Retired Real Madrid and Brazil striker Ronaldo swapped his cleats for an electric bicycle as he set off on a nearly 450-km (280 mile) trip after promising to do so if his club Real Valladolid earned promotion to Spain's top-flight league.

Real Valladolid players celebrate after La Liga promotion. Photo: Twitter

Ronaldo, who also owns Brazilian club Cruzeiro, bought a 51% stake in Valladolid in 2018, and is the president of the Spanish club.

The 45-year-old's trip began at Valladolid's Jose Zorrilla stadium on Sunday and will follow the Camino de Santiago trail, which is travelled by thousands of pilgrims each year, before concluding in Santiago de Compostela.

"It will be beautiful. I know that I will suffer physically, but it will be an unforgettable experience," Ronaldo told reporters at Valladolid's stadium before departing.

Ronaldo Nazario celebrates Real Valladolid's promotion to La Liga. Photo: Twitter

He will be accompanied by his partner, as well as a team of "expert professionals" to aid him in his journey.

Ronaldo's bike trip comes after Valladolid finished second in Spain's second division to earn promotion back to LaLiga, a season after they were relegated.

"When we were relegated, I knew we had to do a lot of work to get back to the first division," Ronaldo said.

"I made the promise, we've done a very good job, especially at the beginning of the year, with all the changes we've made, all the philosophy we've changed.