Many people flock to free weights and weight machines in hopes of building massive muscles. Unfortunately, most are unaware of the science behind weightlifting, particularly muscle growth. There are specific protocols regarding efforts for power/strength development, muscular endurance, and muscular hypertrophy, or growth. Not knowing the intricacies of volume, frequency, intensity, progression or rest may result in benefits, but not necessarily the ones desired.
Theory
Hypertrophy is believed to be a resistance-training adaptation that results in an increase in the diameter of muscle fibers. Muscle fibers are the subcomponents of muscle. Muscle fibers themselves are composed of even smaller myofibrils. Essentially, weightlifting encourages the development of new myofibrils, which are added to the external layer of existing myofibrils. This increased thickness adds to the diameter of the myofibril and, consequently, the muscle fiber.
Intensity
Intensity refers to the level of effort an individual is committing to a task. In weightlifting, intensity is usually identified as a percentage of a one repetition maximum (1 RM) lift, or the most weight you can lift for one rep. A study performed at the University of Mary Hardin Baylor and Baylor University concluded that intensities ranging between 60 and 85 percent 1 RM are most effective for encouraging hypertrophy. Intensity is sufficient when the ability to contract the muscle concentrically (shorten) or eccentrically (lengthen) is difficult.
Volume
The volume of work during weightlifting to maximize muscle growth may vary from person to person and could be influenced by genetics. Some people are genetically predisposed with more "Type IIx" muscle fibers. These fibers tend to be predominant in those individuals who are essentially involved in anaerobic type training or activities. Nevertheless, an accepted range for volume in weightlifting is between six and 12 repetitions for a particular muscle group. The sets could range from 12 to 20 during one training session, spread out over different exercises.
Time
Time discussed here refers to the speed of the movement during weightlifting. The goal of resistance training is to challenge the muscle to the point that additional fibers are needed to support the weight. This is known as muscle fiber recruitment. Fiber recruitment usually transpires during the eccentric (muscle lengthening) phase of the lift. If movement is too fast, the body does not have time or need to recruit additional fibers. Movement of the weight, in this instance, is being orchestrated by momentum and leverage. Taking more time to complete each rep will enhance muscle fiber recruitment and spur muscle growth.
Progression
Simply put, when the selected weight is no longer a challenge once the last rep is achieved, it is then time to increase reps within the six to 12 range. Once 12 reps can be realized without a challenge, it is time to increase the weight and return to six reps.
Rest/Frequency
The timing of rest periods between sets of a training session and rest between training sessions is crucial. For muscle growth, it is important to rest in between sets, however, not to the point of full recovery. Rest period should last between 30 to 90 seconds. Any time short of 30 seconds is appropriate for muscular endurance, and rest greater than 90 seconds is more advantageious for power training. Regarding frequency, as a rule of thumb, workouts should be two to three times a week on nonconsecutive days. However, high intensity of a previous workout may warrant an additional day or two for rest and recovery.
References
- "Essentials of Strength Training and Conditioning," National Strength and Conditioning Association, Thomas Baechle and Roger Earle; 2000.
- "The Journal of Strength and Conditioning Research," Effects of Different Intensities of Resistance Exercise on Regulators of Myogenesis. Colin Wilborn et al; Vol.23:8, Nov. 2009.
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