In a previous post we discussed the morphological adaptations that take place following strength training. But what should your training look like to trigger these adaptations, and how do they occur? One of the key morphological adaptations to strength training is an increase in muscle cross sectional area, aka good old-fashioned muscle hypertrophy.
There is no shortage of reported ways to train for muscle hypertrophy, the typical 3x10, manipulating the time under tension, occlusion training, training to muscle failure are just a few that spring to mind. So let’s take a slightly deeper look at how these adaptations occur, so we can begin to understand where some these methods of developing muscle hypertrophy came from.
Muscle hypertrophy occurs in part due to the metabolic response to resistance training. The metabolic response to resistance training refers to the build up of metabolic by products, mainly lactic acid, within the muscle which causes an increase the secretion of anabolic hormones and increased muscle damage, adding to the training stimulus. Now, if we are trying to maximise lactic acid production then all of a sudden using training methods like occlusion training or training to localised muscle failure using things like drop sets seem to have a bit of merit. If we think back to the energy systems we use during exercise, then using moderate to heavy loads for sets lasting between 20-40s is predominantly going to require energy produced through the glycolytic pathway meaning lactic acid is going to be produced.
This accumulation of lactic acid leads to a change in the muscle environment, reducing muscle PH, increasing muscle acidity and causing a build up of hydrogen ions which is what stimulates increased motor unit activation, increased secretion of growth hormone and increased muscle damage. Taking occlusion training as an example, Takarada and Ishii (2002) found that motor unit activation at 40% 1RM with occlusion was almost the same as using 80% 1RM loads with no occlusion, providing some evidence that the increased lactic acid as a result of the occlusion does lead to increased motor unit activation. In a similar study on occlusion training Takarada, Nakamura and Aruga (2000) found that growth hormone secretion was 290 times higher when occlusion was used versus without.
Training to muscle failure is a method often employed by bodybuilders and does also lead to increases in lactic acid production. The thought process behind this is that as fatigue increases so does motor unit recruitment, leading to more muscle fibres being trained and more adaptation. However, fatigue is a multifaceted thing comprising of both the local muscle environment, but also the central nervous system (CNS), so training to absolute failure may not be optimal, can increase the risk of injury and have a negative effect on the quality of the movement pattern.
With regards to programme design, programmes that have the primary focus of muscle hypertrophy tend to result in the largest increases of blood lactate in comparison to programmes that focus on building strength as a result of neural adaptations. Kraemer, Fleck and Dziados (2003) compared performing 3-5 sets for 5 reps with 3 minutes rest, to performing 3 sets of 10 reps with 1 minute rest, and unsurprisingly found a 433% increase in blood lactate in the 3x10 protocol most likely as a result of the greater workload and time under tension. Considering 3-5 sets of 5 are a very typical rep scheme for strength training, and 3x10 is a very typical rep scheme for hypertrophy training, the difference in the type of adaption these rep schemes produce and how those adaptations occur is clear.
Eccentric training, in the form of pure eccentric only training or increasing the length of the eccentric phase of a movement using tempos has become a popular training method for people looking to develop strength. So does this method of training help induce muscle hypertrophy? As mentioned above, using occlusion training or the classic 3x10 with 1 minute’s rest increase the production of lactic acid which in turn lead to an increased metabolic response and increased muscle hypertrophy. So does using eccentrics or tempos have the same effect? Firstly, let it be said that there are a number of benefits to eccentric or tempo training aside from increasing muscle hypertrophy, but for now that is the only measure we will be focusing on. Cadore et al (2014) compared eccentric and concentric over a 6 week training programme, training twice per week. They found there was no significant difference in muscle hypertrophy between groups but did find a host of other advantages to eccentric training which we will discuss in another post.
In contrast to this Norrbrand, Fluckey, Pozzo and Tesch (2008) found that over a 12 session training programme, muscle hypertrophy when eccentric overload was applied resulted in a two fold increase in muscle hypertrophy in comparison to a regular concentric-eccentric movement pattern. The difficulty in drawing a definitive answer as to whether eccentric training is beneficial more muscle hypertrophy lies in the fact that studies use varying protocols and loading patterns, producing different results.
As you can see, training for the specific adaptation of increased muscle cross sectional area can be done if you apply the right principles. However, whilst increased muscle hypertrophy is one component of developing your strength it is certainly not the only one. In the next blog post we will take a look at methods which can be used to develop some of the neurological adaptations to strength training, before discussing how these may be used in conjunction with each other.