Complex sentence: Marvingt refused to relinquish her ambition and cycled the course after the race, completing the gruelling ride, a feat which only about 30 of the Tour's 100 male riders had managed.
Split into simpler sentences: Marvingt refused to relinquish her ambition and cycled the course after the race. She successfully completed the gruelling ride, a feat which only about 30 of the Tour's 100 male riders had managed.