Fig. 2

a Standard mean differences in HbA1c observed with non-progressive aerobic training and control (no intervention). b Standard mean differences in HbA1c with progressive aerobic training and control (no intervention). (Black square) Study-specific estimates; (black diamond) pooled estimates of random-effects meta-analyses. Std diff standardized difference, CI confidence interval. Letters (a and b) subscribed indicate different aerobic training protocols in a same study