You train them, they cause you significant discomfort each week, you’re proud of them and dare I say it you look at them regularly in the mirror! But do you have a basic understanding of how your muscles work? If you plan your own training then this is crucial and if you have a coach then it will vastly help you to execute your set workouts effectively. Here’s a brief breakdown of the structural, physical, biochemical and energetic characteristics of muscle:
Muscle fibres are long, thin cylinders. They run lengthways or diagonally across the length of the muscle. Connective tissue (fascia- which I’ve posted about previously) surrounds each fibre, groups of fibres and the whole muscle. Blood vessels and nerves wind in between the fibres. Mitochondria sit between the muscle fibres within the cytoplasm (cell fluid).
The contraction of a muscle fibre is due to the coupling and uncoupling of actin and myosin filaments. Using energy derived from ATP they slide past each other and create cross-bridges. As such, muscles basically convert chemical energy into movement via contraction and relaxation.
For simplicity, fibres are categorised as fast-twitch (FT, aka type 2) and slow-twitch (ST, aka type 1). FT fibres are able to shorten at a much quicker rate than ST giving them their name. But how? The main reason is the enzymes within the FT fibres that allows for faster and cross-bridging (coupling/uncoupling) of the actin and myosin filaments. FT fibres have less mitochondria (for aerobic energy production – see below) but as a result they pack in a higher density of filaments. In short, they are designed for force, speed and power. Due to higher densities of both mitochondria and capillaries, ST muscle fibres are better able to utilise carbohydrates and fat (with oxygen) to sustain more prolonged exercise.
Now both types are crucial and in evolutionary terms; its quite easy to see why we would need both the ability to move very quickly and also the ability to continue moving for a long time. Our survival literally depended on it! Now this isn’t generally the case any longer, however your sporting performance does still require you to be aware of these differences and to train with specificity.
Consider the training you practise each week and your chosen sport; do you train your muscles in the way that you will need them come race day? Could you change things up to perform better? Bear in mind that some training adaptations will come quite quickly while others can take months or years to develop. Generally speaking, aerobic adaptations through greater carbohydrate and fat oxidisation, improved mitochondrial density and capilliarisation take a long time. As does muscle growth (hypertrophy). However, co-ordination of muscular activity and enzymatic changes for improved anaerobic ability are likely to improve much more quickly (weeks to months).
If this basic introduction has been of interest then please read further into this area of physiology and adapt your training to suit your goals in the light of your newly gained knowledge.