Collins 2003Low.

Methods	Randomised, double‐blind, placebo‐controlled trial with two‐by‐two factorial design.
Participants	Country: United States of America. Number of participants randomised: 52, mean age 67, 98% males. Inclusion criteria: current diagnosis of peripheral arterial disease, a history of intermittent claudication, and an ankle‐brachial index < 0.95 at rest and/or < 0.85 after exercise. Exclusion criteria: taking any of the following drugs, vitamin E, Coumadin, or pentoxifylline.
Interventions	Participants were randomly assigned in four groups to receive: group 1: PoleStriding exercise with vitamin E (n = 13); group 2: PoleStriding exercise with placebo (n = 14); group 3: vitamin E without PoleStriding exercise (n = 13); group 4: placebo without exercise (n = 12). The dose of vitamin E was 400 IU daily. Participants were supplemented 0.5 year, and followed 2.5 years. PoleStriding is a form of walking that uses muscles of the upper and lower body in a continuous movement similar to cross country skiing.
Outcomes	The primary outcome was: walking ability and perceived quality of life.
Notes	Compliance with the study drug treatment was monitored in two ways: patient self‐report and measured vitamin E levels. Vitamin E levels were obtained at baseline and 3 and 6 months. Investigators did not receive the measured vitamin E levels until the trial ended. For the first 3 months drug compliance was assessed biweekly by the study staff and monthly thereafter. Six randomised participants did not complete the study; 1 participant from the exercise and vitamin E group, 3 participants from exercise plus placebo group, and 2 participants from the placebo group. Vitamin E and placebo capsules were provided by the Henkel Corporation, La‐ Grange, IL). Additional information received through personal communication with the authors.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Sequence generation was achieved using computer random number generation.
Allocation concealment (selection bias)	Low risk	Allocation was controlled by a central and independent randomisation unit, so that intervention allocations could not have been foreseen in advance of, or during, enrolment.
Blinding (performance bias and detection bias) All outcomes	Low risk	The trial was described as blinded, the parties that were blinded, and the method of blinding was described, so that knowledge of allocation was adequately prevented during the trial.
Incomplete outcome data (attrition bias) All outcomes	Low risk	The numbers and reasons for dropouts and withdrawals in all intervention groups were described.
Selective reporting (reporting bias)	Low risk	Pre‐defined, or clinically relevant and reasonably expected outcomes are reported on.
Other bias	Low risk	The trial appears to be free of other components that could put it at risk of bias.