Earlier in the year I bough some crank brother mallet dh, these have a little longer spindle than normal, and I noticed a slight change of emphasis in muscle usage to the core of the thigh muscle, and less pressure on the “teardrop” just above and to the outside of the knee.

I want to replicate the wider q factor on all my bikes,and probably go a little wider still. I am going to try some jtech pedal extenders (kneesavers) on my road bike that sits on the turbo trainer, but I don’t really fancy using them on a mountain bike are there any other decent options for widening the qfactor?

Depends what your current setups are.

-If you run crank bro’s pedals some nave shorter axles, check that’s not what you have.
-MTB 73mm BB cranksets could be replaced with 83mm BB cranksets, but obviously this would affect chainline so again it depends what you currently have if you could make it work.
-Flat pedals come in many widths, buy wide ones and move your feet further out.

-alt option, buy a fatbike with a 100mm or 120mm BB and ride like John Wayne 😀

oh, and your road bike will almost certainly have a q that was narrower than your MTB by more than the distance you added to your mtb with new pedals. So adding extenders to the road bike will probably put your feet at more mtb width (probably, there is so much variation with cranks and pedals its impossible to guess so If you want real help you need to state current models of cranks and pedals you want to ‘improve’)

Speedplay
https://www.stevehoggbikefitting.com/bikefit/2011/04/road-pedals-which-are-best/

http://www.slowtwitch.com/Tech/Stance_Width_2562.html

Pedal Extenders