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Medical Research

There is very little data available on the effects of ultrarunning on the human body. RacingThePlanet has supported medical research at our ultramarathons since 2011 to help the running community understand this field better. The medical research is overseen by Stanford's Emergency Medicine Physician, Dr. Grant Lipman and at every race there is a doctor who is dedicated to gathering data for the medical research project. To date, research has covered topics such a hyponatremia, the affect of NSAID medication (e.g. Ibuprofen) on the kidney function, methods of blister prevention, the effect of ultramarathon running on the kidneys and more.
 
Below you can see information on the medical research undertaken with links to the papers written (many of which have been published).  

 

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Study of Injury and Illness Rates in Multiday Ultramarathon Runners
Races: Gobi March (China) 2005, Sahara Race (Egypt) 2005, Atacama Crossing (Chile) 2006, Gobi March (China) 2006.
Researchers: Brian J. KRABAK, Brandee WAITE, and Melissa A. SCHIFF.
Publication: Medicine Science Sports and Exercise. 2011 Dec;43(12):2314-20
Abstract: 
Purpose:
This study aimed to describe injury and illness rates in runners competing in 7-d, 250-km off-road ultramarathon events.
 
Methods:
Three hundred ninety-six runners competing in the RacingThePlanet 4 Desert Series ultramarathon races from 2005 to 2006 were prospectively followed. Descriptive analyses were used to evaluate overall injury/illness rates, types of injuries/illnesses, and diagnoses for all medical encounters. Multivariate linear regression was used to estimate the risk of number of injuries/illnesses and 95% confidence intervals associated with age, sex, and race completion time.
 
Results:
Eight-five percent of runners representing a total of 1173 medical encounters required medical care. The overall injury/illness rates were 3.86 per runner and 65 per 1000-h run. Almost 95% were minor in nature, owing to skin-related disorders (74.3%), musculoskeletal injuries (18.2%), and medical illnesses (7.5%). Medical illnesses were more likely on the first day of the race, whereas musculoskeletal and skin injuries were more likely on day 3 or 4. A 10-yr increase in age was associated with 0.5 fewer injuries/illnesses, and females had 0.16 more medical illnesses compared with males.
 
Conclusions:
Despite the extreme nature and harsh environments of multiday ultramarathon races, the majority of injuries or illnesses are minor in nature. Future studies are needed to evaluate additional factors contributing to injuries.
 
Click here to download the paper.  
A Prospective Randomized Blister Prevention Trial Assessing Paper Tape in Endurance Distances (Pre-TAPED)
Races: Gobi March (China) 2010, RacingThePlanet: Australia 2010, Sahara Race (Egypt) 2010, Sahara Race (Egypt) 2011, Atacama Crossing (Chile) 2011, RacingThePlanet: Nepal 2011.
Researchers: Grant S. LIPMAN, MD; Mark A. ELLIS, MD; Erica J. LEWIS, MD; Brandee L. WAITE, MD; John LISSOWAY, MD; Garett K. CHAN, PhD; and Brian J. KRABAK MD.
Publication: Wilderness & Environment Medicine. 2014 Dec;25(4):457-61
Abstract:
Objective
Friction foot blisters are a common injury occurring in up to 39% of marathoners, the most common injury in adventure racing, and represent more than 70% of medical visits in multi-stage ultramarathons. The goal of the study was to determine whether paper tape could prevent foot blisters in ultramarathon runners.
 
Methods
This prospective randomized trial was undertaken during RacingThePlanet 155-mile (250-km), 7-day self-supported ultramarathons in China, Australia, Egypt, Chile, and Nepal in 2010 and 2011. Paper tape was applied prerace to one randomly selected foot, with the untreated foot acting as the own control. The study end point was development of a hot spot or blister on any location of either foot.
 
