Bandit – a runner entering a race without qualifying or officially signing up

Bannister, Roger – the runner who originally ran a mile in less than four minutes
Bioelectrical Impedance– a method for determining body composition, by sending electrical pulses through the body to determine the opposition to the current’s flow (electrical impedance), used to determine the body’s water content, which can then be used to determine the body’s fat percentage. In comparison to other methods, bioelectrical impedance is relatively simple and inexpensive, though its results can be inaccurate by several percentage points  

Biomechanics -- research of the process of a living body’s movement

Body Composition – the percentage in fat of a body’s makeup; most guidelines recommend women have 24 percent or less body fat, while men should have 17 percent or less
Bonk – a rapid onset of fatigue during a workout, usually the result of a depletion of “Glycogen” in the muscles and liver  
Carbo-loading – attempting to increase the amount of “Glycogen” stored in the muscles and liver by eating a larger amount of carbohydrates such as bread, spaghetti, etc. and a lighter workout schedule in the days preceding the race; earlier carbo-loading training also included a “Depletion” phase of decreased carbohydrate intake and intense workouts about one week before the race with the objective of emptying the glycogen stores in an attempt to maximize the body’s capacity for storage during the loading phase, though depletion has largely been omitted from the process