i've experience that feeling and its usually because i didn't eat enough during the day before my workout and i pushed myelf too hard. if you are overexherting yourself then it could be that you have low blood sugar and it is causing your dizziness and making you feel light headed. if you are not eating enough during the day before a strenusous workout this could be a side effect. i would try to eat a healthy meal that contains a good balance of protein/carbs/nutrients (try something like a chicken breast and a small sweet potato and maybe a small dinner roll). give your food some time to settle (an hour or two) then during your workout try to sip on a gatorade or vitamin water. try not to over do it when you work out sometimes people push themselves too hard and it can results in injury as well. if you are still experiencing those symptoms after trying this then i would see your doctor to make sure it's not something more serious.
after hard phys exercise sometimes get bad tunnel vision and a big ball of light right where i try to focus my eyes. why? . i've got a heart murmour and my mum dad and all 4 grand parents had diabetes. not a good start! drama is that after particularly cheeky physical exercise i sometimes get really bad tunnel vision and what seems like a big ball of light right where i'm trying to focus feel dizzy and like i've got pins and needles in both hands. lasts for about 2 hours then goes back to normal. asked the med centre on camp and they have no idea.