How to split your open water swim

Have you ever wondered how you should split your open water swim race?  Should you sprint it out for the first half, then hope for the best at the end?  Or should you take it easy and build speed all the way through?  Should you even split, where the first half takes the same amount of time as the second half, or should you even negative split (second half faster than the first half).

This article investigates how elite competitive swimmers typically split long distance swimming races.  The intent is to uncover trends that are applicable to triathletes.  Data from swim races are a great way to do this because splits are reliably timed by electronic touch pads.  Splits are much more difficult to obtain in open-water racing, where current or course markings can dramatically alter the distances in the various stages of the race.  All data was taken from www.swimrankings.net, which lists the fastest European times and all of their splits, timed electronically to 1/100th of a second.

In this analysis, the top 50 men’s times from the year 2008 (Long Course Meters) were averaged for each of the following events:  200 free, 400 free, 800 free, and 1500 free.  The average time (from all 50 swimmers) for each quarter of the race was then calculated and compared.  In order to be consistent from one race to the next, the data is shown as an average per 50 meters.  Thus, each quarter represents 50 meters for the 200 meter distance.  For the 400 meter distance, each quarter represents the average 100 meters, divided by 2.  Since the 1500 free could not easily be broken down into quarters, the first 3 quarters were taken over 400 meters, and the last quarter represented the final 300 meters.  The results are shown in the Figure below. 

An interesting observation is that the splits by quarter have the same pattern regardless of distance.  Every time Q1 was fastest, and every time Q3 was the slowest.  The difference between Q2 & Q3 was small for the longer distances but was present to 90% confidence for the 800 meter race and the 1500 meter race.  Q2 & Q3 differed by approximately 0.5% (which amounts to just 1.5 seconds over 5 minutes of swimming).  Another interesting observation is that the splits tended to flatten out with an increase in race distance.  But even though the splits got closer together for the 1500 free, the pattern of Q3 being the slowest always held. 

A significant percentage of the population had performances with negative splits (second half was faster than the first half).  24% of the 1500 meter free times, 28% of the 800 free times, 14% of the 400 free times and 2% of the 200 free times were negative split.  These percentages are high enough to conclude that a minority of athletes may benefit from negative splitting a swim race, particularly if the race has a long duration.

What can the triathlete gain from this information?   The data suggests that on average, the third quarter is the slowest part of a swimming race regardless of distance.  This may not always be true in the open water, where currents and drafting can affect results.  However, for swimmers the slowest part of the race is always the toughest.  And if it is the toughest part of a race for swimmers then it should be the toughest part of an open water swim for triathletes.  Quarter-3 (or Q3) is the part of the race with greatest opportunity to gain ground on your competitors. 

Using Q3 to your advantage makes sense.  Any mistake made by your competitors in the first half of the swim tends to manifest during the third quarter.  It is too far from the finish to find that last ounce of swimming strength.  And it is too far from the start to feel fresh.  There is typically a turn-buoy at the start of Q3, which is a great opportunity to put your competitors in trouble if you have the energy for it.

So, how do you know you are splitting the race right?  It is ideal to feel like you’ve spent a third of your energy in the first half of the race.  Use half of your remaining energy through that third quarter.  If you get to the first half feeling like you haven’t worked at all, chances are you are taking it too slow.  But if you feel like you’ve spent half your energy, chances are that third quarter is going to hurt and you are going to hit T1 gasping for air.  Ideally, you want to feel like you can slightly pick up the pace at the start of the third quarter.  This means you should feel red in the face, but not in any sort of physical trouble.

Picking up the intensity a little when tired doesn’t mean you actually get faster.  Chances are you will still get slower, though by a small amount.  The reality is you feel like you are getting faster because you aren’t slowing down as much as your competitors.  According to the data, a few people should get faster in Q3 if they are swimming it right, but most should get a little slower.  This is okay.  So many athletes new to swimming have expectations that the second half should be faster regardless of the pain felt in the first half.  Athletes may be used to negative splitting a running race, but this is not typical of a swimming race.

Triathletes have more than just a swim to worry about.  It is important to finish the swim with enough gas in the tank to be able to hop on the bike.  After Q3 of an optimal swim, you should only have a third of a tank of gas left.  You want to save a little of this energy to get through transition.  You should feel like you are exerting a little less during Q4 compared to Q3, even though this may not happen.  It is amazing how much of a mental boost you get when you see the shoreline.  For this reason, your Q4 may get faster even though you feel like you are working with less effort.  Ideally, you want to finish the swim feeling like you left only 95% of your total effort in the water.

A 95% effort means that you have worked your swimming muscles hard but you have not overwhelmed your aerobic/anaerobic systems.  You haven’t generated the lactic acid or muscle tissue damage which can slow you down on the bike or the run.  You should be breathing hard while exiting the water.  But you should expect quick recovery as you begin using your legs for biking, which require a different muscle movement from swimming.  The recovery should be quick enough to achieve full strength within the first mile of the bike.  If the recovery happens later, then you worked the swim too hard.  If you don’t need any recovery on the bike, then you didn’t work the swim hard enough.

Compared to competitive swimmers, triathletes should finish with more energy than a competitive swimmer in a swim-only race.  However, the overall strategy is the same, regardless of the overall energy expenditure.  For triathletes, the energy expenditure is 95%, for competitive swimmers it is 100%.  But the third quarter is always the toughest.  The third quarter is usually the slowest.  And the third quarter is your best bet to drop your competitors.   If you plan your swimming splits the right way, chances are you will swim at your best and with the least total energy expenditure. 

Hopefully, this article enhances your understanding of the optimal way to split a swimming race.  A triathlon swim race is pretty even throughout, with the first and last quarters being a little faster than the quarters in the middle.  To swim even, you should feel that the first half is a lot easier than the second half.  The hardest part of the race is the third quarter.  If you plan your races around this fact, chances are you will be able to swim past any competitors who worked the first half of the swim too hard or are saving too much for the bike and the run.  Until next time, happy training.