Emma Pooley was bitterly disappointed after a lowly Olympic road time trial finish behind Kristin Armstrong, who won a third straight title a day before her 43rd birthday.

Pooley quit cycling after the 2014 Commonwealth Games in Glasgow but was persuaded to come out of retirement by the hilly nature of the 29.8-kilometres time trial route at Pontal.

But the 33-year-old could finish only 14th as the United States' Armstrong won in 44 minutes 26.42 seconds. Pooley clocked 46mins 31.98secs.

'I'm disappointed with the result,' said Pooley, silver medallist behind Armstrong at Beijing 2008 and sixth at London 2012.

'In life you take the opportunities you're given and do the best you can with them. I'm very grateful for them.

'You don't know whether the difference between a medal or not is a tiny thing or a big thing.

'I have to be happy with the decision I made (to come back) and the preparation. I don't think there was anything glaringly wrong with it, just the result.'

Pooley was the 11th of 25 riders to start and had a slight wobble on the ramp.

She said: 'I couldn't clip in with one foot at the start. That occasionally happens. It didn't take long.'

But the diminutive rider never recovered, struggling in wet and windy conditions near the Rio coast.

Pooley added: 'It's winter in Brazil. We knew there was a chance of rain.

'From my point of view, my physiology, it's a bit tougher when there's a strong, blustery wind like that. It makes it a bit harder to control the bike.'

Pooley, who has a PhD in geotechnical engineering and is based in Switzerland, says she does not know what the future holds.

She is entered for more long-distance triathlons, where prize money is good, but is yet to decide whether to compete.

'I'll have to look at my budget. It might be a back to normal job,' she said.

Armstrong won by 5.55s from Russia's Olga Zabelinskaya, who was second in 44:31.97, while road race champion Anna van der Breggen of Holland was third in 44:37.80.

Zabelinskaya claimed bronze medals in the road race and time trial at London 2012, but served an 18-month anti-doping suspension after testing positive for octopamine, a stimulant with fat-burning qualities.

She was initially cleared of wrongdoing by the Russian Cycling Federation, but the UCI, cycling's world governing body, contested the decision at the Court of Arbitration for Sport and her ban was implemented.