Target heart rate

[youknoww]

When calculating your target heart rate you use, as well as your maximun heart rate and your heart rate at rest, an intensity defined between 50 and 85%, more specificly:

Beginner or low fitness level . . .50% - 60%
Average fitness level . . . . . . . . 60% - 70%
High fitness level . . . . . . . . . . . 75% - 85%

What could be the consequences of training at a higher intensity that that reccomende (60-70% being a beginner or 75-85% being average)