Are Changes In Running Economy Associated With Changes In Performance In Runners? A Systematic Review and Meta Analysis

Abstract

Improvements in running economy (RE) are thought to lead to improvements in running performance (P). The identification of modifiable factors that affect RE and by association, P has been the focus of a significant body of research in recent years. Modifiable factors affecting RE are broadly classified as, biomechanical, anthropometric, physiological, extrinsic and training related. Interventions have been used to alter one or more of these factors with a view to improving RE. The underlying assumption is that an improvement in RE will also lead to an improvement in P. PURPOSE: The aim of this study was to assess the effect of interventions of at least 2-weeks’ duration on RE and P and to determine whether there is a relationship between changes in RE (ΔRE) and changes in running performance (ΔP). METHODS: A database search was carried out in Web of Science, Scopus and SPORTDiscus. In accordance with a PRISMA checklist 10 studies reporting 12 comparisons between interventions and controls were included in the review. RESULTS: There was no correlation between percentage ΔRE and percentage ΔP (r = 0.46, P = 0.936, 12 comparisons). There was a low risk of reporting bias in relation to incomplete data sets. There was an unclear risk of selection bias associated with random allocation to intervention and control groups and reporting of baseline differences in RE and P between intervention and control groups. There was also an unclear risk of performance bias relating to the monitoring of non-intervention training, detection bias associated with differences in determination of the performance outcome measure and attrition bias associated with reporting of participant dropout. Meta-analyses found no statistically significant differences between interventions and control for RE (SMD (95% CI) = -0.37 (-1.43, 0.69), 204 participants, p = 0.49) or for P (SMD (95% CI) = -0.65 (-26.02, 24.72, 204 participants, p = 0.99). CONCLUSIONS: Methodologies for subject allocation to intervention and control groups and the reporting of differences in baseline characteristics of control and intervention groups and reporting of participant dropout were infrequently applied in the included studies. Studies of greater statistical power, with standardised measures of performance and greater control of non-intervention training are required.