In a 2002 study for example scientists looked at what happened when women performed various resistance exercises at different weights and repetitions (85 percent of their maximum ability for 8 reps versus 45 percent for 15). Subjects lifting more weight fewer times burned more energy and had a greater metabolic boost after exercise.
In another study published last year scientists followed 122 women for six years. They found that those who were assigned to do resistance exercises three times a week — sets of 8 reps at 70 to 80 percent of their ability — lost the most weight and body fat. A similar two-year study of women who did strength training with challenging weight twice weekly found similar effects on body and “intra-abdominal” fat.
THE BOTTOM LINE
For better tone try fewer reps and more challenging weights.