Making Sport of Physics

StarTalk’s Playing with Science

I meant to write a blog post about my appearances on StarTalk‘s Playing with Science, but my life, both professional and personal, has kept me extremely busy in recent months.  Appearing on the show and talking about sports physics has been a lot of fun!  Chuck Nice and Gary O’Reilly are great hosts of the show and I always enjoy my interactions with them.  Below is a list of the episodes I’ve appeared on.  Click on the links to access the episodes.

Check out all the other great episodes with fascinating guests from the world of sports and science by clicking on the image below.


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Froome Wins 4th and We’re Nearly Perfect!

After his performance in the Alps and in yesterday’s time trial, there was no doubt that Chris Froome would win his fourth Tour de France.  He now has a three-peat (should I send Pat Riley money for using that term???).  Froome didn’t win a stage this year, but was clearly the best cyclist.  Staying near the winners in the mountains and in the time trials, Froome was simply better than everyone else.  His Team Sky mates played a large role in his victory.  It doesn’t hurt to be supported by a powerful team!

Dutch cyclist Dylan Groenewegen won today’s final stage.  How did our model perform today?  We saved our best for last, as you’ll see below.

  • Stage 21:  2h 25′ 39″ (actual), 2h 25′ 50″ (prediction), 00′ 11″ slow (0.13% error) 

As tough as it is to predict the mostly-ceremonial final stage, I’m thrilled to end this year’s Tour de France with a near-perfect prediction.  How did our model perform overall?  After summing the stage-winning times, I found we were 1.11% slow.  I’ll definitely need to spend time thinking about how much athletes and technology have improved since last year.

I never cease to be amazed by elite athletes.  A total of 167 cyclists finished the Tour de France.  I would be hard-pressed to finish a long flat stage during daylight hours.  As for those grueling mountain stages, forget it.  I need more time in the gym!  My model estimates energy burn, i.e. internal energy burn with an average efficiency of about 20% and not just energy output needed to power the bike.  During the entire race about 115,000 Calories could have been burned.  Published cyclists’ data may be below that number, but an estimate has to be made of internal energy efficiency.  Our published papers on Tour de France modeling cite sources that are consistent with our energy estimates.  The point is that a LOT of energy is burned during the three-week race.  At 550 Calories apiece, those 115,000 Calories amount to nearly 210 Big Macs.  That averages to 10 Big Macs per stage!  I don’t recommend eating Big Macs before cycling, but it does give you some idea of how much energy those cyclists burn each day.  You may have heard that 3500 Calories matches the energy content in a pound of fat.  That’s roughly true, but you may have to burn about twice the Calories to get a pound of fat off because of the complicated way the body converts energy.  Either way you think about it, 115,000 Calories represent one or two bowling balls of fat weight.  No wonder elite cyclists stay in such great shape.  Their job is a wonderful form of exercise!

I once again thank rising high-school senior Ryan Wainer from New York for his work this year.  He acquired all the terrain data, which led to a successful set of predictions.  How successful?  We had one bad prediction with Stage 5 (9.24% error) and five good-a-decade-ago-but-want-to-do-better-today predictions in the error range of 4% – 8%.  But that leaves 15 predictions to better than 4%, 11 of which were better than 2%.  Five of those 11 were better than 1%, including our best prediction today.  A nice way to end!

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Froome Seals the Deal!

Chris Froome did what he needed to do in today’s individual time trial.  He came in third, just six seconds behind Poland’s Maciej Bodnar.  Froome now leads the overall classification by 54 seconds over Colombia’s Rigoberto Urán Urán.  Unlike the first individual time trail in Stage 1, today’s result was slower than I thought it could be.  We were a bit more than 5% off, as you’ll see below.

  • Stage 20:  28′ 15″ (actual), 26′ 42″ (prediction), 01′ 33″ fast (-5.49% error)

One of the first things to look at after this year’s Tour de France will be the two individual time trials.  We were short on power in the first time trial and had too much power today.

Tomorrow’s final stage will be mostly ceremonial until the big sprinters go for the stage win once they are in Paris.  Froome will probably be seen with some champaign and four fingers up (three in a row!).  The last stage is always tough to predict because of the ceremonial nature of the stage.  We’ve done well in the past by backing off on power.  Our final prediction is given below.

  • Stage 21:  2h 25′ 50″ (prediction)

  Chris Froome showed today why he’s the best cyclist in the world.

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Hagen Makes Norway Proud!

Norwegian cyclist Edvald Boasson Hagen won today’s flat stage, which was the longest stage of this year’s Tour de France.  We had a good prediction, as you’ll see below.

  • Stage 19:  5h 06′ 09″ (actual), 5h 11′ 09″ (prediction), 05′ 00″ slow (1.62% error)
That makes 12 of 19 stages that we’ve hit better than 3%.  Strategies on long flat stages are hard to predict because the peloton dictates so much of the pacing.  Boasson Hagen and 19 other cyclists came in within two minutes of the winning time.  Chris Froome and the rest of the peloton came in 12′ 27″ after Boasson Hagen.  I would therefore claim that our prediction was spot on!
Tomorrow’s individual time trial will be the last chance Romain Bardet (23 s back) and Rigoberto Urán Urán (29 s back) have of catching Chris Froome.  Below is our prediction.
  • Stage 20:  26′ 42″ (prediction)
We were a bit slow on the first individual time trial, which was the opening stage this year.  I’ll be anxious to see if we do a little better tomorrow.
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Barguil Puts Us Under 1%!

