His heart was beating somewhere near heart-attack level.
With each breath he gulped six litres of air.
Sprinting along the home stretch in Montreal, Canada, blood was pumping through John Walker's 24-year-old body at a phenomenal 30 litres per minute.
A year earlier, New Zealand's star runner had claimed the fastest mile run ever - 3min, 49.4 seconds in Sweden.
Now, on July 31, 1976, he was the favourite to win the 1500m final at the Montreal Olympics. The status was partly because he was the best but also because his main rival, and good friend, Filbert Bayi was ruled out of the race by political and health issues.
Walker did not race to the lead. For much of the race in the 60,000-capacity Le Stade Olympique, he was hemmed in somewhere near the back.
He broke cleanly to a narrow lead going into the final lap. On the back stretch he lengthened his lead, then down the home stretch he gave it everything.
His biggest contenders - Irish runner Eammon Coghlan, Belgian Ivo Van Damme, and West German Paul-Heinz Wellman - tried hard but couldn't catch him. Arms outstretched he bounded over the finish line for gold.
A Listener article in the lead-up to the Olympics had the stats: A normal person doing normal activity pumped five litres of blood through their body. Walker in full flight was pumping six times that amount. His heart beat 200 times per minute - "coronary level for most". With each beat it pumped 150 millilitres of blood - far more than double the average.
Each breath he drew in six litres of air, compared with an average of four.
Among the 60,000 people in the packed stadium that warm summer day was coach Arch Jelley. He and Walker roomed together in Montreal. The day before the big race they both lay down for a nap and slept for two hours. Awake and at the stadium , the atmosphere was "fantastic", he remembered this week. Before the race they had three strategies. It was left to Walker, on the track, to decide which was best.
Many commentators thought Walker - the strongest runner there - should have led from the front. That would have been an "absolute disaster", turning Walker into simply a pace maker, Jelley said.
After winning, Walker would say: "I had a great feeling as I crossed the line. I thought how glad I was it was all over."
As would become a theme for New Zealand sport, the issue of the South African apartheid regime had tainted the 1976 Olympics.
Many African, Asian, and Carribean countries had wanted New Zealand banned from the games because the All Blacks had played South Africa, journalist Ron Palenski, who covered the Montreal Olympics, remembered.
The International Olympic Committee refused and many countries boycotted the games in protest - denying what would have been one of the great athletic showdowns.
In the 1974 Commonwealth Games in Christchurch, Tanzania's Filbert Bayi beat Walker to the gold in the 1500m final.
The next year Bayi set a new record for the mile but in Sweden shortly after Walker snatched the crown from him, in the process becoming the first person to run a mile in under 3min 50sec.
"The Olympic Games were seen as a showdown," Palenski said this week, though Walker and Bayi were - and remained - "good mates".
But with Tanzania boycotting the games it was not to be. Even without the boycott it would have never happened as Bayi was suffering a bout of malaria.
Walker - who had never been in an Olympic Games before - was the clear favourite.
"He knew he had to win."
After the race, Palenski went under the stadium as Walker came off the track.
"In those days security was barely heard of."
The pair hugged each other.
"I think he was more relieved than ecstatic . . . He didn't have the pressure on him any more."
- The Dominion Post
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