Metabolic and nutritional adaptations to exercise
1. Enzymatic mechanisms and regulations
More than 2,000 reactions rule the transformation of nutritional substrates into energy (ATP). All, except for one, are catalysed by specific proteins (enzymes). These reactions are regulated (activated or constrained) by molecules (ligands), which ensure the energy expenditure.
2. Specific use of energy substrates
The human organism uses energy substrates originating from its carbohydrate, lipid and protein reserves, as well from its nutrition. The principal stages of these transformations will be detailed with regard to their regulations.
3. Oxydative stress and adaptations
All physical activity generates an excess of production of « free radicals » from oxygen and nitrogen. These are very reactive and deleterious for the structure of the organic compounds (proteins, carbohydrates, lipids, AND). Specific enzymes and vitamins reduce the production of this “oxidative stress” in the subject undergoing physical exercise.
4. Mechanisms of muscle fatigue
An excess of physical exercise generate muscle fatigue the effects of which can have repercussions at the level of the central control. The different peripheral and central factors will be addressed in order to envisage a physiological behaviour which counteracts consequences leading to overtraining.
Metabolic specificities linked to exercise in relation to age and sex
1. Specific adaptations in the child.
Genetically, the biochemical muscle characteristics result from both parents, but the mitochondrial capacities depend essentially on the maternal potential. The oxidative capacity, the enzyme adaptation and thermoregulation increase with age.
2. Female specificities linked to training
Female muscle power is dependent of the quantity and the percentage of muscle fibres. The use of energy substrates is characteristic but an excess of physical activity can lead to an overflow: the Female Athlete Triad Syndrome.
3. Senescence and muscle activity
Aging (after 50 years of age) generates a progressive decline in muscle mass as well as an increased oxidative stress. These deleterious effects can be mitigated by practicing a regular physical activity (strength and endurance training). Appropriate training generates a more generous life, a lessened dependency towards others and a reduced social cost for social security.
Nutritional aspects and exercise
1. Applied digestive physiology
This brief overview of the digestive mechanisms is mainly oriented towards the quantitative aspects at the various levels of the oral gastrointestinal tract. It will focus on the energy limitations both during rest and exercise.
2. Food and nutritional supplements to exercise
The main food items (water, various products) will be addressed with regard to their energy efficiency. Nutritional supplements originating from the food industry will be examined with regard to their effectiveness in contributing to an active life style.
3. Diets before, during and after exercise
If the energetic consumption becomes substantial (> 1500 kcal), it is necessary to foresee a balanced diet in preparation to training (when, how), during training (why, how) and following the end of the training.
The adequate use of rehydration (without excess of salts), a replenishment of the protein and carbohydrate reserves will be addressed according to the specificities of the physical activity.
Metabolic diseases and physical activities
1. Type 1 diabetes, nephropathies
Type 1 diabetes is compatible with a regular physical activity associated with an appropriate temporal diet.
The benefits of exercise are recognised and accepted in the fight against this illness both for the child and adult. Exercise for the subject on dialysis, the renal transplanted subject, is recommended within specific conditions in relation with their particular medication.
2. Metabolic syndrome and obesity
Type 2 diabetes in adults can be subdued by practicing a regular physical activity, combined with nutritional hygiene, including as a preventive measure in children and adolescents.
