The Kona Standard: What Age-Grading Says About How Much Slower You Really Get

For decades, Kona qualifying was simple to explain: finish near the top of your age group at a qualifying race and take one of that group's slots. From the 2026 season, IRONMAN changed that. Most slots now depend on how your time compares with an age-graded standard, which means the qualifying system has a built-in answer to a question every masters triathlete asks: how much slower should I expect to be as I get older?

This article explains how the Kona Standard works, what its numbers imply about ageing, and what research on Ironman results says about age-related decline in swimming, cycling and running, and about men and women. It isn't a guide to qualifying for Kona, and the factors may change for 2027.

How the new qualifying system works

IRONMAN announced performance-based qualifying in July 2025, and the first 2026 Kona slots were awarded under it. TrainerRoad's guide, updated for the 2027 qualifying season in October 2026, summarises the structure:

1. Automatic slots. Each age-group winner at a qualifying race gets one automatic slot. If they decline, it rolls down to second, then third.
2. Performance Pool. Any slots left over go into a pool, ranked by age-graded time.
3. Age-graded time. Your finish time multiplied by the Kona Standard factor for your age group and sex.
4. Separate pools for men and women. Since November 2025, men and women are ranked separately, with each pool's size set by its share of the start list.

The 2027 IRONMAN World Championship is on Saturday 9 October 2027 in Kailua-Kona, with men and women racing on the same day. TrainerRoad's guide says the 2027 qualifying season keeps the same structure, but whether the factors change for 2027 hadn't been made public when it was updated.

Why the women's pool was split

When the system launched, men and women were ranked together in one Performance Pool. Slowtwitch reported on 14 November 2025 that IRONMAN had found approximately 96% of Performance Pool slots were going to men and 4% to women. In the first third of qualifying races, men made up 84.4% of finishers and women 15.6%.

IRONMAN responded by splitting the pool by gender, sizing each pool to match the eligible age-group starters at each race, and keeping roll-down slots within each gender. It also reallocated slots retroactively, with 44 slots awarded to women from races already completed. The change took effect from IRONMAN Arizona in November 2025.

At Kona 2026 itself, Big Island Now reported that 689 of the roughly 2,427 amateurs were women, about 27% of the age-group field.

Where the Kona Standard factors come from

According to TrainerRoad's guide, each factor is based on the top 20% of Kona finishers in that age group over a rolling five-year window, and IRONMAN re-evaluates the factors every year. The 30-34 age group is the reference, with a factor of 1.0000.

The factors published in TrainerRoad's October 2026 guide were:

• Men: 18-24 0.9698; 25-29 0.9921; 30-34 1.0000; 35-39 0.9895; 40-44 0.9683; 45-49 0.9401; 50-54 0.9002; 55-59 0.8667; 60-64 0.8262; 65-69 0.7552; 70-74 0.6876; 75-79 0.6768; 80-84 0.5555; 85-89 0.5416.
• Women: 18-24 0.9543; 25-29 0.9982; 30-34 1.0000; 35-39 0.9877; 40-44 0.9699; 45-49 0.9470; 50-54 0.9051; 55-59 0.8665; 60-64 0.8041; 65-69 0.7606; 70-74 0.7173; 75-79 0.6150; 80-84 and 85-89 not published.

The men's factors are from the July 2025 table. The women's factors are from the November 2025 revision, which benchmarks women against women aged 30-34. Check IRONMAN's own Kona Standard page before relying on any number here.

What the factors imply

Inference: a factor is roughly the ratio between the reference group's time and your age group's time. If a 50-54 man's factor is 0.9002, the best men in that group were, on average, about 10% slower than the best 30-34 men. Dividing 1 by the factor gives the implied slowdown:

• 40-44: about 3% slower than 30-34 for both men and women.
• 50-54: about 10-11% slower.
• 60-64: about 21% slower for men and 24% slower for women.
• 70-74: about 45% slower for men and 39% slower for women.

These are our calculations from the published factors, not figures IRONMAN has stated, and they come with important caveats:

• They describe Kona, not ageing in general. One course, one set of conditions and only the athletes who qualified and started.
• The top 20% of older groups is a small number of people, especially above 70. A handful of exceptional athletes can move a factor.
• Selection matters. Older athletes at Kona are survivors: those still fit, healthy and motivated enough to qualify.
• The youngest group, 18-24, is also slower than 30-34, which reflects experience and the depth of the field, not physiology alone.

