Although idi probak can in theory be carried out on any reasonably flat surface, the preference is to conduct them on specially constructed proba tokiak (test places).
During the year, they are taken for walks of around 5 km in the hills and mountains daily to maintain their strength.
The goal of the competition is to complete as many plaza (the distance between the two ends of the proba toki) as possible within a given period of time.
The itzaina leads the team from the front, the akuilutzaile tries to steer both the oxen and the rock from the back.
Ideally a team completes a full plaza without stopping as it costs a lot of energy to get the rock moving.
At the end of the competition, the referees announce the results both in plazak and meters raced.
Although the number of cases is low, the Basque regional governments started introducing anti-doping measures in 1997 and created the office of Official Veterinarian in 2005 to help ensure good practice.