Suggestions for braking with severe osteoarthritis in both hands

A coaster brake for the rear comes to mind as a main brake. Refer Sheldon Brown ), however for safety you need more than one brake. A high quality MTB disc brake is designed for low force i.e. single finger for normal use, and high end come with a vast array of lever adjustments so you can get the levers close to the bars to reduce the reach needed.

With Hydraulic disc brakes only need to provide hydraulic pressure from a hose to make them work, it may be possible to fabricate something that allows you to generate the required hydraulic pressure from something that suits you hand ability, you may find a specialist who already has such a device.

Ideas for avoiding using hands to brake:

Coaster brake

A coaster brake is a rear brake which you operate by pedalling backwards. Suits urban bikes in flat places very well. Think 'Dutch' bikes. Fit a front brake too in support but use the rear most of the time.

Track cycling

Velodrome cycling features fixed gear bikes, with no brakes. The speed is controlled purely by the pedals. You can't stop pedalling so it's great exercise and lots of fun! Burnaby Velodrome is apparently near Vancouver.

Tandem cycling

Front seat rider operates the brakes and gears, rear seat rider contributes through the pedals. Pick somebody you like to spend time with but good for roaming a bit further afield.

In addition to a coaster brake on the back, there are solutions to allow both hands to operate the same brake. Problem Solvers make one that goes inline, and JTek have one that goes on the brake. These could perhaps provide a front brake if you have sufficient strength on both hands combined. These are for cable brakes; I'd use them with disc- or V-brake, with good quality pads.

I'd suggest using them with 2 fingers of each hand to brake, and handlebar grips chosen to be reasonably secure without any need for actual gripping except over bumpy bits of road. Some of the grips made by Ergon work well; I've got GP3s on my hybrid, upgraded from GP2s and I can ride with my hands just resting on them much of the time.

There is a lot of options of different handlebar arrangements and brake types. Some have very small operating force. Also the brake levers can be rotated to an angle that is most comfortable.

I would suggest to find a good local bike shop, and get in contact with them. Chances are that they can arrange for you to try out many different models and will help adjust them to your needs.

Even for people without medical conditions, professionally fitting a bike to the rider makes a big difference. I would assume that will be even more true when you have needs that differ from the majority.

Have you tried hydraulic disk brakes? They use a lot less force for braking, because most of the force of a cable-brake goes into stretching the cable. Also the power of the disk brake counts a lot: the more powerful it is, the less pressure is required to activate it.

Also, note that reclining two-wheelers and trikes are worth having a go on, they give you many options of changing the brake lever so that you can push the brake with your palm/elbow/leg.

It's possible to re-purpose a grip shift throttle/gears if they use a cable, and also check [old-fashioned gear shifters][1].

I'd say add a disk brake and arrange a push-lever on some kind of touring handlebars, else try a trike and add third brake on a push-lever and a pad somewhere near your elbow. perhaps even try a third brake near your knee when it's raised and have a sideways knee pad on the frame.

Take up african-trance dancing!!! There are lots of dancing videos (search "choreography + alice/julie/fatima", and with Covid-19 I find them very useful. Africans go into a trance when they dance, and that is true of every sport: When your body gets into a rythm, it's possible to keep going for 30 minute or an hour, especially if you put in some upbeat dancing music.

Honestly, for Covid-19, I have learnt to dance into a trance to keep fit, sprint with your arms while hopping around in circles, slash the air like a tiger round and round and up and down and left to right while also hopping left and right and around, pretend that you are 4 years old and jumping up and down for your birthday, go frenetic, and you can sprint 100 meters in 1 minute, or keep it chilled and get your heart to 120 for 30 minutes, it's mostly a factor of finding a rythm and going into a trance, I also have weights in my sports room lol. choreography videos give you 1000'ds of complex body moves to copy, and sweating hyperactive young people to emulate, and you can always play your own music in the background.

Also check your swimming center for exercise groups and walk up mountains :)

Consider getting yourself an Electric-bike. Not so much for the pedal assist, but for the electrically powered braking systems they can provide. (usually hub based hydraulic off mechanical levers, but there are powered options available)

But yes, speak to a decent bike shops. They are the experts, and should be able to help you much better than we here can.