From Ergo-Log
You lose strength if you close your eyes during physical exertion sports scientists at Samford University in the US discovered when they did an experiment involving 27 students. But if you are used to doing the movement then the reduction as a result of sight loss is negligible.
The researchers got the students to do leg press exercises on two occasions, using 60 percent of the weight at which they could just manage 1 rep. On one occasion the students were blindfolded once they had got onto the machine; on the other occasion they weren’t.
The lack of vision reduced the power the subjects were able to develop, and therefore also the speed with which they could push the weight away from themselves.
In the men and women who did weight training in the gym twice or more per week, the loss of power as a result of loss of vision was negligible. The men lost 0.6 percent power, the women 1.8 percent.
In the students who were doing leg-press exercises for the first time ever, the effect of loss of vision was greater. The women in the group lost 15.9 percent of their power, the men 8.1 percent.
T = trained; U = untrained; W = women; M = men; black = without blindfold; white = with blindfold.
Studies have shown that the mind can help improve strength performance. A visualised training makes people stronger, as does visualising a movement between sets. A muscle works harder during a set if you direct your attention to that particular muscle. Imagining you are using a muscle seems to activate the same paths in your brain as the ones that are activated when you actually do move it, which helps you to better direct a particular muscle.
Visual input helps these mental processes. Studies suggest that you become stronger during physical exertion even if all you do is look at a photo of a tensed muscle. Which is why training with your eyes shut may be less effective than training with your eyes open.
Source:
J Strength Cond Res. 2012 May 29. [Epub ahead of print].
