Numerous studies have shown that the incidence of depression is higher in the elderly.  It has been suggested that this pattern is associated with serotonin, a brain chemical that influences mood and behavior.  Normal aging is associated with a decline in serotonin levels.  At the same time, there have been many documented studies showing that people who exercise experience less depression.  These studies suggest that exercise provides a protective effect against the development of depression in older individuals. 
 
A recent study published in Medicine and Science in Sports and Exercise may help explain the beneficial impact of exercise on depression.  The researchers measured the effect of exercise on the level of tryptophan in men aged 57-70.  The amino acid tryptophan is an important precursor for the manufacture of serotonin.  The researchers surmised that serotonin levels would be higher in elderly individuals who exercise regularly, and that is exactly what they found based on changes in tryptophan metabolism..  There was a corresponding increase in serotonin synthesis during exercise and serotonin remained elevated during post-exercise recovery.  This study elucidates an important reason for the positive mental benefits derived from exercise.

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Peer-reviewed studies show, compared to carbohydrate only sports drink, Accelerade: 

     · Increases endurance by 29% 
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     · Increases endurance in subsequent workout by 40%