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1.
Repeated-sprint training in the fasted state during Ramadan: morning or evening training?
Aloui, A, Driss, T, Baklouti, H, Jaafar, H, Hammouda, O, Chamari, K, Souissi, N
The Journal of sports medicine and physical fitness. 2018;(7-8):990-997
Abstract
BACKGROUND The present study assessed the optimal moment of the day for repeated-sprint training in the fasted state during Ramadan. METHODS Thirty amateur soccer players were randomly assigned to a morning training group (MTG, training at ~08:00 a.m., N.=10), an evening training group (ETG, training around 06:00 p.m., N.=10), and a control group (N.=10). Training sessions, conducted on alternate days, consisted of 3 sets of 6×40-m shuttle sprints (2×20 m with 180° direction changes). A 20-second passive recovery and a 4-minute passive recovery were allowed between repetitions and sets, respectively. Before and after Ramadan, performance was assessed at both 08:00 a.m. and 06:00 p.m. by Countermovement Jump (CMJ), Repeated-Sprint Test (RST), and Yo-Yo Intermittent Recovery Test Level 1 (YYIRT1). RESULTS After Ramadan, YYIRT1 performances were enhanced for both groups in the morning (7.82% and 6.29% for MTG and ETG, respectively, P<0.05), and in the evening (6.61% and 11.20%, respectively, P<0.05). Relative changes in YYIRT1 (P=0.33) and RST (-2.13% and -3.44% for MTG and ETG, respectively, P=0.49) at the specific time of training were similar for both groups. No differences were observed in CMJ performances before and after Ramadan for any group (P>0.05). CONCLUSIONS Morning or evening repeated-sprint training conducted in the fasted state during Ramadan enhanced soccer-specific endurance similarly.
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2.
Differences in Knee and Hip Adduction and Hip Muscle Activation in Runners With and Without Iliotibial Band Syndrome.
Baker, RL, Souza, RB, Rauh, MJ, Fredericson, M, Rosenthal, MD
PM & R : the journal of injury, function, and rehabilitation. 2018;(10):1032-1039
Abstract
BACKGROUND Iliotibial band syndrome has been associated with altered hip and knee kinematics in runners. Previous studies have recommended further research on neuromuscular factors at the hip. The frontal plane hip muscles have been a strong focus in strength comparison but not for electromyography investigation. OBJECTIVE To compare hip surface electromyography, and frontal plane hip and knee kinematics, in runners with and without iliotibial band syndrome. DESIGN Observational cross-sectional study. SETTING Biomechanics research laboratory within a university. PARTICIPANTS Thirty subjects were recruited consisting of 15 injured runners with iliotibial band syndrome and 15 gender-, age-, and body mass index-matched controls. In each group, 8 were male runners and 7 were female runners. Inclusion criteria for the injured group were pain within 2 months related to iliotibial band syndrome and a positive Noble compression test. Participants were excluded if they reported other lower extremity diagnoses within the last year or active lower extremity or low back pain not related to iliotibial band syndrome. Controls were excluded if they reported a history of iliotibial band syndrome. Convenience sampling was used based on referrals from local running clinics and orthopedic clinics. METHODS Three-dimensional motion capture was performed with 10 high-speed cameras synchronized with wireless surface electromyography during a 30-minute run. The first data point was at 3 minutes, using a constant speed of 2.74 meters per second. A second data point was at 30 minutes, using a self-selected pace by the participant to allow for a challenging run until completion at 30 minutes. MAIN OUTCOME MEASUREMENTS Motion capture was reported as peak kinematic values from heel strike to peak knee flexion for hip adduction and knee adduction. Surface electromyography was reported as a percentage of maximal voluntary contraction for the gluteus maximus, gluteus medius and tensor fascia latae muscles. RESULTS Injured runners demonstrated increased knee adduction compared with control runners at 30 minutes (P = .002, control = -1.48°, injured = 3.74°). Tensor fasciae latae muscle activation in injured runners was increased compared with control runners at 3 minutes (P = .017, control = 7% maximal voluntary isometric contraction, injured = 11% maximal voluntary isometric contraction). CONCLUSION The results of this study suggest that lateral knee pain in runners localized to the distal iliotibial band is associated with increased knee adduction at 30 minutes. Increased tensor fasciae latae muscle activation at 3 minutes is noted, but more investigation is needed to better understand the clinical meaning. These findings are consistent with but not conclusive evidence supporting the theory that neuromuscular factors of the hip muscles may contribute to increased knee adduction in runners with iliotibial band syndrome. We advise caution using these findings to support treatments intended to modify tensor fasciae latae activation, given the small differences of 4% in muscle activation. Increased knee adduction in runners at 30 minutes was over 5° and beyond the minimal detectable difference. Additional research is needed to confirm whether the degree of knee adduction changes earlier versus later in a run and whether fatigue is a clinically relevant factor. LEVEL OF EVIDENCE III.
