Fig 1.
Schematic representation of the experimental procedure.
Fig 2.
Individual data: Interbeat intervals and frequency analysis during rest periods with spontaneous breathing and during HRV-BFB training.
(A) Example of interbeat intervals during four minutes of a resting state. Changes in RR are small and irregular. (B) Example of interbeat intervals during five minutes of HRV-BFB training. Changes in RR are large and regular due to respiration. (C) Frequency analysis during 5 minutes in a resting rate indicates low amplitude of L and HF. (D) Frequency analysis during 5 minutes of HRV-BFB training indicates very high amplitude LF oscillation at a single frequency.
Table 1.
Baseline psychological (trait anxiety) and physiological, temporal and frequency indices obtained for the both experimental groups.
Fig 3.
Mean (standard error) cardiac coherence scores obtained from each HRV-BFB training session (morning, M and evening, E) recorded with the application URGOfeel® (URGOTECH).
Fig 4.
Individual anxiety states in each group at exam1 and exam2.
Note the significant decrease in anxiety in the HRV-BFB group only. The dotted line represents high levels of anxiety state (data from Spielberger D. 1966). *** p < 0.001 between the two sessions of examination.
Fig 5.
Autonomic function evaluated by HRV analysis in time and frequency domains at baseline, at 5 weeks post BFB-HRV training (Post5), and at Exam1 and Exam2.
Mean values of RMSSD were reported at the top of the Figure. Sympathovagal balance calculated from HF in normalized units (HFnu) was reported at the bottom of the Figure. *** p < 0.001; ** p < 0.01 indicate significant differences between sessions.
Fig 6.
Principal component analysis for BFB-HRV group.
(A) data recorded at Exam1, (B) data recorded at Exam1 and at Exam2.