Match Your Strengths in Swim, Bike ,or Run to These Triathlons — Triathlete

In a previous article, we analyzed more than 1,000 professional Ironman-distance races to figure out which leg actually decides who places well – not which leg takes the longest, but which one matters most for the final pro podium. The answer for pro racing was clear: The run has traditionally been the decisive leg, but the bike is catching up, and the swim and transitions punch surprisingly above their weight.

But does any of that apply to age groupers? Do the same rules that guide the world’s best professional men also hold for the female 45–49 athlete looking to qualify for Kona? Or does the balance shift when races take longer, hours-wise, when participants are older, fields are wider, the gaps are bigger, and almost nobody runs a sub-3-hour marathon after 112 miles on the bike?

To gain deeper insights into this question, we’ve examined more than 200,000 individual finishes from Ironman and Ironman 70.3 races between 2023 and 2025. (Many thanks to Russell Cox for providing the raw data.)

Breaking it down by age groups with a meaningful number of finishers, that’s more than 7,500 different editions to calculate the relative importance for. This post presents the results from this analysis, compares pro and age-group patterns, and provides suggestions on how to apply these findings when choosing an event that’s best suited to your own personal triathlon profile.

The big picture

Let’s get started by establishing baselines and comparing the results for pros and age groupers. The following table brings together the duration and relative importance across different distances.

First of all, we only show one line for duration in the table above. That’s because the breakdown by duration is almost the same whether looking at pros or age groupers, and across both iron and half-iron distances.

The relative importance numbers tell a more nuanced story. For age groupers, the run leads at both distances (by 3.3% for Ironman and 1.0% for 70.3s), echoing the long-term finding for pros. However, the table focuses on the last three years, and for these years, the importance of the pro bike has increased — a trend that’s interestingly absent from the age-group data. This could be a general difference between pro and age-group racing, or a trend that will take time to filter through. Whether and when that happens remains to be seen.

The swim and transitions account for only a small share of the overall time, but their importance for the final outcome is much greater and even more important for age groupers than for pros. This suggests that most pros have worked enough in the water so that gaps after the swim are smaller and decide very little of the outcome.

In age-group fields, swim ability varies far more widely, and those early gaps carry far more weight. Transitions are also more important for age groupers, a reminder that time lost in T1 and T2 can be costly for the final result, and investing more training time in learning quick transitions can pay off in the end. This aligns with a maxim that coaches have been banging on for years.

Breakdown by gender and age group

The overall age-group numbers show a story broadly consistent with the pro data. But averages across all age groups and genders can mask meaningful differences, and when the data is broken down by age group and gender, a consistent pattern emerges: Run importance actually increases with age.

For both men and women, run importance climbs from under 40% in the 18-24 groups to about 44% in the 55-59 groups, a rise of more than four percentage points across the age spectrum. In short, the older you get, the more the race is decided on the run.

Differences for older athletes in the swim and bike are smaller, leading to smaller relative importance percentages. One explanation is that declining physiological capability shows up first on the run.

Another possible interpretation is that finding the right balance between the three legs becomes even harder for older athletes: Reduced endurance manifests more starkly toward the end of the race, and swimming and biking a bit too aggressively can result in struggling on the run. For Masters athletes in particular, the data is clear: The run is where the race is decided and Kona slots are secured.

Course specifics

Average numbers can hide course-specific information. As an example, the following table shows the numbers for the recent 70.3 World Championship races.

To make it easier to spot if the run or the bike matters more, the table shows the relative importance for the swim and the difference between the run and the bike. Positive numbers mean that the run is more important; negative numbers indicate that the bike dominates.

First of all, the swim importance numbers in all three 70. 3 World Championship races are much smaller than the average from all races. This reflects that the front of the field at 70.3 worlds is much more even in the swim – to do well at worlds, you can’t afford to have a weak leg.

Probably even more relevant is that all three 70.3 World Championships have been bike dominant, and not one of them has had a positive “Run vs. Bike” value. Even Taupo, the most balanced of the three, sits well below the average 70.3 number of +1.0%.

Marbella 2025 stands in a category of its own. Last year’s “Run vs. Bike” of -19.2 is one of the most extreme values in the entire dataset, even more bike-dominant than the Nice Ironman World Championship in the pro analysis.

The hilly Marbella bike course, winding above the Costa del Sol, created time gaps often too large to overcome on the run. Athletes who climbed well simply rode away from the field and held on.

Lahti 2023 sits in the middle ground: It was bike-dominant at -3.3%, but the Finnish bike course still allowed the strong runners to place well.

The broader lesson for age-group athletes racing 70.3 worlds: These are not normal 70.3 races, so don’t treat them that way (in case you were). The bike matters far more than at a typical qualifying event, and your preparation should reflect that, particularly in years when the 70.3 World Championship venue features significant climbing on the bike.

The best Ironman and 70.3 courses for strong swimmers, bikers, and runners

But before you even think about world championships, the Ironman gods require qualifying. The overall findings tell us which leg matters most on average, but for an age grouper planning their race calendar, the more useful question is: Given my strengths, should I target a specific course?

Here’s a map we’ve created with the data that shows the Ironman races that favor a strong swimmer (blue), biker (red), or runner (yellow) for North America, Europe, Oceania, and Rest of the World (since there are not enough races to differentiate between South America, Africa, and Asia):

The numbers shown are the swim importance and the “Run vs. Bike” importance (lower numbers show that the bike is more important, while higher numbers show races that put a bigger weight on the run).

The corresponding map for 70.3s shows which race to pick from the 2026 events:

A few patterns stand out. Strong swimmers are particularly rewarded in Asia – 70.3 Shanghai tops the table at 23.1% – and across most of Africa and South America, likely reflecting open-water conditions and potentially smaller, less evenly matched fields that create larger gaps.

Strong cyclists will find their best opportunities in Europe, where hilly courses like Mallorca and Lanzarote create significant bike gaps. Runners are well served in North America, with Chattanooga appearing in both distances.

What it all means

The headline finding from the pro analysis holds surprisingly well for age groupers: The run is the most decisive leg at the full Ironman distance, and the swim and transitions both punch well above their weight relative to their share of race time. These patterns clearly correlate from pros to age groupers, which gives plenty of evidence to help the rest of us inform the way we train and focus.

But the age-group data holds important nuances, too. At the 70.3 distance, the swim becomes more decisive, and the run’s edge narrows, a pattern that becomes more pronounced at world championship level, where more evenly matched fields keep gaps smaller than would normally emerge in the swim.

The bike, meanwhile, is more dominant in recent pro racing than in age-group fields, suggesting that the equipment and training advantages that have driven the bike’s rise at the top of the sport have not yet fully filtered through to the age-group ranks. This could even serve as a strong signal for those who haven’t yet tried to follow pro trends when it comes to gear or training techniques. However, both the full and half-distance world championships have consistently proven bike-dominant, regardless of venue.

The most striking age-group-specific finding is the relationship between age and run importance. As athletes get older, the run increasingly sorts the field, rising from around 39% for the youngest age groups to over 44% for athletes in their mid-50s and beyond. For Masters athletes in particular, the run is not just important — it is dominant and crucial.

For athletes trying to plan their race calendar, it’s important to pick a race that rewards their strengths: A powerful European cyclist should consider Mallorca or Lanzarote; a runner who can survive the bike should be rewarded in Chattanooga at both the full and half distances.

While the data can’t choose your race for you, it can definitely help you make a smarter choice.