In part 1 of this article, I discussed the contemporary history of how powerlifting has influenced bodybuilding in the last decade or so. In doing so, I presented a list of aspects of powerlifting training we know are beneficial for bodybuilding and a list of aspects we know are detrimental. In part 2, I’ll discuss what we don’t yet know:

Is it Ever Beneficial to Lift Heavy? The Influence of Powerlifting on Bodybuilding, Part 2:

I previously held the position that getting stronger allows one to use heavier loads across all rep ranges, and this would provide greater overall tension and volume (recall volume is sets x reps x load) over time, and optimize long term hypertrophy. However, my current perspective is the relative volume performed is what is important, not absolute volume.

If you double your strength, going from a 200lbs to a 400lbs squat, your old max of 200lbs is now just 50% of your 1RM. Doing 3 sets of 10 with 200lbs would crush the old volumes you could previously perform with 3 sets of 10 when 200lbs was your max. However, considering you can probably do 20 reps with 50% 1RM, 3×10 with 200lbs would produce minimal hypertrophy as low loads require training near to failure to produce significant growth (6). So, while getting stronger is important as a bodybuilder for progressive overload, how strong you get, is not. Rather, it matters only if you are working at an appropriate effort level for your strength. Therefore, relative volume is likely more important than absolute.

Another frequently asked related question is whether the rate of strength gain matters; meaning, does getting stronger at a more rapid pace help you hypertrophy faster? Well, that’s looking at it backwards. Hypertrophy is a component of strength (1-3), not the other way around. Gaining strength more quickly might indicate a faster rate of hypertrophy is occurring, but it is not causing it. Since you can get stronger in any rep range and create progressive overload, why would you lift heavy ever given the higher injury risk and greater time cost? This is where the meat of the “we don’t know” comes into play.

First, there is debate as to whether hypertrophy is just a function of motor unit (MU) recruitment (motor units are the neurons that innervate muscle fibers and those fibers), or whether there are different effects at a mechanistic level between low load training to failure, and heavy load training. It has been theorized the mechanical tension provided by heavy loads is an independent stimulus for hypertrophy, beyond the fact the heavy loads recruit all MUs (8). Also, it has been theorized the metabolic effects of training to fatigue are an independent stimulus for hypertrophy, beyond the fact that training to failure likely (we think) ends up recruiting all MUs eventually (9). Currently, there is not yet consensus on this issue. As it stands, it is unknown whether tension or metabolic fatigue truly have an additive or independent effect on hypertrophy, or whether hypertrophy is just a function of MU recruitment.

Unfortunately, the primary tool we have for measuring MU recruitment, EMG (placing electrodes that measure muscle activity on the surface of muscles), doesn’t measure MU recruitment directly. EMG measures total electrical activity, but it can’t differentiate which MUs are firing.

All we know for sure is EMG activity at any time point is highest with heavy loads (5). But, studies comparing heavy to light loads to failure, head to head, with volume matched, show similar hypertrophy (4, 10). How can that be? If muscle activity is higher but volume is matched, shouldn’t heavy loads be superior? Well there are three possibilities I can think of in which equal hypertrophy from low and high load training could occur:

1. MU recruitment is greater in heavy training. But, when similar work is performed with light loads to failure, an added stimulus of metabolic fatigue puts the protocols on equal footing, and the fibers that are recruited during low load training get an additional stimulus due to metabolic fatigue [as theorized here (10)].

2. MU recruitment ends up the same. Lifting heavy recruits all MUs immediately and effectively trains them. On the other hand, during low load training high threshold MUs are intermittently brought in to keep force production going to compensate for low threshold MUs as they fatigue. Thus, while the peak EMG values at any time point are never as high during low load as during heavy load training, all MUs eventually are trained to a similar degree [as explained as a possibility here(11)].

3. Much the same as possibility 2, except it is possible that in high load training, type I fibers (with more endurance) are not recruited for a long enough period to optimize their growth. Similarly, during low load training, high threshold MUs and their associated type II fibers are not cycled in frequently enough and recruited long enough to get an optimal stimulus before failure occurs. Thus, similar global hypertrophy, but dissimilar fiber specific hypertrophy occurs [as theorized here (7)].