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3.
Acute Ingestion of Caffeinated Chewing Gum Improves Repeated Sprint Performance of Team Sport Athletes With Low Habitual Caffeine Consumption.
Evans, M, Tierney, P, Gray, N, Hawe, G, Macken, M, Egan, B
International journal of sport nutrition and exercise metabolism. 2018;(3):221-227
Abstract
The effects of acute ingestion of caffeine on short-duration high-intensity performance are equivocal, while studies of novel modes of delivery and the efficacy of low doses of caffeine are warranted. The aims of the present study were to investigate the effect of acute ingestion of caffeinated chewing gum on repeated sprint performance (RSP) in team sport athletes, and whether habitual caffeine consumption alters the ergogenic effect, if any, on RSP. A total of 18 male team sport athletes undertook four RSP trials using a 40-m maximum shuttle run test, which incorporates 10 × 40-m sprints with 30 s between the start of each sprint. Each participant completed two familiarization sessions, followed by caffeine (CAF; caffeinated chewing gum; 200 mg caffeine) and placebo (PLA; noncaffeinated chewing gum) trials in a randomized, double-blind manner. RSP, assessed by sprint performance decrement (%), did not differ (p = .209; effect size = 0.16; N = 18) between CAF (5.00 ± 2.84%) and PLA (5.43 ± 2.68%). Secondary analysis revealed that low habitual caffeine consumers (<40 mg/day, n = 10) experienced an attenuation of sprint performance decrement during CAF relative to PLA (5.53 ± 3.12% vs. 6.53 ± 2.91%, respectively; p = .049; effect size =0.33); an effect not observed in moderate/high habitual caffeine consumers (>130 mg/day, n = 6; 3.98 ± 2.57% vs. 3.80 ± 1.79%, respectively; p = .684; effect size = 0.08). The data suggest that a low dose of caffeine in the form of caffeinated chewing gum attenuates the sprint performance decrement during RSP by team sport athletes with low, but not moderate-to-high, habitual consumption of caffeine.
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4.
Carbohydrate mouth rinse does not affect performance during a 60-min running race in women.
Chryssanthopoulos, C, Ziaras, C, Oosthuyse, T, Lambropoulos, I, Giorgios P, P, Zacharogiannis, E, Philippou, A, Maridaki, M
Journal of sports sciences. 2018;(7):824-833
Abstract
This study examined the effect of carbohydrate mouth rinsing on endurance running performance in women. Fifteen female recreational endurance runners, who used no oral contraceptives, ran two races of 1-h duration on an indoor track (216-m length) at 18:00 h after an 8-h fast with a 7-days interval between races, corresponding to the 3rd-10th day of each premenopausal runner's menstrual cycle, or any day for the postmenopausal runners. In a double-blind random order, participants rinsed their mouth with 25 ml of either a 6.4% carbohydrate (RCHO) or a placebo solution (RP). No fluid was ingested during exercise. Serum 17β-Εstradiol (P = 0.59) and Progesterone (P = 0.35) did not differ between treatments. There was no difference in 1-hour running performance (RCHO: 10,621.88 ± 205.98 m vs. RP: 10,454.00 ± 206.64 m; t = 1.784, P = 0.096). Furthermore, the mean percentage effect (±99%CI) of RCHO relative to RP, 1.67% (-1.1% to 4.4%), and Cohen's effect size (d = 0.21) support a trivial outcome of RCHO for total distance covered. In conclusion, carbohydrate mouth rinsing did not improve 60-min track running performance in female recreational runners competing in a low ovarian hormone condition, after an 8-h fast and when no fluid was ingested during exercise.