Results
One hundred thirty-six participants were enrolled with 90 (66%) having completed data for analysis. There were 36% women, with a mean age of 40 ± 9.4 years (range, 25–40 years) and pack weight of 11 ±1.8 kg (range, 8–16 kg). All participants developed blisters, with 89% occurring by day 2 and 59% located on the toes. No protective effect was observed by the intervention (47 versus 35; 52% versus 39%; P = .22), with fewer blisters occurring around the tape on the experimental foot than under the tape (23 vs 31; 25.6% versus 34.4%), yet 84% of study participants when queried would choose paper tape for blister prevention in the future.
 
Conclusions
Although paper tape was not found to be significantly protective against blisters, the intervention was well tolerated with high user satisfaction.
 
Click here to download the paper.  
Incidence and Prevalence of Acute Kidney Injury During Multistage Ultramarathons
Races: RacingThePlanet: Jordan 2012, Atacama Crossing (Chile) 2012, Atacama Crossing (Chile) 2013, Gobi March (China) 2013.
Researchers: Grant S. LIPMAN, MD; Brian J. KRABAK, MD; Sean D. RUNDELL, DPT, PhD; Katherine M. SHEA, MD; Natalia BADOWSKI, MD; and Colin LITTLE, MD.
Publication: Clinical Journal of Sport Medicine. 2016 Jul;26(4):314-9
Abstract:
Objective
Determine prevalence, incidence, and risk factors of acute kidney injury (AKI) during multistage ultramarathons.
 
Design
Prospective observational cohort study.
 
Setting
Jordanian Desert 2012; Atacama Desert, Chile 2012 and 2013; and Gobi Desert 2013 RacingThePlanet 250 km, 6-stage ultramarathons.
 
Participants
One hundred twenty-eight participants (384 measurements) from the Jordan (25, 19.5%), Gobi (35, 27.3%), 2012 Atacama (24, 18.8%), and 2013 Atacama (44, 34.4%) races.
 
Interventions
Blood samples and weights were gathered and analyzed immediately after stage 1 (40 km), 3 (120 km), and 5 (225 km).
 
Main Outcome Measures
Changes in serum creatinine (Cr), cumulative incidence, and prevalence of AKI were calculated for each stage with “risk of injury” defined as 1.5 x baseline Cr and “injury” defined as 2 x Cr.
 
Results
Cumulative incidence of AKI was 41.4%. Stage 1 had 56 (43.8%) with risk of AKI and 24 (18.8%) with injury; in stage 3, 61 (47.7%) were at risk, 41 (32%) had injury; in stage 5, 62 (48.4%) runners were at risk and 36 (28.1%) had injury. Acute kidney injury was significantly associated with females [odds ratio (OR), 4.64; 95% confidence interval (CI), 2.07–10.37; P < 0.001], lower pack weight (OR, 0.71; 95% CI, 0.56–0.91; P < 0.007), and percentage weight loss (OR, 0.87; 95% CI, 0.78–0.97; P < 0.015). Lowest quintile of finishers was less likely to develop AKI (OR, 0.18; 95% CI, 0.04–0.78; P < 0.022).
 
Conclusions
Prevalence of AKI was 63%–78% during multistage ultramarathons. Female sex, lower pack weight, and greater weight loss were associated with renal impairment.
 
Click here to download the paper.  
A Prospective Cohort Study of Acute Kidney Injury in Multistage Ultramarathon Runners: The Biochemistry in Endurance Runner Study (BIERS)
Races: Gobi March (China) 2008, Sahara Race (Egypt) 2008, RacingThePlanet: Namibia 2009.
Researchers: Grant S. LIPMAN; Brian J. KRABAK; Brandee L. WAITE; Sarah B. LOGAN; Anil MENON; and Garrett K. CHAN
Publication: Research in Sports Medicine. 2014;22(2):185-92
Abstract:
The purpose of the study was to evaluate the prevalence of acute kidney injury (AKI) during a multi-stage ultramarathon foot race. A prospective observational study was taken during the Gobi 2008; Sahara 2008; and Namibia 2009 RacingThePlanet 7-day, 6-stage, 150-mile foot ultramarathons. Blood was analyzed before, and immediately after stage 1 (25 miles), 3 (75 miles), and 5 (140 miles). Creatinine (Cr), glomerular filtration rate (GFR), and incidence of AKI were calculated and defined by RIFLE criteria. Thirty participants (76% male, mean age 40 + 11 years) were enrolled. There were significant declines in GFR after each stage compared with the pre-race baseline (p < 0.001), with the majority of participants (55–80%) incurring AKI. The majority of study participants encountered significant renal impairment; however, no apparent cumulative effect was observed with resolution of renal function to near baseline levels between stages. 
 