Slowtwitch's opinion writer Ryan Heisler argued in November 2025 that basing the factors on a single race builds bias into the system. That's a reasonable criticism, and it's another reason to read the factors as a practical ranking tool rather than a precise model of ageing.

What research says about ageing and endurance

The Kona factors follow a pattern that physiologists have described for years. In a 2008 review in The Journal of Physiology, Hirofumi Tanaka and Douglas Seals summarised the shape of the decline in masters endurance athletes:

• Peak performance is maintained until about 35.
• Performance declines modestly between about 50 and 60.
• The decline becomes progressively steeper after that.

They identified three main determinants of endurance performance: maximal oxygen uptake (VO2max), lactate threshold and economy. In endurance-trained adults, economy didn't appear to change with age. Importantly, they concluded that the declines were largely mediated by the lower training intensity and volume that older athletes sustain.

A 2016 mini review in Frontiers in Physiology by Romuald Lepers and Paul Stapley added more detail:

• VO2max is the parameter most affected by age, largely through a fall in maximal heart rate of about 0.7 beats per minute per year, a rate that appears similar in sedentary, active and masters athletes.
• Endurance decline ranges from about 8% per decade in male 100 km ultramarathon runners to about 15% per decade in female Ironman triathletes.
• Cycling declines less than running and swimming in triathlon.

Swim, bike and run don't age equally

Lepers and colleagues, in the International Journal of Sports Medicine in 2010, analysed the top 10 male finishers in each five-year age group from 20 to 70 at the 2006 and 2007 world championships, over both the Olympic and Ironman distances.

• Cycling declined less than swimming or running. The difference became significant after age 50 at Ironman distance, and after 55 at Olympic distance.
• Ironman produced larger declines than the Olympic distance in cycling (beyond 55) and running (beyond 50).
• Swimming declined at a similar rate over both distances.

The authors concluded that race duration strongly influences how age affects triathlon performance. Inference: if you're an older age-grouper, your bike split is likely to be your most age-resistant leg, and the marathon your most vulnerable. That fits the experience of many masters athletes, but this study included only men, and only the fastest ones.

Men, women and age

Lepers and Maffiuletti, in Medicine & Science in Sports & Exercise in 2011, analysed the top 10 men and women aged 18 to 64 at the Hawaii Ironman from 2006 to 2008.

• The sex difference in total time was stable until 55, then increased significantly.
• The sex difference in time was smallest in the swim (12.1%), larger on the bike (15.4%) and largest on the run (18.2%).
• In estimated power output, the gap was largest on the bike (38.6%), compared with the swim (27.5%) and run (32.6%).

A 2019 review by Lepers in Frontiers in Physiology put the overall sex difference in triathlon at roughly 10% to 20%, depending on distance and ability. At the elite end of Ironman, it fell from about 15% in the 1990s to 11% by 2012.

Inference: the wider gap after 55 may reflect biology, but it probably also reflects participation. Far fewer women race in older age groups, so the top 10 is drawn from a smaller pool. That's one reason sex-specific factors and separate pools make sense, and why the women's factors for the oldest age groups have yet to be published.

TriForward's "Menopause and the Triathlete" covers what we do and don't know about midlife women specifically.

Older athletes keep getting faster

A 2013 study in Age by Lepers, Rüst, Stapley and Knechtle looked at 25 years of Hawaii Ironman results, from 1986 to 2010, for the top men and women aged 18 to 69.

• Masters athletes made up a growing share of the field, and athletes under 40 a shrinking share.
• Men older than 44 and women older than 40 improved significantly in all three disciplines and in total time.
• The gap between men and women narrowed in age groups from 40-44 to 55-59.

The Lepers and Stapley review noted that the best men aged 60-64 had improved by around 20% over that period. In other words, part of what we think of as the cost of ageing has turned out to be a cost of not training, not racing, or not believing older athletes could go faster. The Kona factors will keep shifting as that continues, which is one reason IRONMAN re-evaluates them every year.

What you can influence

Tanaka and Seals' conclusion that much of the decline comes from training less and less hard is the most useful part for an age-grouper. Inference from the research above:

• Keep some high-intensity work. VO2max is the parameter most affected by age, and intensity is what tends to drop first when life gets busy.
• Protect the run. It's the leg most vulnerable to ageing in Ironman. Strength work and gradual load progression matter more as you get older; see TriForward's "Two Sessions a Week".
• Build in recovery. Older athletes often need more time between hard sessions. TriForward's "After the Finish Line" covers post-race recovery.
• Don't confuse a factor with a forecast. Your own trajectory depends on your training history, health and consistency more than on the average of the fastest people in your age group.

