Tuesday, February 12, 2008

Negative Splits

One of the hardest things to teach athletes who do steady state events such as triathlons, bike time trials and road running races is negative splitting the course. In other words, the second half should be slightly faster than the first half. Last week I spoke at the Serotta International Cycling Institute (SICI), in part, on this topic. The following are points I made in the talk.

The 51-49 principle
* Generally, the first half of a 10-minute or longer time trial should be completed in 51% of total finish time (Foster 1993, Robinson 1958)
* In road running nearly all world records have been set with the first half run slightly slower than second half (50.5 – 49.5)

Reasons behind the 51-49 principle
* Go out too slowly and you never ‘catch up’
* Go out too fast and acidosis increases rapidly (acidosis is inevitable for steady-state events lasting less than ~60-75 minutes)
* It’s easier to tolerate high acidosis for short periods than long
* It’s easier to tolerate high acidosis at the end rather than the beginning

Why don’t riders follow the 51-49 principle?
* They lack confidence that they can finish strongly
* They have a misguided belief that time ‘gained’ early in the race is greater than that gained late in race
* They have the best of intentions but lack self-control

Accompanying are two examples of steady state rides by the same athlete. In the negative splits example he split the course 50.1-49.9. Nearly perfect. In the positive split example he went 47.4-52.6. In both races the courses were not substantially different in terms of grade changes in the first versus the second halves. If you look on the left side of both charts you will see his “VI” (Variability Index) for the negative split was 1.08 and for the positive split it was 1.15. The lower this number is the more steadily the athlete rode and generally the less energy that was wasted due to frequent accelerations. This, again, lends credence to the adage of negative splitting the course.

While for longer steady state events it is almost a certainty that you will race better by holding back a bit at the start, it is a rare athlete who actually does it. I find this is the most difficult skill there is to teach the athletes I coach and yet the most basic to their success. We work on it frequently in training. But training doesn’t have the same emotional baggage that racing has. The key to negative splitting successfully in a race is to mentally prepare yourself to hold back initially. This can be very difficult to do if you are in a duathlon or running race and scores of people are passing you for the first mile. It takes great discipline to hold back, but realize that all of them will come back to you later. Failure to get this basic skill right generally means the athlete will seldom achieve their potential in such events.
Thanks to Arnie Baker for contributing thoughts to this post from his excellent book, Smart Cycling.


At February 13, 2008 7:19 AM , Blogger Tom said...

I'm wondering. What exactly do you mean you say "We work on it frequently in training." I guess I mean how do you coach your athletes to hold back? Would I be correct in assuming that in training athletes just practice going the 51% for half the session?

At February 13, 2008 11:30 AM , Blogger Dean Yobbi said...

Interesting topic that I've battled in my head before, during and after mountain bike races. But here's my question:

When I line up, I know the racers I need to stay close to in order to have a chance to finish on the podium. If I lose contact with them early in order to follow the 51-49 principal, I get worried I'll never see them again and I have to essentially ride by myself.

In this case, is it worth sacrificing early in order to stay with the leaders? That way, if you succeed, you're with them when the pace calms down and you can start battling for podium position.

By the way, I'm an expert class mountain bike racer doing race distances anywhere from 24-27 miles.

At February 13, 2008 11:44 AM , Blogger Dean Yobbi said...

Interesting topic that I've mulled before, during and after expert class mountain bike races.

Here's my question: When I line up, I know the racers I need to stay close to in order to have a chance to finish on the podium. Is it worth the risk to burn precious energy early to stay with them? If I follow the 51-49 principal and allow them to break away, I worry I'll never see them again and I'll have to ride solo and it feels like I'm not competing, which I think mentally hurts me.

If I try to stay with them and succeed, I feel great and realize now the race has begun and I'm a player in it.

Isn't it worth burning matches early to be a player in a race even at the expense of a slower last lap time?

At February 13, 2008 1:30 PM , Blogger Joe Friel said...

In interval workouts I emphasize that they hold back on the first one. When doing steady state efforts I check to make sure they held back early on. I try to make this second nature to them but it is still hard in the heat of battle not to give it everything from the gun.

At February 13, 2008 1:32 PM , Blogger Joe Friel said...

Dean--A MTB race isn't a steady state race. It's variably paced, just not quite as much as a road race. It typically requires going out hard to be in contention.

At February 13, 2008 7:45 PM , Anonymous Anonymous said...

Hi Joe,

I noticed that you tried my last recommendation to remove the plus signs and it didn't work. I had the same problem you are having with your profile and I was able to readjust my posts and force my profile to pop back up. I think the two charts in this blog are over the size and are restricting your profile. Try readjusting them just a little smaller. I hope this works for you. I really enjoy the information on your blog I have two of your books and you are a big inspiration to me. Thanks Joe,


At February 15, 2008 12:19 PM , Blogger D a v e P said...

Hi Joe, how would I approach the 51/49 principle in a full distance Ironman? I wouldn't think I would try to negative split each sport (err, or would I?), but rather use it as a guideline/reminder to leave a little energy for the last half of the marathon?

At February 17, 2008 5:30 PM , Blogger Joe Friel said...

