Martin D. Hoffman

Background: Leading sports medicine and nutrition organizations recommend replacing sodium losses during prolonged exercise; however, practical guidance for implementing sodium replacement strategies remains limited. Estimating sodium needs during exercise requires assessment of both whole-body sweat sodium concentration (WBSSC) and sweat rate. Objectives: This study focused on WBSSC by examining its temporal stability, reproducibility, and predictability during prolonged cycling exercise while drinking according to two hydration strategies. Methods: Using a randomized, crossover, counterbalanced design, eight highly trained men completed two 5 h cycling sessions (183 ± 14 W, 30 °C) while consuming fluids either in a programmed (P) or ad libitum (A_L) fashion. Sweat was collected with patches applied on the forearm for ~20 min before sampling, which occurred at ~40, 130, 220, and 290 min. Local sweat sodium concentration was converted to WBSSC using a validated equation. Results: A main effect of time was observed for WBSSC (p < 0.05), with only the 40 min time point differing from later measurements; no condition or interaction effects were detected. The within-trial typical variation in WBSSC was 7.2 mmol·L⁻¹ for P and 6.1 mmol·L⁻¹ for A_L, while the between-trial typical variation was 5.6 mmol·L⁻¹. The WBSSC measured at 40 min predicted mean exercise WBSSC with good precision and moderate stability (y = 0.2738 + 1.3397x, R² = 0.87, standard error of the estimate = 5.4 mmol·L⁻¹, 95% confidence interval slope = 0.82–1.86 mmol·L⁻¹). Conclusions: These findings indicate that during prolonged cycling exercise, WBSSC (1) varies trivially within and between trials; (2) can reasonably be predicted using a single sweat sample and; (3) is not influenced by P or A_L drinking.

The psychological aspect of ultrarunning is of interest in sports medicine. Ultrarunners are described as mentally tough, and have been shown in studies to be goal oriented, and intrinsically motivated. It is unknown how the personality traits of this group compare to the general population. 734 ultramarathon runners participated in this large longitudinal study. Ultramarathon runners scored significantly lower in extroversion (3.74 vs 4.44, p<.0001), and agreeableness (5.10 vs 5.23, p=.0099) compared to a control population. They scored higher in conscientiousness (5.93 vs 5.4, p<.0001), and emotional stability (5.28 vs 4.83, p<.0001), while statistically similar in openness to experiences (5.33 vs 5.38, p=0.4174). The current study dimensions of relatively low agreeableness (competitive), and extroversion (able to stay within oneself), combined with relatively high conscientiousness (organized, goal-directed), and emotional stability (stable in stressful circumstance), quantify the differences between a large ultramarathon runner population and a control group.

A drinking strategy aiming to replace a given percentage of the sweat losses incurred during exercise should result in reproducible fluid intake volume and, hence, fluid balance from one exercise session to the other performed under similar scenarios. Whether this may also be the case with ad libitum drinking during exercise is unclear. We characterized the repeatability of ad libitum fluid intake during repeated 1 h exercise sessions and examine its effect over time on fluid balance and selected physiological functions and perceptual sensations. Twelve (3 women) healthy individuals participated in this study. At weekly intervals, they completed 4, 2 x 30 min walking/jogging exercise bouts (55% VO2max, 40°C, 20-30% relative humidity) interspersed by a 3 min recovery period. During exercise, participants replaced water (20°C) ad libitum. There were no significant differences among the 4 exercise sessions for absolute fluid intake volume (~ 1000 mL · h-1), percent body mass loss (~ 0.4%), sweat rate (~ 1300 mL · h-1) and percent of sweat loss replaced by fluid intake (~ 80%). Heart rate, rectal temperature and perceived thirst and heat stress did not differ significantly between the first and fourth exercise session. Perceived exertion was significantly lower during the fourth vs. the first exercise session, but the difference was trivial, < 1 arbitrary unit. In conclusion, ad libitum fluid intake during 4 successive identical 1 h walking/jogging sessions conducted in the heat will result in similar fluid intake volumes and perturbations in fluid balance, heart rate, rectal temperature and perceived thirst, heat stress and exertion.

Background: The foot and ankle play a critical role in ultramarathon running. Because foot and ankle injuries are the most common location of injury in this group, proper care is essential for prevention. In this sport, small issues can become big problems over such long distances, and understanding the preventative measures taken by ultramarathon runners may provide insight for other athletes looking to avoid similar problems. The purpose of this study was to examine the routine and preventative care of the foot and ankle, as well as injury rates, in this group of high-risk athletes. Methods: The Ultrarunners Longitudinal TRAcking (ULTRA) Study is the largest known prospective longitudinal study of ultramarathon runners. In this portion of the study, participants reported general health status, running behavior and performance, as well as foot and ankle care, injuries, stretching frequency, and shoewear. Results: A total of 734 ultramarathon runners participated in the study. This group ran a median of 40.2 km per week. Overall, 71.2% of active ultramarathon runners reported a foot or ankle injury in the previous 12 months. The most common injuries reported were plantar fasciitis (36.3%), Achilles tendinitis (24.0%), nonspecific foot pain (14.0%), and stress fractures (13.4%). Sit and reach flexibility test showed that 63.7% of runners could not reach past their toes. There were no significant correlations for sit and reach flexibility or stretching frequency with injury rate. Conclusion: The high prevalence of foot and ankle injuries in ultramarathon runners does not appear to be influenced by arch type, foot strike pattern, orthotic usage, stretching behavior, or actual flexibility. A high percentage of the study runners used comfort as a shoe selection method, independent of alignment or foot strike pattern. These findings guide the clinician in shared decision making with runners about routine care, including injury prevention and shoe selection. Level of Evidence: Level II, prospective study.

The incidence of acute kidney injury (AKI) associated with ultramarathon running is varied partially because onsite measurement of serum creatinine concentration (Cr) is rarely performed at races due to logistical challenges. We conducted a prospective observational study using blood samples from volunteer athletes before and immediately after the Leadville Trail 100 Run in August 2014. The goals of our study were to determine the incidence of those meeting the AKI criteria immediately following the ultramarathon race and to evaluate the utility of using medical equations to back-calculate creatinine levels for runners without known baseline creatinine levels and to identify possible risk factors for developing AKI. We were able to collect pre-race and post-race blood samples on 64 and 84 volunteers, respectively. AKI was defined as a Cr increase (≥1.5 times or ≥0.3 mg/dl from baseline). Of the 37 runners for whom we had both pre- and post-race blood samples, 18 (49%) met the criteria for AKI. Using two different methods of back-calculating baseline estimated creatinine (a fixed eGFR [estimated glomerular filtration rate] and an aged-based eGFR), 6 (16%) and 22 (59%) of 37 runners met the criteria for AKI, respectively. We found that there is no accurate way to estimate baseline Cr in this population.

Nausea and vomiting are common for runners during ultramarathons and often contribute to non-finishes. We aimed to determine the efficacy of ondansetron, a commonly used antiemetic, to treat nausea and vomiting in runners during an ultramarathon. Runners who had a previous history of frequent nausea or vomiting during races and entered in 160, 80, and 55 km ultramarathons in 2018 and 2019 were randomized in a double-blind fashion to 4 mg ondansetron or placebo capsules to use if they developed nausea or vomiting during the race with the ability to take three additional doses. Study participants completed a post-race online survey to assess medication use and efficacy. Of 62 study participants, 31 took either ondansetron (20) or placebo (11). In this small study, there were no group differences in those reporting any improvement in nausea and vomiting (p = 0.26) or in the amount of improvement (p = 0.15). We found no evidence that ondansetron capsules improve nausea and vomiting during ultramarathons.