An ambulatory exercise machine comprising walking path surface means having left and right walking surfaces, and control means for controlling running of the left and right walking path surfaces, independent from each other, wherein the control means incorporates a first control means detecting a condition of the left and right walking path surfaces, for controlling the left and right walking path surfaces, independent from each other, a second control means for fixing one of the left and right walking path surfaces and for controlling the other one of the left and right walking path surfaces, and means for selecting one of the first and second control means.