Abstract: We included two trials involving 54 participants with CVI. Many of our review outcomes were not reported or reported by only one of the two studies. The intensity of disease signs and symptoms was measured in both studies but using different scales; we were therefore unable to pool the data. One study reported no difference between the exercise and control groups whereas the second reported a reduction in symptoms in the exercise group. In one study, increases in change in ejection fraction compared with baseline (mean difference (MD) 4.88%, 95% confidence interval (CI) 3.16 to 6.60; 30 participants; P < 0.00001), half venous refilling time (MD 4.20 seconds, 95% CI 3.28 to 5.12; 23 participants; P < 0.00001) and total venous refilling time (MD 9.40 seconds, 95% CI 7.77 to 11.03; 23 participants; P < 0.00001) were observed in the exercise group compared with the control group. One study reported no difference between the exercise and control groups with regard to quality of life or ankle range of motion. Although muscle strength assessed by dynamometry at slow speed did not differ between the two groups in this study, variable peak torque at fast speed was lower in the control group than in the exercise group (2.8 ± 0.9 compared with -0.3 ± 0.6, P < 0.03). The incidence of venous leg ulcers, incidence of surgical intervention to treat symptoms related to CVI and exercise capacity were not assessed or reported in either of the included trials. We rated both included studies as at high risk of bias; hence, these data should be interpreted carefully. Due to the small number of studies and small sample size, we were not able to verify indirectness and publication bias. Therefore, we judged the overall quality of evidence as very low according to the GRADE approach. There is currently insufficient evidence available to assess the efficacy of physical exercise in people with CVI. Future research into the effect of physical exercise should consider types of exercise protocols (intensity, frequency and time), sample size, blinding and homogeneity according to the severity of disease.

Plain-language summary: This review included two clinical trials, involving a total of 54 participants, that compared directly the effects of physical exercise and a control intervention (evidence current until May 2016). One study reported no difference between the exercise and control groups whereas the second reported a reduction in symptoms in the exercise group. At the end of the study, an improvement in venous blood return was observed in the exercise group compared with the control group. The included studies did not report on new cases of venous leg ulcers. No difference between the exercise and control groups was observed with regard to participants' quality of life, the range of motion of the ankle joint or overall muscle strength. The overall finding of an improvement in venous blood return in the exercise group favours the idea that physical exercise improves blood flow conditions in people with CVI, but we found the risk of bias due to blinding or randomisation to be high for both studies. We therefore consider that there is currently not enough information to determine whether physical exercise is effective in the management of CVI. Quality of the evidence We judged the overall quality of evidence as very low: the two included studies were small (54 participants in total) and were at high risk of bias based on their methods of blinding or randomisation.