International  Journal  of
Environmental Research
and Public Health
Article
Celebrating 40 Years of Ironman: How the
Champions Perform
Lucas Pinheiro Barbosa 1,†, Caio Victor Sousa 1,2,†
, Marcelo Magalhães Sales 3
,
Rafael dos Reis Olher 1, Samuel Silva Aguiar 1
, Patrick Anderson Santos 1, Eduard Tiozzo 2,
Herbert Gustavo Simões 1, Pantelis Theodoros Nikolaidis 4
and Beat Knechtle 5,6,*
1
Graduate Program in Physical Education, Catholic University of Brasília, 71966-700 Brasília, Brazil;
lduarte.barbosa@gmail.com (L.P.B.); cvsousa89@gmail.com (C.V.S.); rﬂolher@gmail.com (R.d.R.O.);
ssaguiar0@gmail.com (S.S.A.); patricksantospas@gmail.com (P.A.S.); hgsimoes@gmail.com (H.G.S.)
2
Miller School of Medicine, University of Miami, Coral Gables, FL 33124, USA; etiozzo@med.miami.edu
3
Physical Education Department, Goias State University, Quirinópolis, 75860-000 GO, Brazil;
marcelomagalhaessales@gmail.com
4
Exercise Physiology Laboratory, 18450 Nikaia, Greece; pademil@hotmail.com
5
Medbase St. Gallen Am Vadianplatz, 9001 St. Gallen, Switzerland
6
Institute of Primary Care, University of Zurich, 8006 Zurich, Switzerland
*
Correspondence: beat.knechtle@hispeed.ch; Tel.: +41-(0)71-226-93-00
†
These authors contributed equally to this work.
Received: 7 February 2019; Accepted: 16 March 2019; Published: 20 March 2019


Abstract: We aimed to determine which discipline had the greater performance improvements in the
history of Ironman triathlon in Hawaii and also which discipline had the greater inﬂuence in overall
race time. Data from 1983 to 2018 of the top three women and men of each year who competed in
the Ironman World Championship were included. In addition to exploratory data analyses, linear
regressions between split times and years of achievement were performed. Further, a stepwise
multiple linear regression was applied using total race time as the dependent variable and split
times as the independent variables. Both women and men signiﬁcantly improved their performances
from 1983 to 2018 in the Ironman World Championship. Swimming had the largest difference in
improvements between men and women (3.0% versus 12.1%, respectively). A negative and signiﬁcant
decrease in each discipline was identiﬁed for both women and men, with cycling being the discipline
with the greatest reduction. The results from the stepwise multiple regression indicated that cycling
was the discipline with the highest inﬂuence on overall race time for both sexes. Based on the ﬁndings
of this study, cycling seems to be the Ironman triathlon discipline that most improved overall race
times and is also the discipline with the greatest inﬂuence on the overall race time of elite men and
women in the Ironman World Championship.
Keywords: triathlon; cycling; running; swimming; endurance
1. Introduction
The Ironman triathlon consists of swimming 2.4 miles (3.8 km), cycling 112 miles (180 km),
and running 26.2 miles (42.2 km) and is considered as one of the most challenging ultra-endurance
events worldwide [1,2]. Although triathlon started in San Diego, California, the history of Ironman
triathlon started in 1978 in Hawaii, with the ﬁrst Ironman World Championship being held in
Kailua-Kona (Big Island) three years later, also in Hawaii [1–3].
Int. J. Environ. Res. Public Health 2019, 16, 1019; doi:10.3390/ijerph16061019
www.mdpi.com/journal/ijerph
Int. J. Environ. Res. Public Health 2019, 16, 1019
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Nowadays, the Ironman events take place all over the world, with amateur and professional athletes
competing in these events to qualify for the World Championship in Kailua-Kona. Ironman Hawaii in
considered as the toughest Ironman race in the world due to the course, the environmental conditions,
and the competitiveness of the event [2,4]. The race itself is one of the most popular triathlon events in
the world, with a growing competitiveness and performance improvement in non-elite triathletes [1,5,6].
In addition, it should be highlighted that the best professional triathletes in the world often achieve new
records in Kailua-Kona [7].
