Fatigue Rates of Skill Versus Will

Many people get a charge out of racing against someone with more skill.  It is the true test of self.  How would you respond?  What strengths can you count on if you make up for lack of skill by training 10 times harder?  This article involves a comparison of two athletes and their fatigue rates in swimming.  One has better fitness (professional triathlete David Thompson), and the other has more swimming experience (your humble narrator, Duane Dobko).  Since I have been swimming with David over the past 2 years, I have gained a lot of data on how our systems respond to physical stress. 

The on-paper differences between us couldn’t be more black-and-white.  Thompson is arguably one of the fittest individuals in the world, and is a world class cyclist and triathlete.  However, David’s swimming experience is limited, having learned the sport in his mid 20s, a late age for most pro triathletes.  Conversely, Dobko is a lifelong swimmer but has a fitness level of a weekend warrior.  Throughout this time period, Dobko and Thompson trained swimming together twice a week.  Thompson spent the rest of each week working on cycling and running.  Dobko spent the rest of each week recovering.    

Presented are the average times of Dobko and Thompson in a set of sprint 50s.  The set is 20 x 50 meters (all short course meters), all timed by manual stopwatch to 0.00 resolution.  The sendoff time was long (approximately 3 minutes per repeat).  In addition, the set was broken in half.  After the 10th repeat, we both swam an easy 200, before completing the remaining 10 sprints.  This set was done a total of 4 times over a 2-year period (sets roughly 6-months apart).  The deviation from each athlete’s average time is compared.  Thus, the data for both athletes is centered around zero.  The data is shown in the Figure below.

To be clear, a set of 20 x 50 meters all-out sprint is very difficult and physically demanding.  It may not sound like much to triathletes, who are used to calling an hour effort a “sprint”.  However, it is a different challenge to sprint as fast as you can go, over and over again.  Because you are taking enough rest to catch your breath and recover, you are able to push much further into your pain threshold.  So it hurts a ton even though it doesn’t hurt for very long.  I would never claim that sprint swim training is more or less painful than a running or cycling workout.  But I can say it is no picnic, even for a professional.

Intuitively, the later repeats in the set should favor fitness over ability (Thompson over Dobko).  And the bottom chart in the figure supports this.  The time advantage for Dobko ended after the first 4 repeats of the first group of 10, and evaporated again after the first 3 repeats of the second group of 10.  But for both athletes, the overall fatigue rate was surprisingly similar.    

Dobko had a greater rate of performance decline over the set (to be expected).  In the middle of the set (repeats 5-7 of the first and last 10), the time advantage was about equal between the two athletes.  In the final four repeats of the set, Thompson enjoyed a relatively consistent advantage of 0.2 seconds for every repeat.  It might be expected that superior fitness would provide Thompson an ever-increasing advantage as the set moved forward, but this didn’t happen.  Thompson’s advantage on the home stretch was more or less constant.

Why didn’t fitness allow Thompson to pull away and why was the middle of the set so even?  The years of experience that Dobko had in the water may have made up for lack of fitness.  Such experience helps anticipate what to do when fatigue sets in.  Also, the muscles are more adapted to the motion, and this may have helped reduce the effects of physical stress.  This effect would help so long as Dobko had enough fuel in the tank to hold the stroke together, upon which a more dramatic slow-down should occur.   

On the top chart, Thompson’s fatigue rate is more linear than Dobko’s.  Only on repeat 12 did Thompson get dramatically slower.  Conversely, Dobko got much slower at specific intervals, in particular on repeats 5, 10 and 13.  For Dobko, fatigue was more of a step function.  The results support the reasoning that Thompson’s fatigue is more linear because of superior fitness and Dobko’s fatigue was much more of a step function because of ability and limited fitness.