First let’s talk the effect. When all of us collectively jump at once( a 30cm maybe), we will be able to push our planet Earth, 1/100 of the width of a single hydrogen atom. Is that a big deal? Well.. No, tried our best though;)
For any rotating body, if the mass shifts towards the center, the rate of rotation increases. In this case, the rotating body is our planet Earth and the mass we are talking about, is us.
As the Earth rotates faster, we loose “Time”:(. Powerful earthquakes can redistribute mass. The earthquake in Japan in 2011 moved so much mass toward Earth’s center that every day since then we run 0.0000018 seconds shorter. Thankfully, that’s too short.
So, this clearly explain that our puny little mass( together at one place) cannot effect the rotation of our Planet, but this may cause Earth Quakes.