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Simon J. de Waal, Josu Gomez-Ezeiza, Rachel E. Venter, and Robert P. Lamberts

Purpose: To provide a systematic overview of physiological parameters used to determine the training status of a trail runner and how well these parameters correlate with real-world trail running performance. Method: An electronic literature search of the PubMed and Scopus digital databases was performed. Combinations of the terms “trail run” or “trail runner” or “trail running” and “performance” were used as search terms. Seven studies met the inclusion criteria. Results: Trail running performance most commonly correlated (mean [SD]) with maximal aerobic capacity (71%; r = −.50 [.32]), lactate threshold (57%; r = −.48 [.28]), velocity at maximal aerobic capacity (43%; r = −.68 [.08]), running economy (43%; r = −.31 [.22]), body fat percentage (43%; r = .55 [.21]), and age (43%; r = .52 [.14]). Regression analyses in 2 studies were based on a single variable predicting 48% to 60% of performance variation, whereas 5 studies included multiple variable regression analyses predicting 48% to 99% of performance variation. Conclusions: Trail running performance is multifaceted. The classic endurance model shows a weaker association with performance in trail running than in road running. Certain variables associated with trail running research (such as testing procedures, race profiles, and study participants) hinder the execution of comparative studies. Future research should employ trail-specific testing protocols and clear, objective descriptions of both the race profile and participants’ training status.

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Dale R. Wagner and James D. Cotter

Ultrasound is an appealing tool to assess body composition, combining the portability of a field method with the accuracy of a laboratory method. However, unlike other body composition methods, the effect of hydration status on validity is unknown. This study evaluated the impact of acute hydration changes on ultrasound measurements of subcutaneous fat thickness and estimates of body fat percentage. In a crossover design, 11 adults (27.1 ± 10.5 years) completed dehydration and hyperhydration trials to alter body mass by approximately ±2%. Dehydration was achieved via humid heat (40 °C, 60% relative humidity) with exercise, whereas hyperhydration was via ingestion of lightly salted water. Ultrasound measurements were taken at 11 body sites before and after each treatment. Participants lost 1.56 ± 0.58 kg (−2.0 ± 0.6%) during the dehydration trial and gained 0.90 ± 0.21 kg (1.2 ± 0.2%) during the hyperhydration trial even after urination. The sum of fat thicknesses as measured by ultrasound differed by <0.90 mm across trials (p = .588), and ultrasound estimates of body fat percentage differed by <0.5% body fat. Ultrasound measures of subcutaneous adipose tissue were unaffected by acute changes in hydration status by extents beyond which are rare and overtly self-correcting, suggesting that this method provides reliable and robust body composition results even when subjects are not euhydrated.

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Marco Beato, Sergio Maroto-Izquierdo, Anthony N. Turner, and Chris Bishop

Due to the negative effects that injuries have on performance, club finances, and long-term player health (permanent disability after a severe injury), prevention strategies are an essential part of both sports medicine and performance. Purpose: To summarize the current evidence regarding strength training for injury prevention in soccer and to inform its evidence-based implementation in research and applied settings. Conclusions: The contemporary literature suggests that strength training, proposed as traditional resistance, eccentric, and flywheel training, may be a valid method to reduce injury risk in soccer players. Training strategies involving multiple components (eg, a combination of strength, balance, plyometrics) that include strength exercises are effective at reducing noncontact injuries in female soccer players. In addition, the body of research currently published supports the use of eccentric training in sports, which offers unique physiological responses compared with other resistance exercise modalities. It seems that the Nordic hamstring exercise, in particular, is a viable option for the reduction of hamstring injuries in soccer players. Moreover, flywheel training has specific training peculiarities and advantages that are related to the combination of both concentric and eccentric contraction, which may play an important role in injury prevention. It is the authors’ opinion that strength and conditioning coaches should integrate the strength training methods proposed here in their weekly training routine to reduce the likelihood of injuries in their players; however, further research is needed to verify the advantages and disadvantages of these training methods to injury prevention using specific cohorts of soccer players.

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Jose A. Rodríguez-Marroyo, Beltrán González, Carl Foster, Ana Belén Carballo-Leyenda, and José G. Villa

Purpose: This study investigated the effect of cooldown modality (active vs passive) and duration (5, 10, and 15 min) on session rating of perceived exertion (sRPE). Secondarily, the possible influence of training sessions’ demand on this effect was studied. Methods: A total of 16 youth male soccer players (15.7 [0.4] y) completed 2 standardized training sessions per week across 6 weeks. During weeks 1 to 2, 3 to 4, and 5 to 6, cooldown lengths of 15, 10, and 5 minutes were studied, respectively. Using a crossover design, players were randomly assigned to 2 groups and each group performed 1 of 2 different cooldown interventions. Passive and active cooldown interventions based on static stretching and running exercises were studied. Heart rate and sRPE were recorded during all training sessions. Results: The lowest sRPE was observed when passive cooldown was performed. When the hardest training sessions were considered, a significant main effect of cooldown modality (P < .01) and duration (P < .05) and an interaction effect between these variables (P < .05) on sRPE were obtained. The lowest (P < .01) sRPE was observed during the longest cooldown (15 min). Conclusion: The findings suggest that sRPE may be sensitive to the selected cooldown modality and duration, especially following the most demanding training sessions.

