On Monday, August 3 2020, a tragedy befell the Cypher Siphon team playing Last Call trivia. We were marked wrong on a question that we were sure was correct. This has happened a few other times without much fanfare, but the particular circumstances of this question made me look further into the proposed correct answer from Last Call and there is a story to this one.

The question at the center of this story was simple. It was a bonus question at the end of a round of play. Usually, the bonus questions are somehow related to one of the regular questions during the round. The related regular question during the round was “What part of the body is the iliofemoral ligament attached to?” and we answered “leg” and got that legitimately marked wrong. We will quickly move past that.

The bonus question at the center of this story was:

Bonus: what is the tensile strength of the iliofemoral ligament?
Answer submitted from Cypher Siphon: 690 lbs
Answer accepted by Last Call: 78.68 lbs

Points with bonus questions with Last Call usually work by getting the closest answers. No one is expected to get the exact answer. Answers to bonus questions vary by orders of magnitude all the time. But this caught my eye.

Eagle-eyed readers will immediately note some peculiarities in Last Call’s answer. The value of 78.68 lbs is supposedly how much force the iliofemoral ligament can stand before tearing. Disregarding the fact that each human body is different and has different tolerances, we can assume that this is an average of some kind. 78 lbs is a ridiculously small value. A person hanging upside down would tear the ligament from body weight alone. No leg exercises such as presses or squats would be possible. It is possible that simply running would tear the ligament.

But the ridiculous amount of precision was more alarming to me. Why would something like this involve 1/100s of pounds? I wanted to find out. This seemed like a case of converting from some rough value to another unit and introducing incorrect precision.

Googling for “tensile strength of iliofemoral ligament” quickly leads you to the Guiness World Records page for Strongest Ligament. I reproduce the information on that page below.

Who
ILIOFEMORAL LIGAMENT
What
350 NEWTON(S)
Where
UNITED KINGDOM (ST LOUIS)
When
2014

And there is the text “it has a tensile strength of 350 newtons (78.68 lb-force).”

Ignoring the bizarre UNITED KINGDOM (ST LOUIS) and also ignoring the troubling “lb-force”, things make a little more sense. This is clearly where Last Call got the information. They just copied it from Guiness World Records. And 78.68 lbs is the result of converting from 350 newtons, with no regard for maintaining the correct number of significant digits. 350 seems like a good “estimated” number from some source that Guiness is using. Then Guiness converted to lbs with more precision than appropriate and Last Call copied them.

But either way you write it, 78.68 lbs or 350 N, the value is still laughably wrong.

I decided to go to Wikipedia’s entry for the iliofemoral ligament to try to figure out what is going on, and I see this entry:

With a force strength exceeding 350 kg (772 lbs), the iliofemoral ligament is … the strongest ligament in the human body

Ah ha!

350 kg (772 lbs) are very believable values for the strength of the ligament. And would have got us a point for the bonus question also.

I went through the edit history of the Wikipedia article and saw that there have been various edits changing 350 kg to 350 N and back and forth. Maybe this is to do with someone thinking that kg is the “wrong” unit for force and “knowing” that N is the “correct” unit for force and just changing the unit. Who knows.

The reference given in the Wikipedia article is a book “Color Atlas Of Human Anatomy, Volume 1, Locomotor System” by Werner Platzer. I tracked down this book and verified on page 198 the text:

Among these ligaments is the strongest in the human body, the iliofemoral ligament (10), which has a tensile strength of 350 kg.

I considered this a trustworthy and ended my research.

So, here is the timeline as I see it:

  • 2003: “Color Atlas Of Human Anatomy, Volume 1, Locomotor System” is published, claiming the iliofemoral ligament has a tensile strength of 350 kg.

  • 11 October 2008: 350 N is added to Wikipedia

  • 20 January 2009: Wikipedia changed to say 350 kg

  • 22 September 2009: Wikipedia changed back (!) to 350N

  • 26 July 2011: Wikipedia changed back (!!) to 350 kg

  • ~2014: Someone at Guiness copies from Wikipedia when the bad 350 N was in the article. The printed version of Guinness World Records 2016, page 53 has the bad information and has the text “it has a tensile strength of 350 newtons (78.68 lb-force).”

  • 2017: bad information first appears on Guinness World Records web page

  • ~2020: Someone at Last Call copies from Guiness.

The chain of misinformation created from this was fun to track down. I will be working with Guinness to correct their text, or alternately, I will be submitting a new World Record for Strongest Ligament because technically the record is at a measly 78 lbs right now…

I left a comment on their page for strongest ligament:

Is this value correct? The strongest ligament can clearly withstand more than 78 lbs. Wikipedia lists a strength of 350 kg, which is believable. I think somewhere the correct value of 350 kg was changed to the incorrect 350 N (probably copied from Wikipedia when a version listed 350 N)

The reference that Wikipedia uses, “Color Atlas Of Human Anatomy, Volume 1, Locomotor System”, also lists 350 kg.

But I haven’t heard anything back.

guiness comment

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