I have recently tries to include some hill sprints into my training, but find after a few efforts I feel some nausea (also get an headache). It has cut short a few sessions and makes my stomach feel off for the rest of the day. I have had the same feeling in a few races and on some rides where there is a big increase in pace. My heartrate seems to recover fine, legs and lungs also feel fine. Is it just a case of getting use to the higher intensity short bursts?
I have also found this a problem running though more of a stomach ache. Any ideas how to overcome this?