Fig.3. Changes in LF/HF ratio in controls (a) and patients with IBS (b) on the stress day compared with the rest day. There were no significant group differences. Within-group comparisons showed that, compared with the rest day, there was a significantly greater increase in the LF/HF ratio on the stress day in controls (*p < .05) from stress/rest to recovery (see panel a). This increase did not reach significance in patients with IBS. There was a significant difference between days in change from baseline to stress in patients with IBS (*p < .05) (see panel b). The data are shown as mean and SEM.