Episode 12: Break Step Bridge, Toothbrush Surprise, Rowing Water Skier

Air Date: January 25, 2004

Soldiers marching in unison can cause harmonic oscillation in a bridge and cause it to collapse.


There were some difficulties in testing this myth conclusively.

*The original result was "busted," but when revisited in episode 14 it was changed to "plausible."

A rowing eight can pull a water skier at sufficient speed for him/her to stay upright.


Adam and Jamie recruited Stanford University’s rowing team to help test this myth. After several tries Jamie was able to stay upright for over 40 seconds, with only a few hours experience in waterskiing.

Fecal coliforms bacteria can grow in toothbrush bristles.


Fecal coliforms were indeed found on all the test brushes, including the control ones. However, none were of a level high enough to be dangerous, and experts confirm that such coliforms were impossible to completely avoid.


  1. Mojojojo says:

    I think that Adam and Jamie should test it in a bigger scale, the muth of the soldiers in a bridge would be confirmed at the first try. But the got it at the second time and that’s not bad. Congratulations.

  2. Mojojojo says:

    the word “muth” that I accidentaly used in my comment is “myth”. My mistake.

  3. mwahaha says:

    i think that the bacteria on the tooth brushes 1 shouldn’t be confirmed, i think they need to run more trials and i am sure the myth would be busted!!!!!!!!!!

  4. spud says:

    Hi, my sister and I are doeing a science project on toothbrush surprize. for the school science fair we are doing the same thing but we are actually dipping two toothbrushes in the toilet. and we can not wait to do this experiment.

    I love the show!!!!!

    • brian ivory says:

      the ivory white toothbrush is irrigated through the head so bacteria dont build up sold at walgreens boardman ohio store

  5. Mark S says:

    I only saw part of the episode, but I noticed that the ends of the bridge were not secure, meaning that the desired “Real world,”resonance could not be produced. A few years ago, a hotel atrium bridge was found to have collapsed from guests tapping their feet to a bands music.

    • William P says:

      You’re quite wrong here, sir. As an engineer responsible for reviewing the cause of that walkway collapse, I can tell you with 100% certainty that it was an engineer’s poor physics calculations that caused that collapse. It had absolutely nothing to do with resonance.

      • Marty says:

        Please explain to me how resonance is not physics? Sounds like basic high school physics to me.

  6. Saundra says:

    The toothbrush experiment should be re-evaluated because the method for applying toothpaste to each toothbrush would spread contamination. That is one reason why the toothbrushes not in the bathroom tested positive for fecal matter. Each toothbrush should have it’s own tube of toothpaste and the toothpaste tube should not come into contact with the brush.

  7. Bek says:

    With the oscillating bridge. I know that the bridge was tested for oscillating up and down. But bridges can be oscillated sideways. When we walk we push outwards as well as down in each step. The right foot moves right and the left foot moves left. This could have added to the movement of the bridge.

  8. Tom says:

    Just out of interest, who rowed?

    • Other Tom says:

      The Stanford University rowing team

  9. Michael West says:

    Re the Rowing 8 and the Water Skier: What kind of skis used, how big/heavy the skier and was he/she pulled up out of the water by the crew? If it was regular water skis, normal size human coming out of the water, this is Bolshoi!

  10. josh stephens says:

    This is josh stephens i like the show you palyed last night the date was the 3urd when you did the last a sploshen that was vare big and cool bye.

  11. Gurgi says:

    It would be interesting to have the toothbrushes and toilet flush aerosol repeated with the toilet lid down.

  12. Paul Goodliffe says:

    Hi – I was really disappointed with the initial “busted” result of bridge resonance. While I appreciated the engineering that created the bridge and the boots, the result indicated a lack of knowledge of resonance. This raised my eyebrows; surely these guys should know the basics ? As someone above pointed out, the bridge ends were not secured. This means that any energy introduced into the bridge cannot rebound from the ends. This means resonance is impossible in the structure anyway; the energy is lost. I stopped watching Mythbusters for a while in despair; I was so disappointed in them !
    Do your homework first, guys, but you should already know some basic physics !

    • KR says:

      I totally agree, and i puke everytime Adam Savage uses the word ‘science’ in this show.

