OBJECTIVE: To study whether, during typical-level running, non-rear-foot strikers (non-RFS) or rear-foot strikers (RFS) presented a similar or different extent of neuromuscular fatigue after a prolonged graded run.
METHODS: Sixteen experienced male trail runners (8 non-RFS and 8 RFS) performed a 2.5-hour treadmill graded running exercise. Before and after exercise, neuromuscular tests were performed to assess neuromuscular fatigue of the plantar flexors. Biomechanical gait parameters were acquired with an instrumented treadmill, and electromyographic activity of the lower-limb muscles was collected as an index of muscle activation.
RESULTS: There were no significant time × foot strike interactions for neuromuscular (all P ≥ .742), muscle activation (all P ≥ .157), or biomechanical (all P ≥ .096) variables.
CONCLUSIONS: A dominant level running foot-strike pattern did not directly affect the extent of neuromuscular fatigue during a prolonged graded run. This suggests that no ideal running foot-strike pattern exists to minimize neuromuscular fatigue during prolonged-duration races wherein cumulative uphill and downhill segments are high, such as in trail running.

UNASSIGNED: Trail running is an emerging discipline with relatively few studies performed in ecological conditions. The aim of this work was to investigate if and how spatiotemporal parameters (STP) and kinematics differ between initial and final stage of a field trial.
UNASSIGNED: Twenty trail runners (10 F, 10 M) were recruited and ran a solo 9.1 km trial. During the test, participants wore a GPS watch and an IMU-based motion capture system. Running speed, elapsed time, STP and kinematics were compared between initial and final stage, separately for uphill (UH) and downhill (DH) sections.
UNASSIGNED: Running speed decreased in the final stage ( p < 0.05 ). Total test time was more correlated to the time elapsed in UH sections. In the final stage and in both UH and DH sections, contact time and duty factor increased, whilst stride length and flight time decreased ( p < 0.05 ). In the final stage, ankle joint was more dorsiflexed in stance and swing phases in UH sections and stance phase only in DH sections ( p < 0.05 ). In the final stage, knee joint was less extended in swing phase in UH and DH sections, as well as less extended in stance in UH sections ( p < 0.05 ). In the final stage, hip joint was less flexed in the swing phase in UH and DH sections ( p < 0.05 ). In the final stage, forward trunk lean was higher across the entire gait cycle in in UH sections ( p < 0.05 ). Trunk contralateral axial rotation was lower, in DH sections ( p < 0.05 ).
UNASSIGNED: During the final stage, results indicate a less efficient propulsion phase, in both UH and DH sections. In UH sections, results suggest lower energy generation at the ankle joint. In DH sections, results suggest that the kinematics of swing leg may play a role in sub-optimizing propulsion phase. This study demonstrates how, in UH and DH sections, similar changes in spatiotemporal parameters can be elicited by dissimilar changes in running kinematics. To optimize performance in trail running, coaches and practitioners are advised to work on different (incline-specific) aspects of running technique.

UNASSIGNED: Trail running is a popular off-road sport involving running in natural environments over various terrains, often in remote locations. This study aims to investigate the epidemiology and risk factors of injuries and illnesses, i.e. medical encounters, on race day among trail runners in a high-altitude ultra trail race.
UNASSIGNED: This descriptive cross-sectional study on an ultra trail race (38 km, 65 km and 100 km) in South Africa, included participants 18 years or older. Of the 331 race participants, 285(86.1%) consented to participate in the study. Data collection included demographic details, injuries (body region, specific body area, tissue type, pathology) and illnesses (organ system, symptom cluster, etiology). Risk factor analysis includes sex, age, weight, height, race distance, illness and injury history, training and running experience. Frequency (n, %), prevalence (%) and odds ratios (OR; 95%CI) are reported.
UNASSIGNED: Eighty-nine (31.2%) individuals reported 131 medical encounters [49 injuries (37.4%); 82 illnesses (62.6%)]. Injuries were sustained by 14.7% of athletes, and 22.5% reported illnesses. For injuries, the lower limb was mainly involved (n = 41; 83.7%). Most injuries affected the foot (n = 18; 36.7%), ankle (n = 10; 20.4%) and knee (n = 7; 14.3%). Tissue types mainly involved skin (n = 21; 42.8%), ligament (n = 7; 14.3%) and muscle (n = 7; 14.3%). Multiple (n = 45; 54.9%) and gastrointestinal (n = 17; 20.7%) organ systems were mainly involved in illnesses. Only 100 km runners reported dehydration (n = 28; 31.5%), and one in every six of these runners (n = 5; 17.9%) did not finish. Runners reporting fatigue (n = 21; 23.6%) had a high (n = 8; 38.1%) did not finish rate. Two in every five participants (n = 36; 40.4%) with a medical encounter, did not finish. No medical encounter-associated risk factors were identified.
UNASSIGNED: Illnesses were more common than injuries during the mountainous ultra trail race. Sustaining a medical encounter increased the chance of not completing the race. Further research on the epidemiology of race day medical encounters in trail running is required.

