Fig 3. The association between blood donation or transfusion and change in maximal oxygen uptake (absolute $\dot{\mathbf{V}}{\mathbf{O}}_{\mathbf{2}}\mathbf{m}\mathbf{a}\mathbf{x}$).

Forest plots depicting the effect size of the change of absolute $\dot{\mathrm{V}}{\mathrm{O}}_2\mathrm{m}\mathrm{a}\mathrm{x}$ (standard paired difference) following blood transfusion or donation. Different size symbols indicate relative weights used in meta-analyses and are proportional to study size. Abbreviations: SE, standard error.