Dave-Yes, you should neg split the bike and run legs of an IM. Or at least try to. May not on the swim if your goal is to be on fast feet early in the race.

At February 21, 2008 3:12 PM , Anonymous Stowe Spivey said...

Joe - thanks for explaining negative splits in this way. I have been coached to do it but really completely understood why.

Keep up the great blog!

At February 21, 2008 4:16 PM , Blogger sunvolt said...

Hi Joe, Just wondering does the negative splits hold up for say longer events like 100mile TT? Where mentally it's got to be hard thinking you've got to lift it a bit for the last 2x25splits.


At February 21, 2008 11:27 PM , Blogger nickel said...

This post provided me with a new way of approaching intervals which I hadn't thought of before.

This is off-topic but as a new racer, I was curious about the rides that some clubs do (maybe a Northern thing?): travel to a warm locale, ride 60-80mi days for a week and return home. Is there much benefit for such a long, overloaded week?

At February 22, 2008 1:31 PM , Blogger Joe Friel said...

Geoff--You're thinking about it backwards. It's not that you're going to go harder in the last half; it's that you're going to go easier in the first half so you CAN go faster in the second half.

At February 22, 2008 1:35 PM , Blogger Joe Friel said...

Nickel--There certainly can be. The benefits are not typically immediate. They seem to appear a week or two later depending on how long and intense the camp was. In my books I write about "crash" training which has a supercompensation effect. A camp is essentially crash training.

At March 6, 2008 4:29 PM , Blogger Ron said...


Can the principle hold if say, in the first part, the terrain was not so bad but it gradually became difficult. TIme trialling on rolling hills is tricky. Great advice anyway.

At March 7, 2008 2:54 PM , Blogger Joe Friel said...

Ron--You might think of neg splits as being effort as opposed to time. The idea is to hold the effort down just a bit at the start knowing that it will rise as the race progresses. This, of course, only applies to steady state events like TTs.

At March 11, 2008 6:54 PM , Blogger Steve said...


I figured it would be a good idea to identify the HR pattern I need to run an even split (or slightly negative split) in my next race.

So I did a little research on the treadmill. For those of us used to targetting a constant HR, the results were fascinating! I would recommend this test to every runner.

Basically, assuming you are prepared for a hard session, and warmed-up, set the treadmill to a little slower than your 10k pace, and run 4 or 5 miles whilst monitoring or recording your HR. Critically, do not adjust the speed! I find my HR rises 2 bpm every mile. In the course of a 10k, that's a 12 beat rise!

So, how to use this new information? I know I can hold no more than HR Zone 5b for the final mile (maybe 6 beats above Lactate Threshold). So working back from there, I know the max HR I should allow myself for each mile of the race. Hence my new plan for a 10k race, based on Lactate Threshold (LT):
Mile 1: LT - 4 (178)
Mile 2: LT - 2 (180)
Mile 3: LT (182)
Mile 4: LT + 2 (184)
Mile 5: LT + 4 (186)
Mile 6: Whatever I have left

I wonder what your thoughts are on this approach, if that kind of HR drift is typical, and if you know of any good research?


At March 11, 2008 8:06 PM , Blogger Joe Friel said...

Steve--An interesting approach. I'll be interested to hear how it works in the real world. Keep us posted.

At March 14, 2008 3:39 PM , Blogger SLB said...

This is a really interesting topic and I wondered what you suggest when the course is significantly hillier in the second half?

At March 14, 2008 6:26 PM , Blogger Joe Friel said...

SLB--Plan on trying to achieve a negative RPE (rating of perceived exertion). The challenge is that the first part will feel easy regardless. It's unlikely the RPE will actually be only slightly higher the second half. It will feel much easier in the first half. The trick is to make sure it isn't so hard in the first half that you fade in the second half. So you will need to be extra cautious about how hard you start. The best way to control this is to rehearse it on a similar course, or at least a portion of the course--the first part.

At March 16, 2008 7:10 PM , Blogger Steve said...


Following up on my post above... new PR by 50 seconds!

I put the plan into action today in a local 8k race. It worked great. I held the mile-by-mile HRs to within a beat or two, feeling very relaxed on the way out, letting people go. And they all came back. Most everyone faded in the second half, whereas I felt faster every mile.

All other indications are that I have less run fitness than previous years, but despite that, I managed a huge PR on the same course. The course was hilly, so I couldn't have used pace to engineer an even effort. I'm totally sold on the strategy, i.e. "increment-your-HR-whilst-racing-to-match-your-treadmill-or-trainer-HR-drift".

For me, at 8k pace, that's 2 bpm every mile. I imagine it differs wildy between individuals and for different sports & intensities. I'd love to see some research on this.


At May 22, 2008 7:59 AM , Anonymous Anonymous said...

In theory(!) the negative split theory (or equal split theory) makes sense. But there is a catch. How do you know what's your 100% on the day? Going for 51/49 or 50/50 implies you know for sure what is your 100% on the day. There is no way of knowing. So you guess. Guess right => (great) success. Guess too conservative => missed opportunity. Guess too aggressively => bonk anyway. There could of course be gray areas where the outcome would depend on how conservative/aggressive the faulty guess was. The theory is kind of "play it safe". But probably very sensible - in theory...


Post a Comment

<< Home