What is the relationship between thought and exercise? Why does the classic “nerd” (to use the American parlance) eschew physical exercise? Why does the classic “jock” struggle with his homework? I have always assumed that these two stereotypes were caricatures, extreme portrayals of two tendencies that some people are able to combine quite successfully. Modern culture takes the same view, emphasising both the physical and the mental benefits of exercise. But recently, I have been wondering whether that view is right.

For a number of years I have done a lot of exercise. From September to March I whip into foot hounds (beagles or bassets) in an energetic fashion, and can easily cover 15 miles or more in a busy afternoon. During the summer months I try to keep fit by swimming and running. A large amount of exercise obviously makes you tired, and if I have done a lot of running I find it harder to take in new ideas for a few days afterwards (and feel generally tired). But I had never, until recently, questioned the benefits of regular, moderate exercise. I have long been frustrated that I am often too tired in the evenings to read an interesting book, but I have taken that as a fact of life.

Since I began trading, however, my exercise routine has been quite irregular. Trading requires a lot of work and gives you emotional ups and downs, and I also do some part-time jobs to keep me in funds, and altogether it is harder to keep to an exercise routine than it used to be when I would just call into the pool on the way to work every day (as attested by my waistline). I have increasingly noticed that, while a lack of exercise may make me feel less healthy and less in control of life, slack exercise periods are associated with spurts in reading. For example, I last had a proper run almost two weeks ago (seven miles around Regent’s Park) and I am now half way through my third book in that time.

I think that there are two effects here. First, exercise takes time that could otherwise be spent reading. Second, exercise tires you out, which means it is hard to pick up a book straight after a moderate run. As a result of these effects, other things being equal, people who do regular, moderate exercise do less reading than those who do no hard exercise, and are thus less intelligent (reading being the main way to make oneself cleverer). Hence the jock-nerd distinction.

I am increasingly thinking that that it is impossible to excel as both “jock” and “nerd” and that, since my main ambitions are mental rather than physical, I should become a proper “nerd” — give up on heavy exercise altogether and restrict myself to brisk walks (and a smaller diet). But I do love whipping in to foot hounds, which means a lot of running. This is a conundrum.