Figure 2: Forest plot of effect sizes (unbiased d) of pre vs. post test comparisons on VO2max and Wmap within epo treatments of seventeen epo studies included in the meta–analysis (N = 40 strata). The size of the solid black squares represents the weight the corresponding study exerts in the analysis. The 95%–confidence interval of the estimates is displayed as a horizontal line through the black square. The unfilled diamond presents the pooled estimate. (Source: Lodewijkx et al., 2013).