Looking at it from basic science, when you relax and try to empty your mind and concentrate on 1 point or even concentrate on something, your mind feels relaxed with such activities.
Another point being in todays world we do alot of sitting work, hence, the "solat" we preform gives a brief exercise to the muscles...
And then I once read this thing about the earth's magnetic field helps our our magnetism when we prostrate since I suck big time at Physics I didnt read details nor understood what I read....
In the west, there are many "clinics" which encourage children to go play in nature, to walk barefeet and then there are also scientific explanations of peace with Yoga and Tai Chi...Anyway there are other forms of "science" working when you are one with the earth and standing in silence and concentrating....