Research Article

Stress Recovery Effects of High- and Low-Frequency Amplified Music on Heart Rate Variability

Figure 2

Stress recovery ratio of heart rate variability index. Box plot showing median (central lines) and 25% and 75% quartile ranges around the median (box width) and upper and lower limits. Error bars indicate standard deviation. ; HFM: music with an amplified high-frequency component; HFnu: high-frequency normalized unit; HR: heart rate; LF/HF: low-/high-frequency ratio; LFM: music with an amplified low-frequency component; LFnu: low-frequency normalized unit; OM: original music.