I skied yesterday for the first time in five years. It was lovely but I must admit to a certain amount of discomfort. By lunchtime yesterday some of the muscles in my legs were burning, and this morning there is a dull ache in my calves. Skiing is an exercise in co-ordination and balance. The brain directs the body and makes all the little calculations needed as you shift your weight from foot to foot. I am an inept skier, so my brain is screaming at my legs to respond; hence the muscular pain. The ideas my brain generates require muscles for them to take effect. (Can you think of any influence your brain has that does not require muscles to do the actual work?)
Muscles are efficient at turning fuel (glucose) into motion, they are long-lasting, they are self-healing and they are able to grow stronger with practice.
Individual muscle fibres are made from strands of two different proteins; thin filaments of actin and thicker filaments of myosin. These two sets of proteins interlace and can ratchet together, causing a muscle to contract, by burning up lots of ATP molecules. ATP molecules are the little rechargeable batteries of the cell and they are produced during respiration. Contracting muscles require lots of respiration to be happening. If oxygen cannot be supplied to the cells quickly enough then this respiration becomes anaerobic and lactic acid starts to build up in the muscles. This causes the muscles to ache. The aching passes as the lactic acid is flushed out and oxygen is used, whilst resting, to turn the lactic acid into water and carbon dioxide.
During vigorous exercise you may actually tear your muscle fibres and so they are required constantly to rebuild themselves. ‘No pain, no gain’ as they say. This explains the aching you feel a day or so after heavy exercise – it is evidence of the rebuilding going on within your muscle tissue. Sensible training should produce muscle groups better equipped to deal with the activity you are training for. The muscles will be specifically modelled to suit your body’s needs.
Questions…
- What are the raw materials for respiration?
- What word is used to describe pairs of muscles working together?
- What energy conversion do muscles perform?
- What are the largest and smallest muscles in the human body?
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