In order to help coaches and athletes with both training plans and race strategy, performance
trends have been analyzed in the past few years in many endurance sports [8–11]. Speciﬁcally in
triathlon, relevant studies have been conducted for Olympic distance (1.5 km swim/40 km cycle/10 km
run) [12,13], half-distance (half-Ironman: 1.9 km swim/90 km cycle/21 km run) [13,14], full-distance
(3.8 km swim/180 km cycle/42.195 km run) [14,15], and ultra-triathlons (distance > Ironman) [16,17].
To date, two studies investigated the performance of amateur triathletes [2,5], but none of them
included only elite women and men.
Ofoghi et al. [18] investigated which discipline would have the greater inﬂuence on overall
performance in an Olympic triathlon and concluded that running was the most decisive, followed
by swimming and cycling. On the other hand, Sousa et al. [19] analyzed all sub-8-h performances in
full-distance triathlon (i.e., Ironman) and reported that cycling was the discipline with the greatest
inﬂuence on the overall result, followed by running and swimming. Additionally, it is noteworthy that
in 2018 the female and male winners of the 2018 World Championship improved the course records,
showing that the fastest Ironman triathletes worldwide can further improve their performances.
However, to the best of our knowledge, the only two studies analyzing the Ironman World
Championship results concerned amateur athletes in the analysis, with one of the studies analyzing
races up to 2007 [2] and the other analyzing races from 2002 to 2015 [5]. Therefore, we aimed to analyze
only elite men and women competing in the Ironman World Championship from 1983 to 2018 in
order to determine (i) which discipline had the greatest performance improvement in the last 35 years;
(ii) which discipline had the greatest inﬂuence on overall result; and (iii) whether women were really
closing the gap to men.
2. Methods
2.1. Ethical Approval
All procedures used in the study were approved by the Institutional Review Board of Kanton
St. Gallen, Switzerland, with a waiver of the requirement for informed consent of the participants
given the fact that the study involved the analysis of publicly available data (1 June 2010).
2.2. Data
All data were obtained from a publicly available database (www.ironman.com). All ofﬁcial
overall race and split times from the top three women’s and men’s ﬁnishers of the Ironman World
Championship from 1983 to 2018 were included in the analysis. Table 1 presents the descriptive
distribution of women’s races including the Ironman World Championship Race/Split Record (among
top three ﬁnishers), whereas Table 2 presents men’s data.
Table 1. Women’s total and split race times in the Ironman World Championship from 1983 to 2018.
Race Time
Median
(25–75 Percentile)
Mean
(±SD)
Ironman World
Championship Race/Split Record *
Overall
09:16:48
(09:03:51–09:26:18)
09:19:06
(00:26:14)
08:26:18
Swimming
00:57:00
(00:55:26–01:00:09)
00:57:34
(00:03:24)
00:48:14
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Table 1. Cont.
Race Time
Median
(25–75 Percentile)
Mean
(±SD)
Ironman World
Championship Race/Split Record *
Cycling
05:08:39
(05:00:14–05:17:50)
05:11:22
(00:18:06)
04:26:07
Running
03:08:10
(03:04:09–03:16:31)
03:10:10
(00:10:37)
02:50:26
* Within top three ﬁnishers from 1983 to 2018.
Table 2. Men’s total and split race times in the Ironman World Championship from 1983 to 2018.
Race Time
Median
(25–75 Percentile)
Mean
(±SD)
Ironman World
Championship Race/Split Record *
Overall
08:22:02
(08:14:37–08:33:02)
08:26:28
(00:18:26)
07:52:39
Swimming
00:51:43
(00:51:00–00:53:02)
00:53:18
(00:06:07)
00:48:02
Cycling
04:37:47
(04:30:16–04:46:15)
04:42:15
(00:21:01)
04:12:25
Running
03:08:10
(02:46:42–02:57:00)
02:55:21
(± 00:18:57)
02:39:59
* Within top three ﬁnishers from 1983 to 2018.
