a personal trainer gave me this guide when i asked the same question.
Endurance-15-20 reps for 3 sets,3x's a week for 6 weeks
Hypertrophy(size): 10-12 reps for 5-6 sets,3x's a week for 12 weeks
Strength: 4-8 reps for 3 sets,3x's a week for 12 weeks
"Toning"(he hated this word but this would be definition)12-15 reps 3 sets,3x's a week for 6 weeks.
for endurance and "toning" it would be light/moderate weight to complete the reps but the last few reps almost impossible to do(muscles failing) hptertrophy moderate/heavy, and strength heavy weights again you want muscle failure. i am sure everybody respods differently but he said this was just a general guideline to work with. i haven't followed it to the letter myself i just mix it up every month, one month i will do heavy the next lighter for endurance and take it from there. one of these days when i don't have exercise ADD i will try it with endurance for 6 weeks, hypertrophy for 12 weeks etc etc. although even in a month i see a difference.
HTH
kassia
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