The origins of the run date back to 1974 when a contestant in a horse race covering a course similar to the current WSER successfully completed the distance on foot after his horse had gone lame before the event (7). At the time, the United States was in the midst of an explosion in the popularity of marathon running (9), but there were very few ultramarathons and a 161-km race over mountain trails was unprecedented. In 1975, the horse race was attempted on foot by another man who dropped out only a few kilometers from the finish. Then, in 1976, the event was successfully completed on foot by a different man. The event was established as an official foot race in 1977 with 16 starters of which only three finished. By 1979, the race was recognized as an international event, and there were over 250 starters by 1980. During these early years, there had been recognition that the course was not a full 161 km, and after some course adjustments, the present course was established for the 1986 event. The course has remained unchanged since that time except for modifications to the early sections of the route during some years because of snow conditions and forest fire damage.

Very little has been published on the demographics of ultramarathon runners (19), trends in participation and performance in ultramarathon running (10,15), and factors related to success in competitions of ultramarathon distances (1,4,5,16). This is in contrast to the marathon (42.2 km), which has been discussed in several books and scientific papers (for instance, see [3,6,12,20]). Given that the WSER is the premier 161-km trail running competition and remains one of the largest and most prominent of these events, an analysis of the event is of interest. Thus, the intent of this work was to summarize historical information about the WSER since its inception over 30 yr ago. We were specifically interested in defining the characteristics of the participants and examining changes in runner demographics and performance since the event was established.

Starters of the WSER have ranged in age from 18 to 75 yr, and finishers have ranged from 18 to 71 yr. Between these extremes, the ages of starters are close to normally distributed, and the largest number of runners has been in the 40–49 yr age range. This is comparable to the findings from a limited analysis of participation in ultramarathon runs across a variety of distances in 1982 and 1991 (10). However, the findings differ from what has been observed in shorter road races. For instance, in the New York City Marathon, the largest marathon in the world, the greatest proportion of finishers in 2006 and 2007 was in the 30–39 yr age group (18). Furthermore, among all road races in the United States, the greatest proportion of finishers has been in the 30–39 yr age group during this decade (14).

The average age of participants in the WSER has increased since 1986. For instance, the men averaged around 41 yr of age in 1986 and 1987, and age gradually increased to a plateau of 45–47 yr in 1995. Women have typically averaged approximately 3 yr younger than men but have shown the same trend of an increase in average age over time. This increasing age has largely been accounted for by growth in participation among the older age groups (≥40 yr for women and ≥50 yr for men) and by decreases in participation among men <50 yr old. Examination of data from finishers of all marathons in the United States reveals parallels with the WSER. For marathons, the mean ages of men and women increased respectively from 34 and 31 yr in 1980 to 40 and 36 yr in 2007 (13). Thus, the average age of WSER participants has increased comparably to that for marathon participants, women tend to average 3–4 yr younger than men in the WSER and marathons, and WSER finishers have remained a few years older than marathon finishers across the last two decades.

Participation among women in the WSER has steadily increased since the inception of the event. Whereas they accounted for only 10%–12% of the starters in the late 1980s, women now account for 20%–22%. In contrast, participation by women in road races up to the marathon distance has grown more rapidly than in the WSER. For instance, women accounted for 10.5% of finishers among all marathons in the United States in 1980 and 40% in 2007 (13). Similarly, among all road races in the United States, 21% of the finishers were women in 1987, whereas the percentage was nearly 50% in 2007 (14). Thus, relative to road races up to the marathon distance, the participation among women in the WSER remains relatively low.

WSER participants who finish the race in less than 24 h are awarded a silver belt buckle, whereas those who finish between 24 h and the cutoff time (30 h except for 1995 and 1998 when the time was increased to 32 h because of snow conditions) are awarded a bronze buckle. The distribution of finish times demonstrates the marked effect of these cutoff times (Fig. 7). Whether starters set one of these times as a personal goal before the start of the event or adjusted their goal during the event, the focus on breaking the 24- and 30-h marks is evident. In addition, the distribution of number of WSER finishes shows a relatively greater number of runners have finished 10 times than the general trend would predict for this number of finishes (Fig. 5). This is probably because of the special recognition that individuals receive who have achieved this number of finishes.

