This study intended to investigate participation and performance trends and to determine the age of peak running speed in ultramarathons of more than 200-km race distance. Based upon existing literature, an increase in participation, an improvement in performance, and an age of peak ultramarathon performance between 30 and 40 years were hypothesized. The main findings for both races were that (1) the female participation increased over time, (2) the fastest finishers were approximately 40 to 45 years of age, and (3) the sex difference was at approximately 20% unchanged over years.
Concerning the total numbers of finishes over the history, it appears reasonable that in Badwater considerably fewer athletes competed since the qualifying standards were higher  than in Spartathlon . Another limiting factor may be attributed to the greater financial expenses to participate in the Badwater because there are high additional costs for logistics and the necessity of a supporting team . Across the history of Badwater race, the annual percentage of finishes averaged to 79% versus 43% in the Spartathlon. This relative low percentage of finishes in the Spartathlon may reflect the extraordinary demands on running speed due to rigorous cut-off limits in the Spartathlon.
Regarding the sex-specific participation, female ultramarathoners accounted on average for approximately 22% in Badwater versus approximately 11% in Spartathlon. Since women were generally slower in ultramarathon running than men [2–4], the cut-off limits in the Spartathlon could have a greater influence on women for a successful finish. Present findings were in accordance with other studies regarding the fact of a relatively low female participation in ultramarathon in comparison to shorter running events such as a marathon [3, 4, 9, 10]. For instance, in the 100 km Lauf Biel in Switzerland, female participation was at approximately 13%. Hoffman reported a female participation of approximately 20 to 22% in 161-km ultramarathon events held in North America, which comes close to the female participation in Badwater. Men are over-represented in sports . Generally, men were running faster than women , and the sex difference in relative performance can partially be attributed to men’s greater training motivation . The motivation to train and compete seems different between women and men. The most popular modern male sports require the skills needed for success in male-male physical competition . In contrast, female ultramarathoners were described as task-oriented, internally motivated, healthy, and financially conscious individuals .
The three five-year age groups between 40 and 54 years accounted for the largest participation regardless of sex and race location. This age-related finding, together with the fact of numerous finishes from athletes aged 40 years and older in Badwater (76%) and in Spartathlon (71%), is comparable with the results of other studies investigating the age distribution in ultra-running events [4, 9, 10]. Our data may reflect a lifestyle trend in sports activities towards ultramarathon. Younger athletes are increasingly more attracted by technical sports with higher intensity [10, 30, 31]. The higher participation of elderly athletes may be due to social and psychological factors such as spare time resources connected with an increase in the competitive spirit . Hoffman and Fogard  described 161-km ultramarathoners as master runners at a mean age of 44.5 ± 9.8 years with a range between 20 and 72 years. These runners were generally men (80.2%), married (70.1%), and had higher education with bachelor’s (43.6%) or graduate (37.2%) degrees. A further reason for the high percentage of older finishers across the studied history of both races could be related to the logistic demands, particularly of Badwater. The extraordinary distance over 200 km of both events may require an enormous volume of training over years. In ultramarathoners, previous experience is of importance for a successful race outcome .
The present study adds valuable results considering the change in demographic aspects of participation and performance in two extraordinary strenuous ultramarathons of more than 200 km in length. The improvement in running speed in Badwater might be attributed to a progress in the supporting teams and to an accumulation of pre-race experience [33, 34]. The increase in the number of competitors and finishers might reflect that faster and more experienced runners enter this race [35–37].
In Spartathlon, however, athletes were not able to improve running speed. The stable running speeds in Spartathlon over the same time span could be attributed to the character of this race which is more a pure running event and has not to rely so much on external support in comparison to the Badwater . Analyses of Hoffman and Wegelin  and Knechtle et al.  could not detect a clear improving or declining performance trend for the top ultramarathoners in terms of running speeds. Concerning Badwater, our data give a different impression due to a significant improvement of race speed regardless of sex. On the whole, independent of sex, considerably faster running speeds were achieved by the annual top five finishers in Spartathlon in comparison to the annual top five runners in Badwater. Different speed levels reflect the different physical demands of either race. Interestingly, in 2011 the running speeds in women narrowed. One possible explanation for this finding could be a lower top five elite field in the Spartathlon in that year. Further adverse race conditions may slow down women running speed in the Spartathlon in 2011.
