Exercise nutrition - Pre/Post-exercise meals

It is thought that a release of insulin will occur due to a high rise in blood glucose when GI foods are chosen before exercise. There are however feared side effects of high GI carbs, these are when the insulin causes a big fall in glucose levels before the exercise workout has begun (rebound hypoglycaemia) and also and increased rate of early glucose oxidation. It is thought that better performance in exercise occurs when glycogen sparing occurs with the low glycaemic trial. There is however no clear benefit that research has found. It is mainly thought that low GI foods and high GI foods eaten before exercise show no major differences regarding performance levels.

Drinks containing carbs are highly recommended during exercise for athletes. It has been shown that ingesting carbs is acceptable if the race/match is no longer than 90 mins, the session is longer than an hour or if a pre-exercise meal isn't possible. It can also help improve performance during exercise when consuming isotonic drinks as it delays the onset of fatigue. This can be as effective as consuming a pre-exercise meal. It is also an advantage that fluid is replaced by an isotonic drink.

In particular, during the 2 hours after a training session, the muscles are a lot more sensitive to the effects insulin produces creating a more reliable replacement for the lost glycogen. Immediate consumption of GI carbs helps the high synthesis of muscle glycogen.

The reasons why high GI (glycaemic index) carbs post-exercise are recommended is due to increased glucose availability/uptake, insulin and glycogen synthesis. There are also recommended guidelines, they are as follows: post-training = 1 gram carbohydrate per kg of body mass every 2 hours or 50 grams per meal, the 1st intake to be within 15 minutes of the workout ending and intake over a day = 7-10 grams carbohydrate per kg or 500-700 grams of carbohydrates per day.

Nutrition - Fats/Lipids - structure of Lipids and Triglycerides

So 1st of all, what are the physiological functions of lipids?

Many things... it provides protection for the internal organs, assists in regulation of enzymes, constitutes the majority of the central nervous system and the spinal cord, the formation of all cell membranes, formation of the myelin sheath within the nervous system, the transportation, storage and utilisation of fat soluble vitamins A, D, E and K, a fuel source during lower intensity work loads, storage of energy within adipose tissue, insulation through subcutaneous adipose tissue and lastly the synthesis of steroid hormones.

Lipids that are solid at room temperature are called fats whilst lipids that are liquid at room temperature are called oils.

There are chains/rings of carbon atoms that join together with other atoms which a lot of dietary lipids consist of. These are most commonly oxygen and hydrogen. Smaller units of fats are called fatty acids. Double strength bonds are present, these change the shape of the molecule and allow the lipids to become versatile.

3 fatty acids are attached to a carbohydrate backbone which is called glycerol. Fatty acids are broken off during digestion and used as needed. This happens when fatty acids occur naturally as triglycerides.

Tomorrow I'll move onto the rest about fats/lipids!