It isn't so much about the training as it is about the recovery. Professional cyclists are on the bike for 700-1000 kilometers a week, often with two different training sessions in a day, and multiple days in a row. Same for any endurance athlete, such as triathletes, marathoners, ultra runners, etc.
The bad news is, that if they aren't training, they are resting/recovering with a team of professionals, which you most likely don't have. The good news is, you won't be sustaining the training load that they are either which means that you can easily achieve the commuting goal. So lets look at this from the ground up (if you will pardon the pun).
As was pointed out, the training portion was a bit glossed over. As I understand it, you want the bike commute to supplement training for sport climbing and hiking/mountaineering. I think that cycling would provide an ideal supplement training, as it will increase cardio, is low impact, and more importantly will strengthen the muscles of the leg which in turn will help stabilize the knee.
For the morning commute, not much variation is needed other than the straight ride, as you don't want to arrive at work wiped out for an hour. If you have a desk job, you will have ample recovery during the day for any evening activity. If you have a more active job, make the morning commute as easy as possible. Find a comfortable gear so that you are neither "spinning" rapidly or pushing mightily. It should just feel comfortable.
For the evening commute, on days that you are not intending on walking/hiking at home, you can add in items like getting back up to speed as soon as possible after stops, going out of your way a bit to add in hills, items like that. That will give you some speed work as well as muscle development. If you are intending on walking/hiking/climbing that evening, then treat it as you do the morning commute. Light on the actual work, use it as a warm up. Concentrate on making the "full circle" on the pedals, so that while one leg is pushing down, the other is pulling up. This takes some practice to get used to.
For a sample schedule, I would lay it out something like this:
- Monday - Bike commute if weekend was easy (or you rested on Sunday), otherwise rest or bike 1 way only
- Tuesday - Bike commute easy/easy, easy hike
- Wednesday - Bike commute easy/hard, or no commute + moderate hike
- Thursday - No commute, easy hike or rest
- Friday - Commute easy/hard, no hike
- Saturday - Hike as you want
- Sunday - Same as Saturday or rest
That kind of a schedule should serve you well initially, and there is no real reason that you could not work up to commuting every day and hiking most days as well. That is where the self monitoring comes in, if you know you have a hard hike coming up, rest on the commute portion, or if you are knackered, take a day off from commute/hiking.
For other considerations:
What kind of bike?
Considering your history, the first thing that you want to consider is what kind of bike to get. I personally would recommend either a hardtail mountain bike, or a commuter/cross type bike. A typical racing type bike isn't the best for commuting, and the others would allow you to commute and use it for general recreation. The cycling adage is, you can have light, cheap and reliable. Pick two. I would recommend avoiding the big box stores (Walmart, Target, Dicks sporting, etc) as they will have the lower end. While that is not a bad thing, I don't like the component groups that they come with. YMMV, find one you like. If you can test ride a few even better. If worse comes to worse and you hate cycling, the resale is much better as well. As pointed out in the comments, you can get puncture resistant tires and tubes, and add in a protective slime, the trade off is in the weight of the bike.
Fit is CRITICAL
Even if you buy a big box bike, I would first find a bike shop that offers a fitting service. Usually this is free if you purchase a bike, or may cost a few $$ if you just want the numbers. But, especially with your knee and ankle surgeries, you want the correct saddle height and crank length (The crank is the piece that holds the pedals and the chain). If you don't fit those correctly, you will cause more pain/potential trouble in your legs and potentially hips/lower back. If you have oddly splayed feet (I have feet that point out), you can even get custom clipless pedals with specified spindle lengths (How far out from the crank the pedal is). This lets you pedal with a more natural motion and foot position. Also, find a saddle/seat that you are comfortable on. More people give up cycling because they have an ass hatchet for a seat than anything.
Jeez, man, I'm not even on the bike yet!
Ok, now you have a bike. And a helmet. Never get on a bike without a helmet. If you are new to cycling, then I wouldn't recommend just jumping in and cycling both ways every day. Ease into it, get used to the bike, handling in traffic, all of that before fully committing to the commute.
The good news on that front, is that 18km an hour is right around 12 mph, and that is a relatively leisurely pace. Even a recreational cyclist should be able to sustain that without too much training stress. Some ways that you could also ease into it, is see if bus lines go the same way. Where I live in the US, most buses have bike racks on the front so that you could cycle to work, then take the bus home or partway. Or, if you can leave your car at work, drive to work with your car, cycle home, then cycle back the next day. As another poster suggested, once you get used to it, you can sprint for stop signs, add in small training items without causing too much stress.
If you're tired, simply skip a day. You're doing this for health, not training for a race. The basic back and forth every day should not put enough stress on you that you need tons of recovery, so eating well and getting a good nights sleep should be all you need, especially as you get more used to the exercise. Cycling is also very minimal impact, so you don't have the same recovery requirements as you would for running or other heavier impact items.
Wait, you mean there is more?
Some other items/things to consider as you start on this journey.
- Work accommodations - Is there a place to lock up your bike? A place to change clothes? Possibly shower?
- Clothing - Pack your work clothes, cycle in other stuff. You will get dirty, get chain grease on your leg, get rain/snowed on, etc. Just take a pack with your stuff. If it's going to rain, stuff it in a waterproof container (I used a trash bag, honestly).
- Other items - In addition to the helmet, I have a small pack that fits under my seat. I carry tire irons, extra tubes, some CO2 cartridges for inflation, a little bit of $$ just in case, and a laminated paper with medical/contact information.
- Cycling gear - Helmet, bike shorts (See below), cycling gloves.
- Be prepared - You will crash. There are 2 types of cyclists, those that have crashed and those that lie about it. Either through no fault of your own, or you miss a patch of gravel/ice and slide down. Learn to fall safely.
- Consider upper body weight routines - Cycling is all cardio and lower body. For general lifestyle, I would add upper body exercises to balance. You can find a lot of body weight type exercises that can be done at home without equipment or with minimal investment. (You can check the Fitness stack for some ideas).
You didn't just get in your car and start driving everywhere. You practiced. Same with the bike. Get on a friendly commuter trail and just get used to the bike. If you do get clipless pedals, sit on the bike next to a post or fence for balance, and just practice unclipping and clipping in. Even with that, expect to come to a stop sign and fall over because you can't get your foot out. I do that about 2x a year, honestly. Take the bike into a grassy area or field and fall over. Don't reach out to brace with your hands, you'll break your wrists. Just kind of lean over and roll onto your hips.
Get some comfortable cycling shorts. Remember the point about the saddle? Same goes for clothing. Don't skimp on the contact points. It doesn't have to be the lycra bib looking things (Although they are uber comfortable), but something that will make it more enjoyable to spend some time cycling. Good gloves, with hand padding. Also if you will be cycling in various weather conditions, get weather appropriate clothing. Remember if it is cold and raining, it will be cold, raining and windy on a bike (You create your own headwind). There is nothing more miserable than being cold, tired and hungry with another 20 miles left to go on the ride.
argumentum ad verecundiam (or who is this guy?)
I've been a touring and competitive cyclist for a long time (over 30 years off and on). I've been on two-three week cross country rides covering 100-150k per day, as well as racing both road and mountain. I've cycled in a lot of different conditions on a lot of different bikes. Oh yeah, I also have a degree in exercise kinesiology. :)