  13. Gordon says:

    This morning Dr. Rosefeld on Fox News repeated this idea that a flushing toilet will contaminate nearby items such as toothbrushes and towels. This isn’t the first time I’ve heard this but it doesn’t seem right to me. Does anybody have a definative answer? Seems a concern worthy of a rigorous test.

  14. Greg says:

    I just saw the Dr.’s show and remember this Mythbuster episode. I was surprised to see the response before me. In fact, I think the Dr. could be a good source for a retest. Keep up the great work!

  15. Peter says:

    With regards to resonance and bridges, the millennium footbridge in London is a very good example of this phenomenon.

    The engineering consultants responsible for investigating and fixing the oscillation problem were invited to give a presentation to the British Institution of Structural Engineers and is available on-line. It describes the oscillation and it’s causes for this particular case and may be of interest here.


  16. hank says:

    The toothbrush tests show a correlation, not a direstion.
    So, the brush can get e coli from your mouth (yes!), don’t assume which direction the cause runs.

  17. Tyler says:

    I agree…I just watched this episode again for the first time since it came out. The toothbrush test needs to be revisited. The same tube of toothpaste was used even on the control toothbrushes. Their method of applying the toothpaste is too rub the tube on the brush, hence the contamination of all toothbrushes. REVISIT!!!! Separate tubes for each toothbrush.

  18. Bobby says:

    Just watched an old episode of That’s Incredible from the 70s or 80s in which several rowing teams pulled water skiers in a race…

  19. Paul says:

    In addition to the ends not being fixed, Breakstep Bridge’s excitation frequency was too low, it needed to be between 10 and 40Hz; you have to scale frequency up when you decrease size.

    Even without an engineering background, common sense should have told them that at full scale, mode 1 would be much slower than marching so would be the wrong one to try to reproduce.

  20. Brian says:

    The water ski episode surprised me. I didn’t think there was any way to ski behind a row boat. Now you just have to get the rowing team to row more evenly.

  21. Jen says:

    I think I saw the toothbrush episode. If they used MacConkey agar for the cultures, it was all wrong! If you brush your teeth with the brushes, of course you will grow gram negative, lactose fermenting bacteria from it. There are lots of bacteria in your mouth! They should have mounted the brushes and left them alone, then tested them. The controls should have been in another room and untouched as well. Scientific theory..only change one variable at a time, so this time, don’t brush your teeth with them. this proves the bacteria is from the toilet, not your mouth. Negative controls from another room will prove the bacteria did come from the toilet. If the controls from the other room are positive, the bacteria is from some other source.

  22. AAK says:

    The myth of the Toothbrush needs to be revisited, there are just too many ways that the controls could have been infected.. Like using them to brush teeth that may be infected, or touching the brush with the tube.. + it would be fun to make Adam and Jamie spend another month pooping in the same bathroom.. How do we get this message to them? how can we tell them to redo this myth..

  23. KR says:

    I can’t believe they busted the bridge myth. I now understand it was ‘busted in the name of science’, not due to Adam’s poor bridge building.

  24. Chris says:

    How about an explanation of how fecal coliform get to the toothbrushes? Could it have been whipped up into the air via the turbulence of flush toilets? You could test some toothbrushes that are not used in the bathroom… and others used in bathrooms with dry toilets. (Also “Fecal Coliforme Bacteria” are a functional group that can live under certain conditions in the lab. Maybe normal, healthy bacteria from the mouth could also.)

  25. Raymond says:

    The issue with breakstep I feel was a few issues. 1st like Mojojo stated above he ends of the bridge needed to be secured. Second the foam deck was disrupting the harmonics, and lastly the support cables made from string I feel would break the vibration as well. Maybe if the deck was of plywood and connected securely to the frame creating a firmer surface to resonate without movement of the boards bouncing changing the frequency. I would lose to see the Tesla earthquake machine used on this bridge made to more realistic stabilaties.

  26. willz says:

    Hey guys

    I just realized something…have you considered the variable that maybe there’s some truth to saying, “full of it?”

    Sure, i am being cute here, but since a human is the source of the feces in the first place….some things in life you just don’t wanna kno, Bro…

  27. Curtis says:

    The control toothbrushes were contaminated as soon as they brought them INTO THE BATHROOM to apply them to a petri dish.

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