Dear Speed Lab,
During the recovery phase following a triathlon, which foods are best? I hear conflicting advice about this issue.
Thanks for the question. The most important nutrition-related recovery objective after racing is replenishing muscle glycogen, which is the most important fuel supply for high-intensity exercise.
Early studies on post-exercise glycogen resynthesis recommended that the optimum amount of carbohydrate is about 1 gram per kilogram of body weight, consumed immediately after exercise and at two-hour intervals until the next meal.
Carbohydrates that stimulate a large insulin response by producing a higher blood glucose concentration (i.e., high glycemic-index carbohydrates) are preferable to those that evoke only a low glycemic response. Carbohydrate can be provided in liquid or solid form during the first five hours of recovery with equal benefit.
Although there is good evidence to support the recommendation that a high-carbohydrate diet during the 24 hours following intense exercise will restore muscle glycogen to normal values, there is relatively less information on the extent to which exercise capacity is restored when these dietary recommendations are implemented.
Nevertheless, there are at least two running studies showing that eating a high-carbohydrate diet (9 to 10 g/kg of body weight) following prolonged heavy exercise restores exercise capacity and can, in fact, contribute to a performance boost.
During prolonged exercise, intramuscular triglycerides (i.e., fat stored inside the muscles) appear to contribute to fat metabolism and may even make up for a shortfall in the delivery of fatty acids from fat tissue to muscle.
However, not all researchers agree that intramuscular triglycerides play an active role as substrate for energy production during prolonged exercise. For example, Kiens and Richter reported that, whereas intramuscular triglycerides were not used during prolonged exercise, they were used during recovery, contributing to energy production while muscle glycogen resynthesis progressed to completion.
Can You Become Addicted to Exercise?
Dear Speed Lab,
Is exercise habit forming? Can we become addicted to the runner's high or endorphins? I have no idea, but your thoughts would be most welcome.
Since there is evidence that vigorous exercise can lead to changes in brain levels of peptides such as ?-endorphin, dopamine, norepinephrine and serotonin, and as these peptides and neurotransmitters are known to influence mood states, it is reasonable to speculate that exercise might become habit-forming.
It is also conceivable that habitual exercise could lead to a form of dependence or addiction. The concept of exercise addiction was first introduced by Morgan in 1979 and was based largely on a qualitative analysis of selected exercisers who reported an inability to function without daily exercise.
These individuals appeared to be addicted to exercise since they regarded it as being more important than jobs or careers, significant others and personal health. When given the options of running and losing their job, running received a higher priority; when given the choice of running versus interacting with a spouse, children or friends, running was regarded as being more important; and when given the choice of running versus resting at the recommendation of his/her physician, the runner would elect to run through the pain.
A common criticism of the study by Morgan was that the runners were not addicted to running per se, but motivated, committed, dependent or compulsive.