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5.
The effect of lower limb occlusion on recovery following sprint exercise in academy rugby players.
Williams, N, Russell, M, Cook, CJ, Kilduff, LP
Journal of science and medicine in sport. 2018;(10):1095-1099
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Abstract
OBJECTIVES The effects of vascular occlusion on recovery of physiological and neuromuscular markers over 24h, and hormonal reactivity to subsequent exercise were investigated. DESIGN Counterbalanced, randomised, crossover. METHODS Academy rugby players (n=24) completed six 50-m sprints (5-min inter-set recovery) before occlusion cuff application (thighs) and intermittent inflation to 171-266mmHg (Recovery) or 15mmHg (Con) for 12-min (two sets, 3-min repetitions, 3-min non-occluded reperfusion). Countermovement jumps, blood (lactate, creatine kinase), saliva (testosterone, cortisol), and perceptual (soreness, recovery) responses were measured before (baseline) and after (post, +2h, +24h) sprinting. Saliva was sampled after a 30-min resistance exercise session performed 24h after sprinting. RESULTS Although sprinting (total: 40.0±2.8s, p=0.238; average: 6.7±0.5s, p=0.674) influenced creatine kinase (p<0.001, +457.1±327.3μL-1, at 24h), lactate (p<0.001, 6.8±2.3mmolL-1, post), testosterone (p<0.001, -55.9±63.2pgmL-1, at 2h) and cortisol (p<0.001, -0.3±0.3μgdL-1, at 2h) concentrations, countermovement jump power output (p<0.001, -409.6±310.1W; -5.4±3.4cm, post), perceived recovery (p<0.001, -3.0±2.3, post), and muscle soreness (p<0.001; 1.5±1.1, at 24h), vascular occlusion had no effect (all p>0.05) on recovery. In response to subsequent exercise performed 24h after vascular occlusion, testosterone increased pre-to-post-exercise (Recovery: p=0.031, 21.6±44.9pgmL-1; Con: p=0.178, 10.6±36.6pgmL-1) however Δtestosterone was not significantly different (p=0.109) between conditions. CONCLUSIONS Vascular occlusion had no effect on physiological or neuromuscular markers 2h or 24h after sprinting or in response to a physical stress test.
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Hamstring Injury Prevention Practices in Elite Sport: Evidence for Eccentric Strength vs. Lumbo-Pelvic Training.
Shield, AJ, Bourne, MN
Sports medicine (Auckland, N.Z.). 2018;(3):513-524
Abstract
Hamstring strain injuries are endemic in running-based sports. Given the economic and performance implications of these injuries, a significant body of research has emerged in recent years in an attempt to identify risk factors and develop or optimise injury prevention strategies. Surveys of injury prevention practices among medical and conditioning staff in elite sport suggest that many sporting clubs invest significant efforts in eccentric hamstring conditioning and lumbo-pelvic or trunk stability programmes. The purpose of this narrative review was to critically evaluate the evidence underpinning these practices. Single-exercise eccentric training interventions have proven effective in the prevention of primary and recurrent hamstring strains, when compliance is adequate. However, despite its almost universal acceptance, the authors are aware of only one, very recent, prospective risk factor study examining the effect of lumbo-pelvic motion during sprinting on hamstring injury risk. Furthermore, the interventions exploring the effect of lumbo-pelvic training on hamstring injury rates have not measured stability in any way. An improved understanding of the evidence underpinning commonly employed hamstring injury prevention practices may enable clinicians and coaches to better prioritise effective strategies in the increasingly complex environment of elite sport.
