Many popular strength training programs involve "straight sets" which involve multiple sets with the same weight.
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However, such programs usually involve a very high number of reps in reserve for the early sets, in order for all sets to be completed successfully. This means that although the total number of reps may be quite high, this does not translate to a high number of stimulating reps.
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Strength training volume is a key determinant of the amount of muscle growth that happens after a sequence of workouts. However, exactly how we should best measure volume is unclear.
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Common methods of measuring training volume include counting the number of sets to failure or the volume load (sets x reps x weight), although many approaches have been used by researchers.
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Even so, none of these current methods of measuring volume may be ideal, because they do not accurately record the volume of the mechanical stimulus that triggers muscle growth.
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The mechanical stimulus that triggers muscle growth is the duration of time for which the muscle fibers controlled by high threshold motor units are activated and shorten slowly.
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Contractions that involve faster movement speeds, or which do not activate these particular fibers, do not stimulate much hypertrophy. Sets of light or moderate loads must therefore include some reps that cannot provide any stimulus at all.
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Despite this, most of our current methods for measuring volume will record them as part of the total.
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When measuring volume for bodybuilding, it would be best if we only counted those reps that activate high-threshold motor units while bar speed is slow, and which therefore stimulate muscle fiber growth.
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A theoretically more effective way of training would thus be rest pause training, where the first set brings you close to failure, and subsequent reps remain close to failure.