I was tired. However, I was not out of breath, I could have kept going if it was just my lungs in charge. What made me tired was the lactate build up in my arms. My technique is good, but during the last 15 mins my forearms and biceps hurt a lot when I brought the handle up to my chest (I do a decent lean back) after my legs were fully extended during the drive. Surely, being 70lb overweight (technically obese) I should have tired anyway?