How long does it take to increase muscle mass after beginning a strength training program?
Well, that’s a loaded question. A quick google search opens up thousands of fitness blogs all claiming to have the answer, usually ranging anywhere from days to months. The truth must be somewhere in the middle, right?
First, we need to make sure we are asking the right question.
Each body is unique and each exercise program is unique. As such, we should expect a unique response of that body to that program. It would be unreasonable to expect an 80 year old to respond like a 20 year old, or new exerciser versus an experienced one, or a person working out 4 days a week compared to a person working out 2 times a month.
To help arrive at an appropriate answer, it sometimes helps to understand the physiology of what is happening when we work out.
While there is a degree of disagreement on this issue in terms of timing, most physiologists seem to agree that early strength gains in an exercise program are largely due to increased efficiency of our neurological system. Essentially, we do a better job of contracting elements of the target muscle group, as well as reducing activity of muscles on the other side of the body. We press harder on the gas and let off the brake, but the engine doesn’t get any better (1,2).
Additionally, evidence suggests that even when activating a muscle group on only one side, the opposite side experiences strength gains as well (i.e. doing a right bicep curl increases strength in the left bicep). This suggests an element of neurological involvement (3). These variables help to explain why we often feel stronger relatively quickly when starting to exercise, but lose that rapid improvement after several weeks
This refers to the actual growth of muscle. This may or may not correlate with strength. The majority of research seems to agree that hypertrophy requires exercise induced muscle damage. This muscle damage is followed by cellular processes that stimulate protein to be manufactured and used in the repair process (4).
As long as the amount of protein we produced is greater than what we broke down, we’re good.
Recently, research has shown this can occur as early as 2-3 weeks into an exercise program (1). Of course, it is important to point out, that these changes are occurring at the molecular level and don’t necessarily translate to visual or functional changes. Of interest is a paper from 2011 which concluded that previously inactive men could see hypertrophy within 3-4 weeks of beginning a program, exercising every other day (5). Of course, within 5 days of ceasing training, muscle losses can also be detected (6)
Most fitness research is conducted among young men and women, many of whom are active. As such, it is difficult to extrapolate results to other groups of people.
Future blog posts will get into the specifics of different groups of people, but in general:
- Novice exercisers will see greater early gains than experienced ones
- Men add more muscle, but not necessarily more strength, than women
- The older you are, the slower the process is (but still doable)
- The upper body grows faster than the lower body
- Functional gains still take much longer than the microscopic gains discussed above
- If you have pain, it will take longer (7)
1.Seynnes, O. R., M. de Boer, and M. V. Narici. Early skeletal muscle hypertrophy and architectural changes in response to high-intensity resistance training. J. Appl. Physiol. 2007;102:368-373
- Moore, D. R., S. M. Phillips, J. A. Babraj, K. Smith, and M. J. Rennie. Myofibrillar and collagen protein synthesis in human skeletal muscle in young men after maximal shortening and lengthening contractions. Am. J. Physiol. Endocrinol. 2005;288: E1153-E1159
- Brown, A. B., N. McCartney, and D. G. Sale. Positive adaptations to weight-lifting training in the elderly. J. Appl. Physiol. 1990;69:1725-1733
- Behm, D. G. Neuromuscular implications and applications of resistance training. J. Strength Cond. 1995; 9:264-274, 1995
- DeFreitas J, Beck T, Stock M, Dillon M, Kasishke P. An examination of the time course of training-induced skeletal muscle hypertrophy. Eur J Appl Physiol. 2011;111:2785-2790
- Krentz J, Farthing J. Neural and morphological changes in response to a 20-day intense eccentric training protocol. Eur J Appl Physiol. 2010;110(2):333-340
- Krentz J. Time course of muscle hypertrophy, strength, and muscle activation with intense eccentric training. USask, 2008 (unpublished thesis)