3.2. Heart rate variability
A full summary of the HRV parameters analysed and compared in this study is presented in Table 3. Specific variables that were found to differ within or between treatment weeks are depicted in Fig. 3. Within the silent week no consistent changes were observed in any of the assessed variables, across the two groups (A and B) over the recording day (morning and afternoon). Within the time domain variables, SSTDR and RMSDD and pNN50 differed significantly (P b 0.05) between S1 and S2 but only in the group that received silence first, and only in the afternoon recording sessions. In each case the values observed were higher in the S2 compared to the S1 recording session. A similar pattern of change was observed in SD1 (geometric analysis) with the value seen in S2 in the afternoon for Group A being significantly (P b 0.05) higher than that seen in the S1 recording session, and a sim- ilar trend being seen in SD2 (P = 0.075).