This review concluded, although there were limitations, the evidence suggested that treadmill training could play an important role in improving gait and mobility in patients with Parkinson's disease. These cautious conclusions may be reasonable, but cannot be considered reliable given the apparent methodological shortcomings of the review process.

To review the effect of treadmill training on the gait of patients with Parkinson's disease.

The databases searched included: MEDLINE, EMBASE, Web of Science and the Cochrane Library. Search terms were reported, but search dates were not. References were also checked. Only English language papers published up to August 2008 were considered.

Studies were included if they reported on the impact of a treadmill training intervention for more than three patients with Parkinson's disease.

Included studies investigated either: the immediate effects of treadmill training after one session or four consecutive sessions; or longer term effects of intensive treadmill training which lasted between 3.5 to 12 weeks. All but one of the longer-term studies trained three times per week, for approximately 20 to 40 minutes per session. Control groups were either patients with Parkinson's disease or healthy individuals.

The interventions included conventional gait training, unspecified treadmill training, structured speed dependent treadmill training and limited progressive treadmill training; some of these included body weight support. Control conditions included over-ground walking or physical therapy where relevant.

The most commonly reported outcome measures were gait speed, stride length and the Unified Parkinson's Disease Rating Scale (UPDRS). Other outcomes were also reported.

The authors did not report how many reviewers performed the study selection.

A published grading system, adapted from the Cochrane Musculoskeletal Review Group, was used to assign studies a ranking of platinum, gold, silver or bronze. Gold referred to randomised controlled trials (RCTs) which met all of the following criteria: sample size, blinding, withdrawals, and concealment of treatment allocation. Silver was given to RCTs which failed to meet these criteria, non-randomised controlled studies or high quality case control studies. Bronze referred to high quality case series, pre-post studies or expert opinion.

The authors did not report how many reviewers performed the validity assessment.

The authors did not report how the data were extracted for the review.

The reviewers adopted a narrative synthesis approach, grouping studies by intervention duration in text and tables.

A total of 14 studies were included in this review. The total number of participants was unclear, but there were more than 250. Eleven studies were quality assessed; none were classed as gold, five as silver and six as bronze. Follow-up ranged from one month to five months, where reported, for the longer-term studies.

Treadmill training immediate effects: The immediate effects of treadmill training were assessed by three studies: one cross-over RCT (17 participants), a controlled study (60 participants) and a study comparing three types of treadmill training with over-ground walking (24 participants). The two parallel-group studies used healthy controls rather than patients with Parkinson's disease, but the RCT comprised all Parkinson's disease patients. Overall, the findings suggested that treadmill walking promoted a faster and more stable walking pattern in patients with Parkinson's disease.

Intensive treadmill training effects: Intensive treadmill training was assessed by 11 studies (197 participants), of which six were described as RCTs (143 participants) but only three clearly described the control conditions. All studies reported some benefits immediately post-training compared with pre-training values and/or compared with changes in the control groups.

Treadmill training carry-over effects: Five studies (79 participants) reported on carry-over effects of various types of treadmill training. All suggested some of the beneficial effects continued to persist post-intervention.

The paper also reported quality of life, adverse events and other outcomes.

Although there were limitations, the evidence suggested that treadmill training could play an important role in improving gait and mobility in patients with Parkinson's disease. Additional high quality RCTs are needed before treadmill training can be recommended as an evidence-based intervention.

This review addressed a clear research question with relatively few inclusion criteria. The searches covered some of the relevant databases, but only English papers were considered for inclusion, which opened the review up to the possibility of language bias. Unpublished (grey) literature did not appear to have been accessed, so publication bias could be present. The methodological procedures of the review were poorly reported in terms of how study selection, data extraction and validity assessment were carried out, so reviewer error and/or bias could not be ruled out.

The included studies were broadly quality assessed, but this did not appear to have used within the synthesis. The choice of narrative synthesis may have been appropriate, given the variety of interventions and outcome measures reported. However, individual study results were limited and p-values were not reported. As the authors acknowledged, this review was based on relatively few studies with small sample sizes.

The authors' cautious conclusions may be reasonable, but cannot be considered reliable given the apparent methodological shortcomings.

Practice: the authors stated that further high quality RCTs are required before treadmill training can be recommended with evidence-based support.

Research: The authors stated that further research should examine issues of delivery forms, dosage, frequency, intensity and intervention prescription for treadmill training, and the effects on compliance and outcomes. Research is encouraged to explore whether treadmill training could provide symptomatic relief or if it could modify disease progression.

National Institutes of Health (NIH), grant number AG-14100; National Parkinson Foundation; European Union Sixth Framework Program, FET contract 018474-2, Dynamic Analysis of Physiological Network (DAPHNet) and STREP 045622 (Sensing and Action to support mobility in Ambient Assisted Living, SENSACTION-AAL).

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.