Ashton Eaton of the United States got off to a flying start in the Olympic decathlon on Wednesday with two dominant displays in the first three events.
The world record holder timed 10.35sec in the 100m and managed a best of 8.03m in the long jump, two lead performances which gave him 2,079 points, 134 more than teammate and current world champion Trey Hardee (1,936).
Eaton's long jump effort would have been good enough to clinch a sixth-place finish in the individual long jump.
He then nailed 14.66m in the shot put for 2,848pts, Hardee's 15.28m cutting the lead to 105pts.
There was heartbreak, however, for former world-record holder and 2004 Olympic champion Roman Sebrle of the Czech Republic, who was forced to pull out after the opening 100m, in which he clocked a slow 11.54sec.
"After (the 2012 European Championships) in Helsinki I trained very hard and very well," the 37-year-old said, adding that he was aiming to retire after next year's world championships in Moscow.
"After this I was tired and I started to feel my right heel. it was worse and worse and I could not run for the past 14 days.
"I expected it to be better. It is the Olympics. I kept hoping until this morning. The 100m was OK, for pain, not the time. I tried to compete as long as possible but in the long jump I could not run."
The decathletes will compete in the high jump and 400m in the evening session.
The gruelling 10-discipline event ends with the 110m hurdles, discus, pole vault, javelin and 1500m on Thursday.