Polar and Garmin hrm strap - strange readings...

Hi,

I used Polar H10 for quite a long time and I was happy with it.
Two weeks ago I bought Garmin HRM Run strap and... suddenly my "fitness" statistics have changed dramatically.
After similar training my training load, recovery time and training status etc are much higher than trainings with H10.
I don't think that my fitness level has fallen dramatically so I assume it is because of the new garmin hrm strap.

Is it possible that thanks to extendeed info from garmin strap (vertical oscilation, ground contact, running power etc) these results have changed so much?

Regards
;)