@jal11180 I'll give it a shot.
Same principles always apply to capacity. Phosphocreatine depletion, buildup of glycolytic byproducts...these are showstoppers. As always, breaks slow down these processes, though the importance / frequency / duration of a break depends on the fibers recruited.
An additional issue for gymnastics, however, is
movement economy.
Endurance athletes prioritize running economy. The key ideas are minimizing wasted energy and maximizing energy return from each stride. In short, better running form produces better running economy within genetic parameters like leg length and muscle fiber apportionment. (Yes, runners, I know there is more to it)
Running economy generalizes to movement economy. Movement economy in CrossFit means (a) using as many muscles as possible to accomplish a task and (b) every recruited muscle contributes. This "spreads the load" and delays fatigue. Two examples of high movement economy:
- Double Unders. When an inexperienced athlete does them, they use their arms, shoulders, and wrists. This is poor movement economy; muscles are working but not helping (the rope doesn't turn faster) which means fatigue happens sooner. Advanced athletes flick their wrists and use way less energy to do the same work. That's good movement economy.
- Butterfly pullups. The reason most competitors can do 50 butterfly pullups, but probably only 15-20 strict, is because butterfly pullups bring more muscle fibers to the task. This is good movement economy - lots of muscles helping means more work gets done faster.
Butterfly pullups also allow for use of momentum; you just drop into the next one, arch at the bottom, push into the bar and up you go. Maintaining high movement economy on CTB is much harder. Your chest has to make contact with the bar, and you still need to preserve downward momentum into an arch to smoothly transition into the next rep. Slight imprecisions can mess stuff up. The common errors are:
- Chest doesn't come high enough and you have to correct with a last minute pull
- You hit the bar too hard and it redirects you
In either case, you've just wrecked your movement economy because you've lost momentum. You now have to get
back into position while hanging from the bar. This costs lots of energy because you're not using momentum and you're not in an arch at the bottom; what usually happens is a cascade of lousy reps until you drop.
You're overloading your pulling muscles, the exact muscles that the "butterfly" is supposed to take the load off of. It's actually worse than strict, in energy terms. It's like doing a strict pullup while your lower body is moving all over the place. (Try it! Do strict pullups while swinging and rotating) In simple terms, you're in "negative movement economy" - you're doing
more work with
fewer muscles.
If you continue and do successive bad reps, you fall into fatigue hell and you're not getting out. When you lose your "smoothness" on CTB, get off the bar. Better yet, get off the bar before it goes wrong.
TLDR movement economy is how you win at CF Gymnastics, and maintaining movement economy on CTB Pullups is hard. One might argue that movement economy is downstream from virtuosity.
Hope that makes sense. It's late and I'm tired.
One more consideration:
This study concludes that fatigue degrades motor learning as well as performance, because it causes maladaptive memory formation. The specific maladaptation pertains to miscalculations of force requirements, which is
exactly the kind of thing that can wreck CTB Pullups.
https://elifesciences.org/articles/40578.pdf
Keep in mind this paper is about learning, not performance. But fatigue causes all sorts of compensatory movement patterns, which just causes more fatigue (and also impedes learning). And I suspect that the miscalculation of force happens almost instantly.
Break early, break often.
