The collective evidence indicates that the response to heavy-resistance training in older men and women, even above the age of 90 years, is mediated through a combination of hypertrophy of both muscle fiber types and an adaptation in the nervous system. Data also suggest that weaker, older individuals respond with greater muscle hypertrophy than do relatively active older individuals and that life-long strength training can counteract some of the age-related sarcopenia. The potential for muscle hypertrophy through heavy-resistance training should be incorporated into prevention, treatment, and/or rehabilitation programs for older individuals.