I remember in university coming across a study about a group of subjects who didn’t do any actual strength training but just thought about lifting weights and getting stronger and their strength actually did improve over time. That shows the power of mental strength and the placebo effect. I don’t think this study is talking about the same thing, but it does show some insight on what to focus your attention on during the act of strength training. So next time you’re doing a 100m dash or setting a PR on your bench press, look at some point in the distance, don’t focus on your muscles!
To learn more about focus of attention, read the full article at the CYBEX Institute for Exercise Science.