There is a prominent sex-based difference in athletic performance such that males outperform females by 7%-14% in races from 100 m to marathon. In ultramarathons, the difference is often much smaller, leading to speculation that females are \"built\" for the sport. However, data are confounded by the low number of female participants; just 10%-30% in any given race. This study compared data from two ultramarathons where males and females competed in comparable numbers. There were 116 and 146 starters in the 50 mile and 100 mile races, respectively (52% female). Finish times were compared using t tests or Mann-Whitney U tests, a Chi-squared test of independence examined the relationship between sex and ranking, and multivariable linear regressions examined relationships between sex, age, and finish time. There were 96 finishers in the 50 mile race (46% female) and 91 finishers in the 100 mile race (45% female). The median finish time for 50 miles was 12.64 ± 2.11 h with no difference between sexes (1.2%, p = 0.441). However, the top-10 males finished the race ∼85 min faster than the top-10 females (13.8%, p = 0.045). The mean finish time for 100 miles was 31.58 ± 3.36 h with no difference between sexes (3.2%, p = 0.132) and no difference between the top-10 males and top-10 females (4.4%, p = 0.150). Linear and multivariable regression models using sex and age were unable to predict overall finish time in either race. In conclusion, the sex-based performance discrepancy shrinks to 1%-3% in ultramarathons when males and females compete in comparable numbers. Top-performing males still retain a considerable advantage over shorter distances.

The Xsens Link motion capture suit has become a popular tool in investigating 3D running kinematics based on wearable inertial measurement units outside of the laboratory. In this study, we investigated the reliability of Xsens-based lower extremity joint angles during unconstrained running on stable (asphalt) and unstable (woodchip) surfaces within and between five different testing days in a group of 17 recreational runners (8 female, 9 male). Specifically, we determined the within-day and between-day intraclass correlation coefficients (ICCs) and minimal detectable changes (MDCs) with respect to discrete ankle, knee, and hip joint angles. When comparing runs within the same day, the investigated Xsens-based joint angles generally showed good to excellent reliability (median ICCs > 0.9). Between-day reliability was generally lower than the within-day estimates: Initial hip, knee, and ankle angles in the sagittal plane showed good reliability (median ICCs > 0.88), while ankle and hip angles in the frontal plane showed only poor to moderate reliability (median ICCs 0.38-0.83). The results were largely unaffected by the surface. In conclusion, within-day adaptations in lower-extremity running kinematics can be captured with the Xsens Link system. Our data on between-day reliability suggest caution when trying to capture longitudinal adaptations, specifically for ankle and hip joint angles in the frontal plane.

BACKGROUND: In recent decades the number of endurance events has increased, as well as the number of athletes participating in them. Adequate nutritional and water planning is essential to maintain optimal sports performance and to reduce the incidence of gastrointestinal problems. The main objective of this study is to determine the dietary intake and compliance with nutritional recommendations of athletes in two endurance competitions, as well as to assess the incidence of gastrointestinal complaints.
METHODS: An observational and cross-sectional study was carried out on the consumption of liquids, food, and supplements in 42 triathletes and mountain runners (MRs) participating in a Vi-Half-Gasteiz triathlon and the Ultra Sierra de Cazorla trail run. At the completion of the trials, participants completed a validated questionnaire (NIQEC).
RESULTS: The mean caloric intake during the test of the participants in this study was 192.17 kcal/h, while the mean carbohydrate intake was 43.67 g/h, the mean sodium intake was 267.43 mg/h, and the mean caffeine intake was 15.53 mg/h, with no significant differences between the two sports. The amount of liquids consumed by the participants was 421.21 mL/h, with no significant differences between the triathletes and MRs. As for gastrointestinal problems, it was observed that the participants presented gastrointestinal discomfort in 61.9% of the cases.
CONCLUSIONS: The intakes of energy, carbohydrates, water, sodium, and caffeine were lower than the current recommendations. There were no differences in the energy, carbohydrate, water, sodium, and caffeine intakes between the triathletes and mountain runners. Gastrointestinal problems showed a high prevalence in these athletes.