2.3. Statistical Analysis
Initially, an exploratory analysis of the data was carried out, in which central tendency (median
and mean), dispersion (interquartile ranges (25 and 75 percentiles and standard deviation), and extreme
(lowest value) measures were calculated (Tables 1 and 2). Furthermore, all data were transformed in
seconds and non-linear regressions (second order) were performed between each split time and year
of achievement. Linear regressions were used for splits because the non-linear ﬁtting line was the
same as the linear. The relative difference (percentage) between the ﬁrst (1983) and last (2018) World
Championship’s top three performances was calculated for both women and men. Regarding overall
race time, non-linear regression analyses were performed since the trend line had a better ﬁt than
linear regression. A comparison of average race times between the top three athletes and the chasing
group (4th to 10th place ﬁnishers) was performed. Finally, a stepwise multiple linear regression was
performed using overall race time as the dependent variable and split times as independent variables.
The signiﬁcance level was set as 5% (p < 0.05), and all procedures were performed using SPSS v21.0
(IBM SPSS Statistics for Windows. Armonk, NY: IBM Corp).
3. Results
Men improved in overall race time by 13.3% from 1983 to 2018, whereas women improved by
20.8% (Table 3). Swimming showed the largest difference in improvements between men and women
(3.0% versus 12.1%, respectively), and running showed the smallest difference (12.5% versus 15.5%,
respectively) for the three split disciplines.
Table 3.
Women’s and men’s percentage performance improvements in the Ironman World
Championship from 1983 to 2018.
Total
Total Difference
Decade Average
Decade Average Difference
Overall
Women
20.8%
7.5%
5.20%
1.87%
Men
13.3%
3.33%
Swimming
Women
12.1%
9.1%
3.25%
2.50%
Men
3%
0.75%
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Table 3. Cont.
Total
Total Difference
Decade Average
Decade Average Difference
Cycling
Women
26.4%
9.5%
6.60%
2.37%
Men
16.9%
4.23%
Running
Women
15.5%
3%
3.88%
0.75%
Men
12.5%
3.13%
Both women and men signiﬁcantly improved their performances from 1983 to 2018 in the Ironman
World Championship in Kona, Hawaii (Figures 1 and 2). The world record was improved almost every
three years (see Supplementary Table S1 for accurate race time values from each year’s champions).
Int. J. Environ. Res. Public Health 2018, 15, x FOR PEER REVIEW  
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almost every three years (see Supplementary Table S1 for accurate race time values from each 
year’s champions). 
 
Figure 1. Dispersion and non-linear regression of overall race time performances in the Ironman 
World Championship from 1983 to 2018 of women and men. Gold trophies represent the champion 
in each year. 
Figure 1. Dispersion and non-linear regression of overall race time performances in the Ironman
World Championship from 1983 to 2018 of women and men. Gold trophies represent the champion in
each year.
Int. J. Environ. Res. Public Health 2019, 16, 1019
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Figure 1. Dispersion and non-linear regression of overall race time performances in the Ironman 
World Championship from 1983 to 2018 of women and men. Gold trophies represent the champion 
in each year. 
 
Figure 2. Dispersion and non-linear regression overall race time performances between the top three 
finishers and the chasing group (4th to 10th place finishers) from women and men in the Ironman 
World Championship from 1983 to 2018. 
Figure 2. Dispersion and non-linear regression overall race time performances between the top three
ﬁnishers and the chasing group (4th to 10th place ﬁnishers) from women and men in the Ironman
World Championship from 1983 to 2018.
The linear regression of split disciplines shows a negative and signiﬁcant slope for all disciplines
for both women (swimming: −6.94 to 0.47; cycling: −71.06 to −36.98 *; running: −45.79 to −26.86 *;
Figure 3) and men (swimming: −19.37 to −6.77 *; cycling: −96.01 to −60.52 *; running: −65.06 to
−30.58 *; Figure 4) (* indicates p < 0.001). The greatest slope in both sexes was for cycling.
