I go to the gym 2 or 3 times a week doing some cardio and some weights, mainly on the weights machines. I'm wondering if it is still to do a mixture each time e.g. pull down arms, push arms, pecs, and similar with legs, or is it better to concentrate on pull down arms one day but do more reps, and push up weights during another session again with more reps. And similarly for legs. I'm over 60 if that makes any difference!