Does Xiaomi Smart Band 8 support automatic heart rate monitoring?

Support.
Device turned on:
Device-System-Sort apps-Heart rate, click to view the heart rate details of the day, slide up to the bottom and click "Settings" to set the heart rate monitoring frequency:
Can be set: intelligent monitoring, 1 minute, 10 minutes and 30 minutes. When the smart monitoring is turned on, the band will intelligently adjust the monitoring frequency according to its own activity status.
App open:
Open Mi Fitness App->Device->Health monitoring->Heart rate to enable automatic heart rate monitoring and set the measurement frequency. The strip will automatically measure your heart rate according to the set frequency and record heart rate changes. In different modes, the heart rate measurement frequency is different, which has different effects on the battery life of the band.
After the automatic heart rate monitoring is turned on, the heart rate will be monitored throughout the day, which greatly reduces the battery life of the band. You can set the monitoring frequency by yourself: 1 minute, 10 minutes, 30 minutes and intelligent monitoring;
After the intelligent monitoring function is enabled, the measurement frequency will be automatically increased when it is detected that you are active, and more heart rate changes can be recorded. The heart rate is measured for 25 seconds every 10 minutes when you are quiet, and 25 seconds every 1 minute when you are active;
You can view the heart rate interval distribution of the day through the heart rate application of the band.