scuba steve

so i can't find a solid answer online, was looking to see if anyone had any background on this. i work out pretty regularly, 4-5 times a week. i was doing cardio on saturday, doing sprints with a sled and weight on it when as soon as i was done i felt really light headed, almost dizzy. its not the first time its happened like this, but was the worst. i've noticed this before when i have tried to max out on bench press too. obviously when i'm straining myself is when it happens. i have a trainer but he isn't really medically trained....

is there anything to do to prevent this? i've read everything from eat more to rest to more sugar before? has this happened with anyone?

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