Hello, Wish you had given some more details regarding your age, previous medical status, smoking status and your height/weigh! Let us presume that you are not obese, a non-smoker, in your 30’s or 40’s,and habituated to mountain/off-road biking. You were a regular biker earlier, now exerting during this season without any ‘warm up’, right? ‘Seeing stars’ suggests that your blood pressure would have decreased significantly during your sudden uphill pedaling. This made you to vomit. Taste of blood is a symptom to be worried about. Repeated retching (attempts at vomiting) can burst a few small capillary vessels in the food pipe. Most probably this is the reason. Did you have significant cough with frothy, blood-tasting phlegm (sputum) at that time? That has more medical reasons to be concerned. As you are able to ride normally after the first episode, you do not have much to worry. Be sure to discuss this episode with your family physician during the next visit. Keep exercising regularly and do some trial runs before you actually go to the mountains after a break. Wish you continue to enjoy your biking sessions and thanks for using Healthcaremagic.