a combo of intensity and dropping of blood sugar together.

Tomorrow will be the first day of 20rep squats, and I do expect to get sick.lol I'll have a huge carb meal 2 1/2 hours pre=workout, and have a carb beverage on hand as well. Reason I say a combo of both, is because I've done a set of 15 reps on deads with 315 (when I first started them), and was using the heavy breathing techniques as used with the 20 rep squats to get the last 2-3 reps out. I gagged, got lightheaded and then came the headache. After about 10 minutes of rest and 80g of dextrose I felt "OK." Not great, but I could finish most of my workout, so I think its those super-intense sets that deplete your body of its energy... almost too much physical trauma at once. But doing this every week is what makes your body so much better at training, cause the adaptation to such vigorous work is very quick. The level of percieved exertion will reduce with the same workload in the following week, thus the need for weekly progression (MORE WEIGHT).

My Mom saw me do a set of deads in the garage at all out intensity... she said, "that can't be good for you." Then, she saw me helping some family move furniture from one house to another (moving days suck.lol). She then saw how conditioned I was, as I was quickly moving heavy objects and not that winded. She said, "never mind what I said the other week, it must be doing some good."lol