I heard the legionaries were in excellent shape. And that their physical activities were strenuous such as marching 20 miles carrying their stuff and then immediately after that building a camp with ditches ( you know just digging much can be tiring in the case you're not used to it. Just imagine doing it immediately after a very long march) .Then the next day dismantling it and marching again ( in the case they couldn't stay for more than one night in a particular place )