Using the factors to read your own results

The factors can be a useful, if rough, way to put your own results in context, as long as you remember what they are. A few practical ways to use them, all inference rather than tested methods:

• Compare yourself with your younger self cautiously. If you raced an Ironman in 10:00 at 35 and 10:40 at 52, multiplying the second time by the 50-54 factor gives about 9:36. Inference: on that crude measure, you've held up better than the best athletes at Kona did over the same age span. Course, weather and pacing will matter far more than this calculation.
• Look at splits, not just the total. The research suggests cycling holds up best and running worst. If your run has slipped far more than your bike, that's consistent with the published pattern, but it may also point to run-specific training or injury history that you can address.
• Don't chase a factor-adjusted time with a sudden volume jump. The athletes who set the standard for older age groups have usually been training consistently for years.
• Remember the confidence interval. A factor is a single number built from a small, selected group. Treat differences of a few minutes as noise.

A scenario

The following example is illustrative. Two athletes race the same qualifier. A 52-year-old man finishes in 10:30:00. A 34-year-old man finishes in 9:50:00. Using the 2026 factors, the older athlete's age-graded time is 10:30 × 0.9002, about 9:27. The younger athlete's age-graded time stays at 9:50. Inference: if neither wins his age group, the older athlete ranks higher in the men's Performance Pool, despite finishing 40 minutes behind.

That's the system working as designed. It's also why critics say the factors now matter as much as the training: a small change in a factor can move slots between age groups.

Common mistakes

• Treating the factors as a physiology table. They describe Kona finishers over five years.
• Assuming every leg ages equally. The run is usually the most vulnerable.
• Assuming decline is fixed. Older age groups have improved for decades.
• Using old numbers. Factors are re-evaluated yearly; the women's table changed in November 2025.

What we don't know

• Whether the 2027 factors will change. IRONMAN hadn't said when TrainerRoad's guide was updated.
• How well Kona-based factors fit other courses. Hot, windy Hawaii may not represent a cool, flat qualifier.
• Age-related decline in women over 60. There are too few finishers to be confident.
• How much decline is biology and how much is training. Most research is cross-sectional, comparing different people at different ages rather than following the same athletes over time.

References

• Tanaka H, Seals DR. Endurance exercise performance in Masters athletes: age-associated changes and underlying physiological mechanisms. The Journal of Physiology, 2008;586(1):55–63. doi:10.1113/jphysiol.2007.141879
• Lepers R, Sultana F, Bernard T, Hausswirth C, Brisswalter J. Age-related changes in triathlon performances. International Journal of Sports Medicine, 2010;31(4):251–256. doi:10.1055/s-0029-1243647
• Lepers R, Maffiuletti NA. Age and gender interactions in ultraendurance performance: insight from the triathlon. Medicine & Science in Sports & Exercise, 2011;43(1):134–139. doi:10.1249/MSS.0b013e3181e57997
• Lepers R, Rüst CA, Stapley PJ, Knechtle B. Relative improvements in endurance performance with age: evidence from 25 years of Hawaii Ironman racing. Age, 2013;35(3):953–962. doi:10.1007/s11357-012-9392-z
• Lepers R, Stapley PJ. Master athletes are extending the limits of human endurance. Frontiers in Physiology, 2016;7:613. doi:10.3389/fphys.2016.00613
• Lepers R. Sex difference in triathlon performance. Frontiers in Physiology, 2019;10:973. doi:10.3389/fphys.2019.00973
• TrainerRoad. How to qualify for Kona in 2027: Kona Standard, slots, and what it takes. Updated October 2026. trainerroad.com
• Mackinnon K. IRONMAN revamps Kona qualification system to increase women's performance pool numbers. Slowtwitch, 14 November 2025. slowtwitch.com
• Heisler R. Opinion: IRONMAN's changes to Kona qualification are commendable. They don't go far enough. Slowtwitch, 14 November 2025. slowtwitch.com
• Big Island Now. It's race day: more than 2,500 triathletes will swim, bike and run in IRONMAN World Championship in Kona. 10 October 2026. bigislandnow.com