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Monday, 18 July 2011

What is Muscular Hypertrophy




The Process of Hypertrophy

In order to maximise gains in this area with clients or athletes, it is useful to understand the underlying physiology of how hypertrophy occurs. Under the appropriate hormonal and chemical conditions, muscle cells proliferate and incorporate satellite cells in to their make up. Satellite cells are effectively ‘reserve’ cells that are situated on the periphery of the muscle cells, ready to be used in the case of injury or regeneration. (1) They become relevant once the appropriate signals are received, and they begin to migrate towards the area of damage. Once there, they begin to fuse to the existing myofibres, creating either a repaired cell in response to trauma or an enlarged muscle cell in response to training induced micro trauma.

Aagaard et al (2) have demonstrated that Type II muscle fibres have a better capacity for hypertrophy than slow twitch fibres. With this in mind, it becomes clear that intramuscular tension is a critical factor for producing gains in this physical characteristic. Intramuscular tension is directly affected by ‘load’. Fry et al (3), have suggested that maximum levels of hypertrophy will occur with loads of 80-95% of the system’s capacity. So in practical terms, ensuring hypertrophy work is trained as a high percentage of maximum strength will provide the most efficient stimulus for hypertrophy adaptation. Added to the need for ‘load’ is the consideration of eccentric load and time under tension that both can effect hypertrophy. This idea is less clear, as there are studies to show Eccentric Bias Strength Training (Higbie 1996, Farthing / Chilibeck, 2003 and Vikne, 2006)(4)(5)(6) has a great effect on hypertrophy but recent studies by Blazevich 2007 (7) have shown that concentric bias work causes similar adaptations. Although it is not completely clear, mechanical hypertrophy can be broken down into the following expression.


Mechanical hypertrophy = Time under Tension X Intramuscular Tension X Eccentric Load


To accurately effect hypertrophy, only 1 of the components can be altered at a time, otherwise it is unclear if the stimulus will be significant enough to cause an adaptation. With the research in to eccentric load and time under tension appearing less conclusive, manipulating loadings is an excellent way to promote hypertrophy, especially in the larger, more receptive type II fibres. The protocols below are used with time under tension and eccentric load as a constant.


Practical applications
Max Reps Method

• Select a load that is 80% of 1 Rep max.
• After a sufficient warm up, perform a set of as many reps as possible, before concentric failure.
• Do not use forced reps or allow a spotter to assist on the completion of any reps.
• If you fail mid rep, allow a spotter to take the full weight and unload the bar.
• You should aim for around 7-8 reps at this weight.
• Rest 2.5 minutes.
• Repeat for a 2nd and 3rd set, maintaining 2.5minutes rest in between sets.
• Note the total number of reps attained. 
• The aim for the next session is to add reps completed while maintaining the load and rest periods. 
• A typical rep scheme should look like this; 1st set 7-8 reps, 2nd set 6-7 reps, 3rd set 4-5 reps.
• After 6 weeks, a reasonable progression would be to add 2-3 total reps. If a client is experiencing a plateau, there is the option to add an extra set on to significantly increase the total volume.

Preset Clusters

• Select a load of 82% 1 rep max (6-7 reps).
• Use a preset cluster method, of 3 reps, 15s pause, 3 reps, 15s pause then 2 reps. Use a 2.5. minute rest between sets. Do 3-4 sets and look to increase the total reps by 3-4 over a 6 week cycle. 
Unstructured Clusters
• Use 80% 1 Rep max.
• Perform a set to concentric failure only.
• Rest 15s.
• Perform as many reps as possible.
• Then rest for 2.5 minutes.
• One thing to note is that ‘soreness’ or the amount of DOMS that occurs from hypertrophy is not necessarily a good indicator of the magnitude of the stimulus. Accurate load prescription and the gradual manipulation of total volume is the key for hypertrophy gains. 

Dispelling myths.....

There are other commonly used hypertrophy methods such as supersetting exercises together, splitting reps into partial ranges and performing high reps at lower loads. However, these methods are limited due to the nature of the loading parameters. Without loading exercises to a sufficient level (80% 1RM or above) the muscle fibres that are likely to be recruited are smaller, slow twitch fibres. For example it would be impossible for a client to perform 7 reps at 80% 1rm followed by another exercise and expect to come back to the 2nd set and be able to perform a similar amount of reps. Similarly, if high reps at lower loads are used (in an attempt to increase time under tension) the size principle of motor unit recruitment will become applicable and the high threshold muscle fibres will not be recruited as at no point will the load require them to produce force. Cardinale, Newton and Nosaka (8) state that, ‘loading is probably the most important factor when designing strength training programs where the prime goal is muscle mass.’ 

From personal experience, volume of exposures to a hypertrophic stimulus is more critical than the actual inter session volume. Because of the inverse relationship between intensity and volume, large amounts of inter session volume will inevitably mean a sacrifice of load. Which we know is the critical stimulus for development. 

References

(1)Hawke T. Muscle stem cells and exercise training. Exerc Sports Sci Review, 2005
(2) Aagaard et al.A mechanism for increased contractile strength of human pennatemusclein response to strength training. J Physiol, 2001
(3) Fry A C. The Role of resistance exercise intensity on muscle fibre adaptation. Sports Med, 2004
(4) Higbie E. Effects of concentric and eccentric training on muscle strength, cross sectional area and neural activation. J Appl Physiol, 2000
(5) Farthing, Chilibeck. The effects of eccentric and concentric training at different velocities on muscle hypertrophy. Eur J Appl Physiol, 2003
(6) Vikne H. Muscular performance after concentric and eccentric exercise in trained men. MedSci Sports Exerc, 2006
(7) Blazevich A. Lack of human muscle architectural adaptation after short term strength training. Muscle Nerve, 2007
(8) Cardinale, Newton, Nosaka: Strength and Conditioning: Biological Principles and Practical Applications, 2011

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