In order for a muscle to increase in size/strength it must be fatigued or OVERLOADED in order for an adaptive response to occur. It really doesn't matter whether you fatigue your muscles in one set or several sets - as long as your muscles experience a certain level of exhaustion.
When performing multiple sets, the cumulative effect of each successive set makes deeper inroads into your muscle thereby creating muscular fatigue; when performing a single set to failure, the cumulative effect of each successive repetition makes deeper inroads into your muscle thereby creating muscular fatigue.
Numerous research studies have shown that there are NO significant differences when performing either one, two or three sets of an exercise, provided, of course, that one is done with an appropriate level of intensity (i.e. to the point of concentric muscular failure).
When performing multiple sets, the cumulative effect of each successive set makes deeper inroads into your muscle thereby creating muscular fatigue; when performing a single set to failure, the cumulative effect of each successive repetition makes deeper inroads into your muscle thereby creating muscular fatigue.
Numerous research studies have shown that there are NO significant differences when performing either one, two or three sets of an exercise, provided, of course, that one is done with an appropriate level of intensity (i.e. to the point of concentric muscular failure).