Warren Barguil made France proud today with his second mountain stage win in this year’s Tour de France.  We predicted the two big mountain stages in the Alps really well.  Look below to see how well we did today.

  • Stage 18:  4h 40′ 33″ (actual), 4h 41′ 48″ (prediction), 01′ 15″ slow (0.45% error)

Chris Froome came in fourth today with a group just 20 s behind Barguil.  He has a 23-s lead over Romain Bardet.  The goal for Team Sky in tomorrow’s long flat stage will be to keep Froome with the cyclists just behind him.  The individual time trial on Saturday looks like it could be a lot of fun!  Below is our prediction for tomorrow’s Stage 19.

  • Stage 19:  5h 11′ 09″ (prediction)

If Chris Froome is to secure a three-peat, his team will have to have a great day tomorrow.

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Another Prediction Error Under 1%!

Primož Roglič won today’s Stage 17 by 73 seconds.  We hit the stage by less than two minutes, as you’ll see below.

  • Stage 17:  5h 07′ 41″ (actual), 5h 09′ 36″ (prediction), 01′ 55″ slow (0.62% error)

If riders thought today’s stage was grueling, they’ll enjoy tomorrow’s stage.  It has a delightful Hors catégorie climb to the finish line.  Below is our prediction.

  • Stage 18:  4h 41′ 48″ (prediction)

Froome now has a 27-s advantage over the two riders behind him.  Based on how he looked today, it seems he is headed for a three-peat.

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Matthews Makes it Two out of Three!

Michael Matthews won his second stage today.  Racing turned out to be fast on the downhill, which is what I mentioned in yesterday’s post.  There is no way to predict team strategies!  Below is a comparison between reality and our prediction.

  • Stage 16:  3h 38′ 15″ (actual), 3h 45′ 02″ (prediction), 06′ 47″ slow (3.11% error)
Not a bad error, but yesterday’s result spoils me for more sub-1% predictions.  The next two stages in the Alps will likely decide this year’s winner.  Our prediction for tomorrow’s stage is given below.
  • Stage 17:  5h 09′ 36″ (prediction)
Monster climbs in tomorrow’s stage, but the finish will be a downhill sprint.  Can anyone sneak across the finish line in under five hours?
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Stage 16 Prediction

Below is our prediction for tomorrow’s Stage 16.

  • Stage 16:  3h 45′ 02″ (prediction)
The stage is classified as flat, but it’s quite hilly for the first half.  The middle of the stage is mostly downhill.  Depending on racing strategies coming off a rest day, the above prediction could be slow.  I’ll be anxious to see if cyclists push themselves to high speeds on the downhills.
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Nearly Perfect Prediction!

There are some stages I watch come to an end and hope the winning cyclist can give just a tiny bit more effort in the last kilometer.  Check out the comparison between Bauke Mollema’s winning time with our prediction for today’s Stage 15.

  • Stage 15:  4h 41′ 47″ (actual), 4h 41′ 26″ (prediction), 00′ 21″ fast (-0.12% error)

Come on, Bauke!  Just 21 seconds faster today and we reach perfection.  He won by 19 seconds, so he didn’t need to rush the final few hundred meters.  But I’ll definitely take today’s result.   Missing a nearly five-hour stage by 21 seconds is a lot of fun!  I’m glad I didn’t make the mistake I made with yesterday’s prediction and alter power output.  Our model did its thing today.

Chris Froome remains in yellow.  Nairo Quintana, who I loved watching battle Froome in the mountains in 2015’s Tour de France, slipped to #11 in the overall classification, more than six minutes behind Froome.

Tomorrow is a rest day.  Teams will plot strategies for the next day’s flat stage and the two, grueling stages in the French Alps that follow.  I’ll post our prediction for Stage 16 tomorrow.

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Froome Back in Yellow!

Chris Froome got 25 s on Fabio Aru in today’s Stage 14 and turned a 6-s deficit into a 19-s lead on the Italian cyclist.  Michael Matthews won what I consider to be a slow stage today.  Below is a comparison between the winning time and our prediction.

  • Stage 14: 4h 21′ 56″ (actual), 4h 12′ 56″ (prediction), 09′ 00″ fast (-3.44% error)

We were too slow on hilly Stages 5 and 8, so power was upped slightly for today’s stage.  We would have been under 1% without the change!  Oh well, that’s what makes this so much fun.  We can’t predict team strategies, crashes, and weather.  Below is our prediction for tomorrow’s hilly stage.

  • Stage 15:  4h 41′ 26″ (prediction)

I’m not tweaking the power in our model for tomorrow’s stage.  Will I regret that with a rest day to follow???

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