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Tiago Turnes, Rafael Penteado dos Santos, Rafael Alves de Aguiar, Thiago Loch, Leonardo Trevisol Possamai and Fabrizio Caputo

Purpose: To compare the intensity and physiological responses of deoxygenated hemoglobin breaking point ([HHb]BP) and anaerobic threshold (AnT) during an incremental test and to verify their association with 2000-m rowing-ergometer performance in well-trained rowers. Methods: A total of 13 male rowers (mean [SD] age = 24 [11] y and V˙O2peak = 63.7 [6.1] mL·kg−1·min−1) performed a step incremental test. Gas exchange, vastus lateralis [HHb], and blood lactate concentration were measured. Power output, V˙O2, and heart rate of [HHb]BP and AnT were determined and compared with each other. A 2000-m test was performed in another visit. Results: No differences were found between [HHb]BP and AnT in the power output (236 [31] vs 234 [31] W; Δ = 0.7%), 95% confidence interval [CI] 6.7%), V˙O2 (4.2 [0.5] vs 4.3 [0.4] L·min−1; Δ = −0.8%, 95% CI 4.0%), or heart rate (180 [16] vs 182 [12] beats·min−1; Δ = −1.6%, 95% CI 2.1%); however, there was high typical error of estimate (TEE) and wide 95% limits of agreement (LoA) for power output (TEE 10.7%, LoA 54.1–50.6 W), V˙O2 (TEE 5.9%, LoA −0.57 to 0.63 L·min−1), and heart rate (TEE 2.4%, LoA −9.6 to 14.7 beats·min−1). Significant correlations were observed between [HHb]BP (r = .70) and AnT (r = .89) with 2000-m mean power. Conclusions: These results demonstrate a breaking point in [HHb] of the vastus lateralis muscle during the incremental test that is capable of distinguishing rowers with different performance levels. However, the high random error would compromise the use of [HHb]BP for training and testing in rowing.

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Alireza Rabbani, Mehdi Kargarfard, Carlo Castagna, Filipe Manuel Clemente and Craig Twist

Purpose: To investigate the relationship between accumulated global positioning system–accelerometer-based and heart rate–based training metrics and changes in high-intensity intermittent-running capacity during an in-season phase in professional soccer players. Methods: Eleven male professional players (mean [SD] age 27.2 [4.5] y) performed the 30-15 Intermittent Fitness Test (30-15IFT) before and after a 5-wk in-season training phase, and the final velocity (VIFT) was considered their high-intensity intermittent-running capacity. During all sessions, Edwards training impulse (Edwards TRIMP), Banister TRIMP, Z5 TRIMP, training duration, total distance covered, new body load (NBL), high-intensity running performance (distance covered above 14.4 km·h−1), and very-high-intensity running performance (distance covered above 19.8 km·h−1) were recorded. Results: The players’ VIFT showed a most likely moderate improvement (+4.3%, 90% confidence limits 3.1–5.5%, effect size 0.70, [0.51–0.89]). Accumulated NBL, Banister TRIMP, and Edwards TRIMP showed large associations (r = .51–.54) with changes in VIFT. A very large relationship was also observed between accumulated Z5 TRIMP (r = .72) with changes in VIFT. Large to nearly perfect within-individual relationships were observed between NBL and some of the other training metrics (ie, Edwards TRIMP, Banister TRIMP, training duration, and total distance) in 10 out of 11 players. Conclusions: Heart rate–based training metrics can be used to monitor high-intensity intermittent-running-capacity changes in professional soccer players. The dose–response relationship is also largely detected using accelerometer-based metrics (ie, NBL) to track changes in high-intensity intermittent-running capacity of professional soccer players.

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Liam Anderson, Graeme L. Close, Matt Konopinski, David Rydings, Jordan Milsom, Catherine Hambly, John Roger Speakman, Barry Drust and James P. Morton

Maintaining muscle mass and function during rehabilitation from anterior cruciate ligament injury is complicated by the challenge of accurately prescribing daily energy intakes aligned to energy expenditure. Accordingly, we present a 38-week case study characterizing whole body and regional rates of muscle atrophy and hypertrophy (as inferred by assessments of fat-free mass from dual-energy X-ray absorptiometry) in a professional male soccer player from the English Premier League. In addition, in Week 6, we also quantified energy intake (via the remote food photographic method) and energy expenditure using the doubly labeled water method. Mean daily energy intake (CHO: 1.9–3.2, protein: 1.7–3.3, and fat: 1.4–2.7 g/kg) and energy expenditure were 2,765 ± 474 and 3,178 kcal/day, respectively. In accordance with an apparent energy deficit, total body mass decreased by 1.9 kg during Weeks 1–6 where fat-free mass loss in the injured and noninjured limb was 0.9 and 0.6 kg, respectively, yet, trunk fat-free mass increased by 0.7 kg. In Weeks 7–28, the athlete was advised to increase daily CHO intake (4–6 g/kg) to facilitate an increased daily energy intake. Throughout this period, total body mass increased by 3.6 kg (attributable to a 2.9 and 0.7 kg increase in fat free and fat mass, respectively). Our data suggest it may be advantageous to avoid excessive reductions in energy intake during the initial 6–8 weeks post anterior cruciate ligament surgery so as to limit muscle atrophy.

