Muscle-specific hypertrophy training

School Of Personal Training Posted Feb 26, 2015 Future Fit Training

In the first of a two part series, Future Fit tutor and UKBFF competitor Katie Farnden takes a look at muscle-specific training.

Muscle-specific hypertrophy training

When it comes to hypertrophy training, why should we analyse each muscle? The answer is that the composition of fibre types and movement has very important training implications. Each muscle has a different fibre type composition, typically Type I, Type IIA, Type IIB or a mixture. When we exercise we can rely on these fibres to produce force, increase or decrease contraction speed and determine levels of fatigue. 

Type I fibres are slow twitch, creating ATP from the oxidisation of carbohydrates and fats present. (ATP is critical for muscle contractions because it breaks the myosin-actin cross-bridge, freeing the myosin for the next contraction.) They also have a slow contraction velocity which ultimately makes them resistant to fatigue, allowing muscular activity to be maintained. If we tailor a plan based on this, adopting medium to high repetitions, lighter weight loads with minimum rest is advisable due to their ability to provide aerobic energy through enhanced blood supply. With this in mind we are also able to train these types more frequently.

An example is the glutes, predominantly slow twitch with typically a smaller percentage being fast twitch.  However, it is these fast twitch fibres that have proven the most beneficial to hypertrophy gains, explosive strength and power, for example sprinters compared with endurance athletes.

In comparison the hamstrings are primarily fast twitch Type IIA and Type IIB dominant. For these types the recommended protocol is lower repetitions, a higher load and slightly longer rest intervals, focusing on the muscle’s ability to respond to explosive movements due to fast contraction velocity. Type IIA also has a high capacity for generating ATP and is resistant to fatigue, whereas Type IIB, even though they contain large amounts of glycogen, are anaerobic in output, unable to supply sufficient and lasting ATP and therefore fatigue easily. This means less total weekly volume is needed, with split body part training once per week being adequate.

Referring back to the analysis of the glutes and their dominant slow twitch make-up, for optimal muscular gains we should not ignore the fast twitch presence and ideally try and maximise their recruitment. Can we conclude that it is important to overload the glutes during training with a combination approach? That is, heavier weight and lower repetitions in order to activate all muscle fibres, whilst including higher repetitions to fire up the motor units and deplete glycogen. If this is true then perhaps reverse drop sets are the best option.

In theory, the lighter the load, the more Type I fibres are recruited, whereas as the load increases the body recruits Type IIA and then Type IIb fibres. Therefore, start a set with higher reps at a lower weight to pre-exhaust to recruit as many muscle fibres as possible through the use of slow twitch Type I. We can then continue the set, simultaneously increasing the weight and decreasing the repetitions. Our aim is to now recruit Type IIA fibres and then Type IIB as we increase force and decrease repetitions once again.  This will also ensure Type I and Type IIA continue to fire, thus maximising all fibres throughout the set as effectively as possible.

Next time we will look at contraction types and exercise selection for the glutes and hamstrings.


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