The Physiology of Movement (Part 1)

Physical exercise comes in a number of forms & shapes. However, every form involves movement of muscles. How do your muscles work? How are your genes involved? We have discussed in detail how our muscles work in our earlier blog.

I am going to share briefly about muscle movement. Muscle movement is controlled by the brain through our nervous system. A signal is delivered through our network of nerves that send messages to activate our muscles. This results in force being generated which is exerted on the body parts through muscle tendons. The outer layer of muscle is called Fascia & within that we find muscle bundles that are wrapped in connective tissues. Each bundle contains many muscle fibres called mytocytes, each covered with a layer of connective tissue that contains capillaries & nerves. There are different types of muscle fibres: slow, intermediate fast & fast twitch that have different characteristics & can adapt based on internal (ageing etc) & external factors (training). Your individual ACE genotype gives an indication to distribution of these fibres. II carriers are supposed to have a high proportion of slow twitch to fast twitch while DD carriers are exactly the opposite. The actual force development takes place in the protein of muscle fibres. We have discussed this in our blog- “how our genes impact our muscle composition” & hence I am not going to discuss it in detail here.

Energy production & consumption

To facilitate movement of contractile, the proteins requires a lot of energy. The energy comes from food we consume however the only way our cells can use the energy is through ATP. ATP is found in mitochondria & contains the right amount of fuel to carry our biological processes. Making & consuming ATP at contractile machinery produces a lot of heat & hence we get warm when we exercise . The mitochondria uses oxygen to burn derivatives of fat & carbs & to a lesser extent protein and this explains why we need to breathe. UCP2 & UCP3 are two genes that impact mitochondria. UCP 2 is present in many cells & is said to be associated with higher metabolic efficiency. This essentially means less energy is lost as heat & we get more fuel for movement. UCP3 is found in skeletal muscle fibre & is mainly used in fuel selection of muscle cells. This gene may promote burning of fatty acids for fuel.

The fuel for our mitochondria comes from nutrition & fat reserves but muscles can also store fats & carbohydrate (in the form of glycogen). The amount of protein present in muscle fibre can also be used for energy. However, we should avoid being dependent on this form of energy since it leads to muscle breakdown. The method of energy production that our body selects depends upon PPARA genotype. Individuals who carry the PPARA G variant have been found to have a high level of PPARA protein as compared to those having CC genotype. A high level of PPARA protein enables efficient switching between fuel types thereby giving the G variant a larger pool of energy to draw during a workout.

We shall discuss in detail what happens to your muscle fibres & rest of your body after workout, how the body responds to stress caused due to physical training & how it leads to physical gains in the next blog..