OBJECTIVE: To examined the time-course of the early and late phase of the rate of voluntary force development (RVFD) and muscle damage markers after downhill running.
METHODS: Ten recreational runners performed a 30-min downhill run at 10 km h-1 and -20% (-11.3°) on a motorized treadmill. At baseline and each day up to 4 days RVFD, knee extensors maximum voluntary isometric force (MVIC), serum creatine kinase (CK) concentration, quadriceps swelling, and soreness were assessed. The early (0-50 ms) and late (100-200 ms) phase of the RVFD, as well as the force developed at 50 and 200 ms, were also determined.
RESULTS: MVIC showed moderate decrements (p < 0.05) and recovered after 4 days (p > 0.05). Force at 50 ms and the early phase were not impaired (p > 0.05). Conversely, force at 200 ms and the late phase showed moderate decrements (p < 0.05) and recovered after 3 and 4 days, respectively (p > 0.05). CK concentration, quadriceps swelling, and soreness increased (p < 0.05) were overall fully resolved after 4 days (p > 0.05).
CONCLUSIONS: Downhill running affected the knee extensors RVFD late but not early phase. The RVFD late phase may be used as an additional marker of muscle damage in trail running.

New and promising variables are being developed to analyze performance and fatigue in trail running, such as mechanical power, metabolic power, metabolic cost of transport and mechanical efficiency. The aim of this study was to analyze the behavior of these variables during a real vertical kilometer field test. Fifteen trained trail runners, eleven men (from 22 to 38 years old) and four women (from 19 to 35 years old) performed a vertical kilometer with a length of 4.64 km and 835 m positive slope. During the entire race, the runners were equipped with portable gas analyzers (Cosmed K5) to assess their cardiorespiratory and metabolic responses breath by breath. Significant differences were found between top-level runners versus low-level runners in the mean values of the variables of mechanical power, metabolic power and velocity. A repeated-measures ANOVA showed significant differences between the sections, the incline and the interactions between all the analyzed variables, in addition to differences depending on the level of the runner. The variable of mechanical power can be statistically significantly predicted from metabolic power and vertical net metabolic COT. An algebraic expression was obtained to calculate the value of metabolic power. Integrating the variables of mechanical power, vertical velocity and metabolic power into phone apps and smartwatches is a new opportunity to improve performance monitoring in trail running.

OBJECTIVE: Determine and compare the epidemiology, clinical characteristics, and injury severity among race entrants training towards different ultra-trail race distances.
METHODS: Retrospective cross-sectional study.
METHODS: The six months training period before the 2022 Mac Ultra races (46 km, 80 km, 161 km and 322 km).
METHODS: Of the 245 race entrants, 162 (66% of Mac ultra-trail runners) consented to analyse their data.
METHODS: Injury rate (injuries per 1000 h of running), point prevalence (% of currently injured participants), injury severity (time loss), and the frequency (n, %) of injuries reported during pre-race medical screening in the six months before the race. Using inferential statistics, we compared the injury rates between the different race distance categories (46 km, 80 km, 161 km, 322 km). All tests were performed at a 5% level of significance.
RESULTS: We reported a statistically significantly higher injury rate among 46 km study participants (3.09 injuries per 1000 h) compared to the injury rates reported among 80 km (0.68 injuries per 1000 h; p = 0.001) and 161 km (1.09 injuries per 1000 h; p = 0.028) participants. The lower limb (89%) was the most injured anatomical region, with only 46 km study participants reporting upper limb, trunk, and head injuries (11%). Muscle/tendon was the most reported injured tissue type (56%), with muscle injuries (31%) the most reported pathology type. Shorter distance ultra-trail runners reported the highest injury severity.
CONCLUSIONS: Ultra-trail runners training towards shorter ultra-trail distance races presented with a higher injury rate, more diverse injury profile, and a higher injury severity.

Trail running is an emerging discipline with few studies performed in ecological conditions. The aim of this work was to investigate if and how biomechanics differ between more proficient (MP) and less proficient (LP) trail runners. Twenty participants (10 F) were recruited for a 9.1 km trail running time trial wearing inertial sensors. The MP athletes group was composed of the fastest five men and the fastest five women. Group differences in spatiotemporal parameters and leg stiffness were tested with the Mann-Whitney U-test. Group differences in joint angles were tested with statistic parametric mapping. The finish time was 51.1 ± 6.3 min for the MP athletes and 60.0 ± 5.5 min for the LP athletes (p < 0.05). Uphill sections: The MP athletes expressed a tendency to higher speed that was not significant (p > 0.05), achieved by combining higher step frequency and higher step length. They showed a tendency to shorter contact time, lower duty factor and longer flight time that was not significant (p > 0.05) as well as significantly lower knee flexion during the stance phase (p < 0.05). Downhill sections: The MP athletes achieved significantly higher speed (p < 0.05) through higher step length only. They showed significantly higher knee and hip flexion during the swing phase as well as higher trunk rotation and shoulder flexion during the stance phase (p < 0.05). No differences were found with respect to leg stiffness in the uphill or downhill sections (p > 0.05). In the uphill sections, the results suggest lower energy absorption and more favorable net mechanical work at the knee joint for the MP athletes. In the downhill sections, the results suggest that the more efficient motion of the swing leg in the MP athletes could increase momentum in the forward direction and full body center of mass\' velocity at toe off, thus optimizing the propulsion phase.