30 percent

The large, hypertrophied feathers of the bodybuilding world have certainly been ruffled over the past few weeks. The fitness blogosphere has slowly been set ablaze with news that training at 30% of 1RM produced similar hypertrophy over ten weeks as training at 80% 1RM (1). The idea that such a light training load can be associated with elevated protein synthesis (2) and significant hypertrophy over time (1) is certainly counter-intuitive to traditional methods and the current recommendations out there, but what does this really mean?

Can gyms start saving money by stocking half the number of 45lb plates? Will rows upon rows of dumbbells be replaced by the little vinyl-covered pink dumbbells seen above?

Dramatics aside, what we have here are two great studies that have taken the idea that load is the single important variable controlling hypertrophy and tested it at two ends of the repetition maximum continuum. We’ve heard many arguments about load, time-under-tension and training to failure in the hypertrophy world and we’re still far from settling that debate. Fortunately two recent studies from protein synthesis guru Dr Stu Phillips have shed some light on the relationship between training-load, protein synthesis, and muscle hypertrophy.

Sustained Protein Synthesis with Low-Load Training

Burd et al (2) took 15 recreationally active men familiar with resistance exercise (experienced trainees) and had them perform two of three acute exercise conditions. To test if the post-exercise protein synthetic response was different based on training loads, each participant performed unilateral knee extension at either 90% 1RM to failure, 30% 1RM with the amount of work matched to that of the 90% condition, or 30% 1RM to failure.

The authors measured mixed protein synthesis, thought to be indicative of overall protein synthesis, and also specific fractions (myofibrillar and sarcoplasmic). Mixed protein synthesis was increased post-exercise, but to a greater extent in the 90% 1RM group at four hours post-exercise. When looking at the specific protein fractions, training with 30% 1RM to failure appeared to have a sustained response with increased synthesis for both the sarcoplasmic and myofibrillar fractions persisting 24 hours after the exercise bout. So despite a more pronounced peak in mixed protein synthesis with high-load training, when considering the separate fractions, it appears that there may be an advantage to low-load, high-repetition training.

After these findings, Burd et al (2) proposed that low-load, high-repetition training could actually provide a distinct advantage over the course of a longer-term training program, as the sustained sarcoplasmic and myofibrillar synthesis could produce increased hypertrophy over consistent, higher-load (90% 1RM) training.

Does Low-load training produce increased hypertrophy?

Based on the protein-synthetic response to low-load training Mitchell et al (1) picked up where Burd et al (2) left off to test whether training for 10 weeks at 30% 1RM to failure could produce equivalent, or even greater hypertrophy than higher load (80% 1RM) training.

Eighteen recreationally active men with no formal weight-training experience performed a ten week unilateral knee extension strength training program training three days per week. Conditions of training were somewhat similar to the first study, however this time they performed either three sets at 30% 1RM, 3 sets at 80% 1RM or 1 set of 80% 1RM (instead of 90%), all done to voluntary failure.

After ten weeks the authors found quadriceps volume (assessed by MRI) and muscle fibre area (type one and two fibres) were increased across all groups, regardless of training conditions. This certainly validates the assertion that hypertrophy can be attained with low-load training, but it’s interesting that the sustained myofibrillar and sarcoplasmic synthetic response observed with 30% 1RM in their first study didn’t result in an enhanced hypertrophic response over the course of a training program.

As you might expect, in order to be stronger, you need to lift heavy weights. This data certainly supports that and even though 1RM strength increased across all three conditions, the gain was greatest when training with 80% 1RM. The amount of work completed with 80% 1RM also increased across all conditions, but not as much in the 30% 1RM trained legs. Even though 30% 1RM training can increase hypertrophy to a similar extent as high-load training, those seeking optimal size and strength will still want some sets at 80% 1RM or higher in their training programs.

Is this the opposite of the high-intensity interval training argument?

Dr Martin Gibala, also a professor of kinesiology at McMaster University, has devoted his recent research to the concept of high-intensity interval training. Under this model they’ve found some pretty remarkable mitochondrial adaptations that would be beneficial to an endurance athlete, but have done this training at a fraction of the usual training (work) time (3).

