No I'm getting the physics exactly right my friend.
F=mv^2/r
with a constant radius (lets say 17m for an indoor track), an increase in body mass and/or speed will increase the centripetal force. So the force acting on Josh Hoey at 70kg running 51.5 speed is higher than Keely at 55kg running the same speed. For Keely that force is approximately 197N
And sure, as the radius increases the force reduces - nobody was arguing that. But since you want to talk physics, you'll also understand the impact that the banked angle of an indoor track has on mitigating the increase in force created by the tighter radius. Right?
Most indoor tracks have banked curves between 10 and 18 degrees - for arguments sake lets just split it and say 14 degrees.
Normal force = mg/cos14(degrees) - 556N.
The horizontal component is 556sin14(degrees) - 135N
So the actual centripetal force she needs to overcome is 197-135 or 62N.
The question is, when you balance that extra force vs the benefits of running indoors - primarily in terms of temp, wind and then the inherent spring of indoor tracks because they are laid on hollow structures vs concrete like an outdoor track, where do we land in terms of net benefit/detriment? For me it's all pretty close - but that's just my opinion.
But you're welcome for the physics lesson.