Mucle memory is a weird thing.  
I was a very active sports climber since 2013, with my most active years being
2016 to 2019. My best performance was an 8c flash. For non-climbers, that means
that I completed an 8c route without any prior knowledge to how this route is
build and supposed to be completed. I just went on the wall and did it.  
In late 2019, I hurt the the tendons in my right middle and ring finger. This
put me out of commission for about 6 months. When I finally recovered the gym
was closed because of the COVID-19 virus. I never enjoyed any other forms of
physical activity, so I let myself go and gained about 15 kilograms. At this
point I should add, that during my peak climbing days, I was underweight.
I am 183cm tall and weighed about 63kg, which wasn't exactly healthy.
I now weigh around 77-79kg and I haven't really actively climbed since 2019.
What I mean by "actively climbed" is at least three times a week, which is the
minimum of what I did back then. Nowadays, due to work and a longer commute to
the gym, I go about once every two weeks.  
Now, this is why muscle memory is weird.  
I don't go climbing three times a week like I used to.  
I gained 15kg, most of which is probably fat. I lost muscle.  
AND STILL, after only four climbing sessions, I am back to flashing 7c. 
I know, it is not an 8c, but I expected WAY worse, and I honestly don't
know how I'm even able to do this. I don't think I should be able to do this.
I thought I'd start back at around 6a or so, simply because my shoulders and
back muscles got way weaker. But I can still do these routes without an issue.  
If this is really just muscle memory doing its thing, then I'm really excited
for what I can do, once I get back into climbing regularly.