Physiological responses to six weeks unsupervised walking exercise in patients with intermittent claudication

Abstract

Objective: It is well established that exercise training improves walking distance in patients with intermittent claudication. However the physiological mechanisms responsible for explaining these increases are not fully understood. The aim of this study was to investigate the physiological mechanisms and to provide a rationale as to why patients with intermittent claudication improve pain free and maximum walking distances following a programme of unsupervised exercise. Methods: 10 claudicants with a mean age of 70 years (± 9.84) were studied. Pain free walking distance (PFWD), maximum walking distance (MWD), heart rate (HR), microalbuminuria, ankle brachial pressure index (ABPI), respiratory exchange ratio (RER), C>2 uptake and lactate were measured. Patients performed a graded treadmill protocol at baseline and following six weeks of an unsupervised exercise programme. The exercise programme consisted of patients performing 1 hour of walking per day above and beyond their normal daily activities. Patients were monitored by the use of an exercise diary, pedometer and a weekly phone call. Results: MWD improved by 5% although this difference was not found to be significant. Positive differences were also observed in ABPI (5.5%) and resting lactate levels (10%), once again these differences were not found to be significant. No differences were observed between heart rate, RER and C>2 uptake. A significant difference was observed in PFWD (p = 0.02), Microalbuminuria levels at rest (p = 0.03) and post exercise (p = 0.01), lactate levels at rest (p = 0.0005) and 6 minutes (p = 0.001) post a graded treadmill protocol. Conclusions: Exercise training improves walking distances in claudicants and reduces post exercise lactate levels. Exercise has a significant effect on two of the physiological variables measured (Microalbuminuria and post exercise lactate) and a positive effect on ABPI and resting lactate although no significant difference was found. This could possibly be due to a number of limitations in this study including small sample size (n = 10), the exercise programme was too short and also unsupervised. It is still unclear how exercise improves walking distances in claudicants and further research is required to investigate this.