Abstract
Peripheral Arterial Occlusive Disease (PAOD) patients have a limited exercise capacity that is not well understood. Investigation of underlying disease mechanisms, and the evaluation of treatments, relies upon the precise measurement of exercise capacity and related physiological variables. Compared with single-stage treadmill protocols, incremental treadmill protocols are far more precise; however, even the variability of these latter protocols (Coefficient of Variation: 12-13%) (1;2) might obscure small, but important relationships and treatment effects. We hypothesised that as a patient becomes more familiar with an exercise test, the performance variability would decrease. To investigate this, 15 subjects (42-79yrs) with non-diabetic PAOD were recruited and randomly assigned to one of three test protocols: incremental treadmill (T); incremental cycle (C); and plantar flexion (PF) which incorporated an isokinetic strength test (PFs) and an isokinetic incremental test (PFinc) on both legs. Subjects performed their respective exercise protocols once per week for eight weeks. Maximal exercise duration in T and C did not change over the eight weeks. Coefficients of variation over weeks one to three (cv1-3) were 16.1% and 6.9% in T and C respectively. This variability decreased over the eight weeks to 6.2% (cv6-8) in T (ns) and 2.2% in C (p less than 0.05). HRrest, HRpeak and VO2peak in C and T did not change over the eight weeks, nor did the level of variability associated with each. Performance in the PFs test slightly increased (p less than 0.05) over the eight weeks while there was no change in PFinc performance. On both PF tests, performance of the "best leg", ie. that with the greatest ankle systolic pressure, was greater than that for the "worst leg" (p less than 0.05). PFinc variability fell non-significantly from 18% (cv1-3) to 5.2% (cv6-8) in the "best leg" and 16.6% (cv1-3) to 12% (cv6-8) in the "worst leg". PFs variability initially peaked at 7.2% and 10.2% (cv3-5) in the "best" and "worst" legs respectively before gradually decreasing to 3.5% and 2.6% (cv6-8) (p less than 0.05). These results suggest that performance variability is reduced in PAOD patients as they become more familiar with exercise protocols.