From Military.com:Guest Writer: Jim K from Thessaloniki, Greece
One day I came across in the internet Navy SEAL fitness books (about one year before enlisting for my obligatory Greek military service). I decided to purchase one book which got me into all round fitness, running, lifting weights, swimming & calisthenics (by Dockery), which felt really good by the way. This triggered me to do some further searching on Navy SEALs) and I decided to attempt Stew Smith's "BUD/S warning order". In fact I would have a free weights session at the gym and then get back home for a one hour session of calisthenics (not recommended to anyone since it can cause serious injuries due to severe muscle strain).
My Comment: I started training a month ago, using the PX90 course as my guide. It is tough, and while I am in good shape .... it is still tough for an old guy like me.
I looked at the Navy Seal program, and it certainly is in a different category of fitness. Congrats to Jim K from Thessaloniki, Greece in "surviving" the program and maintaining his form.