Similar to the study of nutrition, the study of exercise science is relatively immature. An enormous amount of controversy surrounds exercise guidelines for health and fat loss. On one side, there are those who only perform endurance-based exercise and whose highlight of the week is the Sunday morning long run. On the other side are those who only lift weights and whose last run was when they were at school. And in between are those who wonder what the right balance is between lifting weights, interval training and aerobic training. One way to gain some direction on the best approach to exercise is to view it from an evolutionary perspective. Part 1 of this series explored human nutrition and health in the light of evolution. In Part 2, we discuss the evolution of humans as endurance athletes and outlines the evolutionary fitness theory. This theory proposes that adopting a lifestyle that mimics the beneficial characteristics of the hunter-gatherer — incorporating daily aerobic, anaerobic and strength exercises — will effectively reduce the chronic degenerative diseases that are so prevalent in modern western society.
It has been often said in the fitness industry that humans have evolved to throw a spear at animals instead of chase after them. Meaning, of course, that humans should lift weights and perform intervals, but avoid continuous aerobic exercise. Some have gone as far to say that continuous aerobic exercise can burn out your adrenal glands, generate excessive oxidative stress and actually make you fat.
But, from an evolutionary perspective, is this correct?
If humans were designed to only perform short bursts of activity — like lifting weights or interval training — then why, from around 2 million years ago, have humans evolved such unique and exceptional anatomical, physiological and behavioral features that enable us to run long distances? In this regard, we are unique compared to other primates, who, by and large, are not good runners; their hands and feet are too large relative to their body limbs, which is useful for climbing trees but terrible for running! Our closest relative, the chimpanzee, can sprint short distances, but does so rarely. Thus, the human’s ability to run long distances is unique among primates (Bramble & Lieberman, 2004).
We are also unique compared to other mammals. Most mammals are good at sprinting because they are either the predator or the prey trying to outrun predators. And most mammals can outsprint humans: the peak running speed of elite sprinters is about 10m/s, which is considerably less than lions (30m/s), cheetahs (35m/s) and horses (19m/s). However, elite endurance runners can sustain speeds around 5.7m/s for over 2 hours, which is similar to the prey of humans: antelopes (5.1m/s) and the wildebeest (5.8m/s). And interestingly, no mammal can cover as greater distances than do elite Kenyan distance runners who may run in excess of 30km a day (Bramble & Lieberman, 2004; Lieberman & Bramble, 2007; Noakes, 2007).
A critical point in human evolution occurred when our ancestors incorporated meat into their diet and began to hunt antelope during the daytime heat on the hot African savannah. The available evidence indicates that hominids started to incorporate meat and other animal tissues in their diet around 2.5 million years ago (Bramble & Lieberman, 2004). But to be a carnivore, one must compete with other carnivores, and most other carnivores are faster than humans! Humans developed remarkable abilities to run long distances, throw with exquisite accuracy, and hit with power despite relatively weak arms (Noakes, 2007).
Of great importance to this end is the fact that humans have unmatched capacity to sweat — as much as 2 to 3 liters per hour during exercise. This advantage allows us to run long distances in the heat. We don’t need a sweat response to outrun predators, but we developed a great ability to sweat to sustain running in the heat of the day when most predators retire to the shade (Lieberman & Bramble, 2007; Noakes, 2007).
Surviving hunter-gatherers like the Bushmen of Southern African have been filmed while running for 4-6 hours in temperatures of 40-460C until the temperatures of their non-sweating prey exceeded 42-450C, causing the animals motor paralysis and capture by the huntsmen (Noakes, 2007). This is called persistence hunting.
