We thank Dr. Venes for his comments. Prospective longitudinal studies are required to address questions of long-term benefits or costs of vigorous exercise programs, given that a randomized clinical trial is neither ethical or practical. (Imagine randomly assigning a large sample to either run 1000 miles a year or to watch television for a decade!) We reported 8-year results of our ongoing study [1]. Please note two arithmetic errors in Dr. Venes's letter. The baseline level of vigorous exertion in the control group was 87.3 minutes per week rather than 77.3. The percentage increase is therefore 42% rather than 61%.

Disability developed in exercisers at only one fourth the rate in nonexercisers, whether we compared our original groups, all exercisers in both groups with nonexercisers, or exercisers and nonexercisers in the community control group. Seven exercisers and 30 controls died.

We recently presented our data after 9 years of study [2] and found that the disability differences between the groups continued. Musculoskeletal pain in exercisers had decreased by one fourth. Medical care costs were also one fourth lower in this group. To date, no total joint replacements have been done in the group that exercised initially. As we reported, exercisers sustain many fractures and other short-term injuries, but these do not affect long-term disability rates. In contrast to Dr. Venes's interpretation, we are impressed that a motivated group of persons exercised vigorously for 9 years at nearly 300 minutes a week while average ages increased from 59 to 68 years and that this group continues to be nearly free of disability through their seventh and eighth decades of life.