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Energy, macronutrient and water intake during a mountain ultramarathon event: The influence of distance.
Martinez, S, Aguilo, A, Rodas, L, Lozano, L, Moreno, C, Tauler, P
Journal of sports sciences. 2018;(3):333-339
Abstract
Adequate dietary strategies are essential for the successful participation in ultra-endurance races. The aim of this study was to evaluate and compare the energy and water intakes of participants during three different mountain ultra-endurance runs. The study took place at the "Ultra Mallorca Serra de Tramuntana" (Mallorca, Spain), an ultra-endurance mountain event with runners participating either in a 44-km (Marathon, n = 51), a 67-km (Trail, n = 109) or a 112-km (Ultra, n = 53) run competition. Participants in the study answered a questionnaire focused on the nutritional intake within an hour after finishing the competition. Mean energy intake during the competitions was 183 kcal · h¯1, with an average carbohydrate intake of 31 g · h¯1 (52.1% of participants consumed less than 30 g · h¯1). No significant differences between competitions were found in these parameters. However, a higher percentage of energy from lipids in participants in the Trail and the Ultra was found (P = 0.034). Furthermore, significant differences were observed in water intake per hour of competition (P = 0.039), with the lowest value for the intake during the Ultra competition. In conclusion, the majority of the participants in the study present low carbohydrate intakes. However, fluid intake seems to be adequate. Different distances did not significantly influence the participants' nutritional strategies.
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Effects of a 15-Day Low Carbohydrate, High-Fat Diet in Resistance-Trained Men.
Waldman, HS, Krings, BM, Basham, SA, Smith, JEW, Fountain, BJ, McAllister, MJ
Journal of strength and conditioning research. 2018;(11):3103-3111
Abstract
Waldman, HS, Krings, BM, Basham, SA, Smith, JW, Fountain, BJ, and McAllister, MJ. Effects of a 15-day low carbohydrate, high-fat diet in resistance-trained men. J Strength Cond Res 32(11): 3103-3111, 2018-This study examined the effects of a 15-day isocaloric low carbohydrate (<25% E), high-fat (>50% E) (LCHF) diet on physiological and metabolic alterations in resistance-trained (RT) men. College-aged RT men (n = 11) completed 4 V[Combining Dot Above]O2max tests using treadmill every 5 days during the 15-day trial. Blood was drawn intravenously pre-exercise across each experimental trial for insulin, cortisol, and glucose. Pulmonary data were collected and substrate oxidation (OXI) was calculated during exercise. Body mass decreased (p < 0.04) with no further changes in anthropometric measures. Time to exhaustion was not affected across each day. Insulin dropped below baseline values (p < 0.0005). Cortisol increased from baseline to day 5 (p < 0.004) but returned back to near baseline at day 10, whereas glucose remained within normal range throughout the duration of the study. Carbohydrate (CHO) OXI dropped (p < 0.001) from baseline to day 5, and fat OXI increased from baseline to day 5 (p < 0.0001). Heart rate decreased from baseline to day 5 (p < 0.001) and again from day 10 to 15 (p < 0.02). Oxygen uptake (V[Combining Dot Above]O2) decreased from day 5 to 10 (p < 0.0001). A nonketo LCHF diet appears to favor RT men by altering metabolic markers without decrements in aerobic performance and be a potential diet intervention used by coaches. However, the reported cardiorespiratory responses should be interpreted reasonably because of the possibility the subjects running economy improved over experimental trials.
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Postexercise Fructose-Maltodextrin Ingestion Enhances Subsequent Endurance Capacity.
