Differentiate between the different types of rates of modulation

Single twitch – muscle fibre is restimulated after it has completely relaxed (the second twitch is the same magnitude as the first) Twitch summation – muscle fibre is restimulated before it has completely relaxed (the second twitch is added on to the first twitch, resulting in summation)   Tetanus – muscle fibre is stimulated so rapidly that it does not have an opportunity to relax at all between stimuli (maximal sustained contraction)