^Bodybuilder has it right

I'm a bodybuilder, and here's the general rule of thumb when it comes to reps. 1-4 reps is for strength, 5-10 is for hypertrophy, and 10-20 is for cardio and maintaining muscles. There's also pyramid sets, cluster sets, single sets, and so on. If your goal is to keep in shape with some muscle definition, I would keep it right where you are 10 reps while changing rest intervals and/or speed of the reps on occaisions. If you want mixture, try free weights, throw in some pylometrics, do kettlebells, push a prowler sled if you have access, TRX, etc....to avoid the plateaus and training stalls once you get into a regular routine.

At 60, with regular weight training you will look and feel great!

Working to failure is good but you should also begin to incorporate free weights because they force you to use additional muscles to stabilize. At 60 (or any age actually) you should also be working on balance and flexibility.

I'm close to 60 and after neglecting exercise for ages am finally getting to the gym 3 times a week and enjoying it in spite of myself.

I'm ramping up on the treadmill for aerobic exercise. For strength training I'm doing circuit training each time. I wonder what the best repetition scheme for me is. Not a bodybuilder, just wanting to keep in shape. Doing an internet search give a wide variation of schemes, so I thought I'd ask for suggestions here.

Here is what I do: I try to do two sets of 10 at each station, smoothly, slowly, in control. When I get to that point, I increase the weight so maybe I can do one set of 10 and then a few more repetitions in the next set, short of the full 10. When I build up to two sets of 10 again, I increase the weight.