The Bell Curve, Outliers, And Training Myths

For many, the bell curve might be a faded memory from a college statistics class. It might be a painful memory at that! But it can also serve as the foundation for many discussions in the health and fitness world.

For those who may have forgotten, S.E. Smith notes that “a bell curve is a graph which depicts a normal distribution of variables, in which most values cluster around a mean (average), while outliers can be found above and below the mean”. A bell curve indicates that the variables are within normal expectations and behaving in a predictable manner.

Although the context and relevance of a normal distribution are well known, it is amazing how these can be selectively forgotten in the health, fitness, and sport worlds. We could put a lot of training myths and fallacies to rest, once and for all, by rigorously testing our assumptions and using what we know about the bell curve.

First, we need a brief refresher class in statistics. Then, with bell curve in hand, we will dive headlong into myth-squashing and envelope-pushing.

Human intelligence can be used as an example of a normal distribution. One standard deviation on either side of the mean (the middle of the bell curve) encompasses about 68% of the population. Two standard deviations on either side of the mean – considered by many to be “normal” for anatomical variations – encompass 95% of the population. That leaves 2.5% of the population on either side of the curve as “outliers”: on the far right side of the curve, those that are extremely intelligent, and on the far left side of the curve, those that have very low intelligence.

Training strategies tend to trickle down to the general public from coaches that have achieved success with a certain group of elite or sub-elite athletes. Coaches associate their athletes’ performance with their imposed training strategies. The general public associates “effective training” with “elite athletes”. If it worked for them, they believe, it must be the right thing to do, right?

But here’s a thought – what about the possibility that some of these athletes are indeed outliers? They could be the 2.5% group that can do anything, recover from anything, and don’t get injured regardless of what they do. They could be the group that would make anyone’s training plan look good, or their injury prevention strategy look downright fabulous. If this is the case, the coach in question could do just about anything with the outliers, attaining some degree of success, and attributing that success to the coach’s training plan.

The assumption is made that elite and sub-elite athletes are, in fact, doing the best training – that is why they are elite and sub-elite - and that what is done by elites is reserved for elites.

If coaches have truly hit on the principles and mechanisms of optimal human performance, then these same principles should be applicable to all. Human anatomy is human anatomy – regardless of the level of athlete. Genetics may contribute to variations in hair and eye color, but the vast majority of training adaptations occur not because of special genes but because of the mechanisms of human physiology that we all share. Remember, 95% of the population are NOT outliers – they would be considered “normal”.

But what we end up with are “principles” that don’t work across the broad spectrum of athletes. When these training strategies don’t work, the onus is put on the athlete: they aren’t working hard enough, or they don’t have enough talent or the correct gene pool.

If the athlete gets injured in the process, they are told that unless they can tolerate the demands of this particular training strategy, they simply won’t be able to attain their best level of performance. They may be told they just don’t have what it takes or that they have some crazy biomechanical mal-alignment limiting their abilities. Or both. Again, the onus is on the athlete’s insufficiencies, instead of their inherent abilities to adapt to the imposed training demands if only the training demands were correct.

The simple fact may be that the coach’s training strategies evolved from a group of outliers in the first place. Instead of basing training strategies on the sports sciences, logic, evidence-based cellular physiology and the scientific method, we end up with training methods based on 2.5% instead of 95%. But if we are going to search for the mechanisms and principles that guide training, we need to find those that apply to all, and not just the outliers on the far right of the bell curve.

Consider, if you will, the Olympic marathon. If Olympic marathon gold was simply a case of having a larger pool of athletes running more and more miles, then the United States would dominate. This is the prevalent belief system among athletes and coaches alike. There are countless American runners logging in 100+ miles per week with the assumption that it is the road to the promised land. Lest I remind you, the last US OIympic marathon gold medalists were Frank Shorter in 1972 and Joan Benoit Samuelson in 1984. That is a lot of years (and running miles) ago.

The right principles, applied correctly, will push the outer limits of human performance beyond what we can imagine now. We’ve seen it with the four minute mile, and I have no doubt we will see it with the sub-two-hour marathon.

Part II will focus on the bell curve’s implications on health care and treatment approaches.

Photo credits: Wikipedia