Whether 6% of premature mortality is related to physical inactivity, 9% or even 15%,

these estimates are all predicated on the presumption that the associations found linking inactivity to

death rates and observational studies constitute cause and effect.

I was surprised by how much controversy there is in the medical literature over whether

or not the apparent longevity benefits of exercise are even real.

A classic study from the 1950s entitled Coronary Heart

Disease and Physical Activity of Work illustrates how difficult it can be to tease out causality

between physical activity and longevity. London bus drivers appeared to have twice the risk of dying

from heart disease compared to

bus conductors who were presumed to be protected by their climbing up and down 500 to 700

steps a day in the famous double-deckers.

However, it was later revealed in a follow-up paper physique of London busmen, that based on the measurements of their

starting uniforms, the bus driver started out significantly heavier. Similar issues surrounding

reverse causality continue to haunt observational exercise studies to this day. Is exercising enabling

good health in seniors, or is good health enabling

exercise in the first place? Is inactivity leading to chronic disease or is chronic disease

leading to inactivity? Then there are the confounding factors. The ARC-Typo-1 being less

smoking among active individuals.

With the exception of elite male power athletes, who may die up to nearly five times

the normal rate, perhaps due to the use of vannobox steroids,

athletes tend to live longer than their sedentary counterparts as much as four to eight years longer.

But think of all the complicating elements, especially among professionals.

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