This article discusses the three biggest myths in the field of how to gain muscle mass, detraining, and fast twitch muscle exercises.


  • High-weight, low-reps workout plans are equally effective for muscle gain as low-weight, high-rep workout plans.
  • Taking time off from the gym does not result in complete muscle loss. Muscle memory allows previously trained lifters to regain muscle faster than those without training experience.
  • Muscle fiber types can switch based on exercise modality.

The fitness community is a place of fitness myths about gaining muscle and losing fat.  Some of the most recent debunked myths are:

In the issue of Biochemist, A paper titled Busting False Myths was authored by some of the leading experts in the field of exercise physiology, Dr. Bagley, Galpin, and Murach.  The review broke down the three biggest myths in the field of how to gain muscle mass, detraining, and fast twitch muscle exercises.


Lift heavy and eating a ton of protein has always been a prerequisite for gaining muscle. All the great bodybuilders of the past that packed massive amounts of muscle, such as Ronnie Coleman and Dorian Yates, lifted heavy weights. The common practice of bodybuilders for increasing muscle mass was using heavier amounts of weight and lower rep ranges.

Using heavier weights, lower rep is thought necessary for muscle hypertrophy. The use of heavy weight for building muscle was based on the premise that progressive overload, in which the muscle used heavier and heavier weights each workout, led to increased muscle growth. It was believed that high-rep workouts (i.e., 20-30 reps) were only good for improving cardiovascular fitness and should only be used by endurance athletes.

Today, it’s well established that you can equally build muscle with heavy and light weights. (Lacio et al., 2021) Higher rep vs. low rep training can result in equal gains in muscle size. A literature review found that using high rep, low weight workouts was equally effective as a high weight, low rep workout for gaining muscle.  (Carvalho et al., 2022)

If strength gains are your focus, then high rep vs. low rep makes a difference. Heavier weights, lower reps are more favorable for strength gains.

The one caveat is that light weight must be used at a high exertion level.(Fisher & Steele, 2017) This suggests that you do not have to train with heavy weights year round; you can alter with periods of lighter weight and make equal gains in muscle mass. A recent study found that when subjects added more weight or added reps, it resulted in similar gains in muscle mass. (Plotkin et al., 2022) So, the old gym myth, “Train heavy or go home,” can be laid to rest.


A long-held belief was that if you stop training, you lose all your muscle gains and start from scratch. Researchers now understand that there is indeed muscle memory. A fascinating study had subjects divided into two groups.

One group trained continuously over 24 weeks, whereas the other group performed periodic resistance training, in which they trained for six weeks and had a 3-week detraining period (i.e., no training). This was repeated twice.

At the end of the study, both groups had similar increases in strength and muscle size.[5] If you thoroughly analyze the study, the group that took off the 3 weeks had initial losses in strength and size, but this was regained rapidly when training resumed. The retraining group gained muscle twice as fast as the continuous group, so by the end of each 6-week retraining phase, the periodic group had caught up with the continuous group.(Ogasawara et al., 2013)

high rep low weight workout high weight low rep high weight low reps heavy weight or light weight for muscle gain muscle gain how to gain muscle mass how to gain muscle
Well-trained lifters re-gain muscle faster when taking time off from the gym.


Nature endows individuals with specific athletic abilities rooted in their genetic composition, particularly concerning the type of muscle fibers they inherit (either slow twitch or fast twitch). The assertion implies that lacking a particular fiber type precludes one from achieving athletic excellence. It’s essential to delve deeper into this claim by examining the myriad factors influencing athletic performance and understanding the significance of genetics in determining an individual’s athletic prowess. Meaning that you are either born to be a distance runner with lots of type I aerobic fibers or a power-oriented athlete with lots of fast twitch, explosive fibers.

It was once thought that you could not change fiber types. The review paper discussed two fascinating studies to disprove that you can’t change fast twitch and slow twitch types.

The first study found that untrained subjects who participated in 16 weeks of marathon training had an increase in slow twitch fibers (i.e., aerobic fibers) by 10%. (Trappe et al., 2006) The other study took muscle biopsies of genetically identical twins 52 years old (i.e., one brother was sedentary his entire life, and the other twin was a sub-elite triathlon athlete).

The sedentary twin had <40% aerobic type I fibers, whereas the active twin had >90% aerobic fibers. The review article discussed how exercise could change muscle fiber types. (Bathgate et al., 2018)

The debate over heavy weight or light weight for muscle gain is dead.  Both are similarly favorable for muscle growth.  To improve workout motivation, it’s advisable to use a combination of heavy and light weight exercises to maximize muscle gains.


Bathgate, K. E., Bagley, J. R., Jo, E., Talmadge, R. J., Tobias, I. S., Brown, L. E., Coburn, J. W., Arevalo, J. A., Segal, N. L., & Galpin, A. J. (2018). Muscle health and performance in monozygotic twins with 30 years of discordant exercise habits. Eur J Appl Physiol, 118(10), 2097-2110.

Carvalho, L., Junior, R. M., Barreira, J., Schoenfeld, B. J., Orazem, J., & Barroso, R. (2022). Muscle hypertrophy and strength gains after resistance training with different volume-matched loads: a systematic review and meta-analysis. Appl Physiol Nutr Metab, 47(4), 357-368.

Fisher, J. P., & Steele, J. (2017). Heavier and lighter load resistance training to momentary failure produce similar increases in strength with differing degrees of discomfort. Muscle Nerve, 56(4), 797-803.

Lacio, M., Vieira, J. G., Trybulski, R., Campos, Y., Santana, D., Filho, J. E., Novaes, J., Vianna, J., & Wilk, M. (2021). Effects of Resistance Training Performed with Different Loads in Untrained and Trained Male Adult Individuals on Maximal Strength and Muscle Hypertrophy: A Systematic Review. Int J Environ Res Public Health, 18(21).

Ogasawara, R., Yasuda, T., Ishii, N., & Abe, T. (2013). Comparison of muscle hypertrophy following 6-month of continuous and periodic strength training. Eur J Appl Physiol, 113(4), 975-985.

Plotkin, D., Coleman, M., Van Every, D., Maldonado, J., Oberlin, D., Israetel, M., Feather, J., Alto, A., Vigotsky, A. D., & Schoenfeld, B. J. (2022). Progressive overload without progressing load? The effects of load or repetition progression on muscular adaptations. PeerJ, 10, e14142.

Trappe, S., Harber, M., Creer, A., Gallagher, P., Slivka, D., Minchev, K., & Whitsett, D. (2006). Single muscle fiber adaptations with marathon training. J Appl Physiol (1985), 101(3), 721-727.

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