Int. J. Environ. Res. Public Health 2018, 15, x FOR PEER REVIEW  
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The linear regression of split disciplines shows a negative and significant slope for all 
disciplines for both women (swimming: −6.94 to 0.47; cycling: −71.06 to −36.98*; running: −45.79 to 
−26.86*; Figure 3) and men (swimming: −19.37 to −6.77*; cycling: −96.01 to −60.52*; running: −65.06 to 
−30.58*; Figure 4) (* indicates p < 0.001). The greatest slope in both sexes was for cycling. 
 
Figure 3. Dispersion and linear regression of split-times performances in the Ironman World 
Championship from 1983 to 2018 of women. 
Figure 3.
Dispersion and linear regression of split-times performances in the Ironman World
Championship from 1983 to 2018 of women.
Int. J. Environ. Res. Public Health 2019, 16, 1019
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Figure 3. Dispersion and linear regression of split-times performances in the Ironman World 
Championship from 1983 to 2018 of women. 
 
Figure 4. Dispersion and linear regression of split-times performances in the Ironman World 
Championship from 1983 to 2018 of men. 
Figure 4.
Dispersion and linear regression of split-times performances in the Ironman World
Championship from 1983 to 2018 of men.
The best-ﬁtting model from the stepwise multiple regression included swimming, cycling,
and running split times for both women and men (Table 4). Cycling was the discipline with the
greatest standardized beta for both sexes. The swimming discipline resulted in a negative standardized
coefﬁcient for the men.
Table 4. Standardized coefﬁcient from stepwise multiple regression using total race time as the
dependent variable of Ironman World Championship from 1983 to 2018.
Standardized β Coefﬁcient
R2
R2aj
Swimming
Cycling
Running
Women
0.129
0.690
0.405
0.857
0.856
Men
−0.290
0.895
0.250
0.781
0.775
4. Discussion
The main ﬁnding of this manuscript was that cycling has been the Ironman triathlon discipline
with the greatest improvement rate throughout the years and also has had the greatest inﬂuence on
overall race time for both women and men. However, apparently both women and men have improved
their performances over the years in all triathlon disciplines. It is worth mentioning that women had a
greater improvement than men in all triathlon disciplines and consequently in total race times.
Jeukendrup and Martin [20] had previously reported that cycling in aero position and the use of
lighter wheels (i.e., elbows on handlebars and carbon wheels, respectively, which had developed for use
in time-trial and triathlon bicycles) makes an athlete signiﬁcantly faster. Thus, cycling performance also
had new technologies that could inﬂuence the performance increase, from the outﬁt to the bicycle itself,
all of which contributed to make the athlete more comfortable, aerodynamic, and consequently faster.
Although cycling is the discipline that encompasses more time in comparison to swimming
and running in Olympic distance and short distances, it does not have an inﬂuence in overall race
time, being the least important of the three disciplines [21]. In Olympic distance and short distances,
athletes normally swim really fast to be able to leave transition one with the ﬁrst pack of cyclists and
stay within the leading and chasing peloton, thus saving the energy for the running [18]. However,
Int. J. Environ. Res. Public Health 2019, 16, 1019
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in Ironman races drafting during cycling is not allowed, making cycling a more competitive discipline,
which means that athletes have to apply some strategy in order to cycle fast enough to remain in a
competitive position but still save energy for the running leg. Similarly, in an analysis only including
top full-distance triathlon performances, the authors reported that cycling was the discipline that most
inﬂuenced overall performance in elite men racing below 8 h of overall race time, followed by running
and swimming [19].
A performance analysis on Ironman races investigated more than 340,000 triathletes racing in
253 different race locations and concluded that the race tactics in an Ironman triathlon should focus on
saving energy during the ﬁrst two disciplines for the running split [22]. This conclusion is different
from the ﬁndings of the present study, which suggest that athletes seem to apply greater effort in cycling
than during running. It is worth mentioning that this analysis was carried out with a majority of age
groupers (non-elite), whereas the present study only considered the top three elite professionals from
each year. It is noteworthy that 4th to 10th place ﬁnishers in the Ironman World Championship seemed
to have a substantial performance improvement in the last decade of the event, with consistently much
closer groupings in the top ten athletes for both men and women.
