One of the most common questions I get from my non climbing friends is, “do you need to be strong to start rock climbing?” And I see a lot of beginners quit climbing early on, assuming that they need to get stronger or lose weight before they can try climbing. My response to this in a gist is, “Climbing is a skill based sport”. Read that a couple of times and let it sink in!
As a beginner rock climber, no training can get you to climb better than just climbing itself. To put this in perspective, learning to climb is like a child learning to crawl or walk. It is so apparent in children how our bodies are gifted at natural learning and it is amazing how it adapts to the needs of the mind. How often have you seen kids crushing it in the climbing gym, while a buffed up guy flails on an easy problem? Do you think it is the strength that he lacks? You just need to keep at it, build a solid base and let your body learn and adapt.
In the initial months of climbing, your brain learns and stores hundreds of new movement patterns every climbing session! The more number of times a specific type of move is repeated, the stronger the imprint it creates in the brain and soon becomes second nature. So, the more time you spend climbing and the more variety of moves you try, the faster you will progress.
In fact, I think that being very strong as a beginner could be detrimental because you would have to put in a conscious effort not to use strength, but to learn efficient techniques. On easier climbs where you can just pull your way up, this may seem silly and quite unnecessary. But if the route is climbed in an inefficient way using upper body strength and poor foot technique, that tends to get stored in our brain instead and relearning technique takes much longer at a later stage. The person using poor technique and muscling his way up, will progress to the next couple of grades faster but will plateau soon after. Whereas a weaker person would be forced to manoeuvre his way up the wall in the most efficient way and thus honing down on his techniques early on!