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Dennis van Erck, Eric J. Wenker, Koen Levels, Carl Foster, Jos J. de Koning and Dionne A. Noordhof

Background: Although cyclists often compete at altitude, the effect of altitude on gross efficiency (GE) remains inconclusive. Purpose: To investigate the effect of altitude on GE at the same relative exercise intensity and at the same absolute power output (PO) and to determine the effect of altitude on the change in GE during high-intensity exercise. Methods: Twenty-one trained men performed 3 maximal incremental tests and 5 GE tests at sea level, 1500 m, and 2500 m of acute simulated altitude. The GE tests at altitude were performed once at the same relative exercise intensity and once at the same absolute PO as at sea level. Results: Altitude resulted in an unclear effect at 1500 m (−3.8%; ±3.3% [90% confidence limit]) and most likely negative effect at 2500 m (−6.3%; ±1.7%) on pre-GE, when determined at the same relative exercise intensity. When pre-GE was determined at the same absolute PO, unclear differences in GE were found (−1.5%; ±2.6% at 1500 m; −1.7%; ±2.4% at 2500 m). The effect of altitude on the decrease in GE during high-intensity exercise was unclear when determined at the same relative exercise intensity (−0.4%; ±2.8% at 1500 m; −0.7%; ±1.9% at 2500 m). When GE was determined at the same absolute PO, altitude resulted in a substantially smaller decrease in GE (2.8%; ±2.4% at 1500 m; 5.5%; ±2.9% at 2500 m). Conclusion: The lower GE found at altitude when exercise is performed at the same relative exercise intensity is mainly caused by the lower PO at which cyclists exercise.

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Nick Dobbin, Jamie Highton, Samantha L. Moss and Craig Twist

Purpose: To assess whether a standardized testing battery can differentiate anthropometric and physical qualities between youth, academy, and senior rugby league players and determine the discriminant validity of the battery. Methods: A total of 729 rugby league players from multiple clubs in England categorized as youth (n = 235), academy (n = 362), and senior (n = 132) players completed a standardized testing battery that included the assessment of anthropometric and physical characteristics during preseason. Data were analyzed using magnitude-based inferences and discriminant analysis. Results: Academy players were most likely taller and heavier than youth players (effect size [ES] = 0.64–1.21), with possibly to most likely superior countermovement jump, medicine-ball throw, and prone Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo IR1) performance (ES = 0.23–1.00). Senior players were likely to most likely taller and heavier (ES = 0.32–1.84), with possibly to most likely superior 10- and 20-m sprint times, countermovement jump, change of direction, medicine-ball throw, and prone Yo-Yo IR1 than youth and academy players (ES = −0.60 to 2.06). The magnitude of difference appeared to be influenced by playing position. For the most part, the battery possessed discriminant validity with an accuracy of 72.2%. Conclusion: The standardized testing battery differentiates anthropometric and physical qualities of youth, academy, and senior players as a group and, in most instances, within positional groups. Furthermore, the battery is able to discriminate between playing standards with good accuracy and might be included in future assessments and rugby league talent identification.

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Francisco J. Amaro-Gahete, Lucas Jurado-Fasoli, Alejandro R. Triviño, Guillermo Sanchez-Delgado, Alejandro De-la-O, Jørn W. Helge and Jonatan R. Ruiz

Purpose: To analyze the diurnal variation of maximal fat oxidation (MFO) and the intensity that elicits MFO (Fatmax) in trained male athletes. Methods: A total of 12 endurance-trained male athletes age 24.7 (4.1) y participated in the study. The authors measured MFO, Fatmax, maximum oxygen uptake (VO2max), and VO2 percentage at ventilatory threshold 2 with a graded exercise protocol performed on 2 days separated by 1 wk. One test was performed in the morning and the other in the afternoon. The authors assessed the participants’ chronotype using the HÖME questionnaire. Results: MFO and Fatmax were greater in the afternoon than in the morning (Δ = 13%, P < .001 and Δ = 6%, P = .001, respectively), whereas there were similar VO2max and ventilatory threshold 2 in the morning, than in the afternoon test (Δ = 0.2%, P = .158 and Δ = 7%, P = .650, respectively). There was a strong positive association between VO2max and MFO in both morning and afternoon assessments (R 2 = .783, P = .001 and R 2 = .663, P < .001, respectively). Similarly, there was a positive association between VO2max and Fatmax in both morning and afternoon assessments (R 2 = .406, P = .024 and R 2 = .414, P = .026, respectively). Conclusion: MFO and Fatmax may partially explain some of the observed diurnal variation in the performance of endurance sports.

