A woman crashed her bicycle and died after suffering a rare condition called cyclist palsy – which froze her hands and stopped her applying the brakes, an inquest heard.
Rebecca Scott, 24, was on a training ride with her father Alan when she lost control riding down a steep hill.
She careered into a wall in front and despite desperate attempts to revive her she died on impact.
No defects were found on the bike or road and investigators told an inquest she may have died of a condition known as cyclist palsy.
It leads to numbness in the hands if they have been locked in the same position for too long – meaning she could not apply the brakes.
Senior investigating officer Pc Rod Lomas told an inquest: "There were no witnesses to the collision and no defects were found on the bike.
"So we look at possible causes for Rebecca to have lost control. The road surface looked in good working order.
"One of the possibilities is she could have suffered from cyclist palsy.
"When a cyclist rides for a distance and hands don't change position there can be a numbing, fatigue and tightening of hands.
"It is just a possibility to try to explain why Rebecca has lost control and was unable to control the speed she descended the hill at and unable to squeeze the brakes."
Rebecca, of Clyst St Mary, near Exeter, who was training for a 100-mile bike ride at the time of the crash, met her father in the early afternoon in August last year to cycle to Beer, Devon, and then on to Branscombe, Dorset.
She had been wearing a helmet but had mentioned during the ride her brakes were not responding as well as they should.
Alan told the inquest, in Exeter, Devon, he heard the collision but did not see the moment of impact.
He said: "It was a social ride and we were chatting for part of it. I said this hill was quite steep so be careful. She was never reckless and we were not racing at all.
"I was in front and riding on the brakes the whole way down. It was quite a long bit of road. Near the bottom she went past me, which was unexpected.
"She was making a noise, it was not a scream, but I knew she was not happy. I released my brakes to chase and catch up with her.
"She went around the corner and was out of sight. I then heard a bang and that was it.
"In no time at all I was there. I did not see the moment of impact but I heard it and was there seconds later.
"It was a sunny day, parts of the roads were a bit bumpy and there was potential she may not have seen a pothole because of the shadows."
The inquest heard the bike she was riding was relatively new but she had used it for a fair amount of time. She had already negotiated several steep descents on the day without any problem.
Coroner Andrew Cox recorded a verdict of accidental death. He said: "Nothing I have heard today shows anything other than a perfectly sensible, well organised family cycle ride.
"Nothing from a mechanical perspective to explain what has gone on here. That means we are at something of a loss to find anything as a cause."