Click here to download the paper.  
Paper Tape Prevents Foot Blisters: A Randomized Prevention Trial Assessing Paper Tape in Endurance Distances II (Pre-TAPED II)
Races: Sahara Race (Jordan) 2014, Gobi March (China) 2014, RacingThePlanet: Madagascar 2014, Atacama Crossing (Chile) 2014.
Researchers: Grant S. LIPMAN, MD; Louis J. SHARP, MD; Mark CHRISTENSEN, MD; Caleb PHILLIPS, PhD; Alexandra DITULLIO, MD; Andrew DALTON, DO; Pearlly NG, MD; Jennifer SHANGKUAN, MD; Katherine SHEA, MD; and Brian J. KRABAK, MD.
Publication: Clinical Journal of Sport Medicine. 2016 Sep;26(5):362-8
Abstract: 
Objective:
To determine whether paper tape prevents foot blisters in multistage ultramarathon runners.
 
Design:
Multisite prospective randomized trial.
 
Setting:
The 2014 250-km (155-mile) 6-stage RacingThePlanet ultramarathons in Jordan, Gobi, Madagascar, and Atacama Deserts.
 
Participants:
One hundred twenty-eight participants were enrolled: 19 (15%) from the Jordan, 35 (27%) from Gobi, 21 (16%) from Madagascar, and 53 (41%) from the Atacama Desert. The mean age was 39.3 years (22-63) and body mass index was 24.2 kg/m (17.4-35.1), with 31 (22.5%) females.
 
Interventions:
Paper tape was applied to a randomly selected foot before the race, either to participants' blister-prone areas or randomly selected location if there was no blister history, with untaped areas of the same foot used as the control.
 
Main Outcome Measures:
Development of a blister anywhere on the study foot.
 
Results:
One hundred six (83%) participants developed 117 blisters, with treatment success in 98 (77%) runners. Paper tape reduced blisters by 40% (P < 0.01, 95% confidence interval, 28-52) with a number needed to treat of 1.31. Most of the study participants had 1 blister (78%), with most common locations on the toes (n = 58, 50%) and heel (n = 27, 23%), with 94 (80%) blisters occurring by the end of stage 2. Treatment success was associated with earlier stages [odds ratio (OR), 74.9, P < 0.01] and time spent running (OR, 0.66, P = 0.01)..
 
Conclusions:
Paper tape was found to prevent both the incidence and frequency of foot blisters in runners.
 
Click here to download the paper.  
Ibuprofen Versus Placebo Effect on Acute Kidney Injury in Ultramarathons: a Randomised Controlled Trial
Races: Gobi March (China) 2015, Atacama Crossing (Chile) 2015, RacingThePlanet: Ecuador 2015, RacingThePlanet: Sri Lanka 2016.
Researchers: Grant S. LIPMAN; Katherine M. SHEA; Mark CHRISTENSEN; Caleb PHILLIPS, Patrick BURNS; Rebecca HIGBEE, Viktoria KOSKENOJA, Kurt EIFLING, Brian J. KRABAK.
Publication: Emergency Medicine Journal. 2017 Oct;34(10):637-642
Abstract:
Background:
Despite concerns that non-steroidal anti-inflammatory drugs (NSAIDs) contribute to acute kidney injury (AKI), up to 75% of ultramarathon runners ingest these during competition. The effect of NSAID on AKI incidence in ultramarathon runners is unclear. 
 
