As I stated in Bodyweight Training and Stretching, in Chapter 14, we have a different perspective on being fit in Japanese natural health. Being fit means having flexible muscles and joints, not necessarily having big muscles.
Today, my son and I went to the upper stream of Echi River in Oku-Eigenji for a swim. Here, water was much colder than that of lake Biwa, so it has a further benefit as bio-hacking. There are three benefits of river swimming as Shizenha Bio-Hacking.
Kayaking can be another form of Shizenha Bio-Hacking. Well, all outdoor sports can. Shizenha people love outdoor sports. Many of them go mountain climbing, cycling, snowboarding, canoeing, and kayaking.