Ever since my tweet earlier today about Alina Zagitova's practice, the skating world has been 1) fascinated by her and Evgenia Medvedeva's multiple-triple combinations in practice, and 2) wondering why neither of them will include them in their programs tomorrow. It has everything to do with the rules set by the ISU Judging System (IJS). Here's a crash course.
Recap/videos: Ladies short program
Five-jump combos aren't allowed
Zagitova's triple lutz-triple loop-triple loop-triple loop-triple loop isn't allowed, though three-jump combos are.
In the short program, singles skaters are allowed to do one jump combination with two jumps, one solo jump, and one solo axel jump - so no jump combos with more than two jumps are allowed there.
In the free skate, singles skaters are allowed to do jump combinations with a maximum of three jumps in them - so the triple lutz-triple toe-triple loop that Zagitova did in practice or the triple sal-triple toe-triple toe that Medvedeva did in practice would be allowed.
So, ok, why don't they do it? Read on.
It's not mathematically-enticing
Another rule for free skates is the women are allowed to do a maximum of seven jumping passes (men currently are allowed eight max), but they are only allowed to repeat a maximum of two triple and quadruple jumps once each. (N.B.: This repeat rule also invalidates two of the triple loops in Zagitova's crazy combo.) In essence, for the women, unless you have a triple axel like Mirai Nagasu does, you max out at seven triples for your seven jumping passes.
What's more, the way that the IJS calculates jump combinations is a simple addition of the base values of those jumps. So even though doing, say, a triple lutz and a triple toe in combination is much more difficult than doing a triple lutz in isolation and a triple toe in isolation, they are worth the same base value.
All of the top women now do at least one triple-triple in their free skate in order to maximize their seven triple jumps, but doing a triple-triple-triple would mean that you just make room for more double jumps, which are just not worth that much ...
It's not worth the risk
... nor are they worth the risk. Adding an additional triple jump to a triple-triple combination just doesn't make any sense when it comes to risk and reward. When you think about the energy expenditure that a triple-triple-triple could potentially have - and even more energy draining if you make a mistake on it - why take the unnecessary risk just to demonstrate that you can do it?
If the IJS ever changes to incentivize combos more by giving them a multiplier greater than 1.0, the attitude toward things like triple-triple-triples might change. A very small number of the men have done them (see: Kevin Reynolds) because they have quads and can benefit more from their jumping passes. But for the women, the incentives are just not in line. Zagitova, Medvedeva, and others do these combos in practice because it helps sustain their stamina.
But no, you won't see a triple-triple-triple tomorrow.