During exercise, there may be a reduction of up to 80% in the blood flow to the abdominal organs, as the body sends more blood to the muscles and skin. This effect may result in nausea, vomiting, stomach pain, and diarrhea. Eating too soon before a workout can also cause nausea.

Why do you get sick after working out?

Nausea also happens during exercise because blood flowing to our GI tract and stomach is rerouted to the muscles we're working, thus slowing digestion and causing discomfort.

Why do I feel dizzy and nauseous after working out?

Your breathing and heart rate increase so that more oxygenated blood can flow into your muscles. If you aren't breathing enough during or after exercise, your heart may not be pumping enough oxygenated blood into your brain. Dizziness can occur whenever the brain is starved for oxygen.