainly sitting!), and they probably had a better endurance capacity than we do today. We have better access to food, medical supplies and shelter, we have the knowledge of the sport science industry, surely we should be in a better physiological position…surely?!

References
Bramble DM, Lieberman DE (2004) Endurance running and the evolution of Homo. Nature 432:345-352
Noakes TD (2006) The limits of endurance exercise. Basic Res Cardiol 101:408-417
 

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