Figure 3

Effect of vitamin C on 0-min postexercise changes for different pulmonary function outcomes according to the study by Schlesinger and Schachter [56]. Effect of vitamin C on the following immediately (0 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 3A, 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 change of -11%, and on the vitamin C day a postexercise FEV₁ change of +19%, which gives the 30 pp improvement shown in Figure 3A. Figure 3D shows the effect of vitamin C in percentages. For example, on the placebo-day, participant #11 had a postexercise FEF₆₀ level of 2.2 L/s, and on the vitamin C day a postexercise FEF₆₀ level of 2.9 L/s, which gives the 32% increase shown in Figure 3D. Figure 3 uses the same identification numbers for participants as those used in the original paper [56]. 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 3A, addition of the placebo-day postexercise FEV₁ change to the model containing the intercept improved the model fit by χ²(1 df) =8.2 (P =0.004). In Figure 3B, addition of the placebo-day postexercise PEF change to the model containing the intercept improved the model fit by χ²(1 df) =10.8 (P =0.001). In Figure 3C, addition of the placebo-day postexercise FEF₆₀ change to the model containing the intercept improved the model fit by χ²(1 df) =5.7 (P =0.02) and in Figure 3D, addition of the placebo-day postexercise FEF₆₀ level to the model containing the intercept improved the model fit by χ²(1 df) =11.4 (P =0.001). For the statistical methods of Figure 3, see Additional file 2.