Methods:
Multisite randomised double-blind placebo-controlled trial in the Gobi, Atacama, Ecuador and Sri Lankan deserts to determine whether ibuprofen (400 mg every 4 hours) would be non-inferior to placebo during a 50-mile (80 km) foot race. The primary outcome was incidence of AKI defined as severity categories of 'risk' of injury of 1.5× baseline creatinine (Cr) or 'injury' as 2× Cr, combined to calculate total incidence at the finish line. Non-inferiority margin for difference in AKI rates was defined as 15%.
 
Results:
Eighty-nine participants (47% ibuprofen and 53% placebo) were enrolled with similar demographics between groups. The overall incidence of AKI was 44%. Intent-to-treat analysis found 22 (52%) ibuprofen versus 16 (34%) placebo users developed AKI (18% difference, 95% CI -4% to 41%; OR 2.1, 95% CI 0.9 to 5.1) with a number needed to harm of 5.5. Greater severity of AKI was seen with ibuprofen compared with placebo (risk=38% vs 26%; 95% CI -9% to 34%; injury=14% vs 9%; 95% CI -10% to 21%). Slower finishers were less likely to encounter AKI (OR 0.67, 95% CI 0.47 to 0.98) and greater weight loss (-1.3%) increased AKI (OR 1.24, 95% CI 1.00 to 1.63).
 
Conclusion:
There were increased rates of AKI in those who took ibuprofen, and although not statistically inferior to placebo by a small margin, there was a number needed to harm of 5.5 people to cause 1 case of AKI. Consideration should therefore be taken before ingesting NSAID during endurance running as it could exacerbate renal injury.
 
Click here to download the paper.    
Exercise-Associated Hyponatremia, Hypernatremia, and Hydration Status in Multistage Ultramarathons
Races: Atacama Crossing (Chile) 2012, Sahara Race (Jordan) 2012, Gobi March (China) 2012, Atacama Crossing (Chile) 2013
Researchers: Brian J. KRABAK, MD, MBA; Grant S. LIPMAN, MD; Brandee L. WAITE, MD; Sean D. RUNDELL, DPT, PhD.
Publication: Wilderness & Environmental Medicine. Dec 2017;28(4)
Abstract:
Objective:
Dysnatremia and altered hydration status are potentially serious conditions that have not been well studied in multistage ultramarathons. The purpose of this study was to assess the incidence and prevalence of exercise-associated hyponatremia (EAH) (Na+<135 mmol·L-1) and hypernatremia (Na+ >145 mmol·L-1) and hydration status during a multistage ultramarathon. 
 
Methods:
This study involved a prospective observational cohort study of runners competing in a 250-km (155-mile) multistage ultramarathon (in the Jordan, Atacama, or Gobi Desert). Prerace body weight and poststage (stage [S] 1 [42 km], S3 [126 km], and S5 [250 km]) body weight and serum sodium concentration levels were obtained from 128 runners.
 
Results:
The prevalence of EAH per stage was 1.6% (S1), 4.8% (S3), and 10.1% (S5) with a cumulative incidence of 14.8%. Per-stage prevalence of hypernatremia was 35.2% (S1), 20.2% (S3), and 19.3% (S5) with a cumulative incidence of 52.3%. Runners became more dehydrated (weight change <-3%) throughout the race (S1=22.1%; S3=51.2%; S5=53.5%). Body weight gain correlated with EAH (r=-0.21, P = .02). Nonfinishers of S3 were significantly more likely to have EAH compared with finishers (75% vs 5%, P = .001), but there was no difference in either EAH or hypernatremia between nonfinishers and finishers of S5.
 
Conclusion:
The incidence of EAH in multistage ultramarathons was similar to marathons and single-stage ultramarathons, but the cumulative incidence of hypernatremia was 3 times greater than that of EAH. EAH was associated with increased weight gain (overhydration) in early stage nonfinishers and postrace finishers.
 
