Muscle Atrophy

As we get older, one of the things that we are going to have to deal with is a decrease in skeletal muscle mass and a corresponding decrease in strength.

Inactivity and aging can lead to a progressive increase in our muscle atrophy (muscle wasting) –  sarcopenia. Now, if that wasn’t enough to deal with, the muscle atrophy will have the greatest effect on our Type II muscle fibres.


Neuromuscular  System 

We have a mix of two  different muscles fibre types in our body that are mixed throughout our muscles (genetics).

Type I Muscle Fibres 

  1. red
  2. slow rate of contraction
  3. don’t develop a lot of force
  4. able to resist fatigue  ( highly oxidative capacity ) .
  5. think aerobic endurance activities

Type II Muscle Fibres 

  1. white 
  2. fast rate of contraction
  3. develop high rate of force
  4. fatigue very quickly
  5. think high intensity anaerobic activities

In the video I alluded to three types of Muscle Fibres – the third type is the subtypes of the Type II Fibres (Type IIa , Type IIb, Type Iic, Type II ab, Type II ac) – which take on different characteristics and are modifiable with different training and training loads.




Fitness over forty




Let’s take a very rudimentary look higher up the chain of command with a muscle contraction. Brain (motor cortex) and it innervates a motor neuron, motor unit and the muscle fibres. Think light switch – the motor cortex turns on the motor unit = motor neuron and the  muscle fibre. This is a very basic diagram. But what’s important to understand is the SIZE PRINCIPLE. The more force that is required the more motor units are required. The less force and less motor units are recruited.

The muscle atrophy effects  the peripheral skeletal muscle , but also the neuromuscular system as a whole. Over time what we don’t use, we will lose -this will vary from person to person and depending on our activity levels. Old unused neural pathways are pruned. New neural connections and pathways are being re wired. Motor Unit remodelling is the process where by a an inactive motor neuron is replaced by a surrounding motor neuron. So what happens is that we will see an increase in our Slow Twitch muscle fibres being innervated. The light switch, so to speak, to turn on our Type II fibres has been replaced.

Do a quick test right now – how high is your vertical jump?


What can we do? Resistance Training

To prevent the atrophy of these Type II fibres we need to take a proactive approach to our training . Resistance Training can help to reverse the atrophy of muscle and the decrease in strength. Just remember that we need to stimulate a higher number of motor units and also take into account the rate of force production. Not all strength training is created equally. Specificity is king, we get what we train for.



What can we do?


get workout - pdf


Indirect Effect

Hey I’m 41 – should I be worried about losing my balance and not having the skeletal muscle mass or strength to pick myself up?

Well what about having that explosive POP to get up on a surf board? Then what …. stand still or another explosive reaction.

Now I am sure that some of you are saying – but I am an endurance athlete why should this matter?

How about all the speed work on the track? What muscle fibres are responsible for those 400 m repeats? What about the hill repeats on the bike? What about the intensity in the pool? Do you train at just one intensity – I am not asking about racing and holding optimal wattages on the bike when you race. The Type II fibres are responsible for the intensity in our training.

What’s happening with the hormonal balance in the body with a decrease of skeletal muscle mass? How will this hamper our ability to absorb our training loads? What will happen to our lean body mass – ie our racing weight. I would be curious as to how this will effect our ability to build muscle mass in the future.

As aging athletes we need to step back and look at what’s working and what isn’t working to optimize our training. The answer isn’t always in the quantity but rather in the quality.

Will you use it or Lose it?