It can be due to several reasons.
Lack of oxygen to the brain. The respiratory and heart rate of a person will accelerate after strenuous exercise, which can lead to hyperventilation, causing a large amount of carbon dioxide to be expelled from the body and triggering respiratory alkalosis, thus causing the patient to experience dizziness, panic, nausea, weakness and other symptoms.
Insufficient blood supply to the brain, the body sweats and loses a lot of water during strenuous exercise can lead to a reduction in blood volume, which can lead to insufficient perfusion of brain tissue, triggering the performance of cerebral ischaemia and hypoxia, which can lead to symptoms of dizziness and nausea.
Hypoglycaemic reaction, strenuous exercise consumes a lot of energy, if not eaten in time, can easily trigger a hypoglycaemic reaction appearing as dizziness, panic and weakness.