Click here to download the paper.    
How Variability in Pain and Pain Coping Relates to Pain Interference During Multi-Stage Ultramarathons
Races: Atacama Crossing (Chile) 2016, Sahara Race (Namibia) 2016, Gobi March (China) 2016
Researchers: Kevin N. ALSCHULER, PhD; Anna L. KRATZ, PhD; Grant S. LIPMAN, MD; Brian J. KRABAK, MD; Dave POMERANZ, MD; Patrick BURNS, MD; Joshua BAUTZ, MD; Claire NORDEEN, MD; Crystal IRWIN, DO; Mark P. JENSEN, PhD
Publication: Pain. 2019 Jan;160(1):257-262
Abstract:
An important and substantial body of literature has established that maladaptive and adaptive coping strategies significantly impact pain-related outcomes. This literature, however, is based primarily on populations with painful injuries and illnesses. Little is known about coping in individuals who experience pain in other contexts and whether coping impacts outcomes in the same way. In an effort to better understand pain coping in such contexts, this study evaluated pain coping in ultramarathon runners, a population known to experience moderate levels of pain with minimal perceived negative effects. This study reports on pain coping in 204 entrants in 2016 RacingThePlanet multistage ultramarathon events. Participants provided data over 5 consecutive days on pain severity, paininterference, exertion, and coping. Results demonstrated that the study participants were more likely to use adaptive than maladaptive coping responses. However, maladaptive coping, but not adaptive coping, was positively associated with percent time spent thinking about pain and pain-related interference. Taken together, the study supports the idea that this high functioning group of individuals experiencing pain emphasizes the use of adaptive coping strategies over maladaptive strategies, reinforcing the perspective that such a pattern may be the most effective way to cope with pain. Within the group, however, results supported traditional patterns, such that greater use of maladaptive strategies was associated with greater pain-related interference, suggesting that optimizing pain coping may be critical to reducing factors that may interfere with ultramarathon performance.
 
Click here to download the paper.    
Accuracy of Estimated Creatinine in Multistage Ultramarathon Runners
Races: Sahara Race (Egypt) 2008, RacingThePlanet: Namibia 2009, Gobi March (China) 2009, Atacama Crossing (Chile) 2012.
Researchers: Colin E. LITTLE, MD; Grant S. LIPMAN, MD; Daniel MIGLIACCIO, MD; David S. YOUNG, MD; Brian J. KRABAK, MD
Publication: Wilderness & Environmental Medicine. 2019 June;30(2):129-133
Abstract:
Introduction:
Ultramarathon running is increasing in popularity worldwide, as is the growing body of research on these athletes. Multiple studies have examined acute kidney injury through estimated baseline creatinine (Cr) and glomerular filtration rate (GFR). Values are estimated through an age-based formula of GFR and the modification of diet in renal disease (MDRD) equation. However, the accuracy of this practice in a cohort of healthy athletes is unknown.
 
Methods: 
A prospective analysis of the first 40-km (25-mi) stage of 6-stage 250-km (155-mi) multistage ultramarathons in the Sahara, Namibia, Atacama, and Gobi Deserts. Runners had prerace measured baseline Cr compared to estimated values through age-based estimated GFR and back calculation of Cr through the MDRD equation.
 
Results:
Forty-eight participants (27% female, age 39±10 y) had Cr values analyzed. The mean measured Cr was 0.99±0.17, which was 11% higher than an estimated Cr of 0.88±0.14 (P<0.01). Estimated age-based GFR was 95.9±5.8 mL⋅min-1 compared to GFR based on measured Cr and MDRD of 86.1±14.6 (P<0.001).
 
Conclusions:
Estimated values of GFR and Cr by standard age-based values and MDRD equation were significantly inaccurate, which would overinflate the incidence of acute kidney injury. Future studies should devise a new model for estimation of baseline Cr that is validated in this population.
 
