Study participants
The sample size was calculated using G*Power version 3.1 software. The number of participants needed for the independent t-test with a significance level of 0.05 in the bilateral test, a power of 0.8, and an effect size of 0.7 was 68. The planned sample size was 96, considering a dropout rate of 40%, and 100 participants were actually included in this study. The dropout rate was set fairly high because the subjects were college students or working adults. Out of a total of 101 subjects, 86 were selected, excluding 15 who declined to participate or did not meet the criteria. Subjects were then randomly grouped into two groups: a saline gargle group as the control group and an LC gargle group as the test group, with 43 people in each group. Consequently, 63 people were selected as final analysis subjects, excluding 12 subjects who did not complete the 5-d course and 11 subjects with insufficient data for analysis (Fig. Flowchart of the study