A Significant Muscular Imbalance

[KangTsai]

I have more developed quads, hip flexors and calves compared to most people of my age group. For martial arts, this means better kicking and a big part of good movement.

I have however had a crushing realisation recently.

In proportion to the thicc 2/3 of my legs, my hamstrings, although flexible, were pathetically weak.
I may be able to do 100 bodymass squats without breaking a sweat, but I need to rely on my back to squat a good chunk of 735.75 Newtons of weight. My roundhouse kicks and front kicks may be strong as HECK, but in proportion my (spinning) hook kicks, (turning) side kicks and (spinning) back kicks, although in my opinion, pretty good in technique and execution, fall off in SO MUCH power.
I coined the term "Slav legs" to describe this. To find my reference, execute the pose in my profile picture, heels to ground, and hold for five minutes at least. You will notice your quads and ankles are exhausted, with no effort from your hams or butt. Now Google 'Slav squat.'

I am as of now working my butt off (literally) to resolve this.

 

[drop bear]

Conditioning is every bit as involved as the martial art you are doing.

 

[Dirty Dog]

My roundhouse kicks and front kicks may be strong as HECK, but in proportion my (spinning) hook kicks, (turning) side kicks and (spinning) back kicks, although in my opinion, pretty good in technique and execution, fall off in SO MUCH power.

If your spinning kicks are (as it sounds like you're saying) less powerful than your "straight" kicks, then you need to take another look at your technique. One of the prime reasons for doing the spinning version of the kick is to generate more power.

 

[Charlemagne]

Work in some Romanian Deadlifts and Walking Lunges along with your traditional Back Squat, and make sure you are squatting deep (past 90 deg) and your problems will be solved from a Hamstrings Strengthening perspective. The Back Squat is more of a Quad dominant, and Glute dominant lift if it is done with proper depth. If it is not done with proper depth, it merely becomes quad dominant. The role of the hamstrings in the Back Squat is to prevent the tibia from translating forward on the femur at depth, which is why you see the timing of recruitment happen when one gets deep in the lift and the tibia is in danger of sliding forward in a shearing fashion. It's good that the HS is recruited then as it takes load off of the ACL, which otherwise could be compromised in that position. However, the HS is not loaded significantly, so it is not going to be strengthened as effectively from squatting as it is in other lifts.