Keeping your strength training routine fresh, from Harvard's Strength and Power Training Special Health Report
The evidence supporting strength training (and exercise in general) is so compelling that the U.S. Department of Health and Human Services recommends that adults do muscle-strengthening exercises for all major muscle groups at least twice a week. Ideally, this should be combined with at least 150 minutes of moderate (or 75 minutes of vigorous) aerobic activity per week, as well as balance and flexibility exercises. Strength and Power Training: A guide for adults of all ages, a newly updated Special Health Report from Harvard Medical School, offers the following tips—and more—for varying your routine, cranking up the challenge, and making strength training a lifelong endeavor.
Try new equipment. Substitute one type of equipment for another. For example, work out with machines instead of free weights one day a week, or switch from one brand of machine to another. Or try exercises using a medicine ball, resistance bands, or resistance tubing.