Types of studies

We included randomised controlled trials (RCTs) in which an exercise programme was used as the main or adjunctive treatment in individuals non‐ulcerated CVI.

Types of participants

We included RCTs involving individuals with non‐ulcerated CVI regardless of sex and ethnicity.

We used the CVI diagnosis as given by trial authors because the classification of CVI could differ between studies: some may have included individuals with a CEAP C score of 3‐5, and others may have included individuals with less severe clinical manifestation, as designated by a CEAP C score of 2, and defined them as having CVI.

We included studies conducted in both non‐ulcerated and ulcerated CVI participants provided the outcomes for these two groups were reported separately. This is because the major outcomes for individuals with leg ulcers (for example, percentage reduction in ulcer area or percentage of fully healed ulcers) differ from those in people with non‐ulcerated CVI and it would be difficult to assess them within the same review. However, if data for the two groups were not analysed and presented separately and the exercise treatment was carried out in some individuals with CVI and leg ulcers, we included the study only if these participants comprised less than 25% of the total number of study participants.

We did not assess the effects of exercise on venous leg ulcer healing in this review.

We did not include studies in which the exercise treatment was investigated in individuals with PAD, unless the results were reported separately for the CVI subgroup.

Types of interventions

We compared supervised or unsupervised prescribed exercise programmes as the main or adjunctive treatment in individuals with non‐ulcerated CVI with either the same protocol without exercise or without treatment. We considered studies using compression stockings in the exercise or control group for inclusion.

Types of outcome measures

Electronic searches

The Cochrane Vascular Information Specialist (CIS) searched the Cochrane Vascular Specialised Register (May 2016). In addition the CIS searched the Cochrane Central Register of Controlled Trials (CENTRAL); 2016, Issue 4) via the Cochrane Register of Studies (CRS) Online. See Appendix 1 for details of the search strategy used to search the CRS. The Cochrane Vascular Specialised Register is maintained by the CIS and is constructed from weekly electronic searches of MEDLINE, Embase, CINAHL, AMED, and through handsearching relevant journals. The full list of the databases, journals and conference proceedings which we searched, as well as the search strategies we used are described in the Specialised Register section of the Cochrane Vascular module in the Cochrane Library.

The CIS searched the following trial databases (May 2016) for details of ongoing and unpublished studies using the terms (incompetence and exercise) and (insufficiency and exercise):

• World Health Organization International Clinical Trials Registry (http://apps.who.int/trialsearch/);

• ClinicalTrials.gov (http://clinicaltrials.gov/);

• ISRCTN Register (http://www.isrctn.com/).

Searching other resources

We searched the bibliographies of relevant publications identified through the above strategies for further studies. We attempted to contact trial authors to obtain unpublished data and information as required.

We imposed no restrictions on language or publication status for studies eligible for inclusion in the review.

Selection of studies

Two review authors (DA and FD) independently screened the titles and abstracts of the studies identified by the search strategy against the inclusion criteria. We obtained full versions of articles that appeared to fulfil the inclusion criteria for further assessment. We intended to resolve any discrepancies by discussion with a third review author (GF), but this was not necessary. We recorded all reasons for study exclusion. We have presented our study selection process as a PRISMA (Preferred Reporting Items for Systematic Reviews and Meta‐Analyses) flow diagram (Liberati 2009) (see Results of the search).

Data extraction and management

Two review authors (DA and FD), working independently, extracted data, summarised details of trials using a standard data extraction sheet and entered data into Review Manager 5.3 (RevMan 2014). We then compared the data extractions and agreed a final version after discussion. We intended to resolve any discrepancies by discussion with a third review author (GF), but this was not necessary. If data were missing from reports we attempted to contact the trial authors to obtain the missing information. Where reported, we extracted the following information according to methods described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011a):

• country of origin;

• study authors and year of publication;

• publication type;

• study design;

• care setting;

• type of participants;

• method of recruitment of participants;

• types of outcome measures;

• unit of investigation (per participant, cluster);

• number of participants randomised to each trial;

• eligibility criteria and key baseline participant data (gender, age, ethnicity, disease duration, prevalence of comorbidities such as diabetes and PAD);

• details of the treatment regimen received by each group;

• type of exercise;

• details of any cointerventions;

• primary and secondary outcome(s) with definitions;

• outcome data for primary and secondary outcomes (by group);

• overall sample size and methods used to estimate statistical power (relates to the target number of participants to be recruited, the clinical difference to be detected and the ability of the trial to detect this difference);

• duration of treatment period;

• duration of follow‐up;

• number of withdrawals (by group with reasons);

• statistical methods used for data analysis;

• 'Risk of bias' criteria (sequence generation, allocation concealment, blinding, incomplete outcome data, selective outcome reporting);

• adverse events;

• source of funding.

