Figure 2. Baseline and daily natural logarithm of the root mean square differences between adjacent normal R-R intervals (Ln rMSSD). BL = baseline; RD-1 = one day before race day; RD = race day; RD+1 = one day post-race; RD+2 = two days post-race. The shaded gray area represents the smallest worthwhile change in Ln rMSSD.