A walker was airlifted from the slopes of Pen-y-ghent after collapsing.
The 29-year-old man was training with with a group for an attempt on the Yorkshire Three Peaks challenge on Saturday.
The Cave Rescue Organisation was alerted about 10.15am.
A spokesperson said the walker was ascending the path above Brackenbottom when he told his companions: “I think my heart has stopped,” before collapsing.
The spokesperson said: “His colleagues started [cardiopulmonary resuscitation] and kept this up until the arrival of Yorkshire Air Ambulance paramedics.
“CRO assisted by carrying the casualty to the air ambulance for onward evacuation to hospital.”
The team said the walker was alive when he was airlifted from the fell.