Assessment of risk of bias in included studies

Two review authors (DA and FD) independently assessed each included study using the Cochrane Collaboration's tool for assessing risk of bias. This tool addresses six specific domains, namely random sequence generation, allocation concealment, blinding of participants and personnel, incomplete outcome data, selective outcome reporting and other sources of bias (see Appendix 2 for details of the criteria on which we based our judgements). We assessed blinding and completeness of outcome data for each outcome separately. We intended to search the protocols of all included RCTs in order to assess selective outcome reporting. When no protocol was identified, we made a judgement based on the congruence of information in the methods and results sections of the reports of RCTs. We completed a 'Risk of bias' table for each eligible study and classified them as being at high, low or unclear risk, according to the methods described in Chapter 8 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011b).

We present our assessment using a 'Risk of bias' summary figure, which presents all of our judgements in a cross‐tabulation of study by entry. This display of internal validity indicates the weight the reader may give the results of each study.

We judged trials to have an overall high risk of bias if we rated them as high for any one of three key criteria (randomisation sequence, allocation concealment and blinded outcome assessment). We classified RCTs as being at overall unclear risk of bias if any one of the three key domains was rated as unclear. RCTs were judged to be at overall low risk of bias only if we rated all three key domains as low risk.

Measures of treatment effect

We performed data analysis according to Cochrane guidelines. One review author (DA) entered quantitative data into RevMan 5.3 (RevMan 2014); these were checked by another review author (FD) and analysed using Cochrane‐associated software. We present a narrative overview of all included RCTs, with results grouped according to the comparator intervention. We present the outcome results for each trial with 95% confidence intervals (CIs). We report estimates for continuous outcomes (such as ejection fraction and venous refilling time) as mean differences (MDs) and overall effect size (with 95% CIs). We planned to report dichotomous outcomes (such as ulcer incidence) as risk ratios (RRs) with associated 95% CIs.

Unit of analysis issues

We treated the number of individual participants as the unit of analysis in this review. When data were reported using the number of limbs instead of individual participants, we attempted to carry out the appropriate adjustments for data analysis. We planned to include cluster‐randomised trials in the analysis. If any cluster‐randomised trials had been identified, we would have adjusted the results when the unit of analysis in the trial was presented as the total number of individual participants instead of the number of clusters. We intended to adjust the results using the mean cluster size and intracluster correlation coefficient (Deeks 2011); however, no cluster size trials were included in this review. For meta‐analysis, we planned to pool data from individually randomised trials using the generic inverse‐variance method, as described in Chapter 16 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011c).

Dealing with missing data

We contacted the original investigators to request any missing data whenever possible. No additional data were provided by study authors. If a trial did not specify participant group number prior to dropout, we present only complete case analyses for primary and secondary outcomes.

Assessment of heterogeneity

If, for future updates, we are able to include a sufficient number of studies, we will pool data for meta‐analysis using RevMan (RevMan 2014). We will consider clinical heterogeneity (that is the degree to which trials appear similar in terms of type of participants, type and duration of intervention, and type of outcome) and statistical heterogeneity. We will assess statistical heterogeneity using the Chi² test (a significance level of P < 0.10 will be considered to indicate significant heterogeneity) in conjunction with the I² statistic (Higgins 2003). The I² statistic examines the percentage of total variation across trials due to heterogeneity rather than variation due to chance (Higgins 2003). Heterogeneity will be categorised as follows: I² values ≤ 40% will indicate a low level of heterogeneity and ≥ 75% will represent very high heterogeneity (Deeks 2011).

Assessment of reporting biases

If, for future updates, we are able to include a sufficient number of studies (10 RCTs or more), we will attempt to assess publication bias using funnel plots as described in the Cochrane Handbook for Systematic Reviews of Interventions (Sterne 2011). If asymmetry is present, we will explore possible causes, including publication bias, poor methodological quality and true heterogeneity.

Data synthesis

We included insufficient studies to pool data for meta‐analysis and so present a narrative overview of the included RCTs. For future updates we plan to present a narrative overview of the combined studies with a meta‐analysis of outcome data using RevMan 2014 where appropriate. Our decision to include studies in a meta‐analysis will depend on the availability of treatment effect data and an assessment of heterogeneity. For comparisons where there is no apparent clinical heterogeneity and the I² value is ≤ 40%, we will apply a fixed‐effect model. Where there is no apparent clinical heterogeneity and the I² value is > 40%, we will apply a random‐effects model. However, we will not pool data where heterogeneity is very high (I² values ≥ 75%).

Subgroup analysis and investigation of heterogeneity

If, for future updates, we are able to include sufficient data (10 RCTs or more) and identify substantial heterogeneity we will conduct subgroup analyses. We plan to carry out subgroup analyses according to differences in the following variables: studies that report the treatment in the presence or absence of compression therapy independent of type (elastic or non‐elastic) or level (moderate or high) of compression.

Sensitivity analysis

If, for future updates, we are able to include a sufficient number of studies, we plan to undertake sensitivity analyses according to risk of bias, excluding RCTs that we judged as being at overall high or unclear risk of bias.