Physiological Determinants of Ultramarathon Trail-Running Performance

International Journal of Sports Physiology and Performance, (Ahead of Print) https://doi.org/10.1123/ijspp.2020-0766 © 2021 Human Kinetics, Inc. ORIGINAL INVESTIGATION Physiological Determinants of Ultramarathon Trail-Running Performance Alexandra M. Coates, Jordan A. Berard, Trevor J. King, and Jamie F. Burr Context: The physiological determinants of ultramarathon success have rarely been assessed and likely differ in their contributions to performance as race distance increases. Purpose: To examine predictors of performance in athletes who completed either a 50-, 80-, or 160-km trail race over a 20-km loop course on the same day. Methods: Measures of running history, aerobic fitness, running economy, body mass loss, hematocrit alterations, age, and cardiovascular health were examined in relation to race-day performance. Performance was defined as the percentage difference from the winning time at a given race distance, with 0% representing the fastest possible time. Results: In the 50-km race, training volumes, cardiovascular health, aerobic fitness, and a greater loss of body mass during the race were all related to better performance (all P < .05). Using multiple linear regression, peak velocity achieved in the maximal oxygen uptake test (β = −11.7, P = .002) and baseline blood pressure (β =3.1,P = .007) were the best performance predictors for the men’s 50-km race (r =.98,r2 = .96, P < .001), while peak velocity achieved in the maximal oxygen uptake test (β = −13.6, P = .001) and loss of body mass (β =12.8,P = .03) were the best predictors for women (r = .94, r2 = .87, P =.001).Inthe 80-km race, only peak velocity achieved in the maximal oxygen uptake test predicted performance (β = −20.3, r = .88, r2 = .78, P < .001). In the 160-km race, there were no significant performance determinants. Conclusions: While classic determinants of running performance, including cardiovascular health and running fitness, predict 50-km trail-running success, performance in longer-distance races appears to be less influenced by such physiological parameters. Keywords: prolonged exercise, performance predictors, dehydration, running economy, fitness Predicting ultramarathon running performance is a unique dehydration has been shown to negatively alter endurance exercise challenge, as ultramarathon races can vary greatly in distance, performance,13 yet faster marathon runners typically lose more weight duration, and physiological demand. Ultramarathon running races over the course of a race than slower runners, and a loss of upwards of range from any race exceeding the marathon distance (>42.2 km) to 3% of body mass has been demonstrated in runners who completed multiday events and commonly include diverse terrains and envi- marathons in <3 hours.14 Loss of body mass following 161-km ronmental conditions.1,2 This results in vastly different physiologi- races is similar to that of marathons (∼2%)15; however, there is only cal requirements between races and can make comparison across a weak relationship to faster racing times.16 Furthermore, in contrast to races challenging. The demographic of athletes racing ultramara- shorter distance running, body mass loss cannot be solely attributed to thons is typically older than those who run shorter distances and is dehydration in ultramarathon,17 which may complicate the relation- composed primarily of masters and recreational participants, rather ship between body mass loss and performance. Finally, while peak than elite athletes.1 Proposed contributors to successful ultramara- performance in the marathon is typically achieved around the age thon performance include high aerobic fitness,3,4 an ability to of 30 years, the age of the fastest 160-km runners worldwide is mitigate injuries,5 avoidance of gastrointestinal issues,6 delays approximately 37 years for men and 39 years for women,18 with of fatigue,2 and psychological fortitude.3 experience being a greater determinant of success than age.18 This The physiological determinants of running performance in stan- may further suggest a shift in the importance of certain physiological dard distances from 5000 m to the marathon have been highly parameters, such as aerobic fitness, which decreases with age. investigated and primarily include measures of aerobic fitness such To date, a comparison of the physiological determinants of performance across increasing ultramarathon race distances, and as maximal oxygen uptake (VO2max), lactate threshold or the 7 within similar racing conditions, has not been performed. The percentage of sustainable VO2max, and running economy. Aerobic fitness seems likely to be a determinant of ultramarathon performance objective of this study was to examine whether common indicators of running performance