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Grégoire P. Millet, Rosalie Trigueira, Frédéric Meyer, and Marcel Lemire

Aims: It has been hypothesized that altitude training may alter running mechanics due to several factors such as the slower training velocity with associated alteration in muscle activation and coordination. This would lead to an altered running mechanics attested by an increase in mechanical work for a given intensity and to the need to “re-establish” the neuromuscular coordination and running biomechanics postaltitude. Therefore, the present study aimed to test the hypothesis that “live high—train high” would induce alteration in the running biomechanics (ie, longer contact time, higher vertical oscillations, decreased stiffness, higher external work). Methods: Before and 2 to 3 days after 3 weeks of altitude training (1850–2200 m), 9 national-level middle-distance (800–5000 m) male runners performed 2 successive 5-minute bouts of running at moderate intensity on an instrumented treadmill with measured ground reaction forces and gas exchanges. Immediately after the running trials, peak knee extensor torque was assessed during isometric maximal voluntary contraction. Results: Except for a slight (−3.0%; P = .04) decrease in vertical stiffness, no mechanical parameters (stride frequency and length, contact and flight times, ground reaction forces, and kinetic and potential work) were modified from prealtitude to postaltitude camp. Running oxygen cost was also unchanged. Discussion: The present study is the first one to report that “live high—train high” did not change the main running mechanical parameters, even when measured immediately after the altitude camp. This result has an important practical implication: there is no need for a corrective period at sea level for “normalizing” the running mechanics after an altitude camp.

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Reuben G. Stables, Andreas M. Kasper, S. Andy Sparks, James P. Morton, and Graeme L. Close

The remote food photography method, often referred to as “Snap-N-Send” by sport nutritionists, has been reported as a valid method to assess energy intake in athletic populations. However, preliminary studies were not conducted in true free-living conditions, and dietary assessment was performed by one researcher only. The authors, therefore, assessed the validity of Snap-N-Send to assess the energy and macronutrient composition in experienced (EXP, n = 23) and inexperienced (INEXP, n = 25) sport nutritionists. The participants analyzed 2 days of dietary photographs, comprising eight meals. Day 1 consisted of “simple” meals based around easily distinguishable foods (i.e., chicken breast and rice), and Day 2 consisted of “complex” meals, containing “hidden” ingredients (i.e., chicken curry). The estimates of dietary intake were analyzed for validity using one-sample t tests and typical error of estimates (TEE). The INEXP and EXP nutritionists underestimated energy intake for the simple day (mean difference [MD] = −1.5 MJ, TEE = 10.1%; −1.2 MJ, TEE = 9.3%, respectively) and the complex day (MD = −1.2 MJ, TEE = 17.8%; MD = −0.6 MJ, 14.3%, respectively). Carbohydrate intake was underestimated by INEXP (MD = −65.5 g/day, TEE = 10.8% and MD = −28.7 g/day, TEE = 24.4%) and EXP (MD = −53.4 g/day, TEE = 10.1% and −19.9 g/day, TEE = 17.5%) for both the simple and complex days, respectively. Interpractitioner reliability was generally “poor” for energy and macronutrients. The data demonstrate that the remote food photography method/Snap-N-Send underestimates energy intake in simple and complex meals, and these errors are evident in the EXP and INEXP sport nutritionists.

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Eurico P. César, Cleito S.R. Júnior, and Raphael N. Francisco

Purpose: To compare the effect of static stretching (SS) and cold-water immersion (CWI) on strength performance and blood lactate levels of jiu-jitsu athletes. Methods: A total of 21 male Brazilian jiu-jitsu fighters were randomly assigned to SS (9 × 30-s carpal extension), CWI (3 × 3 min at 10°C), or a control group (CG); their maximal handgrip strength, handgrip muscle endurance, dynamic kimono grip strength test, and blood lactate concentration were assessed before and after a simulated Brazilian jiu-jitsu fight and after one of the recovery interventions. Results: There was an interaction (F = 9.075; P = .002) and a time effect (F = 11.792; P = .003) for dynamic kimono grip strength test, showing a decrease in performance for the CG (P = .0001; effect size [ES] = 0.52, moderate) and after SS (P = .006; ES = 0.43, small). There was an interaction (F = 3.592; P = .015) and a time effect (F = 122.631; P = .0001) for blood lactate concentration, showing lower levels after CWI versus CG (P = .028; ES = 0.93, moderate) and after CWI versus SS (P = .042; ES = 0.82, moderate). There was an interaction (F = 9.617; P = .001) for handgrip strength, showing an impairment in performance after SS (P = .001; ES = 0.67, moderate). Conclusion: CWI promoted restoration of muscle strength and endurance and reduction in blood lactate levels after the simulated fight and can thus be used by jiu-jitsu athletes as a recovery strategy between fights.

