Recovery nutrition should be near the top of any cyclist’s list of priorities. That’s because immediately after training, your muscles are primed to absorb nutrients such as carbohydrate (to restore muscle glycogen) and protein (to repair damaged muscle fibres), both of which are essential to rapid recovery before the next session or race.
Quick releasing (high GI) carbs such as sugars are favoured right after training. This is because sugars rapidly enter the bloodstream and muscles and so maximise carbohydrate uptake during the post-training ‘window of opportunity’.
Slow releasing (low GI) carbs on the other hand are not thought to be optimum for post-training recovery because their slower release supposedly makes them less suitable for glycogen replenishment. However, a new British study calls this conclusion into question.
In the study, scientists sought to discover the effects of consuming low and high-GI meals on the post-exercise physiological responses of time trial cyclists over five kilometres. To do this, seven male cyclists performed a long bout of cycling in order to significantly deplete their muscle glycogen stores on two occasions.
Each occasion consisted of two-minute bouts of cycling at 90 per cent maximum work rate, interspersed with two minutes at 50 per cent maximum work rate, repeated over and over. When participants were unable to maintain 90 per cent of max work rate for two minutes, the work rate was lowered to 80 per cent and then 70 per cent of maximum. The exercise was terminated when the cyclists couldn’t even maintain 70 per cent of maximum work rate for two minutes.
There then followed a three-hour recovery period, at the beginning of which the cyclists consumed either a high or low-GI meal, both of which provided exactly the same amount of carbohydrate (two grams per kilo of bodyweight). During the rest of the recovery period, the researchers measured the cyclists’ blood levels of the hormone insulin.
Insulin is responsible for driving glucose into muscle cells where glycogen synthesis can take place, therefore a big ‘spike’ in insulin following a post-exercise meal is usually considered a good thing. They also measured blood lipid (fat) levels. Finally, at the end of the three-hour recovery period, the cyclists were asked to complete a five-kilometre time trial as quickly as possible.
In a nutshell
When the cyclists consumed the high-GI meal, they burned more carbohydrate and less fat during the recovery period than after the low-GI meal. Also, their blood insulin levels were higher after the high-GI meal compared to the low-GI meal.
However, when it came to the time trial the expected benefits of the high-GI weren’t apparent. In fact the times (8.4 minutes following the high-GI meal and 8.5 minutes after the low-GI meal) were effectively the same in statistical terms.
These results seem to fly in the face of conventional wisdom. However, we don’t know what would have happened had the cyclists had to perform a longer time trial.
Also, no measures of muscle glycogen were taken before and after the two meals. Clearly, though, a low-GI meal/snack after training won’t hurt your subsequent performance!