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What changes take place in the body with exercise

By Denise Elliot

Exercise, or being physically active, is vital to living a long, healthy, productive life. It makes us feel more alert, helps with maintaining a positive outlook on life, while lifting our attitude and lessening mood swings. Exercise can trigger a number of neurotransmitters (brain chemicals) that offer us a feel good, life is great attitude.

Sugar into Energy

To fuel up our muscles the body mainly uses glucose (sugar). Carbohydrates such as fruit, bread, pasta and cereals are common sources of glucose. The body stores glucose (in the form of glycogen), for when energy is required to contract muscles to achieve movement. It also uses energy molecules stored in the cells (ATP - Adenosine triphosphate = an energy molecule).

When these supplies are used, the body then requires further oxygen to create more ATP and the volume of blood is increased to the exercising muscles. This extra blood flow provides more oxygen creating more ATP which then can release more energy (the Krebs cycle).

Fat Burning

When glucose fuel is depleted, the body then turns to burning fat. Hormones regulating blood sugar levels then activate a fat burning enzyme called lipase which releases triglycerides (glycerol and fatty acids stored in fat cells). These individual components enter the blood stream and are used for energy.

Too much sugar/glucose in the body and not enough high intensity exercise can mean the body does not deplete the glucose levels and does not enter the fat burning phase.

Lactic Acid and Muscle Growth

If oxygen is limited, lactic acid is produced in the tissue of the muscle, which is eventually flushed from the body after a workout. When your muscles feel sore after exercising, it can be a build-up of lactic acid, or the small tears that take place when working the muscle. These will repair and consequently enable the muscle to grow.

Sweat and Electrolytes

This sweat is a mixture of water, salt and small amounts of electrolytes (alkalinizing minerals such as calcium and magnesium) which are also eliminated. Fluids are vital for hydration, as a dehydrated muscle will not work efficiently and will lack energy.


Protein is vital for supporting the growth of any muscle, so quality protein powders do have a place along with exercise. If you do not fuel up your body correctly you may put yourself at risk of breaking down muscle instead of building it up.

After intense exercise the body filters increased protein through the kidneys to be eliminated as urine. Simply put, to grow a muscle, requires protein and you must work the muscle. Consuming a protein drink while just sitting on the couch watching sport will not reap any physical rewards.


Fitting our summer clothes increases our motivation to burn a bit of winter fat accumulated from our warming winter meals. Correct nutrition pre and post work out will allow slow and steady weight loss, while retaining and building muscle.

It is vitally important to keep quality fluids high (to replace what is lost), and provide quality proteins and complex carbohydrates. If a steady energy level (mental and physical) is required, avoid refined foods as these will only create ups and downs in blood sugar levels. Whole foods are important for mood, energy and general well-being.

Good luck with any extra summer exercise and remember to build your fitness up slowly, increasing more each day/week, as this will lessen any chance of injury.