if you sleep light or wake up early, Left foot（for better digestion)
if you hard to fall asleep, or wake up before 3 pm, Right foot.(for liver store and process blood)
trial: I use an apple watch to monitor my sleep, every time I massage my Left foot for 20min, my deep sleep time will increase to more than 2 hours before my deep sleep time only 40min around. I had bad digestion
when I feel hard to sleep, or coffee afternoon, I massage my right foot.