We use Kepler/K2 lightcurves to measure rotation periods of brown dwarfs and very low mass stars in the Upper Scorpius star-forming region .
Our sample comprises a total of 104 periods .
Depending on the assumed age of Upper Scorpius , about a third of them are for brown dwarfs .
The median period is 1.28 d for the full sample and 0.84 d for the probable brown dwarfs .
With this period sample , we find compelling evidence for early rotational braking in brown dwarfs , caused by the interaction between the central object and the disk .
The median period for objects with disks is at least 50 % longer than for those without .
Two brown dwarfs show direct signs of ‘ disk-locking ’ in their lightcurves , in the form of dips that recur on a timescale similar to the rotation period .
Comparing the period samples for brown dwarfs at different ages , there is a clear need to include rotational braking into period evolution tracks between 1 and 10 Myr .
A locked period over several Myr followed by spin-up due to contraction fits the observational data .
We conclude that young brown dwarfs are affected by the same rotational regulation as stars , though they start off with significantly faster rotation , presumably set by initial conditions .