Click here to download the paper.    
Pain Is Inevitable But Suffering Is Optional: Relationship of Pain Coping Strategies to Performance in Multistage Ultramarathon Runners
Races: Sahara Race (Namibia) 2016, Gobi March (China) 2016, Atacama Crossing (Chile) 2016.
Researchers: Kevin N. ALSCHULER, PhD; Brian J. KRABAK, MD; Anna L. KRATZ, PhD; Mark P. JENSEN, PhD; Dave POMERANZ, MD; Patrick BURNS, MD; Joshua BAUTZ, MD; Claire NORDEEN, MD; Crystal IRWIN, DO; Grant S. LIPMAN, MD
Publication: Wilderness & Environmental Medicine. 2020 March, 31(1): 23-30.
Abstract:
Introduction:
Ultramarathon runners commonly endure musculoskeletal pain during endurance events. However, the effect of pain coping skills on performance has not been examined.
 
Methods: 
A prospective observational study during three 250 km (155 mi), 6 stage ultramarathons was conducted. Finish line surveys were completed after each of the four 40 km (25 mi) and one 80 km (50 mi) stages of racing. Variables gathered included pain intensity, pain coping strategy use, pain interference, finishing position (quintile), and successful race completion.
 
Results:
A total of 204 participants (age 41.4±10.3 y; 73% male) reported average pain intensity of 3.9 (±2.0) and worst pain intensity of 5.3 (±2.3) on a 0 to 10 scale. They used greater adaptive pain coping strategies (3.0±1.3) relative to maladaptive strategies (1.3±1.1). Worst pain and pain interference increased over each stage of the race for all runners (P<0.001), with worst pain being significantly different by finishing status (P=0.02). Although all runners endured increased pain and interference, the nonfinishers (28 [14%]) had significantly greater differences in changes in pain intensity (P<0.01) and pain interference (P<0.001). Maladaptive pain coping strategies were more common in nonfinishers; with each 1-point increase (0-6 scale), there was a 3 times increase in odds of not finishing the race.
 
Conclusions:
Although increased pain intensity and pain interference was found in all multistage ultramarathon runners, successful event completion was significantly associated with less maladaptive pain coping. Training in coping with pain may be a beneficial part of ultramarathon preparation.
 
Click here to download the paper.    
Click here to listen to the Wilderness & Environmental Medicine Live! podcast review of this article, presented by Kevin N. Alschuler.    
Effect of Sodium Supplements and Climate on Dysnatremia During Ultramarathon Running
Races: RacingThePlanet: Patagonia 2017, Atacama Crossing (Chile) 2017, Sahara Race (Namibia) 2018, Gobi March (Mongolia) 2018, Atacama Crossing (Chile) 2018.
Researchers: Grant S. LIPMAN, MD; Patrick BURNS, MD; Caleb PHILLIPS, PhD; Jacob JENSEN, DO; Colin LITTLE, MD; Carrie JURKIEWICZ, MD; Bryan JARRETT, MD; Anne WALKER, MD; Nicky MANSFIELD, MD; and Brian J. KRABAK, MD
Publication: Clinical Journal of Sport Medicine. February 2020.
Abstract:
Objective:
Analyze the effect of sodium supplementation, hydration, and climate on dysnatremia in ultramarathon runners.
 
Design: 
Prospective observational study.
 
Setting:
The 2017 80 km (50 mile) stage of the 250 km (150 mile) 6-stage RacingThePlanet ultramarathon in 2017 Chilean, Patagonian, and 2018 Namibian, Mongolian, and Chilean deserts.
 
Participants:
All race entrants who could understand English were invited to participate, with 266 runners enrolled, mean age of 43 years (±9), 61 (36%) females, average weight 74 kg (±12.5), and average race time 14.5 (±4.1) hours. Post-race sodium collected on 174 (74%) and 164 (62%) participants with both the blood sample and post-race questionnaire.
 
