i have been training for 6 years, it started happening about a year ago. with legs i do leg extensions 8x3, squats 10x1, 8x1, 6x1, 4x1, standing hamstring curls 8x3, standing calve raises 8x3. i don't get nausea but sometimes i get the feeling like i am going to pass out. i breathe properly when i do work out and post meal is about the same after every workout.