If you read my recent series, How Do Muscles Grow, Part 2, Part 3, Part 4 and Part 5, (and I hope you did, because if you didn’t, what are you waiting for?) then you have a very good understanding of what happens from training until the recovery process is complete and new muscle tissue is built to build a stronger and larger muscle. Related to this I would like to discuss functional hypertrophy, which refers to muscle growth that improves maximal force production (or strength in simpler terms) and non functional hypertrophy, which refers to gains in muscle size that are not related to an improved capacity to generate force (in other words muscle gains that don’t make you stronger).
We have all seen the little guy who can lift massive weights and conversely we have all seen the giant muscle head with the huge chest that can’t bench even close to what the chubby and out of shape looking powerlifter can press, right? So obviously the little guy and the powerlifter have loads of functional hypertrophy as their muscles can lift heavy weights and the huge bodybuilder does not possess much in the way of functional hypertrophy. Seems simple enough, doesn’t it? If you’ve spent any time reading here you know nothing is ever as simple as it appears, and this case is no exception. I’m going to give this one away right from the start: there is no such thing as non-functional hypertrophy, and in this series I aim to prove why.
Let me begin with a little context to help give this article somewhat of a foundation on which to build. When we train with weights, we are building strength and muscle size by training our muscles to adapt to the stimulus that we are putting them under. The transfer of this strength and muscle mass that we build will never be perfect. We are building something that wasn’t there to begin with. If you train to become stronger at the one rep max in the deadlift, then chances are you are going to get good at that lift, even though you’ll build little in the way of muscle. If you train to build muscle by deadlifting in the 6 to 12 rep range, then chances are you are going to get stronger in that rep range and pack on a few pounds of muscle too, even though your one rep max in this lift may not dramatically improve. Do you see where I’m going here? Your body will adapt to the specific stimulus that you give it.
There is the issue of both myofibrillar hypertrophy and sarcoplasmic hypertrophy as well to consider. I have spoken in-depth many times about these two forms of muscle-building, but this needs to be revisited in order to fully understand what I’m getting at. The myofibrils are made out of protein and are commonly known as muscle fibers. These myobibrils are what are responsible for what most believe to be functional hypertrophy as strength is mainly a function of the amount of protein contained in the myofibrils. The fluid surrounding the protein is what is known as sarcoplasm, and is generally believed to be non functional hypertrophy as the sarcoplasm does not contract or directly do the heavy lifting of the weights.
Also of note is that it is incorrectly believed that the rep range that you use can directly influence which type of hypertrophy you are focusing on. Heavy weights for low rep sets are believed to favor the growth of myofibril and build strength and are responsible for all of the functional strength within the muscle. Higher rep and lighter weights are believed to favor the growth of the sarcoplasm and because the sarcoplasm has no contractile elements, it is therefore possible to build big muscles that do not contribute to strength gains. This is why many believe big bodybuilders to not be as strong as they appear.
This is why athletes choose to train in the low rep ranges using heavy weights. An athlete does not want to build non-functional strength as this will not cross over into their chosen sport for any useful benefit.
None of what is believed is actually accurate. It has become to be understood that the amount of sarcoplasm is limited to the size of the myofibrils. A muscle cell can only hold as much sarcoplasmic fluid as the size of the myofibril within the cell will allow. Also worthy of note is that many studies (1-5) have shown that regardless of the rep range used, myofibrillar hypertrophy will always trump sarcoplasmic hypertrophy by 2 or 3 times. These studies showed that it was impossible to influence sarcoplasmic hypertrophy without influencing myofibrillar hypertrophy more so. That set of 18 reps is still building functional strength, in other words.
Yes, sarcoplasmic hypertrophy technically is in fact non-functional hypertrophy, but it is not possible to grow sarcoplasm without growing the functional portion of the muscle cell as well. It’s a very large difference. Non-functional hypertrophy can be best summed up as glycogen storage. When we train our muscles and drain the energy stored within it, otherwise known as glycogen, then our body reacts by storing even more glycogen than it did previously, and this contributes to the size of the muscle.
When we meet again next week I’ll look more into how much glycogen we can actually store and in turn how much of our muscle mass can be made up of it. I’ll also look into other reasons why non functional hypertrophy is misunderstood and try to get to the bottom of what is and isn’t functional within our muscles. Until then my friends,
(1) Selective activation of AMPK-PGC-1alpha or PKB-TSC2-mTOR signaling can explain specific adaptive responses to endurance or resistance training-like electrical muscle stimulation. FASEB J. 2005 May;19(7):786-8. Epub 2005 Feb 16.
(2) Stimulation of human quadriceps protein synthesis after strenuous exercise: no effects of varying intensity between 60 and 90% of one repetition maximum (1RM). J Physiol 547.P, P16.
(3) No effect of creatine supplementation on human myofibrillar and sarcoplasmic protein synthesis after resistance exercise. Am J Physiol Endocrinol Metab. 2003 Nov;285(5):E1089-94.
(4) Coordinated collagen and muscle protein synthesis in human patella tendon and quadriceps muscle after exercise.J Physiol. 2005 Sep 15;567(Pt 3):1021-33.
(5) Protein synthesis rates in human muscles: neither anatomical location nor fibre-type composition are major determinants. J Physiol. 2005 Feb 15;563(Pt 1):203-11. Epub 2004 Dec 20.