The usual advice when it comes to weights is straightforward. To tone up, use light weights and more reps. To bulk up and build muscle, use heavy weights and fewer reps.
New research is showing that this trusted fitness mantra may need some tweaking. What’s going on?
Building up muscles is actually an exercise in controlled damage. The skeletal muscles are made of thousands of fibres, linked by connective tissue which carries blood supply and connects muscles to bones.
There are thought to be two types of muscle fibres. Type 1 are ‘slow twitch’ for endurance, and type 2 are ‘fast twitch’ for anaerobic and explosive effort.
For most people, the number of muscle fibres is fixed, but their size can be increased. This mechanism is stimulated by loading the muscle, which causes tiny tears in the fibres.
Muscles actually grow when you stop working out. As you rest, the muscle fibres are repaired and will increase in size. To do this, the body needs a good dose of protein as well as a correct balance of other nutrients.
So you need to give your muscles time to recover in order to make them bigger.
Here’s the clever bit. It is the type 2 fibres that have the most potential for growth, but to do that you need to activate them.
The body uses the type 1 fibres first, and it is only when fatigue sets in that the type 2 fibres get involved.
So the type 2 fibres can be activated either by short sessions with heavy weights or longer sessions with lighter weights.
A small study has shown that either method will work, although bigger weights will build more strength.
Training to fatigue is the key. To do this, stop counting your reps and keep going to the ‘AMAP’ point. That stands for ‘As Many as Possible’ - a good target!
As always, look to your technique, choose kit that works for you and take advice from the professionals.
Very useful information, thanks. Good to remember that muscles grow when you rest, so I don't feel I need to work at it all the time.
HI Sasha, thanks for the reply. not sure where I got short and long twitch from! It was stuck in my memory from years ago and I'd never questioned it!
Hi Matthew - type 1 fibres are the same as slow twitch fibres, and type 2 are fast twitch. Not short and long twitch!!
I have heard of short twitch fibres and long twitch fibres. is this the same thing as type 1 and type 2?
This is great information. I don't think I have ever heard the IMAP acronym before, but I don't think I will forget this simple approach to exercise now.
I always try to work towards a new PB each session. This could be in reps or this could be in a heavier weight. I always want to increase what I can lift and like the competition with myself to try and lift heavier. Good to know that when I plateau and have a few off-weeks of no increases I'm still building muscle though.
well I never - even the most holy grail of fitness truths may not be 100% accurate! Reassuring to know that I'm not wasting time with lighter weights.