Pa. Ades et al., SKELETAL-MUSCLE AND CARDIOVASCULAR ADAPTATIONS TO EXERCISE CONDITIONING IN OLDER CORONARY PATIENTS, Circulation, 94(3), 1996, pp. 323-330
Background Older coronary patients suffer from a low functional capaci
ty and high rates of disability. Supervised exercise programs improve
aerobic capacity in middle-aged coronary patients by improving both ca
rdiac output and peripheral extraction of oxygen. Physiological adapta
tions to aerobic conditioning, however, have not been well studied in
older coronary patients. Methods and Results The effect of a 3-month a
nd a 1-year program of intense aerobic exercise was studied in 60 olde
r coronary patients (mean age, 68+/-5 years) beginning 8+/-5 weeks aft
er myocardial infarction or coronary bypass surgery. Outcome measures
included peak aerobic capacity, cardiac output, arteriovenous oxygen d
ifference, hyperemic calf blood flow, and skeletal muscle fiber morpho
metry, oxidative enzyme activity, and capillarity. Training results we
re compared with a sedentary, age- and diagnosis-matched control group
(n=10). Peak aerobic capacity increased in the intervention group at
3 months and at 1 year by 16% and 20%, respectively (both P<.01). Peak
exercise cardiac output, hyperemic calf blood flow, and vascular cond
uctance were unaffected by the conditioning protocol. At 3 and 12 mont
hs, arteriovenous oxygen difference al peak exercise was increased in
the exercise group but not in control subjects. Histochemical analysis
of skeletal muscle documented a 34% increase in capillary density and
a 23% increase in succinate dehydrogenase activity after 3 months of
conditioning (both P<.02). At 12 months, individual fiber area increas
ed by 29% compared with baseline (P<.01). Conclusions Older coronary p
atients successfully improve peak aerobic capacity after 3 and 12 mont
hs of supervised aerobic conditioning compared with control subjects.
The mechanism of the increase in peak aerobic capacity is associated a
lmost exclusively with peripheral skeletal muscle adaptations, with no
discernible improvements in cardiac output or calf blood flow.