Understanding Strength Part 3 - Hypertrophy
It’s commonly known that to build muscle or increase strength, we need to lift heavy things - but few lifters understand exactly how the process works. In this part of the series, I’m going to simply explain the science behind increasing strength and building muscle - a process commonly known as ‘hypertrophy’.
UNDERSTANDING MUSCLES
Muscle is made up of fibres, bound together into bundles of tissue. Within each muscle, there are two types of fiber – one designed for endurance (known as type I, or 'slow twitch' fibres), and one designed for strength (known as type II, or 'fast twitch' fibres).
Type I (slow twitch) fibres aren’t very strong, but they have high levels of endurance. Surrounded by blood vessels, these muscle fibres have a high supply of oxygen, making them more resistant to fatigue.
Type II (fast twitch) fibres are the opposite – they’re extremely powerful, but they fatigue quickly. Whilst slow-twitch fibres can create a weak movement, against lesser resistance, for a long period of time (i.e. walking or jogging), fast-twitch fibres will create a powerful movement against a greater resistance (i.e. lifting or sprinting) for an extremely short period of time. The higher the intensity of the activity, the faster they will fatigue.
The difference between fast and slow twitch fibres could be characterised by a sprinter and a distance runner. Both are strong in their field, although a distance runner has a much higher level of muscular endurance and is more oxygen efficient. A sprinter is extremely powerful, but they fatigue very quickly at high speed.
A bigger engine = more speed and power = greater fuel consumption
A smaller engine = less speed and power = better fuel economy
WHAT IS HYPERTROPHY?
Muscular hypertrophy is a term for the growth and increase of the size of muscle cells. The most common type of muscular hypertrophy occurs as a result of physical exercise and strength training.
In order for muscles to get stronger and grow, we need to ‘stimulate adaption’ by applying enough resistance to overload them; this is known as ‘progressive overload’.
Progressive overload involves systematically applying a training stimulus that forces the body
to adapt and grow.
Put very simply; if you lift heavy things, your muscles will get stronger and grow. However, there are training variables that will affect the way muscles will respond.
This adaption stimulus followed by sufficient recovery (which includes solid nutrition principles and sufficient sleep) will trigger a period of ‘super compensation’, during which the body will improve. This process is called the 'Training Adaption Cycle’.
Exercise causes stress to the body, and triggers it to change these fibres. Sufficient recovery can increase the size, strength and endurance of your muscles. There are 3 ways to trigger changes to your muscle:
Progressive tension overload - ‘Tension’ refers to the length of time we use our muscles; and by gradually increasing the weight and duration of our exercises, we trigger the muscles to adapt.
Muscle fiber damage - Exercise can damage the muscle, triggering the body to repair and strengthen the affected muscle fibres.
Cellular fatigue - By pushing a muscle to its limit, we exhaust all of the muscle fibres, and cause adaptation.
Strength training can trigger hypertrophy through all 3 mechanisms - but your body’s response will vary according to the type of exercises you perform and the type of stimulus applied.
TYPES OF HYPERTROPHY
There are two very different types of hypertrophy that can take place within the muscle. These are known as ‘sarcoplasmic hypertrophy’ and ‘myofibrillar hypertrophy’. Both types require a different kind of ‘stimulus’.
Sarcoplasmic hypertrophy is an increase in the volume of the muscle cell fluid, called ‘sarcoplasm’ and this fluid accounts for 25-30% of the muscle’s size. Although the size of the muscle increases, the density of the muscle fibres decrease, meaning there is little or no increase in muscular strength. Sarcoplasmic hypertrophy is mainly a result of ‘bodybuilder’ type training.
Put simply - more sarcoplasm = more size. More size = bigger muscles
Myofibrillar hypertrophy is an enlargement of the muscle fiber as it gains more myofibrils, which contract and generate tension in the muscle. As the number of myofibrils increase, there is a significantly greater ability to exert muscular strength. Myofibrillar hypertrophy is mainly the result of specific strength/power training.
Put simply - more fibrils = more tension. More tension = more strength.
