Exercise Variability and Muscular Hypertrophy

📝 Weekly paper summary

Does Varying Resistance Exercises Promote Superior Muscle... : The Journal of Strength & Conditioning Research

ining exercises in program design as a strategy to enhance muscular adaptations. However, it remains uncertain whether such an approach offers advantages over a fixed-exercise selection. The objective of this review was to review the effects of exercise variation on muscle hypertrophy and strength.…

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Does Varying Resistance Exercises Promote Superior Muscle Hypertrophy and Strength Gains? A Systematic Review (Witalo et al., 2022)

Category

Systematic Review

Context

I share a lot of content about how researchers and practitioners can assess and promote movement variability to improve training-related outcomes. Usually, that's centred around how people move, but that's not the only training adaptation that we tend to seek. For example, muscle hypertrophy may be another important (or even just desirable) adaptation for trainees. Therefore, if we're promoting movement variability in strength and conditioning contexts, it's also essential to understand how these programs may influence how much muscle someone may put on (or sacrifice putting on). This review aimed to summarise the relevant literature on the topic, which can help practitioners more deeply understand the implications of promoting movement variability during training.

Correctness

I won't comment much on the review methods because they are relatively standard, but one thing I should mention is the "areas" of movement variability:

1. Between reps, within a set
2. Between sets, within a training session
3. Between training sessions

The studies highlighted in this review focused entirely on (2) and (3), so we have gaps in our understanding of how (1) may influence muscle hypertrophy.

Secondly, this review focused much more on exercise variation than movement variation (mainly because that's the literature that currently exists). While these are very similar concepts, they are not synonymous (i.e., you could do the "same exercise" on paper but still have considerable movement variability depending on the instructions, feedback, demands imposed, etc.). Again, not a limitation but something to be aware of when interpreting the existing (limited) literature!

Contributions

Of the eight existing studies that satisfied the review criteria, here are some key quotes from the authors:

"When considering the literature as a whole, it can be inferred that exercise variation may enhance hypertrophy in a regional-specific manner over relatively short-term periods (8–12 weeks; 8–27 sessions), but these changes are less evident in surrogate measures of whole muscle mass. Unpublished data from our research group (see Supplementary Material, http://links.lww.com/JSCR/A324) indicated similar increases in DXA-derived measures of total-body muscle mass for nonvaried and varied groups by 1.2 kg (ES 5 0.30) and 1.0 kg (ES 5 0.26), respectively, lending further support to this conclusion." (pg. 6)

"...exercise selection for hypertrophy-related goals should not simply involve random selection among diverse exercises but rather an integrated strategy designed to target each muscle group" (pg. 7)

"It seems likely that very frequent rotation of exercises may not be as effective as more moderate variations to induce muscle hypertrophy, potentially because of the difficulty of achieving and quantifying the progressive overload. Also, if the exercise rotation is very frequent (e.g., different exercises every training session), it is likely that the individual will experience more prolonged fatigue, conceivably because of the exercise-induced muscle damage promoted by an unaccustomed stimulus (12). This may have detrimental consequences on training frequency and volume and, consequently, impair the magnitude of hypertrophic adaptations." (pg. 8)

• To crudely summarise this paper and tie in some previous concepts, such as differential learning, perhaps there could be a trade-off at times between promoting the exploration of movement solutions and building muscle. However, with a more targeted approach to guiding the exploration of movement solutions, perhaps we don't have to sacrifice as much potential muscle hypertrophy. As the authors pointed out in this paper, we need more data on the topic. Nevertheless, this review provides interesting data to consider when promoting (movement) variability during training.

🧠 Fun fact of the week

Carrots were not originally orange. Instead, carrots were initially purple, and those were the norm. Over time, some mutations resulted in yellow and white carrots. In the 17th century in Holland, some carrot farmers cultivated these yellow and white carrots in the more familiar orange carrots we know today. The purple carrots still exist but are rare and don't taste quite as nice as the orange carrots we are used to eating.

🎙 Podcast recommendation

🗣 Quote of the week

"You can only grow if you're willing to feel awkward and uncomfortable when you try something new."

- Brian Tracy