There’s no question that steady-state training has dominated the realm of endurance exercise, which is necessary since this is the usual mode for competitive races. But what about the general public or those interested in the physique side of training? Given that limited time is the number one concern of most potential exercisers, inducing similar adaptations in a fraction of the work time would be a preferred exercise strategy. This reduced time comes at a price: near maximal intensity during the work interval, much higher than what would occur with conventional steady-state endurance exercise.

Coming back to our hypertrophy studies, haven’t we just done the reverse here with low-load, high-repetition induced hypertrophy? We’ve dialled down intensity (from 80-90% 1RM to 30% 1RM) and in doing so, more than doubled the time spent actually lifting the weight, as evidenced by the time-under-tension data from the first paper (16.3 seconds for the 90% 1RM set to 43.3 seconds for the 30% 1RM set).

So while increased protein synthesis and ultimately hypertrophy aren’t directly linked to training-load, I would say that increasing load allows you to gain the same hypertrophic effects and additional strength gain with a fraction of the time spent under the bar as compared with low-load training. Maybe it just comes down to personal preference?

What’s important: training load, time-under-tension, muscle activation or fatigue?

After these two studies, it becomes apparent given the different training loads and times-under-tension that neither of these parameters are likely the chief determinant of the resultant protein synthesis or hypertrophy. Rather it’s the intention to recruit and use as much of the target muscle as possible, whether this high activation is achieved with high training loads (Henneman’s Size Principle) or through fatigue-induced recruitment of additional motor-units.

Even after these two studies we’re still left with the age-old question, is failure required for optimal muscle growth and if not, where does that fine line between fatigue and failure lie?

What would you choose?

I think there’s no question that an optimal training program contains a blend of multiple training loads, and not one that adheres to a single %1RM across all exercises. That’s program design 101.

From a strength perspective, if you want to lift heavy weights, you need to spend time moving heavy weights, and the strength testing results from this study support this (1). When considering training efficiency and economy of time, I think the 80% condition provides an optimal blend of hypertrophy and strength, while the 30% condition certainly provided hypertrophy with a moderate strength gain.

That being said, in elderly populations and those who have severely limited experience with weights, a 30% protocol could be an ideal trade off. Sure working time of the set is increased, but the exercise may just be more approachable for your 90-year old Grandma than a fully loaded barbell. And what about the days when you’re not feeling your strongest, when even an empty bar feels too heavy? If your focus is hypertrophy, you may not sacrifice any progress at all by simply cutting the training load for the day while working to failure.

So even though you may not run out and start cutting all your training loads in half or more, and this is obviously not what the authors intended, there’s some important points that apply to hypertrophy training in general, regardless of the percentage of your 1RM you decided to train at:

• Attempt to use as much muscle as possible: This seems like a no-brainer, we’ve been conditioned to favour large-muscle group exercises and use as much muscle as possible for years. These two studies highlight (indirectly) that you can achieve high amounts of muscle fibre recruitment through either high training loads (think Henneman’s size principle) or through fatigue (high-repetition sets to fatigue).
• Increase training volume as you decrease intensity: As evidenced in Burd et al (2), training to failure at 30% 1RM had an increase protein synthetic response as compared to 30% 1RM work matched to the 90% 1RM condition, which had significantly less repetitions and work overall. Based on the size principle of motor unit recruitment, as load decreases overall muscle activation decreases so there should be increased emphasis on ensuring a high volume is performed to fatigue, at least from a hypertrophic standpoint, so that cycling of alternate motor units as fatigue sets in ensures high muscle involvement.
• Don’t be afraid to fail: I’m not going to advocate failing on every set on each exercise, but what I will say is that we shouldn’t be as scared of this concept as many are. The participants in these studies trained to failure over ten weeks and lived to tell the tale, so it may not be as life-threatening as we’ve made it out to be.

If you’re interested in muscle hypertrophy you need to take some time to sit down and read these two papers. The concept of training loads, time-under-tension and muscle activation are pivotal to the development of effective strength training programs to promote muscle hypertrophy.