Mixed
Progressive resistance training (75% 1-RM, 3 sets of 8 reps, 3x/week) performed for one year by healthy elderly adults (mean age 68.2) significantly increases muscle strength (30-97% increase) and causes hypertrophy of both Type 1 and Type 2 muscle fibers.
If you are over 60 and healthy, you can build significant muscle strength and size by lifting weights 3 times a week. Start with a weight you can lift 8 times with good form, do 3 sets, and gradually increase the weight as you get stronger. You do not need to lift extremely heavy weights; moderate intensity (75% of your max) is highly effective and safe.
With exercise, muscle strength increased, average increases ranging from 30% (hip extensors) to 97% (hip flexors)... Cross-sectional area of type 1 muscle fibers increased in exercisers by 15 weeks (29.4 ± 1%, p < .02) and after 30 weeks (58.5 ± 13.7%, p < .002)... Type 2 fiber area did not change at 15 weeks, but increased by 30 weeks of training (66.6 ± 9.5%, p < .0002).
Why this rating
Randomized controlled trial with a control group, though the biopsy sample size was small (n=8 exercisers).
Source
Muscle Strength and Fiber Adaptations to a Year-long Resistance Training Program in Elderly Men and Women
G. Pyka et al. · Journal of Gerontology · 1994
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