There is a lot of information on the Paleolithic Diet on the web (if you are interested see http://paleodiet.com/ to get started). The basic premise is that we should eat more like our hunter gatherer ancestors. Why? Basically because human physiology has not changed over the last 30,000 years, but grains have only been available for the last 10,000 years. Advocates of Paleo diets have a pretty good logical argument to support their beliefs. Similarly, when we develop an exercise program I think we should consider how our ancestors would have "exercised". Clearly Paleolithic humans didn't have a planned exercise program, but to stay alive they had to be active. Per Astrand, a world renowned exercise physiologist, argues that major adaptations for human survival "were consistent with habitual physical activity, including endurance and peak effort alternated with rest." We evolved performing lots of endurance activities such as tracking animals, moving with the seasons, gathering food and materials, building shelters, carrying infants, etc. However, we also required very short-duration outputs of peak power during fights and sprints (to chase, or flee, an opponent or animal). Hence, sprinting distances of 10 to 40 meters and/or having the physical strength to fight are probably the most fundamental physical survival skills we ever developed as humans. If you were fleeing a more powerful animal you probably would be sprinting a short distance to safety or shelter. If you were too far away from safety you would have to turn and fight. Either way, you needed to be powerful and the outcome, good or bad, was probably decided in a matter of seconds. The above description of the type of exercise our ancestors were engaged in would appear, like the Paleo diet argument, to be quite logical. Hence exercise programs that lack high intensity components and do not target the entire musculature, are by definition not suitable to allow the correct expression of our genetic make-up. To reach your genetic potential your environment must be conducive to your genetic make-up. An extreme example would be trying to live in an underwater environment........you wouldn’t last long. Another example of a poor environment (which includes diet and exercise) is highlighted by the fact that 65% of Americans are obese or overweight. Sedentary lifestyles and carbohydrate based diets do not match the human genetic constitution and have wrecked havoc in the North American population. One ideal exercise program would be a letter carrier (lots of low level habitual exercise) who also does power, sprint and fight training. That is obviously not possible for most of us, so CrossFit is the best alternative, especially for those who do not have active jobs. CrossFit programming includes exercise at the high intensities that would have been required for survival in the Paleolithic era. Heavy powerlifts, high power Olympic lifts, climbing ropes, sprinting, etc. all simulate the intensity of a fight or the avoidance of a fight. And as I have discussed in the past the tough metabolic conditioning workouts in the 20+ minute range that target all muscle groups are excellent at building muscular and cardiovascular endurance. So CrossFit programming allows us to "cover the bases" without having to put hours and hours into our program every day. But despite that……if you get the chance to go for a long hike…..take it! Eating like our ancestors is a very difficult task because the food available to us is very different. Even the meat we eat is different from the meat from the game animals they would have eaten. However, to exercise like our ancestors is a lot easier……so there are no excuses! Tony Leyland is a Senior Lecturer, School of Kinesiology, Simon Fraser University. He has taught at the university level for 25 years and has been heavily involved in competitive sports such as soccer, tennis, squash, and rugby as both an athlete and a coach for over 40 years. He is a professional member of the National Strength and Conditioning Association, a Canadian National B-licensed soccer coach, and a level-1 CrossFit trainer. He can be reached at firstname.lastname@example.org.