When no external force acts on a body its angular moment remains conserved. From law of conservation of angular momentum, we have J = lω = constant where I is moment of inertia of the body and ω is angular velocity. Also I=
1
2
MP2 (for disc) where M is mass and R is radius of disc. J=
1
2
MR2ω− constant Since, man moves towards the centre of the disc, distance of mass distribution R decreases hence, co increases.