Browse

You are looking at 1 - 10 of 5,244 items for :

  • Physical Education and Coaching x
  • Sport and Exercise Science/Kinesiology x
Clear All
Full access

Alannah K.A. McKay, Peter Peeling, David B. Pyne, Nicolin Tee, Marijke Welveart, Ida A. Heikura, Avish P. Sharma, Jamie Whitfield, Megan L. Ross, Rachel P.L. van Swelm, Coby M. Laarakkers and Louise M. Burke

This study implemented a 2-week high carbohydrate (CHO) diet intended to maximize CHO oxidation rates and examined the iron-regulatory response to a 26-km race walking effort. Twenty international-level, male race walkers were assigned to either a novel high CHO diet (MAX = 10 g/kg body mass CHO daily) inclusive of gut-training strategies, or a moderate CHO control diet (CON = 6 g/kg body mass CHO daily) for a 2-week training period. The athletes completed a 26-km race walking test protocol before and after the dietary intervention. Venous blood samples were collected pre-, post-, and 3 hr postexercise and measured for serum ferritin, interleukin-6, and hepcidin-25 concentrations. Similar decreases in serum ferritin (17–23%) occurred postintervention in MAX and CON. At the baseline, CON had a greater postexercise increase in interleukin-6 levels after 26 km of walking (20.1-fold, 95% CI [9.2, 35.7]) compared with MAX (10.2-fold, 95% CI [3.7, 18.7]). A similar finding was evident for hepcidin levels 3 hr postexercise (CON = 10.8-fold, 95% CI [4.8, 21.2]; MAX = 8.8-fold, 95% CI [3.9, 16.4]). Postintervention, there were no substantial differences in the interleukin-6 response (CON = 13.6-fold, 95% CI [9.2, 20.5]; MAX = 11.2-fold, 95% CI [6.5, 21.3]) or hepcidin levels (CON = 7.1-fold, 95% CI [2.1, 15.4]; MAX = 6.3-fold, 95% CI [1.8, 14.6]) between the dietary groups. Higher resting serum ferritin (p = .004) and hotter trial ambient temperatures (p = .014) were associated with greater hepcidin levels 3 hr postexercise. Very high CHO diets employed by endurance athletes to increase CHO oxidation have little impact on iron regulation in elite athletes. It appears that variations in serum ferritin concentration and ambient temperature, rather than dietary CHO, are associated with increased hepcidin concentrations 3 hr postexercise.

Open access
Restricted access

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.

Restricted access

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.

Restricted access

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.

Restricted access

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.

Restricted access

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.

Restricted access

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.