Maunder, E, Podlogar, T, Wallis, GA
Medicine and science in sports and exercise. 2018;(5):1039-1045
Abstract
PURPOSE Restoring skeletal muscle and hepatic glycogen content during short-term (<6 h) recovery from prolonged exercise is pertinent for athletes seeking to maximize performance in repeated exercise bouts. Previous research suggests that coingestion of fructose-glucose carbohydrate sources augments hepatic and has equivalent effects on skeletal muscle glycogen storage during short-term recovery from prolonged exercise compared with isocaloric glucose ingestion. The aim of the present investigation was to determine whether this has a discernible effect on subsequent exercise capacity. METHODS Eight trained endurance runners and triathletes performed two experimental trials in a single-blind, randomized, and counterbalanced crossover design. Trials involved treadmill running to exhaustion at 70% V˙O2max, a 4-h recovery with 90 g·h of glucose-maltodextrin (GLU + MAL) or fructose-maltodextrin (FRU + MAL) ingestion (1:1.5 ratio), and a second bout of treadmill running to exhaustion at 70% V˙O2max. RESULTS Exercise capacity in bout 2 was significantly greater with FRU + MAL (81.4 ± 22.3 vs 61.4 ± 9.6 min, P = 0.02), a large magnitude effect (effect size = 1.84 ± 1.12, 32.4% ± 19.9%). Total carbohydrate oxidation rates were not significantly different during bout 1 or 2 between trials, although total carbohydrate oxidized in bout 2 was significantly greater with FRU + MAL (223 ± 66 vs 157 ± 26 g, P = 0.02). Ingested carbohydrate oxidation rates were greater during bout 2 with FRU + MAL (P = 0.001). Plasma glucose and nonesterified fatty acid concentrations were not significantly different between trials. Plasma lactate concentrations were significantly greater during recovery before bout 2 with FRU + MAL (P = 0.001). Self-reported nausea and stomach fullness during bout 2 were marginally in favor of FRU + MAL. CONCLUSION Short-term recovery of endurance capacity was significantly enhanced with FRU + MAL versus GLU + MAL ingestion during recovery.
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10.
Zinc status at baseline is not related to acute changes in serum zinc concentration following bouts of running or cycling.
Chu, A, Petocz, P, Samman, S
Journal of trace elements in medicine and biology : organ of the Society for Minerals and Trace Elements (GMS). 2018;:105-110
Abstract
Zinc status is implicated in physiological functions related to exercise performance and physical activity. We have previously demonstrated significant changes in serum zinc concentrations following a bout of aerobic exercise, suggestive of a relationship between zinc metabolism and exercise-related functions. In the present study, we aim to determine the association between pre-exercise serum zinc concentration and immediate changes in serum zinc concentration following an aerobic exercise bout. We have previously conducted a systematic literature search of PubMed, Web of Science, Scopus and SPORTDiscus, for studies that investigated the acute effects of aerobic exercise on zinc biomarkers. In the current study, we undertook a secondary analysis using mixed effects meta-regression modelling to determine the relationship between baseline serum zinc concentration and the change in serum zinc concentration immediately after exercise. Meta-regression models revealed no significant relationship between baseline serum zinc concentration and the change in serum zinc concentration following a bout of exercise when all comparisons were included (slope -0.11 ± 0.07 [standard error]; P > 0.05). When comparisons were stratified by exercise modality, no significant relationships were observed for exercise bouts involving cycling or running. The current analyses were limited by the available literature and low statistical power of the meta-regression models. Based on the current available data, the present analysis revealed limited evidence for a relationship between pre-exercise serum zinc concentration and immediate changes in serum zinc levels following a bout of aerobic exercise. Subgroup meta-regression analyses stratified by the mode of exercise bouts did not differ from the overall results. This suggests that zinc status at baseline is not related to acute changes in serum zinc concentration following bouts of aerobic exercise.