FYI..I am not a coach and don't pretend to be. I'm going to share some training observations here that work for me related to climbing. They may or may not work for you. The fitness comments I make are just the tiny tip of the iceberg on training. To train and get stronger you really need to educate yourself on the subject and all that it incorporates. Or do both and climb! Climb a lot! Because I don't "climb a lot", I train. I typically train to my weaknesses, endurance and physical strength. You have to know what you want from the training first, to get what you need out of the training.
For most who will read this with some interest it is likely because "high impact" training hurt or has injured you previous.
I have never been a big runner. But I have ran and I do run now. But for most running on pavement will tear you up given enough miles. Running on pavement is rough on everything from joints to tendons. Well it at least tears me up, has in the beginning as a teenager and does now in middle age. Hilly trail running (which can be a lot more "dangerous") for me is a lot softer impact sport. I am forced into a forefoot strike instead of a heel strike and the surface is generally a lot more forgiving. Not to say it isn't easier to trip and bust your ass or an ankle running trails instead of you local high school track, paved trails or the side streets. And you can run with a forefoot strike anywhere once you learn (relearn?) the skill.
Foot strike is important.
more here on foot strike:
But running is not a low impact sport. Generally you learn early on if you can run. You either don't get injured running or you do and it becomes a problem trying to keep running. I am good up to 1/2 marathon distances both for racing and training. At full marathon distances my body is telling me the mileage and the race efforts are just too much. I don't have a runner's body at 200# and 6'1" so no surprise. But even at 180# marathon distances still hurt and take a long time to fully recover from. Too long if I want to climb during the summer and the risk of injury training, just too great.
So I limit how much running I do. But there are two low impact sports I try to do a lot of. I really like them both simply because I have been doing them for as long as I can remember. Swimming and riding a bike.
And in a controlled environment I don't have to worry about dying doing either. Both are mindless activities the majority of time for me. But not always if you up the environmental hazards. And with even a tiny bit of care neither will hurt you significantly physically even during hardest work outs.
And the fourth sport is Skiing. Downhill on the lifts, back country and side country on 3 pin gear and Skimo gear. It is all skiing to me. And like the bike or swimming something I have been doing a long time.
Here is where I start to define what I want from my training. If you don't know what you want from your exercise efforts you'll likely never get what you want from your exercise efforts.
Running Goals? (running is always training for the mtns eventually)
Olympic and Sprint Tri racing
1/2 IM race finishes
trail running for endurance
uphill running to simulate and strengthen my climbing
Bike goals? (biking is always training for something)
200+ mile days (road bike)
Tri and TT racing
endurance days in the mtns = endurance days on the bike
Swimming goals? (swimming is generally training for swimming/tris)
IM distance swims
Sprint and Oly distance races
Skiing goals (skiing is generally for fun but sometimes it is to better my skills or training for endurance)
technical or steep skiing
endurance days in the mtns
And then there is number FIVE which is also low impact
Rock/Ice climbing or crag climbing goals?
get stronger physically as a climber for the mtns or to just up my abilities on tech terrain
Back to the "Principle of Specificity"
But I know why and how I train. Do you?
You can never be too strong, too rich or too pretty :) Which is why others advocate the benefits of a crossfit or similar strength training programs. I don't generally partake but I suggest others do for the obvious benefits to be gained.