A few years ago German researchers conducted an interesting study that looked at the effects of people's thoughts as they ran. Volunteers were asked to run on a treadmill at a constant speed while focusing their attention on their body movements, breathing or the external environment. The test was repeated three times with the focus of attention changing in random order until all of the volunteers had completed the test in all three conditions.
While the subjects ran, they breathed into a mask that measured their oxygen consumption. The researchers found that the subjects consumed more oxygen at the same speed when their attention was focused on their bodies than in either of the other two conditions. They consumed the least oxygen when thinking about the external environment. This meant that they ran most economically when their attention was externally focused, and less economically when it was internally focused.
While perhaps counterintuitive, these findings are consistent with a large body of research in the field of human biomechanics, which has shown that people learn motor skills faster when they think about key parts of their surrounding environment instead of the movements of their bodies.
For example, in one study novice golfers improved their putting accuracy significantly more when they were instructed to focus on the club head than when they were told to focus on their hands. And in another study, subjects improved their balance performance on something called a stabilometer much faster when they were instructed to focus on markers placed on the balance surface than when they were instructed to focus on their feet.
Why do people learn motor skills faster and move more efficiently when their attentional focus is external rather than internal? The full answer to this question is rather complicated. The short answer is that our movements are less constrained when we focus on the task at hand rather than on the hand itself, so to speak.