(1) The position statement of the American College of Sports Medicine (ACSM) recommends that rest periods should be 2-3 minutes for multi-joint exercises (i.e., squats, deadlifts, bench press) and 1-2 minutes for single-joint exercises (i.e., leg extensions, bicep curls).

(2) The National Academy of Strength and Conditioning (NSCA) recommends 2-5 minutes for strength, 2-5 minutes for power, 30 seconds-1.5 minutes for hypertrophy (muscle growth), and less than 30 seconds for muscular endurance.

(3,4) A 2007 study, showed the influence of different rest interval lengths in multi-joint and single-joint exercises. This was reviewed in the November Strength and Conditioning Research Review  by Bret Contreras and Chris Beardsley.  They came away with the following key points:

When subjects performed both the multi-joint bench press and the single-joint machine chest fly, they performed a reduced number of repetitions when short rest periods (1-3 minute) were used than when longer rest periods (3 minutes) were used.

There was a progressive reduction in the number of repetitions performed for both the bench press and the machine chest fly across all sets.

The reduction in the number of repetitions was less when longer rest periods were used, irrespective of whether the exercise was a single-joint or a multi-joint exercise.