The context is key here. As a general rule, the training diet should be based around low GI carbohydrates at mealtimes, containing more fibre, so they provide more sustained conversion into energy during training.
There are specific times where higher GI carbs can be beneficial; such as during a heavy training session or competition – For example, sports drinks and gels contain high GI carbs, so that these can be quickly converted into energy for muscles (and brain).
Some of the most common examples include endurance sports such as marathon and triathlon – but these can also be important for match performance in team sports such as Football and Rugby too.
The use of any high GI carbs should be carefully planned, as providing carbohydrate, can dampen the desired training improvements (or adaptation).