Pacing a Half Ironman

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Pacing a Half Ironman


For triathletes that have been racing a long time or are new to the sport and are thinking about doing a longer triathlon then the half ironman distance can be the perfect distance! Beginners tend to think all about ironman, but the half ironman can be the perfect solution for those looking to go longer. It can be just long enough where PACING has to be taken into consideration, but not so long like an ironman distance where more can wrong and nutrition has to be as close to perfect as possible. The half ironman distance won’t take up as much training time as an ironman, so your significant other will love this distance also! If you have trained properly most also find they are “racing,” where in an ironman only the top men and women are truly “racing.” Next month, I will be racing in my 30th half ironman and while my fastest times are long gone, the pacing and effort is still the same.


Pacing for a half ironman is critical whether a beginner or seasoned veteran. If you have done the optimal training to put together your best possible finishing time and you finish in the front of the pack or are an elite triathlete in most triathlons then this blog is geared towards you. Let’s dissect the race in chronological order starting with the swim. For those coming from doing olympic distance, you will find the effort in the swim portion to be the same. Unless you are lacking in your cycling and run endurance that will show up hours from the start, then most triathletes can handle a MODERATELY HARD to even HARD effort for the duration of the swim. That first 100-400 meters should be taken out HARD to not be trapped by slower swimmers behind you or sometimes unfortunately the ones that lined up in front of you that didn’t seed themselves accordingly. Once you are past this point, then you can settle into a nice rhythm and hopefully are sitting behind someones feet nicely. The swim will go by relatively fast and before you know it you will be on land running to your bike. A few pointers for a good swim time are the following – a. try and do a warm-up before the start (especially if the water temperature is cold)  b. get accustomed to the course and if there is a current as well as which way it is going    c. seed yourself accordingly before the swim based on your current swim fitness   d. in training do several sessions of 100-400 meters where you practice going out HARD and then settle into a nice rhythm for the rest of the prescribed interval  e. before the start go over where you will enter the water before the start (if beach start) as well as where you will exit the water.


Now that you have left the water and and have gotten on your bike its time to talk about bike pacing. The cycling portion of any triathlon is always the longest. Unless 1 of the 3 sports is a big limiter for you, then you will be on your bike the longest amount of time. When I first started the sport I was recommended the book “The Triathletes Training Bible” by Joe Friel which structures triathlon training based on heart rate zones, perceived exertion, and lactate threshold. This method of training can be quite advantageous today, and for simplicity I will use zone training to gauge effort for this blog (even though training by power is quite effective for cycling today, but expensive.) Using training zones 1-5, as well as the exertion scale of EASY/STEADY/MODERATELY HARD/HARD can really simplify this for some. For front of the pack triathletes I like to break the bike ride up into 1/3’s. The first 1/3 you will focus on getting your heart rate down from the swim transition and building to a bottom zone 2 effort (STEADY/ 25-30 beats under lactate threshold.) The middle portion of the bike should build to the middle of zone 2 (STEADY/ 20-25  beats under lactate threshold), while the last section will build to the top of zone 2 ( STEADY/ 15-20 beats below lactate threshold.) Keep in mind like most races, regardless of fitness ability, a lot of it can depend on how your feeling, the terrain and conditions as well as your current cycling fitness. That last 1/3 of the bike can really set the tone for the run, so you will want to make sure your hydration levels have been met, as well as any kind of caloric deficit taken care of. If you are someone that finishes in the top 10 overall or races as an elite, I like to break the bike into 2 sections. The first section is the first 40 miles, while the last section is the last 16 miles. That first section you should be focusing on keeping your heart rate in check after the swim transition, as well as dialing in your heart rate zone to the bottom of zone 3 (MODERATELY HARD/ 15 beats below lactate threshold.) The bottom of this zone is roughly 15 beats below lactate threshold so you will want to have a lot of experience with this effort and make sure you don’t get too carried away and get close to your threshold. At mile 40 in my opinion, is where the race starts ( an ironman starts at mile 80.) If you have paced properly, and are feeling “ok,” then you can bump the effort up slightly to the middle of zone 3 (MODERATELY HARD/ 10-15  beats under lactate threshold.) Some top pro’s and elite age group triathletes can bump up into the top of zone 3 ( 8-10 beats under lactate threshold,) but have to pay attention to their body,how they are feeling and better have quite a base of endurance to be able to run 13.1 miles after this!


Now that you are finally off the bike and most of the race is over it is time to start the run. The run in 90% of all triathlons is the most important sport. If you are a top of the pack triathlete I like to break the half marathon into 2 sections. This first section can be used to go over how your feeling, hydration levels, fuel needs, and leg fatigue. You will want to start the run at the bottom of zone 3 (MODERATELY HARD/ 15 beats below lactate threshold) if you paced optimally. For those that went too hard on the bike this 13.1 miles can turn into survival mode, so monitoring how you feel in the beginning of the run is critical! Once you get to the halfway point and are still feeling ok, you can safely increase your effort up to the middle of zone 3 ( MODERATELY HARD/ 10-12 beats under lactate threshold.) You should still be monitoring how you feel and focusing on the finish line at this point! Things can go south fast, so don’t get carried away! If you are a top level/elite triathlete, and paced properly, then this last 13.1 miles can be taken out as hard as an olympic distance triathlon and for the very fastest, a sprint triathlon run ( 5k.)  I like to break their half-marathon into 2 sections. The first section is the first 5k, where you should be at the bottom of zone 4 (HARD/ 5-8 beats under lactate threshold.) It is very easy to go out too hard in the beginning of the run, so I find it is best to make sure you use this 2 section approach! With this in mind, statistically it is best to try and “positive split” the half-marathon run (first half is slightly faster than second half in minutes per mile pace.) At this level and effort, no one will “negative split” their run time, and it is best to go out slightly faster than your goal time, but not overly inflated! Only the very fastest runners in the sport don’t need to break this part up, but most of them are racing others and not paying attention to “pacing” as much. If you have paced properly, then that last 10 miles you can run right at threshold effort ( HARD/ lactate threshold to 5 beats under lactate threshold.) You will still have to monitor how you are feeling, as well as maintaining hydration and fuel needs.

Half ironman racing can be quite rewarding for triathletes. Like I mentioned earlier, you will definitely have felt like you accomplished something (for those that like longer races,) and the training volume, as well as the long swim bike run sessions won’t be as timely! Most top of the pack and elite triathletes will find the half ironman to be the perfect mix of endurance and speed for a tough distance to race.