Short rest periods should be used to maximize muscle pump and growth hormone levels. Long rest periods are best only for strength athletes.
PROSECUTION
Metabolic stress produced by short rest periods is only one factor in producing a growth stimulus. Load stress and total training volume are also very important for long-term growth as well as continued strength gains.
EVIDENCE
Results of blood-flow-restriction exercise clearly show that metabolic stress is a key factor in stimulating muscle growth. Short rest periods produce higher metabolic stress and stimulate production of satellite cells.
Research shows that short rest periods ultimately limit the total volume that can be done due to fatigue.
Greater increases in growth hormone are often seen with shorter rest periods. When compared with longer rest periods, however, the difference becomes smaller and smaller until around Week 10, at which point both short and long rest periods cause only small changes in growth hormone release.
Studies controlling for growth hormone changes have shown that the temporary spikes in growth hormone that occur during a weight training workout have no impact on muscle and strength gains.
When compared directly, the difference in gains using short vs. long rest periods is not significant. In fact, some studies have shown longer rest periods (for example, 2.5 minutes) actually produce greater gains in muscle size.
VERDICT: NEITHER
Both short and long rest periods offer their own specific advantages. Short rest periods produce more metabolic stress, and long rest periods allow you to handle more weight and more volume.
SENTENCING
Rest periods should be manipulated just as you manipulate other important variables in your training plan. At the start of a training cycle, short rest periods increase the efectiveness of lighter weight loads and stimulate muscle satellite cells that will be important for later muscle-damaging workouts.
As you progress through your cycle, gradually increase the weight and increase the rest periods. This will allow a consistent increase in training loads. When rest periods reach the three-minute mark, perform a dropset on the last set or perform one high-rep set following the last set for each muscle group.
