What are genes or what are genetics?

Genes and genetics are what makes you you. They determine your eye colour, your height, your body shape, and if the Set Point theory is to be believed, the weight you are going to be.

So how can this help us, if it is all predetermined?

To start with, it means you shouldn't worry about weight.

But it does help us when we are thinking about our goals and what we can expect from a structured exercise programme. Our muscles are made up of 2 different types of muscle fibres; slow twitch and fast twitch. Slow twitch muscle fibres are used for burning fat and slow movement. Marathon runners will be predominately slow twitch, at somewhere between 60-70% of their muscle fibres being slow. Fast twitch fibres are used for faster movements like sprinting. Sprinters and will be predominately fast twitch at somewhere between 60-70% of their muscle fibres being fast twitch. But all muscles are used by the body in the same way, slow twitch first and then fast twitch. It is the force of the exertion from the sprinter that makes their muscles recruit the fast twitch fibres to move them quickly. 

Most of us are about 50/50. So if genetics have decided what our main muscle type is, or if we don't have a propensity towards elite fitness, what does this mean.

Well, firstly you are going to struggle to put on lean tissue. Without the aid of steriods a dedicated body builder could expect to build about 4lbs of lean tissue a year. So if you start training once or twice a week, you are unlikely to look like the incredible hulk.