could be used to predict performance in as well, as lactate threshold and VO2max are related to distance covered in a 24-hour treadmill run,4 and peak treadmill running athletes who raced either a 50-, 80-, or 160-km ultramarathon, on velocity achieved during an incremental test is the best laboratory the same day and over a common course. predictor of performance for races ≤90 km.8 Lower body mass index (BMI) and body fat percentage are typically related to improved Methods endurance running performance9,10; however, the correlation of BMI and ultramarathon performance is equivocal,6,9,11,12 and performance Experimental Design 9,12 is more strongly related to training volumes than BMI. Excessive Fifty-one recreational runners who were registered in the Sulphur Springs trail races (Ancaster, Canada) for the 50-, 80-, or 160-km The authors are with the Human Performance and Health Research Laboratory, Dept distances were recruited via e-mail for this cross-sectional study. of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, The race was composed of 20-km hilly trail loops (∼620 m of Canada. Burr ([email protected]) is corresponding author. cumulative elevation gain per loop). Participants were all healthy 1 2 Coates et al and nonsmoking individuals between the ages of 18 and 60 years increase running speed or incline at the end of the test was designed so and provided written informed consent prior to testing. In the that those athletes unfamiliar with running at faster velocities could month prior to the race (mean 12 [7] d prior to race day), still achieve VO2max. Athletes were not instructed to stop upon participants underwent baseline testing, including a training and reaching a plateau in oxygen consumption, and the highest VO2 value racing history questionnaire, basic anthropometrics, resting blood achieved using a 30-second rolling average was taken as maximal pressure, heart rate (HR), and HR variability (HRV), a venous (VO2max). Peak velocity was recorded as the highest velocity blood draw to assess hematocrit, and an incremental running test to achieved during the maximal test if the treadmill incline was kept exhaustion. Participants were asked to refrain from caffeine and at 1% or was calculated as peak velocity = max velocity + (% grade × heavy meals for ≥3 hours, drugs and alcohol for ≥24 hours, and 0.2 kph).23 Ventilatory thresholds were determined as previously intense exercise for ≥48 hours prior to baseline testing. On race described by Pallarés et al.24 morning, all athletes were weighed immediately prior to racing. Running economy was assessed as both oxygen cost (milliliter Immediately following the race, postrace weight and hematocrit per kilogram) and caloric unit cost (kilocalorie per kilogram) per measurements were collected to assess dehydration status. km in the last minute of the 3-minute running stage prior to the first The study was carried out under approval of the University of ventilatory threshold25 at a 1% treadmill grade. As such, while the Guelph ethics board and in accordance with the Declaration of velocities of running were not the same across participants, the Helsinki and was part of a larger study on ultramarathons and relative intensity of running was, and, mathematically, running cardiovascular fatigue.19,20 velocity was not included in the calculation.25 Training and Racing History Questionnaire Fluid Alterations and Body Mass Body mass was assessed directly prior to the race start on a standing In a written questionnaire, athletes were asked to report on their fi previous month of training, including how many hours and kilometers scale positioned on a rm platform, and postrace mass was taken per week they ran, how many hours of strength or resistance training immediately following the races on the same scale. Brachial venipuncture was performed to collect a 10 mL sample for blood they underwent each week, and how many additional hours were 19 spent on cross-training. They were also asked to report the kilometers analysis in a related study, with hematocrit assessed onsite by per week completed on average in the past year. Finally, athletes sampling from the vacutainer and using a microcapillary reader reported the number of years of past endurance run training and how (Damon/IEC Division, Needham Heights, MA). many marathons and ultramarathons they had previously completed. Statistical Analysis Cardiovascular Health Race performance was determined as percentage difference of winning time, accounting for race distance and sex ([subject time – Age, height, and body mass were recorded. Supine blood pressure winning time]/[winning time] × 100). Thus, the best performance was taken in triplicate using an automated oscillometric device would be noted as 0% different

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