What the Science Says About Weight Training for Muscle Building

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This article takes a look at the position stand of the American College of Sports Medicine titled "Progression Models in Resistance Training for Healthy Adults, 2009." Included is a summary of the evidence from a well-qualified group of experts for the effectiveness of various procedures and practices in resistance and weight training programs.

American College of Sports Medicine Recommendations Related to Weight Training

Note that in this version of the ACSM stand, the authors have graded the quality of the evidence as follows:

  • A - Best class of evidence (randomized controlled trials (RCT))
  • B - Second level of evidence (fewer RCT)
  • C - Third level (observational only, not RCT)
  • D - Least quality of evidence (panel consensus judgment, clinical experience)

Muscle Building (Hypertrophy)

Progressive overloading is necessary for maximal muscle fiber recruitment and size increases. That is to say, although exercise can help individuals get stronger and build muscle, their progress will stall if they keep doing the same workouts. In order to gain additional strength and muscle, individuals need to continually increase the intensity of their workouts.

The guidelines below are for muscle building specifically (as opposed to training for strength or endurance). RT stands for "resistance training" in the following discussion.

Muscle Action

Evidence category A. "Similar to strength training, it is recommended that concentric, eccentric, and isometric muscle actions be included for novice, intermediate, and advanced RT."

Loading and Volume

Evidence category A. "For novice and intermediate individuals, it is recommended that moderate loading be used (70-85% of 1 RM) for 8-12 repetitions per set for one to three sets per exercise."

Evidence category C. "For advanced training, it is recommended that a loading range of 70-100% of 1 RM be used for 1-12 repetitions per set for three to six sets per exercise in a periodized manner such that the majority of training is devoted to 6-12 RM and less training devoted to 1-6 RM loading."

Exercise Selection and Order

Evidence category A. "It is recommended that single- and multiple-joint free-weight and machine exercises be included in an RT program in novice, intermediate, and advanced individuals."

Evidence category C. For exercise sequencing, muscle-building and strength guidelines both recommend "large muscle group exercises before small muscle group exercises, multiple-joint exercises before single-joint exercises, [and] higher-intensity exercises before lower-intensity exercises."

Rest Periods

Evidence category C. "It is recommended that 1- to 2-minute rest periods be used in novice and intermediate training programs. For advanced training, rest period length should correspond to the goals of each exercise or training phase such that 2- to 3-minute rest periods may be used with heavy loading for core exercises and 1-2 minutes may be used for other exercises of moderate to moderately high intensity."

Repetition Velocity

Evidence category C. "It is recommended that slow to moderate velocities be used by novice- and intermediate-trained individuals. For advanced training, it is recommended that slow, moderate, and fast repetition velocities be used depending on the load, the repetition number, and the goals of the particular exercise."


Evidence category A. "It is recommended that a frequency of 2-3 days/week be used for novice training (when training the total body each workout)."

Evidence category B. "For intermediate training, the recommendation is similar for total-body workouts or 4 days/week when using an upper/lower body split routine (each major muscle group trained twice per week)."

Evidence category C. "For advanced training, a frequency of 4-6 days/week is recommended. Muscle group split routines (one to three muscle groups trained per workout) are common enabling higher volume per muscle group."

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By Paul Rogers
Paul Rogers is a personal trainer with experience in a wide range of sports, including track, triathlon, marathon, hockey, tennis, and baseball.