Different types of stress cause different types of muscle growth, so both types of hypertrophy require a different kind of stimulus. Strength training can trigger both hypertrophy mechanisms; but your body’s exact response will vary according to the type of exercises you perform.
TRAINING METHODS
Sarcoplasmic hypertrophy will generally occur by applying the following stimulus:
Lighter weight (e.g. 50-70% 1RM)
Higher rep ranges (10-20 reps)
Slower, controlled reps (e.g. 2-3 second lifting phase, 2-3 second lowering phase)
Shorter rest periods between sets (30-90 seconds)
Higher training volume i.e. more reps and sets (depending on training experience) anything between 3-10 sets can be used
Intensity can be increased by manipulating training volume and rest periods
Programs generally include multiple exercises for each muscle group and individual muscles, i.e. bicep curls, tricep extensions, lateral raises, etc.
Examples of programs which may illicit sarcoplasmic hypertrophy:
Traditional ‘bodybuilding’ training splits, such as a PPL split (push, pull, legs) including multiple exercises per body part to fully fatigue the muscles, or an upper/lower body split
German volume training (GVT) which involves 10 sets of 10 reps with short rest periods
FST-7 (Fascial Stretch Training) another program that uses high training volume and short rest periods to overload the muscles
Myofibrillar hypertrophy will generally occur by applying the following training stimulus:
Heavier weight (e.g. 70-95% 1RM)
Lower rep ranges (1-5 reps)
Faster, more explosive reps (e.g. explosive lifting phase, controlled or fast lowering phase)
Longer rest periods between sets (2-5 minutes between sets)
Lower training volume due to lifting heavier weights
Most programs will primarily focus on ‘compound’ movements; squat, deadlift, bench press, overhead press, power cleans, etc.
Examples of programs which may illicit myofibrillar hypertrophy:
Olympic weightlifting programs
Specific strength-speed training
5x5 programs (characterised by doing 5 sets of 5 reps of heavy compound movements)
5/3/1
Cube Method
Texas Method
Conjugate Training Method (a combination of multiple training modalities)
A continued increase in muscle and/or strength requires ‘progressive overload’ – a consistent increase in the difficulty of your workouts over time.
Put simply - by making exercises harder as your body adapts, you’ll force your body to continually increase strength and/or muscle.
IN SUMMARY
Muscles are made of type I/slow twitch and type II/fast twitch muscle fibres, which each adapt to a specific training ‘stimulus’
Slow-twitch (type I) fibres aren’t very strong, but they have high levels of endurance - fast-twitch (type II) fibres are extremely powerful, but fatigue quickly
Slow twitch (type I) fibres are generally trained using higher rep/lighter weight moved slower - fast twitch (type II) fibres are generally trained using lower rep/heavy weight moved faster
Sarcoplasmic hypertrophy is an increase in muscle cell fluid (sarcoplasm) - more sarcoplasm = more size. More size = bigger muscles
Myofibrillar hypertrophy is an enlargement of the muscle fiber as it gains more myofibrils - more fibrils = more tension. More tension = more strength.
RECENT THEORIES ON THE CURRENT MODEL
The jury is out on the belief that varying training methods will specifically illicit either sarcoplasmic or myofibrillar hypertrophy and studies are ongoing. Some recent theories challenge the current hypertrophy model based on the following arguments:
Specific strength training has a large skill component; and strength athletes simply become more efficient at lifting heavier weights due to neuromuscular efficiency (According to the National Academy of Sports Medicine, neuromuscular efficiency refers to the ability of the nervous system to properly recruit the correct muscles to produce force and dynamically stabilise the body's structure in all three planes of motion)
Sarcoplasmic expansion occurs from increased glycogen and sarcoplasmic proteins
It is questionable that different training methods have meaningful impact on sarcoplasmic growth
Training in any rep range promotes increases in contractile muscle proteins; it's never simply an increase in intracellular water
There is no evidence that sarcoplasmic hypertrophy occurs in an absence of contractile hypertrophy
However, the obvious differences in the way strength athletes and bodybuilders have trained in the last 50 years gives us a clear idea of the difference each training modality can deliver to physical performance and physique.
