Why Does Not Loading Hurt?
Why does not loading hurt?.
Have you had the experience that not climbing made your fingers just as sore as loading them? This is due to the anatomy and mechanics of the synovial joint.
Synovial joints are comprised of:
Joint capsule - passive stabilizer to the joint made of fibrous tissue. Its job is to provide stability and detect joint position (proprioception)
2-layered Synovium - (AKA) synovial membrane on the inside of the joint capsule. The bottom portion has small blood vessels responsible for producing fluid inside the joint.
Synovial fluid - The primary nutrient delivery mechanism to cartilage. Because the joint itself has little blood, it is the job of this fluid to fill in the gaps (pun intended). It also serves as a mechanism to reduce friction between bony surfaces.
Cartilage - Hyaline cartilage is incredibly slippery stuff. It is an avascular tissue designed to promote "gliding" through motion.
Note that synovial fluid is a bit of a misnomer.
It's a non-newtonian fluid whose behavior is dependent on the rate (power output) and magnitude (total force) of the load.
Higher rate = more surface tension (stiffness).
Lower rate = Less surface tension (stiffness).
This is part of why hard climbing sessions promote stiff joints. A lot of high-rate loading leads to stiffness in the tissue. In addition, the net exchange of fluid inside the joint errs on the side of fluid loss, not balance.
Takeaways
Too much mechanical stress (mechanical loading) drives more fluid out of the joint, promoting an inflammatory response. After these long sessions (don't make them every session), leaving it alone for a few days is a good idea, but not exchanging the fluid inside the joint for an extended time is not helpful.
Without mechanical stress (loading), there is no mechanism to deliver nutrients and remove waste. This is why our fingers are stiffer while not loading them for too long.
Hormesis: Anything at too high a dosage is toxic. Too much loading should be considered maladaptive and thus toxic. But so is too little loading. That is if you expect to get back on the wall.