With regard to performance throughout the race, the performance analysis of the Ironman
World Championship with amateurs reported a performance increase in all disciplines for men and
women [23]. However, the authors suggest that this improvement in performance may be due to
an increased number of athletes and morphological changes [23]. The overall performance increase
throughout the years can be mostly attributed to the development of new nutrition and training
strategies [24–27]. A controversial result was the negative coefﬁcient for the swim split in men, which
would mean that a slower swim could lead to a better overall race time. We believe that this statistical
outcome is due to the speciﬁcity of the sample, as only the top three athletes in the overall race were
considered, and these athletes are not always the best swimmers. For example, in the 2018 World
Championship, none of the top three overall athletes were among the top 10 swimmers.
Concerning the performance gap between men and women, it has markedly reduced in the last
decades. At the 2018 Ironman World Championship, women improved by 21% while men improved
by 13%; the absolute gap between them reduced from 1 h and 38 min to 33 min. Indeed, in the 2018
Championship, the female champion Daniela Ryf crossed the ﬁnish line ahead of 20 elite professional
men who ﬁnished the race. Some previous studies have concluded that women have been closing the
gap in swimming [28,29], in running [30,31], and even in triathlon [2]. We believe that women may
still close the gap in an Ironman someday despite the body composition and physiological differences
that exist between men and women. One of the possible explanations for this can be attributed to
cultural changes that have favored a greater participation of women in all sports, including triathlon,
thus increasing competitiveness and therefore performance [7,9,10,32].
When comparing performance with other endurance modalities such as ultra-triathlon and
marathon running, the performance gaps between women and men are getting smaller each year.
Knechtle et al. [33] investigated the performance trends of Double Iron ultra-triathlon (2I; 2x Ironman
distance), Triple Iron ultra-triathlon (3I; 3x Ironman distance), and Deca Iron ultra-triathlon (10I;
10x Ironman distance) from 1985 to 2009 and reported a smaller sex difference in 2I and 3I. Conversely,
Nikolaidis et al. [31] investigated the performance of male and female athletes running the marathon
and concluded that men are still faster than women, but the performance gap remained unchanged for
the past few years.
Regarding the speciﬁc Ironman World Championship, Kailua-Kona is one of the toughest races
within the entire Ironman circuit, which typically requires athletes to swim in choppy waters, cycle with
a lot of wind, and run in hot and sunny weather [34,35]. The race course has not always been the
same in Ironman Hawaii, with small changes every two or three years in order to accommodate safety
precautions and/or local transit logistics. Although this may affect the overall race time, the distances
remained standard and we believe that any small course changes affecting a speciﬁc split race time are
diluted within the sample and do not represent a great confounder to the general results of this study.
Int. J. Environ. Res. Public Health 2019, 16, 1019
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5. Conclusions
In conclusion, cycling seems to be the triathlon discipline that most improved overall race times
and is also the discipline that had the greatest inﬂuence on the overall race time in elite men and
women in the Ironman World Championship. Furthermore, within the last 40 years of Ironman Hawaii,
both men and women improved overall time performance, but women improved more, thereby closing
the gap to men.
Supplementary Materials: The following are available online at http://www.mdpi.com/1660-4601/16/6/1019/
s1, Table S1: Overall times in the Ironman World Championship from 1983 to 2018 for women and men.
Author Contributions: Conceptualization: C.V.S., L.P.B., P.T.N., and B.K.; methodology: C.V.S., L.P.B., M.M.S.,
R.d.R.O., S.S.A., P.A.S., P.T.N., and B.K.; formal analysis: C.V.S., L.P.B., and M.M.S.; writing—original draft
preparation: C.V.S. and L.P.B.; writing—review and editing: C.V.S., L.P.B., M.M.S., P.A.S., E.T., H.G.S., P.T.N.,
and B.K.; visualization: C.V.S., L.P.B., M.M.S., P.A.S., E.T., H.G.S., P.T.N., and B.K.; supervision: P.T.N. and B.K.;
project administration: P.T.N., and B.K.
Funding: This research received no external funding.
Conﬂicts of Interest: The authors report no conﬂicts of interest in this work.
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Celebrating 40 Years of Ironman: How the Champions Perform.
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