The purposes of this study were to assess the magnitude of the reduction in free-living daily physical activity of claudicants compared with age-matched controls, and to examine the relationship between the severity of peripheral arterial occlusive disease (PAOD) and free-living daily physical activity. Eighty-five PAOD patients with intermittent claudication and 59 non-PAOD subjects with a resting ankle/brachial index (ABI) of 0.63 +/- 0.20 and 1.21 +/- 0.08, respectively, were monitored for 2 consecutive weekdays with an accelerometer and pedometer worn on each hip. The times to onset and to maximal claudication pain were also measured in the claudicants during a graded treadmill test to assess the functional limitations imposed by PAOD. The PAOD group had a 42% lower energy expenditure as measured from the accelerometer (357 +/- 238 kcal/day versus 616 +/- 363 kcal/day; p < 0.001) and a 45% lower pedometer reading (4737 +/- 2712 steps/day versus 8672 +/- 4235 steps/day; p < 0.001) than the non-PAOD group. Furthermore, the relationship between free-living daily physical activity and ABI in PAOD patients was significant for both the accelerometer (r = 0.41; p < 0.001) and the pedometer (r = 0.41; p < 0.001). The rate of decline in free-living daily activity was 42 kcal/day and 612 steps/day per 0.10 drop in ABI. The correlation between free-living daily physical activity and time to maximal claudication pain (6:25 +/- 3:30 min:s) in the PAOD group was significant for both the accelerometer (r = 0.30; p = 0.05) and the pedometer (r = 0.36; p = 0.03). However, the time to onset of claudication pain (3:02 +/- 2:22 min:s) in the PAOD group was not related to either the accelerometer (r = -0.02; p = 0.86) or the pedometer (r = 0.18; p = 0.28) activity values. In conclusion, free-living daily physical activity was 42% to 45% lower in PAOD patients with intermittent claudication than in apparently healthy subjects of similar age. Moreover, claudicants were progressively more sedentary with an increase in PAOD severity.

The effect of exercise rehabilitation on the oxygen cost of ambulation in patients with peripheral arterial occlusive disease (PAOD) was evaluated with specific emphasis on the effects of exercise rehabilitation on the slow component of VO2. Because the slow component of VO2 represents an increase in VO2 despite constant-intensity exercise, it can profoundly affect the relative energy cost of exercise in individuals with a low functional capacity. Twenty-six patients with intermittent claudication performed treadmill walking at 2.0 mph/0% grade for 20 min or until maximal claudication pain before and after 4 months of rehabilitation. The slow component of VO2 during the treadmill test was defined as the difference between the end-exercise VO2 and the VO2 observed at minute 3. Ankle/brachial systolic pressure index (ABI) was measured before and immediately following the exercise test. Rehabilitation consisted of 3 d x wk(-1) of treadmill walking for 15-30 min at 60-70% of VO2peak. The slow component of VO2 and end-exercise VO2 at pretraining (0.75 +/- 0.90 and 11.12 +/- 2.10 mL x kg[-1] x min[-1]) were significantly reduced after 4 months of exercise rehabilitation (-0.07 +/- 1.11 and 10.07 +/- 1.80 mL x kg[-1] x min[-1]; P < 0.05). Exercise rehabilitation also significantly (P < 0.05) increased the post-exercise ABI (pre-rehabilitation = 0.36 +/- 0.26, post-rehabilitation = 0.43 +/- 0.25). These data suggest that 4 months of exercise rehabilitation: 1) improves walking economy in PAOD patients because of a decreased slow component of VO2, and 2) increases post-exercise ABI.