Left hand shifters tend to be for front mech on chainset.
Right hand shifters tend to be for rear mech gear changes.
The higher end groupset shifters tend to have sealed bearings in the mech and have a lighter feel than the cheaper bushed units.
Gripshift may be an option.
In other words.... shifters, should be viable to upgrade a unit for less effort at the hand.
Thanks very much for getting in touch, it's her right hand that is causing the issue unfortunately, holding and pushing with it can cause her some pain. That's definitely helped me narrow things down, thank you!
Which hand is the thumb issue ?
Left hand shifters tend to be for front mech on chainset.
Right hand shifters tend to be for rear mech gear changes.
The higher end groupset shifters tend to have sealed bearings in the mech and have a lighter feel than the cheaper bushed units.
Gripshift may be an option.
In other words.... shifters, should be viable to upgrade a unit for less effort at the hand.