Be Fit as a Marine - William H Rankin - Bog

Exercise without effortBe physically fit in seconds
In this book Colonel Rankin adapts the famous principles that have developed thousands of raw recruits into fighting Marines, and he makes those principles available to every reader.

The exercises can all be performed without the tedious stress and strain usually associated with physical fitness. They can be made a part of the normal day's activity, and incorporated into the reader's own particular routines or schedules without loss of time. None of them require special equipment.
Based on the idea of isometric contractions - a series of exercises which utilize all the muscles of the body - anyone who is willing to spend ten minutes a day can be assured of noticeable improvement in his physical well-being within one month.