Average finish times in the WSER among all finishers between 1986 and 2007 increased fairly linearly with age for both men and women. However, the fastest times did not follow this pattern. The fastest times, averaged during the 22 yr, were slower in the <30 yr age bracket than the 30–39 yr age bracket for both sexes. The fastest times were in the 30–39 yr age group among women and spanned the 30–39 and 40–49 yr age brackets among men. Data are available for comparison with two other endurance events, the marathon and the Olympic distance triathlon (1.5-km swim, 40-km cycle, 10-km run), both of which are typically performed in less than one-seventh of the amount of time as the WSER. Jokl et al. (6) examined the finish time data for the top 50 finishers in each age group of the New York City Marathon between 1983 and 1999 and found that, regardless of sex, times either were comparable for the 20–29 and 30–39 yr age groups or were slightly slower for the younger group, followed by a curvilinear increase in times over the older age groups. Furthermore, review of the United States all-time best marathon performances (21,22) reveals that the fastest times have typically been achieved at ages of 25 to 35 yr. In contrast, an analysis of top 10 finish times in each age group at the Olympic distance triathlon World Championships in 2006 and 2007 demonstrated that top-level performances were maintained to 40 yr for women and to 45 yr for men (17). Thus, it appears that the fastest finish times extend into slightly older ages at the WSER compared with the marathon but are comparable to what has been observed for the Olympic distance triathlon.

In addition to comparing best finish times across different age groups, we looked for trends in the age of top performers across the history of the WSER. The average age of the top 5 finishers at the WSER has typically remained within the 30–39 yr range since 1978 (Fig. 9). However, the average age of the top 5 finishers has increased over the history of the event from the early 30s to the upper 30s. This rate of increase in average age of the top 5 finishers is comparable to the increase in average age of all starters (approximately 0.2 yr in age per calendar yr). Thus, not only has the WSER been attracting an increasingly older group of participants, but the ages of the best runners have also been gradually increasing.

From 1986 to 2007, the WSER course has remained essentially unchanged. During these years, the yearly finish rates varied between 51% and 80% and were similar for men and women when compared without consideration of age or other individual characteristics (Fig. 6). On the whole, men have been faster than women when compared across age groups whether considering the entire group of finishers or the fastest finishers for each year (Fig. 8). Yet, the performance gap between men and women has been narrowing.

Finish times for the men, whether for the top 5 finishers among all men or within different age groups, did not change between 1986 and 2007 (Figs. 10 and ​and11).11). In contrast, finish times improved for women who placed in the top 5 among all women (Fig. 10, top), in the top 5 within the 30–39 and 40–49 yr age groups (Fig. 11, top left), and among all women in the 30–39 yr age group (Fig. 11, bottom left). As a result, the women finishing in the top 5 overall averaged 25% slower than the corresponding group of men in 1980 but were only 14% slower in 2007. This 14% difference between men and women in average top 5 finish times at the 2007 WSER is comparable to the 12% differences between the sexes in average top 5 finish times for both the 2007 Hawaii Ironman and the 2007 New York City Marathon.

Across the history of the WSER, the fastest women have narrowed the performance gap relative to the fastest men by approximately 4% per decade. This is comparable to the relative improvement of 2.8% per decade for the top 10 women over the top 10 men in the run portion of the Hawaii Ironman Triathlon across the time span of 1988 to 2007 (8). Although the total time for the Ironman is approximately half that for the WSER and the run portion, at 42 km, is much shorter than the WSER, the fact that the run follows a 3.8-km swim and 180-km cycle may help account for the similar findings.

The improvements in finish times among the fastest women along with the relative improvement for the women compared with men may reflect advances for the women in training programs, an accumulation of experience at such events, and a general increase in the level of competition associated with the larger number of women starters. As a measure of the depth of the highest level of competition at the WSER, we examined trends in the difference in finish times between the fifth and first finishers. The concept of this measure is attributed to Lepers (8) and his analysis of Hawaii Ironman Triathlon results where he referred to the proportional difference between the 10th and 1st finishers as the “performance density.” We chose to refer to this entity as a “time spread” and examined the difference between fifth and first because fewer people participate each year in the WSER than in the Hawaii Ironman. We anticipated a decrease in the top 5 time spread among women and found this to be the case when the regression model was limited to the period between 1990 and 2007. In this model, the time spread in 2007 was not significantly different for women than for men. This is similar to the finding of Lepers (8) for the Hawaii Ironman in that he showed the top 10 performance densities for men and women to approach the same value across the period between 1988 and 2007.