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The ever-evolving nature of science creates a never-ending obligation to reevaluate our prior training practices and recommendations against recent developments in the field. This obligation only increases when you write about these opinions publicly. Before we head into the Canada Day long weekend, I thought I’d take a quick look at a few recent studies and how they influence my training practices and recommendations. This isn’t an exhaustive review, but these studies have certainly grabbed my attention as they relate to some of my previous posts.
Is there an optimal volume for muscle growth?
When we first published our meta-analysis (1) on optimal training volumes for muscle growth, it stirred up more controversy than I expected. And while I know to “never read the comments”, I couldn’t help but notice the uproar to Jeff Nippard’s excellent discussion on training volume referencing our work.
After whittling 1474 studies down to 15 that matched our criteria, we concluded that there was a dose-response relationship between training volume across five sets, five to nine sets, and ten or more sets per muscle group per week. While we acknowledged that there was likely a point of diminishing returns, where excess volume overwhelms the ability of the muscle to adapt, we lacked data on high training volumes to determine where this point occurred.
Please note that the Barbalho papers discussed in this section have been retracted. Retraction notices can be found here and here.
A recent study by Barbalho et al (2) suggests that the hypertrophy ceiling may be lower than we thought. The researchers had women (three years training experience) perform either five, 10, 15 or 20 sets per muscle group per week, training to momentary muscular failure three times per week over 24 weeks. While all groups increased muscle strength (10RM) over the training period, generally the groups completing 5-10 sets had greater changes than those in the 15-20 set range. For muscle thickness, a similar pattern emerged, all groups increased with training, yet 5-10 sets produced greater changes than those in the 15-20 set range. A follow-up study in men demonstrated somewhat similar results, favoring five to ten sets for muscular strength, and the authors note a trend for diminishing hypertrophy returns with increasing volume (3).
While many thought our 10 sets per muscle per week was low, Barbalho’s (2,3) work suggests it might not be that low after all. Yet the volume debate is far from settled.
While the Barbalho papers (2,3) indicates a relatively low ceiling, work from Brad Schoenfeld (4) blows the roof off. When comparing one, three or five sets per exercise in a three times per week total body training program (equivalent of 6-9, 18-27, and 30-45 sets per muscle group per week for the upper and lower limb respectively) over eight weeks, Brad demonstrated greater changes in muscle thickness in the five set group over the single set group, and to a lesser extent the three set group. Strength was less sensitive to increased volume, leading the authors to conclude that 1) large increases in strength can be achieved with limited training (three 13-min sessions per week) and 2) the dose-response relationship between muscle hypertrophy and training volume may extend over a greater range than has been previously demonstrated (1).
While we can’t fully reconcile these conflicting studies into a singular training volume recommendation, starting with 10 sets per muscle group per week is likely still prudent, adjusting based on response, and considering that factors like training status and other program parameters (i.e. training frequency) may influence the required training volume to maximize muscle growth.
Does Tempo Matter for Muscle Growth
Back in 2013 I outlined how the research at the time did not support the overly complicated rep speed recommendations commonly seen in hypertrophy training programs. This led to a 2015 meta-analysis with Brad Schoenfeld and James Krieger (5) where we concluded:
“… a fairly wide range of repetition durations can be employed if the primary goal is to maximize muscle growth.”
and
“…. Training at volitionally very slow durations (>10s per repetition) is inferior from a hypertrophy standpoint…”
Tempo prescriptions for muscle growth are simple: lift at the speed you like to lift at.
A recent study by Formenti et al (6) has reignited some debate on the use of slow tempos to increase metabolic stress, and thereby promote greater muscle growth. In this study, participants completed three sets of knee extensions at 50% 1RM with tempos of one, three and five seconds per phase (two, six and ten second total repetition durations) until concentric failure. The investigators used near infrared spectroscopy (NIRS) to observe changes in oxygenated, deoxygenated, and total hemoglobin in the vastus lateralis (and the pre-frontal cortex but I’ll ignore that).
To no one’s surprise, the total number of repetitions were reduced and the rating of perceived exertion (RPE) was higher with each increase in repetition duration. Within muscle, the change in oxygen saturation was lower for the two second duration against both the six and ten second repetitions. The authors conclude that the greater deoxygenation with long duration repetitions may create increased metabolic stress and therefore provide a greater hypertrophy stimulus than faster rep speeds.
This a prime example of using an indirect outcome (muscle oxygenation) to predict a long-term outcome (muscle hypertrophy), when data on the outcome of interest (muscle growth) already exists (5). If tempos between 0.5-8s produced comparable growth, it’s unlikely that differential muscle oxygenation would be directly relevant to hypertrophy. That’s not to say it may not be relevant to other physiological response to exercise, but you probably shouldn’t justify your tempo selections in hypertrophy training based on this measure.
Myofibrillar versus sarcoplasmic hypertrophy
When I first started the site, I did a series of posts on the primary flaws with the theory that training in differing repetitions ranges results in differing subcellular adaptations, whereby sarcoplasmic components are affected more by higher repetition training, and the myofibrillar by higher load, lower repetition programs. In one post, I discussed an early study (7) finding that sarcoplasmic volume is elevated in both powerlifters and bodybuilders and may be a general consequence of strength training. Now this was an older study, with somewhat limited and poorly described methodology, but an interesting look at subcellular adaptations to strength.
Recently Cody Haun completed what is likely most detailed analysis of sub-cellular contributions to muscular hypertrophy in previously resistance trained men (8). In a detailed analysis of high responders to resistance training (that I will oversimplify here), Haun et al. (8) demonstrated:
- A 23% increased in fibre cross sectional area over six weeks of training
- No change in glycogen concentrations
- A 24% reduction in citrate synthase activity levels
- A 30% reduction in actin and myosin concentrations
- Up-regulation of proteins related to glycolysis, acetylation, gluconeogenesis and cytoplasmic components
Taken together, this suggests that high-volume strength training over six weeks results in a subcellular response consistent with sarcoplasmic hypertrophy. While this is the most specific observation of sarcoplasmic hypertrophy to date, it’s important to note that it does not address the often-stated theory that sarcoplasmic and myofibrillar fractions respond differently based on training loads (heavy vs light). This is well acknowledged by the authors, and I hope that means they have a study in the works to determine whether training with different loads influences these adaptations.
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