We have nothing other than anecdotal evidence to support that.

For extremely rare events, even anecdotal evidence can be pretty good. If you were told something happened to 1 in a billion people, and you met 3 such people, you'd have pretty good evidence that something odd is going on (the rate is a lie, you're mistaken about meeting them, or something unusual is concentrating them in your presence). Rhabdo isn't nearly that rare, but it's pretty rare. That rareness, and a very reliable base rate for rhabdo in the overall population, means that the anecdotes actually get us a lot further than you might expect. I will demonstrate with some Fermi estimates and a little bit of statistical reasoning:

Wikipedia says:

In 1995, hospitals in the U.S. reported 26,000 cases of rhabdomyolysis.

262m people in the USA in 1995, so the base rate is: 26000 / 262764948

Alright, so that's the base rate for the general population. Now we need a rate for CrossFitters, number of CF rhabdo cases divided by number of people doing CF:

1. How many anecdotes are we dealing with? I took Nancy's Medium link, followed each link in it (ignoring any other links in this LW thread), and tallied how many specific, concrete, anecdotal cases of rhabdo were reported in each; sorted by date:

   • http://www.nytimes.com/2005/12/22/fashion/thursdaystyles/22Fitness.html?pagewanted=all&_r=0 Dec 2005 : 1 ("Brian Anderson"), 6 ("as many as six"), assume double-count of Anderson to be conservative: 5
   • http://library.crossfit.com/free/pdf/CFJ_Wright_Rhabdo.pdf June 2011 : "In recent months, there have been a few incidents of rhabdomyolysis in our affiliates"; 'a few' must be at least 2
   • http://www.menshealth.com/fitness/cult-crossfit/page/4 October 2011 : 1 (Makimba Mimms)
   • http://www.crossfitsantacruz.com/crossfit_santa_cruz/my-rhabdomyolysis-story.html December 2011 : 1
   • http://www.crossfitreality.com/?p=381 August 2012 : 4 (author, 3 commenters)
   • https://medium.com/health-fitness-1/97bcce70356d September 2013 : 1 (friend of author)

   • http://www.endofthreefitness.com/rhabdomyolysis-know-thyself/ September 2013 : 1

     These all sound reasonably exclusive (the 2011 CF paper is specifically about a different time period than the cumulative-to-2005 CF estimate of 6, the comments all seem to be by different people, etc), so we can sum to get 5+2+1+1+4+1+1=15 anecdotal cases of CF. You can argue that some of this is double-counting that I just didn't notice, but if I looked at a few more threads I could probably add some more aneccdotes, so let's just call it even.

2. How many CFers?

   Crossfit was founded in 2000; there are now 6100 affiliated gyms. The 2013 CrossFit Games Open apparently had 138k registrations; this was a sort of virtual online competition, it seems, so it seems like a reasonable proxy for total Crossfit participants. Let's say half didn't bother to register, so in 2013, there were really more like 300k CrossFit people. That makes 50 CrossFitters per affiliate, which given the high cost of CrossFit and intensive time-demanding training sounds pretty reasonable. How many CrossFit people have there ever been? Making the completely arbitrary assumption that the average CFer lasts one year and assuming linear growth from 1 person in 2000 to 300k in 2013, then there's been 150k * 13 = 1950000 CFers.

3. hence, just from these anecdotes, we might estimate a lower bound on the rate of 15/1950000

As it happens, (15 / 1950000) < (26000 / 262764948). To get the CF rate just barely above the base rate, I'd have to increase the number of CF rhabdo cases to 193, since (193 / 1950000) > (26000 / 262764948).

So if you believe the null hypothesis that CFers suffer rhabdo at the exact same rate as the general population, then according to this set of numbers, I apparently managed to get 8% (15/193) of the way to the entire population of CF rhabdo cases just by reading 7 links. As much as I admire my own reading and link-clicking skills, I don't find that very plausible.

Now, with this set of numbers, how many cases of CF rhabdo would we need before we had something statistically-significant? We'd need another 206 cases of rhabdo to hit p<0.05:

R> binom.test(c(221,  1950000), p=(26000 / 262764948))

    Exact binomial test

data:  c(221, 1950000)
number of successes = 221, number of trials = 1950221, p-value = 0.04758
alternative hypothesis: true probability of success is not equal to 9.895e-05
95% confidence interval:
 9.887e-05 1.293e-04

So our little handful of anecdotes gets us 7% of the way to the claimed conclusion. For the much-maligned anecdote, this seems pretty impressive, IMO.

I declare my future self to be another person who I wish to bend to my will.

"bending to ones will" is unprofessional and might cause "retaliation" (e.g. breaking out of the pattern).

You can better better influence your future self by giving yourself an environment where you want to do and enjoy the things.

The classical example to support a long-term bond is by making shared investments e.g. a house. You can motivate your future self to stay in a long-term relationship by building a large shared base. This will give you additional montivation to keep it and the relationship (works the other way around too probably).

The precommitments work best if you are know to hold your word and there are many who nail you to it. But the literal meaning of the commitment allows for interpretation on both sides and can cause side effects indeed.

I try to motivate my future self via long-term development and shared investments.

Yes. Even as wrong as downloading 15 chapters of fanfic in one command line and binging them for an afternoon would be while seeming to use the connection for around 3 seconds... that isn't what would normally happen.