Objectives - To investigate the effects of a 24-week program of upper- and lower-limb aerobic exercise training on walking performance in patients with symptomatic peripheral arterial disease (PAD) and to study the mechanisms that could influence symptomatic improvement.Methods - After approval from the North Sheffield Local Research Ethics Committee, 104 patients (median age, 69 years; range, 50 to 85 years) with stable PAD were randomized into an upper- or lower-limb aerobic exercise training group (UL-Ex or LL-Ex), or to a nonexercise training control group. Training was performed twice weekly for 24 weeks at equivalent relative exercise intensities. An incremental arm- and leg-crank test (ACT and LCT) to maximum exercise tolerance was performed before and at 6, 12, 18, and 24 weeks of the intervention to determine peak oxygen consumption (VO(2)). Walking performance, defined as the claudicating distance (CD) and maximum walking distance (MWD) achieved before intolerable claudication pain, was assessed at the same time points by using a shuttle-walk protocol. Peak blood lactate concentration, Borg ratings of perceived exertion (RPE) and pain category ratio (CR-10) were recorded during all assessments.Results - CD and MWD increased over time (P <.001) in both training groups. At 24 weeks, CD had improved by 51% and 57%, and MWD had improved by 29% and 31% (all P <.001) in the UL-Ex and LL-Ex groups, respectively. An increase in peak heart rate at MWD in the UL-Ex group (109 +/- 4 vs 115 +/- 4 beats/min; P <.01) and LL-Ex group (107 +/- 3 vs 118 +/- 3 beats/min; P = .01) was accompanied by an increase in the amount of pain experienced in both groups (P <.05), suggesting that exercising patients could tolerate a higher level of cardiovascular stress and an increased intensity of claudication pain before test termination after training. Patients assigned to exercise training also showed an increase in LCT peak VO2 at the 24-week time point in relation to baseline (P <.01) and control patients (P <.01), whereas ACT peak VO2 was only improved in the UL-Ex group (P <.05).Conclusions - Our results suggest that a combination of physiologic adaptations and improved exercise pain tolerance account for the improvement in walking performance achieved through upper-limb aerobic exercise training in patients with PAD. Furthermore, that both arm- and leg-crank training could be useful exercise training modalities for improving cardiovascular function, walking performance, and exercise pain tolerance in patients with symptomatic PAD.