So, what does this mean? Well, if possibility 1 or 3 is true and MU recruitment is not the same or adequate to produce an optimal stimulus to certain fibers, including some loads in the 1-6RM range (along with moderate and low load training) would probably optimize hypertrophy as 90% 1RM loads show higher EMG values than 70% (5). However, if possibility 2 is true, then there actually would be no benefit to using heavy loads, and arguably the time cost and injury risk might make it a bad idea. Unfortunately, we have very few training studies that compare training with multiple loading zones simultaneously to a singular loading zone. This is the nature of science; we attempt to isolate one variable and compare it against another. This is an effective way to find out how two things compare, but often creates the false perception that the two things are mutually exclusive and can’t be combined for even better results.

Now I’m sure you’re wondering, what do I think is the answer? Well, there is a recent study which would suggest a slight advantage might be conferred for using the full spectrum of training; 2-4RM, 8-12RM and 20-30RM loads within the same week compared to only using the 8-12RM range on all days (7). The differences between the constant load and varied load groups weren’t much, but they were there. Which I find interesting given that the constant load group did slightly more volume than the varied group. However, it’s impossible to know whether this advantage was due to the addition of heavy or the addition of light loading, or the synergy of two or all three loading zones.

In the end based on the limited evidence we have thus far, my personal hunch is that possibility 1 or 3 is likely correct. This is the reason I currently recommend a small portion (~25% or so) of training should be performed with 6RM and heavier loads for bodybuilders.

References

1. Appleby B, Newton RU, and Cormie P. Changes in strength over a 2-year period in professional rugby union players. Journal of strength and conditioning research 26: 2538-2546, 2012.

2. Baker D, Wilson G, and Carlyon R. Periodization: The Effect on Strength of Manipulating Volume and Intensity. The Journal of Strength & Conditioning Research 8: 235-242, 1994.

3. Erskine RM, Fletcher G, and Folland JP. The contribution of muscle hypertrophy to strength changes following resistance training. European journal of applied physiology 114: 1239-1249, 2014.

4. Klemp A, Dolan C, Quiles JM, Blanco R, Zoeller RF, Graves BS, and Zourdos MC. Volume-equated high- and low-repetition daily undulating programming strategies produce similar hypertrophy and strength adaptations. Applied Physiology, Nutrition, and Metabolism 41: 699-705, 2016.

5. Looney DP, Kraemer WJ, Joseph MF, Comstock BA, Denegar CR, Flanagan SD, Newton RU, Szivak TK, DuPont WH, Hooper DR, Hakkinen K, and Maresh CM. Electromyographical and Perceptual Responses to Different Resistance Intensities in a Squat Protocol: Does Performing Sets to Failure With Light Loads Produce the Same Activity? Journal of strength and conditioning research 30: 792-799, 2016.

6. Ogasawara R, Loenneke JP, Thiebaud RS, and Abe T. Low-load bench press training to fatigue results in muscle hypertrophy similar to high-load bench press training. International Journal of Clinical Medicine 4: 114, 2013.

7. Schoenfeld B, Contreras B, Ogborn D, Galpin A, Krieger J, and Sonmez G. Effects of Varied Versus Constant Loading Zones on Muscular Adaptations in Trained Men. International journal of sports medicine 37: 442-447, 2016.

8. Schoenfeld BJ. The mechanisms of muscle hypertrophy and their application to resistance training. Journal of strength and conditioning research 24: 2857-2872, 2010.

9. Schoenfeld BJ. Potential mechanisms for a role of metabolic stress in hypertrophic adaptations to resistance training. Sports Medicine 43: 179-194, 2013.

10. Schoenfeld BJ, Ratamess NA, Peterson MD, Contreras B, Tiryaki-Sonmez G, and Alvar BA. Effects of different volume-equated resistance training loading strategies on muscular adaptations in well-trained men. Journal of strength and conditioning research 29: 2909-2918, 2014.

11. Vigotsky AD, Beardsley C, Contreras B, Steele J, Ogborn D, and Phillips SM. Greater electromyographic responses do not imply greater motor unit recruitment and ‘hypertrophic potential’ cannot be inferred. Journal of strength and conditioning research, 2015.