i have a friend who competes in the 400 meter run. one time i worked out with him; we ran 4 x 400. run one lap, walk one lap, repeat.
the first lap, he smoked me. when i caught up with him during the walk, he was huffing and puffing like crazy. hands on his head, it took him nearly the entire lap to catch his breath. on the other hand, i felt fine after 10 seconds.
on the second lap, i beat him. i thought he had to be taking it easy on me... my time had barely dropped, whereas his had dropped by a drastic amount (something like 10 seconds). same story on the third and fourth laps.
each time, he barely caught his breath in time for the next lap, and his time kept dropping. my time dropped very little (especially compared to his dropoffs), and i always caught my breath maybe 1/8 to 1/4 into the walked lap. afterward, he told me he was giving 100% on every lap.
i realized there was simply no way i could "run hard enough" to become as drained as he was. and it's not like he was out of shape -- he had trained for many months and reduced his 400 time dramatically from his untrained effort (something like 70 second to 57 seconds, at that time).
he once told me he wore a fitbit during a similar workout, which calculated his average heart rate to be 157! If I'm running steady state, I have to be going pretty hard to get to ~160, and then when I stop, I'm down to ~110 in seconds. If the fitbit is accurate, that means his heartrate averaged ~160 throughout an entire track workout... which consists mostly of rest!!
Ritch's posts remind me of these experiences. Personally, I could always kill myself with light weights... heavy weights? Not so much. If I used sufficient weight such that I could only get 6-8 reps, I could never drain myself that much. A weight where I can get 20+ reps? That set can become a nightmare.
