DALLASSeven-time Tour de France winner Lance Armstrong found his endurance stretched 'almost to the breaking point' last Friday by a three-hour, 30-song concert presented by his fiance, pop-folk singer Sheryl Crow. 'It was a pretty tough slog,' Armstrong told reporters after the event, which he was obligated to attend as part of his new role as Crow's future husband. 'I was really straining around The First Cut Is The Deepest'I don't mind telling you, I just couldn't catch my breath. When we reached 'All I Wanna Do (Is Have Some Fun),' I felt like I'd been through that territory about a million times, and I seriously considered just giving up and collapsing for the first time in my career.' Armstrong, who is revered by millions for fighting through cancer, antagonism from abusive fans, and steroid-abuse allegations, would not comment on whether this latest obstacle would prove too much for him to overcome. 