In one embodiment, a computing system accesses a first tracking record of a first user during a first movement session. The first tracking record comprises a plurality of locations of the first user and associated time measurements. During a second movement session, the system determines a current location of a second user and an associated current time measurement. From the plurality of locations in the first tracking record, a first location of the first user in the first movement session is determined based on (1) the associated time measurement relative to a start time of the first movement session and (2) the current time measurement relative to a start time of the second movement session. The system determines a display position of a virtual object on a display screen of the second user based on the first location relative to the current location of the second user.