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Background: Blisters are the most common dermatologic problem in ultraendurance runners. Their incidence, localization, pain scores, and risk factors in field conditions are poorly understood.Methods: We conducted an observational field-based cohort study during the 5-day multistage 2010 and 2011 Al Andalus Ultimate Trail (219 km). Daily postrace data on blister frequency, localization, severity, and preventive measures from 50 ultramarathon runners were collected through the direct interview technique.Results: After 4 days of running (182 km), blisters occurred in 76 of the participants (P< .001 versus stage 1) compared with 34 after day 1, 54 after day 2, and 72 after day 3 (P< .001 versus stage 1). Most of the blisters formed on the toes (65) (P< .001), followed by blisters on other locations of the foot: the ball of the foot (16), heel (14), and sole (5). Blisters were more painful toward the end of the race, and those on the sole and heel tended to be the most painful, although this did not reach statistical significance. Prophylactic measures studied (type and fabric of socks; application of antiperspirants, talcum powder, or lubricant to feet; and prophylactic taping) did not show any reduction in blister rates. The only predictive marker for reduced blister incidence was previous ultramarathon experience in men (r  −0.44, P< .05).Conclusions: Blisters are extremely common in multistage ultramarathon races. Race experience in male ultramarathon runners is associated with reduced blister rates.

Context: Dehydration is assumed to be a major adverse effect associated with rapid loss of body mass for competing in a lower weight class in combat sports. However, the effects of such weight cutting on body fluid balance in a real-life setting are unknown.Objective: To examine the effects of 5 or greater loss of body mass within a few days before competition on body water, blood volume, and plasma volume in elite amateur boxers.Design: Case-control study.Setting: Sports medicine laboratory.Patients or Other Participants: Seventeen male boxers (age 19.2 ± 2.9 years, height 175.1 ± 7.0 cm, mass 65.6 ± 9.2 kg) were assigned to the weight-loss group (WLG; n 10) or the control group (CON; n 7).Intervention(s): The WLG reduced body mass by restricting fluid and food and inducing excessive sweat loss by adhering to individual methods. The CON participated in their usual precompetition training.Main Outcome Measure(s): During an ordinary training period (t-1), 2 days before competition (t-2), and 1 week after competition (t-3), we performed bioelectrical impedance measurements; calculated total body water, intracellular water, and extracellular water; and estimated total hemoglobin mass (tHbmass), blood volume, and plasma volume by the CO-rebreathing method.Results: In the WLG, the loss of body mass (5.6 ± 1.7) led to decreases in total body water (6.0 ± 0.9), extracellular water (12.4 ± 7.6), tHbmass(5.3 ± 3.8), blood volume (7.6 ± 2.1; P< .001), and plasma volume (8.6 ± 3.9). The intracellular water did not change (P> .05). At t-3, total body water, extracellular water, and plasma volume had returned to near baseline values, but tHbmassand blood volume still were less than baseline values (P< .05). In CON, we found no changes (P> .05).Conclusions: In a real-life setting, the loss of approximately 6 body mass within 5 days induced hypohydration, which became evident by the decreases in body water and plasma volume. The reduction in tHbmasswas a surprising observation that needs further investigation.