If continuous aerobic exercise really burned out the adrenal glands, generated excessive oxidative stress and actually made people fat, then why, by natural selection over millions of years, have humans evolved such unique physiological and anatomical features to perform such prolonged aerobic exercise to obtain food, clothing and shelter? If continuous aerobic exercise were so destructive, we would have the anatomy and physiology to perform only anaerobic and strength-oriented activity — and we know this is not the case. It is interesting to note that the current exercise guidelines published by the ACSM suggest that adults perform aerobic exercise on most, if not, all days of the week for optimal health (ACSM, 1998; 2009). This is consistent with the hunter-gatherer fitness model.
Humans Have Developed Unique Anatomical Structures Designed for Long Distance Running
Bramble & Lieberman (2004) have identified 20 anatomical features of the human musculoskeletal system, which are specific adaptations for sustained walking and running for prolonged periods (from hours to days). Of note, humans use elastic energy stored in the many tendons of the legs to propel us in gait, which doesn’t happen when we walk. Further, the spring-like ligaments and tendons in the feet, Achilles and ITB are absent or tiny in apes (Raichlen et al., 2011). Secondly, running requires greater stability demands than walking. But humans have evolved a number or anatomical features that help stabilize the center of mass when running, which have little to no role when walking. We have an enlarged gluteus maximus, which does not contract much during walking (Lieberman et al. 2006), and a narrow waist with a highly mobile thorax that is decoupled from the neck to permit counter rotation of the arms and trunk. Finally, we have enlarged semicircular canals, which are the interconnected tubes located inside each ear, which allow humans to take in sensory information while running but not walking (Bramble & Lieberman, 2004; Spoor et al., 1994).
Humans Have Excellent Capacity for Endurance
When Stu Mittleman was 50 years old, he ran just under 5000km across America — from San Diego to New York City — in 56 days. This is more than two marathons a day for 56 consecutive days.
Consider Tour de France cyclists, who cycle around 3500km in 3 weeks. This includes mountain stages in the Alps and Pyrenees, where the hourly energy expenditure is around 2000kcals! These athletes maintain an average speed over 40km/hr and expend around 8000-9000kcals/day. This totals around 168,000 kcals for the event!
Or consider Yiannis Kouros, who has held every men's running world record from 100 miles to 1,000 miles and from 24 hours to 10 days. His record for 100 miles was 11 hours, 46 minutes, which is 13.7 km/h, and his record for 1000 miles was 10 days, 10 hours and 30 minutes, which is 6.5 km/h. He has run 163km in 12 hours (14km/hr), 305.5km in 24 hours (13km/hr) and 474km in 48 hours (10km/hr).
In March 1987, Kouros ran from Sydney to Melbourne, which was a total of 1,127km. The race took him 5 days, 14 hours. This means he covered an average of 205km per day at an average speed of around 8km/hr. His daily energy expenditure was estimated to be between 9000-16000kcals, expending a total of 56,000kcals throughout the event (Rontoyannis et al., 1989)!
Finally, consider Robert Scott’s Polar party during the 1911-1912 British Antarctic Expedition. Scott and his team hauled sleds with their provisions through the snow for 10 hours a day for 159 consecutive days. They covered 2500km in freezing conditions and expended 1 million kcals, making their effort the greatest sustained endurance athletic performance of all time (Noakes, 2007).
Daily exercise favorably alters gene expression, improves cardiovascular and musculoskeletal health, glucose and lipid metabolism, blood pressure, mood, sleep quality and immunity (O'Keefe et al. 2010a; 2010b).
From the inception of the human genus Homo around 2.4 million years ago, our ancestors lived as hunter-gatherers for approximately 84,000 generations. Survival as a hunter-gatherer required great amounts of daily energy expenditure to obtain food and water, for social interaction, to escape predators, and maintenance of shelter and clothing. Humans remain genetically adapted to large amounts of daily expenditure.
Improvements in technology that resulted in the Agricultural Revolution 350 generations ago, the Industrial Revolution seven generations ago and the Digital Age two generations ago have resulted in massive reductions in the amount of daily physical activity required by humans today (O'Keefe et al. 2010a; 2010b).
