[Kyle O’Toole is a graduate assistant strength and conditioning coach at George Mason University. He is a certified strength and conditioning specialist, a corrective exercise specialist, certified personal trainer, and a USA weightlifting level 1 coach. Kyle completed the Mentorship Program at Athletic Lab in 2018 and is currently pursuing his Master’s Degree. He can be reached on Instagram @coach.kyleotoole]
The notion that larger, sculpted muscles means a person is stronger or more athletically gifted has been around for ages. Go back and watch footage of Eugene Sandow and his amazing feats of strength from the late 1800s and you could be convinced this is the case. Sandow, regarded as “The Father of Modern Bodybuilding” and a true pioneer of fitness, was not only a symmetrical physical specimen; he was also one of the strongest men on the planet during his lifetime. In spite of his astounding performances and displays of strength, there may be something more worth looking into with regards to muscular development and its influence on optimal performance for athletes. There are differences between bodybuilding hypertrophy, which focuses on aesthetic symmetry and maximizing muscle mass, and hypertrophy for athletic development, which focuses on increasing muscle mass and optimizing performance through neural and muscular adaptations. These differences are brought on by slight variations of training variables, that each impose separate adaptations. Those differences along with an overview of hypertrophy training of each case will be discussed in detail below.
What is Hypertrophy?
Before the differences in hypertrophy between bodybuilding and athletic development are discussed, let us first understand what muscle hypertrophy is. Muscle hypertrophy is an increase in muscle size through increases in the cross-sectional area of muscle. It is achieved by increasing the muscle protein content or increasing the storage capacity of high-energy substrates and enzymes within muscle. Hypertrophy occurs when the contractile elements become larger and the extracellular matrix surrounding those elements expands to support the growth (10).
The increases in muscle size occur when sarcomeres and myofibrils are added in series or in parallel. The majority of exercise-induced hypertrophy from traditional resistance training programs results from increases in sarcomeres and myofibrils that are added in parallel (8). In-series hypertrophy has been shown to occur when a muscle is forced to adapt to a new functional length, like in repeated eccentric muscle actions (7).
To induce muscle hypertrophy, it is recommended to employ sets with moderate loads (6-12 reps, 65-85% 1RM) with rest periods of approximately 60-90 seconds (7). Even within these suggested guidelines there is plenty of room for strength coaches to build their own approach based on the goals of the program. If looking to build muscle to be applied to force output, then it is suggested that you predominantly work at the lower end of the volume scale with higher loads and longer rests. If looking to build physique, where force output is not a requirement of your sport, you would work at the top end of the volume scale with much lighter loads and shorter rest periods.
Types of Hypertrophy Training
Trying to increase lean body mass through resistance exercise is an aim for many different populations of people. Whether you’re a recreational lifter, an athlete, or a bodybuilder there is a very good chance that you’re pursuing better muscle development in some way. It is important to remember that the goal of resistance training is to push some form of adaptation. Attempting to create specific adaptations will involve modifying training variables like intensity, volume, repetition speed, and rest time. Many of those variables that lead to the adaptations listed above, are different between bodybuilders and more conventional athletes. Bodybuilding is a sport where maximizing muscle size is necessary to compete. However, increased muscle size is rarely beneficial to sport performance (few exceptions include younger or lower-level athletes, combat or contact sports, and throwing events in track-and-field) (1). Over the years two separate forms of hypertrophy training have surfaced, to help clarify the differences in training methodologies between bodybuilding and athletic development.
Functional Hypertrophy Training
Functional hypertrophy training looks to increase the size and strength of the muscle, with most of the emphasis being applied to strength development. Think of this as hypertrophy training for athletic development. The overarching goal of this form of hypertrophy training is to create a stronger muscular engine that is prepared to receive and apply nervous system signals (1). The central nervous system (CNS) activation is one key factor that separates functional hypertrophy training from non-functional hypertrophy training. The CNS influences force production and rate of force development which are both important factors to account for in athletic development. The more efficient your nervous system becomes, the more you potentially get from the muscle you currently have.
The theory behind this type of hypertrophy training is that the number of sarcomeres, or contractile elements of muscle fibers, is increased over time. Although hypertrophic changes occur in both fast-twitch and slow-twitch muscle fibers, more changes take place in fast-twitch fibers with functional hypertrophy training (8). Athletes who undergo this type of training should be reminded to move the weight as quickly as possible during the concentric portion of the lift. Functional hypertrophy training also uses heavier weights, with a lower number of reps, and longer rest intervals, to stimulate a higher level of CNS involvement (1).
Non-Functional Hypertrophy Training
Non-functional hypertrophy training looks to increase the size and strength of the muscle, with most of the focus directed toward size development. This type of hypertrophy training is most commonly seen within the bodybuilding community; where the focus is to train with moderate loads and shorter rest intervals that induce high amounts of metabolic stress within the muscle (7). It is believed that this type of hypertrophy is augmented by increases in noncontractile elements and fluid within the sarcoplasm of the muscle (4-6). As such, this form of hypertrophy training is commonly referred to as sarcoplasmic hypertrophy. You will generally see higher volumes of work being done, at slower speeds, with much more of an emphasis being applied to isolation exercises, when compared to functional hypertrophy training measures.
Studies on conventional bodybuilding hypertrophy training programs that utilized a moderate load technique showed increases in blood lactate levels, intramuscular lactate levels, and glucose levels that significantly increased the acute anabolic hormonal responses to exercise (2,3,9). It is also not uncommon to see techniques like drop sets, supersets, and rest-pauses being used regularly to further increase total time under tension. Non-functional hypertrophy training has less effect on the CNS; therefore, it leads to less improvement in the capacity to produce force when compared to functional hypertrophy training.
The purpose of this article is not to distinguish which approach to muscle hypertrophy is better than the other. There is no definitive answer to a question like that, because each of the above approaches addresses athletes with very different goals in mind. Instead, this article focuses on clearly affirming how each approach has its place in a structured strength training program. As a strength coach it is important to remember what desired outcomes you are after with your programming. The methods we have our athletes apply during training should get them to those desired outcomes.
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