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Diogo V. Leal, Lee Taylor, and John Hough

Purpose: Physical overexertion can lead to detrimental overreaching states without sufficient recovery, which may be identifiable by blunted exercise-induced cortisol and testosterone responses. A running test (RPETP) elicits reproducible plasma cortisol and testosterone elevations (in a healthy state) and may detect blunted hormonal responses in overreached athletes. This current study determined the salivary cortisol and testosterone responses reproducibility to the RPETP, to provide greater practical validity using saliva compared with the previously utilized blood sampling. Second, the relationship between the salivary and plasma responses was assessed. Methods: A total of 23 active, healthy males completed the RPETP on 3 occasions. Saliva (N = 23) and plasma (N = 13) were collected preexercise, postexercise, and 30 minutes postexercise. Results: Salivary cortisol did not elevate in any RPETP trial, and reduced concentrations occurred 30 minutes postexercise (P = .029, η 2 = .287); trial differences were observed (P < .001, η 2 = .463). The RPETP elevated (P < .001, η 2 = .593) salivary testosterone with no effect of trial (P = .789, η 2 = .022). Intraindividual variability was 25% in cortisol and 17% in testosterone. “Fair” intraclass coefficients of .46 (cortisol) and .40 (testosterone) were found. Salivary and plasma cortisol positively correlated (R = .581, P = .037) yet did not for testosterone (R = .345, P = .248). Conclusions: The reproducibility of salivary testosterone response to the RPETP is evident and supports its use as a potential tool, subject to further confirmatory work, to detect hormonal dysfunction during overreaching. Salivary cortisol responds inconsistently in a somewhat individualized manner to the RPETP.

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Ryan Anthony, Michael J. Macartney, and Gregory E. Peoples

Delayed onset muscle soreness (DOMS) following eccentric exercise is associated with increased inflammation which can be debilitating. Incorporation of long-chain omega-3 polyunsaturated fatty acids (LC n-3 PUFA), eicosapentaenoic acid, and docosahexaenoic acid into membrane phospholipids provides anti-inflammatory, proresolving, and analgesic effects. This systematic review aims to examine both the quality of studies and the evidence for LC n-3 PUFA in the attenuation of DOMS and inflammation following eccentric exercise, both which of course are empirically linked. The Scopus, Embase, and Web of Science electronic databases were searched to identify studies that supplemented fish oil for a duration of ≥7 days, which included DOMS outcomes following an eccentric exercise protocol. Fifteen (n = 15) studies met inclusion criteria. Eccentric exercise protocols varied from single to multijoint activities. Risk of bias, assessed using either the Cochrane Collaboration tool or the Risk of Bias in Nonrandomized Studies of Interventions tool, was judged as “unclear” or “medium,” respectively, for the majority of outcomes. Furthermore, a custom 5-point quality assessment scale demonstrated that only one (n = 1) study satisfied current recommendations for investigating LC n-3 PUFA. In combination, this highlights widespread inappropriate design protocols among studies investigating the role of LC n-3 PUFA in eccentric exercise. Notwithstanding these issues, LC n-3 PUFA supplementation appears to have favorable effects on eccentric exercise-induced DOMS and inflammatory markers. However, the optimal LC n-3 PUFA supplemental dose, duration, and fatty acid composition will only become clear when study design issues are rectified and underpinned by appropriate hypotheses.

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Andrew N. Bosch, Kirsten C. Flanagan, Maaike M. Eken, Adrian Withers, Jana Burger, and Robert P. Lamberts

Elliptical trainers and steppers are proposed as useful exercise modalities in the rehabilitation of injured runners due to the reduced stress on muscles and joints when compared to running. This study compared the physiological responses to submaximal running (treadmill) with exercise on the elliptical trainer and stepper devices at three submaximal but identical workloads. Authors had 18 trained runners (male/female: N = 9/9, age: mean ± SD = 23 ± 3 years) complete randomized maximal oxygen consumption tests on all three modalities. Submaximal tests of 3 min were performed at 60%, 70%, and 80% of peak workload individually established for each modality. Breath-by-breath oxygen consumption, heart rate, fuel utilization, and energy expenditure were determined. The value of maximal oxygen consumption was not different between treadmill, elliptical, and stepper (49.3 ± 5.3, 48.0 ± 6.6, and 46.7 ± 6.2 ml·min−1·kg−1, respectively). Both physiological measures (oxygen consumption and heart rate) as well as carbohydrate and fat oxidation differed significantly between the different exercise intensities (60%, 70%, and 80%) but did not differ between the treadmill, elliptical trainer, and stepper. Therefore, the elliptical trainer and stepper are suitable substitutes for running during periods when a reduced running load is required, such as during rehabilitation from running-induced injury.