All about base excess â to BE or not to BE. In 1948, Singer and Hastings introduced the concept of buffer base (BB). The change in BB from normal was called deltaBB (Î´BB). This change in BB was an expression of the non-respiratory (metabolic) component of an acid-base disturbance.
Empirically from http://www.usaswimming.org/_Rain..., free style is the fastest stroke. This is also called the front crawl (see Front crawl). However as Swimming stroke notes, there are at least 6 variations of that technique.
Butterfly stroke is the least used swimming stroke and probably the most strenuous of all four swimming strokes. It requires quite a lot of and effort propel you through the water and is considered the most challenging of all four strokes to swim with an emphasis on the back trunk and lower limb muscle groups.