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Is there a most important training aspect to increase muscle size?

A common training goal is to improve body composition, meaning lose fat gain muscle. Beginners to resistance training usually see rapid gains in strength and then subsequent gains in muscle growth. However, as a people advance continually increasing muscle size may be difficult. The best mechanism for hypertrophy has been debated and researched. It is generally accepted that muscle tension, metabolic stress, and muscle damage are the cause of muscle growth but it is unknown whether causing more than one of these scenarios is additive or redundant (3). Simply stated, is muscle tension + metabolic stress better than muscle tension or metabolic stress on its own?


Mechanical tension is absolutely necessary for muscle growth, without a training stimulus, muscle will atrophy. However, muscle growth has been seen with low training intensities (30-40%) with blood occlusion training.

Lowery et al. conducted a study with the purpose of comparing low intensity blood flow restriction to volume matched high intensity training and its effects on biceps muscle hypertrophy. Blood flow restriction was applied either on week’s 1-4 or weeks 5-8 to subjects aged 23 +/- 5 years with a minimum of one year of resistance training experience. The blood flow restriction group would perform 3 sets of 30 repetitions with 30% of their 1 repetition maximum. The high intensity group would perform two times the load with half of the repetitions. It was discovered that the high intensity and low intensity blood flow restriction groups comparably increased biceps muscle thickness regardless of when blood flow restriction took place (2). This lends support to the theory that metabolic stress and the muscle pump may have a comparable effect to mechanical tension for muscle hypertrophy.


Schoenfeld et al. recently came out with a novel study on muscle hypertrophy in previously trained male subjects to examine volume equated resistance training programs. The study had two groups, a strength training group which employed high levels of mechanical tension and a hypertrophy training group which employed high levels of metabolic stress. The strength group did 3 reps per set with 3 minutes rest compared to the 10 reps and 1.5 minutes rest in the hypertrophy group.

The end result was that there was no significant difference in muscle hypertrophy for the biceps brachii. However, the mean duration for the strength training group was 70 minutes compared to 17 minutes in the hypertrophy training group. The authors stated:

“Metabolic stress is redundant rather than additive with respect to increasing muscle protein accretion… any hypertrophic advantages seen with hypertrophy type training are due to greater volume loads as opposed to inherent aspects of the protocol itself” (4).

Brad has written about his study here and has done a brief podcast on the topic here.

So what is the best mechanism for muscle hypertrophy? It would seem that volume is the main determinant of growth and in order to get the most work done in a time efficient manor, moderate loads with moderate intensities and short rest periods seem to be the best option.

However, it should be noted that strength training is beneficial for hypertrophy training. Firstly, through mechanical tensions, strength training does help to add muscle mass as was shown by Schoenfeld. The increased muscle from strength training may be due to increased contractile protein hypertrophy compared to noncontractile protein hypertrophy from a bodybuilding style of training (1). This is called sarcoplasmic hypertrophy which doesn’t necessarily mean increased strength (3).

Strength training may also help with motor unit recruitment which could lead to the trainability of previously unused muscle fibers. Finally, the ability to lift more weight means that it is possible to lift heavier weight for increased repetitions which would further increase the hypertrophic response (1).

If the main goal is to increase muscle size stick with multijoint exercises with varying intensities within the hypertrophy training zone (roughly 65-80%). Add in strength training blocks as well so more weight can be lifted, meaning increased volume, which is probably the main factor in muscle growth.

Kai Greene makes the point that weight lifters and body builders train differently. Also if you have seen pumping iron you see that bodybuilders chase the pump (metabolic stress) rather than train at highly intense weights. Brad Schoenfeld had another great review on the muscle pump called The muscle pump: Potential mechanisms and applications for enhancing hypertrophic adaptations


  1. Bloomer RJ and Ives JC. Varying neural and hypertrophic influences in a strength program. Strength Cond J 22: 30-35, 2000.
  2. Lowery RP, Joy JM, Loenneke JP, de Souza E, Machado M, Dudeck JE, Wilson JM. Practical blood flow restriction training increases muscle hypertrophy during a periodized resistance training programme. Clin Physiol Funct Imaging 34: 317-321, 2014.
  3. Schoenfeld BJ. The mechanisms of muscle hypertrophy and their application to resistance training. J Strength Cond Res 24: 2857-2872, 2010.
  4. Schoenfeld BJ, Ratamess NA, Peterson MD, Contreras B, Tiryaki-Sonmez G, & Alvar BA. Effects of different volume equated resistance training loading strategies on muscular adaptations in well trained men. J Strength Cond Res

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