Sex difference in ultra-running performance
In both Badwater and Spartathlon, the sex difference in running performance was at approximately 20%. Generally, the sex difference in endurance performance is at approximately 11 to 12% [12, 13]. The analysis of world best times in 1,500 m and marathon running from 1980 to 1996 revealed that men were approximately 11% faster than women . In a further widespread investigation of running distances between 100 m and 200 km, men were approximately 12% faster compared to women accompanied by the tendency that longer distances were associated with greater sex differences in endurance performance .
Regarding the sex difference in elite ultramarathon running, our data are in accordance with the previous studies. Hoffman  reported for 161-km ultramarathoners that the fastest women were approximately 20% slower than the fastest men. In a comparable race, the 100 km Lauf Biel in Switzerland, the top ten women were approximately 22% slower than the top ten men . In the current discussion about sex difference in ultramarathon running, exceptional findings do exist supporting the assumption that women could outperform men in ultra-endurance sports. For instances, Bam et al.  compared long-distance performances in both men and women and observed that men were faster over distances up to marathon, but this was not evident in a 90-km ultramarathon. Also Knechtle et al.  described a female overall winner in a multi-stage ultramarathon.
Looking upon the sex-related running speed difference between the top elite runners over the 2000 to 2012 period, it is notable that in the 2002 and 2003 Badwater races, the sex difference in top five running speed was close to zero. Moreover, female winners even outperformed male winners in these years. In 2003, the hottest climate conditions have ever been registered in Death Valley with the highest drop off rate of 37% was published for this year . Thus, these results from 2002 to 2003 appeared to reflect a possible better coping against heat among women. Jacob et al.  reported that increasing ambient temperatures had less adverse effects on running speed for women than for men in 161-km ultramarathons. Our findings do underline the assumption that top running speed of women does not converge with or even surpass those of men apart from exceptional women top running speed as seen in the Badwater in 2002 and 2003.
The higher sex difference in performance in these ultramarathoners might be explained by differences in anthropometry, physiology, training, and motivation between women and men. Ultramarathon running leads to a decrease in skeletal muscle mass . Since male ultramarathoners  have a higher skeletal muscle mass compared to female ultramarathoners , the lower muscle mass in women might be a limiting factor for ultramarathon performance. However, physiology still plays an inevitable roll that sex differences probably will continue in the future. Sex difference in performance is considered due primarily to inherent gender-specific differences in body composition and oxygen transport capacity [12, 44–46]. Considering training and motivation, female and male ultra-endurance athletes were trained for about the same weekly hours, but men were training faster than women [47, 48]. Furthermore, men pay closer attention to male sports than women do and male champion athletes obtain a higher status .
The age of peak ultra-running performance
From 2000 to 2012, for both men and women, the age of the annual top five finishers remained at 39 to 45 years in Badwater and Spartathlon. Women achieved their peak running speed at higher age than men in either event. Our data were comparable with other studies in ultramarathon running events. By investigating the top ten runners in the 100 km Lauf Biel, the age of the best performance was found at approximately 39 to 40 years . Across the history of the 161-km ‘Western State Endurance Run’ in North America, the average age of the top five finishers gradually increased from the early 30s to the upper 30s .
Furthermore, existing literature and our findings suggest that with the increasing length of running events, athletes achieved their peak of running speed at higher age than in shorter running events [9, 49, 50]. The analysis of the ‘New York City Marathon’  documented that among the top fifty performers, no runner was older than 39 years independent of gender. The present data of Badwater and Spartathlon are also consistent with the findings of Schulz and Curnow , reporting a relationship between the age of peak performance and specific events already in the 1980s. Taken as a whole, the present and previous findings [9, 10] evidenced that among the top ultramarathon, elite runners were master athletes defined as participants older than 35 years of age . Usually, however, these older athletes are considered to have either finished their formal competitive careers, to be ‘weekend warriors’ who sporadically train and compete, or to have start again dynamic exercises after a long time span of physical inactivity . Thus, present and other findings appear to suggest that the definition of master runners need to be revised for ultramarathoners.
This cross-sectional data analysis is limited since aspects such as anthropometry [35–37], the physiology [54, 55], and the training [35–37] of the runners, their previous experience [34–37], their pacing strategy , the environmental conditions , and both nutrition [58–60] and fluid intake [61, 62] were not considered.