Our innate exercise capabilities and requirements that evolved via natural selection over 2.4 million years remain essentially the same as our hunter-gatherer ancestors. Compared with the slow pace of genetic evolution, modern technological evolution has occurred rapidly. This discordance has left us genetically adapted for the rigors of life as a hunter-gatherer, despite the fact that we are inhabitants of a high-technology, sedentary, overfed, and emotionally stressed-out 21st century environment (O'Keefe et al. 2010a; 2010b).
The mismatch between indigenous exercise patterns and modern behavior is a large contributor to prevalence of obesity, type II diabetes and heart disease. Based on several published studies investigating the fitness of hunter-gatherers (O'Keefe et al. 2010a; 2010b), here are some concluding practical applications to incorporate into your personal training sessions with clients:
- We are designed to perform large amounts of background daily movement, such as walking. Hunter-gatherers were estimated to move between 6 and 16km a day. Have clients incorporate daily walking before, during and after work and to and from work, whenever possible.
- As part of a well-designed program, progressively and sensibly increase the incorporation of running and walking in minimal footwear on natural surfaces, where appropriate for a client’s individual biomechanics and strength/fitness levels.
- As much as possible, perform aerobic exercise outdoors to increase vitamin D levels.
- Include interval training once to twice a week.
- Include strength training, two to three times a week.
Personal trainers are in a unique position to help clients adopt a lifestyle that mimics the beneficial characteristics of the hunter-gatherer by incorporating daily aerobic, anaerobic and strength exercises, and food selections consistent with unprocessed, unrefined, plant-based, high fiber Paleolithic nutritional principles as outlined in Part 1. Making these changes will effectively reduce heart disease (the leading cause of death) and the chronic degenerative diseases that are so prevalent in modern western society.
- Bramble & Lieberman. (2004). Endurance running and the evolution of Homo. Nature 432: 345–352.
- Donnelly, J.E.; Blair, S.N., Jakicic, J.M.; Manore, M.M.; Rankin, J.W., Smith, B.K. (2009, February). ACSM Position Stand: Appropriate Physical Activity Intervention Strategies for Weight Loss and Prevention of Weight Regain for Adults. Medicine & Science in Sports & Exercise. 41(2): 459-471.
- Lieberman & Bramble. (2007). The evolution of marathon running: capabilities in humans. Sports Medicine 37 4-5: 288-90.
- Lieberman, et al. (2006).The human gluteus maximus and its role in running. Journal of Experimental Biology 209: 2143-55.
- Noakes. (2007).The limits of human endurance: what is the greatest endurance performance of all time? Which factors regulate performance at extreme altitude? Adv Exp Med Biol, 618: 255-76.
- O'Keefe, et al. (2010, Dec). Organic fitness: physical activity consistent with our hunter-gatherer heritage. Phys Sportsmed 38(4): 11-8.
- O'Keefe, et al. (2010, Dec). Achieving hunter-gatherer fitness in the 21st century: back to the future. American Journal of Medicine 123(12): 1082-6.
- Pollock, M.L., Gaesser, G.A., Butcher, J.D., Després, J.P., Dishman, R.K., Franklin, B.A., Garber, C.E. (1998, June). ACSM Position Stand: The Recommended Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory and Muscular Fitness, and Flexibility in Healthy Adults. Medicine & Science in Sports & Exercise. 30(6): 975-991.
- Raichlen D.A., Armstrong, H. & Lieberman, D.E. (2011) Calcaneus length determines running economy: implications for endurance running performance in modern humans and Neandertals. Journal of Human Evolution 60(3): 299-308.
- Rontoyannis, G.P., Skoulis, T. & Pavlou, K.N. (1989). Energy balance in ultra marathon running, American Journal of Clinical Nutrition, 49: 976-979.
- Spoor, F., Wood, B. & Zonneveld, F. (1994). Implications of early hominid labyrinthine morphology for evolution of human bipedal locomotion. Nature 369: 645–648