Intervention:
Weight change and finish line serum sodium levels were gathered.
 
Main outcome measures:
Incidence of exercise associated hyponatremia and hypernatremia by sodium ingestion and climate.
 
Results:
Eleven (6.3%) runners developed EAH, and 30 (17.2%) developed hypernatremia. Those with EAH were 14 kg heavier at baseline, had significantly less training distances, and averaged 5 to 6 hours longer to cover 50 miles (80 km) than the other participants. Neither rate nor total ingested supplemental sodium was correlated with dysnatremia, without significant differences in drinking behaviors or type of supplement compared with normonatremic runners. Hypernatremic runners were more often dehydrated [8 (28%), -4.7 kg (± 9.8)] than EAH [4 (14%), -1.1 kg (± 3.8)] (P < 0.01), and EAH runners were more frequently overhydrated (6, 67%) than hypernatremia (1, 11%) (P < 0.01). In the 98 (56%) runners from hot races, there was EAH OR = 3.5 [95% confidence interval (CI), 0.9-25.9] and hypernatremia OR = 8.8 (95% CI, 2.9-39.5) compared with cold races.
 
Conclusions:
This was the first study to show that hot race climates are an independent risk factor for EAH and hypernatremia. Sodium supplementation did not prevent EAH nor cause hypernatremia. Longer training distances, lower body mass, and avoidance of overhydration were shown to be the most important factors to prevent EAH and avoidance of dehydration to prevent hypernatremia.
 
Click here to download the paper.    
Prospective Observational Study of Weightbased Assessment of Sodium Supplements on Ultramarathon Performance (WASSUP)
Races: RacingThePlanet: Patagonia 2017, Atacama Crossing (Chile) 2017, Sahara Race (Namibia) 2018, Gobi March (Mongolia) 2018, Atacama Crossing (Chile) 2018.
Researchers: Grant S. LIPMAN; Tamara HEW-BUTLER; Caleb PHILLIPS; Brian J. KRABAK; and Patrick BURNS, MD
Publication: Sports Medicine - Open. February 2021.
Abstract:
Background:
Sodium supplements are ubiquitous in endurance running, but their impact on performance has been subjected to much debate. The objective of the study was to assess the effect of sodium supplementation as a weight-based predictor of race performance in ultramarathon runners.
 
Methods: 
Prospective observational study during an 80 km (50 mi) stage of a 6-stage 250 km (155 mi) ultramarathon in Chile, Patagonia, Namibia, and Mongolia. Finish line hydration status as measured by weight change, point-of-care serum sodium, and questionnaire provided sodium ingestion categories at 33rd percentile and 66th percentile both for weight-adjusted rate and total sodium consumption, then analyzed for significant relationships to race performance, dysnatremia, and hydration.
 
Results:
Two hundred sixty-six participants were enrolled, with 217 (82%) with complete sodium supplement rate data, 174 (80%) with finish line sodium, and 161 (74%) with both pre-race weights and total sodium ingestion allowing weight-based analysis. Sodium intake ranged from 131–533 mg/h/kg (2–7.2 gm), with no statistically significant impact on pace, race time, or quintile rank. These outcomes did not change when sodium intake was analyzed as a continuous variable or by sub-group analysis of the 109 (68%) normonatremic runners. When controlled for weight-adjusted sodium intake, performance was poorly correlated with hydration (r = − 0.152, 95% CI − 0.348–0.057). Dehydrated runners outperformed those overhydrated, with 11% of top 25th percentile finishers dehydrated (versus 2.8% overhydrated), with 3.6 min/km faster pace and time 4.6 h faster finishing time.
 
Conclusions:
No association was found between sodium supplement intake and ultramarathon performance. Dehydrated runners were found to have the best performance. This reinforces the message to avoid overhydration.
 
Keywords:
Electrolytes, Supplements, Performance, Ultramarathon, Running, Endurance, Dehydration, Overhydration, Exercise-associated hyponatremia.
 
Click here to download the paper.