Effect of vitamin C on 5-min postexercise changes for different pulmonary function outcomes according to the study by Schlesinger and Schachter . Effect of vitamin C on the following 5 min after exercise: A) the postexercise FEV1 change, B) the postexercise PEF change, C) the postexercise FEF60 change, and D) the postexercise FEF60 level. Figures 2A, B, and C show the effect of vitamin C in percentage points (pp). For example, on the placebo-day, participant #11 had a postexercise FEV1 decline of 52%, and on the vitamin C day a postexercise FEV1 decline of 33%, which gives the 19 pp improvement shown in Figure 2A. Figure 2D shows the effect of vitamin C in percentages. For example, on the placebo-day, participant #11 had a postexercise FEF60 level of 0.2 L/s, and on the vitamin C day a postexercise FEF60 level of 0.5 L/s, which gives the 150% increase shown in Figure 2D. Figure 2 uses the same identification numbers for participants as those used in the original paper . The dash lines indicate equality between vitamin C and placebo. If vitamin C had no effect, the observations would be located randomly and symmetrically around the dash lines. The continuous lines indicate the regression lines. In Figure 2A, the addition of the placebo-day postexercise FEV1 change to the model containing the intercept improved the model fit by χ2(1 df) =16.5 (P =0.0001). In Figure 2B, the slope did not significantly differ from the null effect and therefore the regression line is not shown. In Figure 2C, addition of the placebo-day postexercise FEF60 change to the model containing the intercept improved the model fit by χ2(1 df) =10.5 (P =0.001). In Figure 2D, adding the two spline segments with the knot at 1.1 L/s to the model containing only the intercept improved the model fit by χ2(2 df) = 24.7 (P = 0.000004). For the statistical methods of Figure 2, see Additional file 1.