Many years ago, before I became an acupuncturist I was in Honolulu riding the bus and saw an elderly Chinese man vigorously rubbing and pressing on the outside of both of his legs just below the knee.
He was stimulating this point: Stomach 36 or Zusanli, which translates as "leg 3 miles". The meaning implies that if you treat this point you will be able to walk 3 more miles, even if exhausted.
The importance of the this point in Chinese medicine cannot be underestimated. One of the most widely used, Stomach 36 is indicated for any kind of digestive problem, lack of energy, and for overall health.
You can stimulate this point yourself by pressing on the outside of your lower leg about 3 fingers width below the knee cap and just to the outside of the tibia (the pointy bone felt in the front of your lower leg). You should feel a depression there. Just press and rub that spot (you should feel a little tenderness there) to relieve digestive symptoms as needed, or stimulate a few minutes daily for good health!