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David M. Shaw, Fabrice Merien, Andrea Braakhuis, Daniel Plews, Paul Laursen and Deborah K. Dulson

This study investigated the effect of the racemic β-hydroxybutyrate (βHB) precursor, R,S-1,3-butanediol (BD), on time-trial (TT) performance and tolerability. A repeated-measures, randomized, crossover study was conducted in nine trained male cyclists (age, 26.7 ± 5.2 years; body mass, 69.6 ± 8.4 kg; height, 1.82 ± 0.09 m; body mass index, 21.2 ± 1.5 kg/m2; VO2peak,63.9 ± 2.5 ml·kg−1·min−1; W max, 389.3 ± 50.4 W). Participants ingested 0.35 g/kg of BD or placebo 30 min before and 60 min during 85 min of steady-state exercise, which preceded a ∼25- to 35-min TT (i.e., 7 kJ/kg). The ingestion of BD increased blood D-βHB concentration throughout exercise (0.44–0.79 mmol/L) compared with placebo (0.11–0.16 mmol/L; all p < .001), which peaked 1 hr following the TT (1.38 ± 0.35 vs. 0.34 ± 0.24 mmol/L; p < .001). Serum glucose and blood lactate concentrations were not different between trials (all p > .05). BD ingestion increased oxygen consumption and carbon dioxide production after 20 min of steady-state exercise (p = .002 and p = .032, respectively); however, no further effects on cardiorespiratory parameters were observed. Within the BD trial, moderate to severe gastrointestinal symptoms were reported in five participants, and low levels of dizziness, nausea, and euphoria were reported in two participants. However, this had no effect on TT duration (placebo, 28.5 ± 3.6 min; BD, 28.7 ± 3.2 min; p = .62) and average power output (placebo, 290.1 ± 53.7 W; BD, 286.4 ± 45.9 W; p = .50). These results suggest that BD has no benefit for endurance performance.

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Alaaddine El-Chab, Charlie Simpson and Helen Lightowler

Discrepancies in energy and macronutrient intakes between tests are apparent even when a solid prepackaged diet (Sdiet) is used to standardize dietary intake for preexperimental trials. It is unknown whether a liquid prepackaged diet (Ldiet) leads to improved adherence, resulting in lower variability in energy and macronutrient intakes. This study assesses the ability of athletes to replicate a diet when an Ldiet or Sdiet was used as a dietary standardization technique. In a cross-over design, 30 athletes were randomly assigned to either Sdiet or Ldiet. Each diet was consumed for two nonconsecutive days. Participants were instructed to consume all the meals provided and to return any leftovers. The coefficient of variation (CV) was calculated for each nutrient for the two methods and reported as the average CV. The Bland–Altman plots show that differences between Days 1 and 2 in energy and macronutrient intakes for both diets were close to zero, with the exception of some outliers. The %CV for Sdiet was higher than Ldiet (5% and 3% for energy, 5% and 3% for carbohydrate, 5% and 2% for protein, and 5% and 3% for fat, respectively). There was a strong positive correlation for energy and all macronutrients between Days 1 and 2 for both methods (r > .80; p < .05). Ldiet is an effective technique to standardize diet preexperimental trials and could be used as an alternative to Sdiet. Furthermore, Ldiet may lead to additional improvements in the compliance of participants to the diet and also decrease the cost and time of preparation.

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Brian J. McMorrow, Massimiliano Ditroilo and Brendan Egan

Purpose: Resisted sled sprinting (RSS) is an effective tool for improving sprint performance over short distances, but the effect on change-of-direction (COD) performance is largely unknown. The present study investigated the effect of heavy RSS training during the competitive season on sprint and COD performance in professional soccer players. Methods: Over 6 wk in-season, an RSS training group (n = 6) performed RSS at a sled load of 30% body mass for a total program running distance of 800 m, whereas an unresisted sprint (URS) training group (n = 7) performed the same distance of unresisted sprinting. A 20-m maximal sprint with split times measured at 5, 10, and 20 m and the sprint 9-3-6-3-9 m with 180° turns COD test were performed before and after the intervention. Results: Sprint performance (mean, 95% confidence limits, qualitative inference) was improved in both groups over 5 m (URS, 5.1%, −2.4 to 12.7, likely moderate; RSS, 5.4%, 0.5–10.4, likely moderate), 10 m (URS, 3.9%, −0.3 to 8.1, very likely moderate; RSS, 5.0%, 1.8–8.0, very likely large), and 20 m (URS, 2.0%, −0.6 to 4.5, likely moderate; RSS, 3.0%, 1.7–4.4, very likely moderate). COD was improved in both groups (URS, 3.7%, 2.2–5.2, most likely large; RSS, 3.3%, 1.6–5.0, most likely moderate). Between-groups differences were unclear. Conclusion: Heavy RSS and URS training matched for running distance were similarly effective at improving sprint and COD performance in professional soccer players when performed in the competitive phase of the season.

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Dana M. Lis and Keith Baar

Nutritional strategies to improve connective tissue collagen synthesis have garnered significant interest, although the scientific validity of these interventions lags behind their hype. This study was designed to determine the effects of three forms of collagen on N-terminal peptide of procollagen and serum amino acid levels. A total of 10 recreationally active males completed a randomized double-blinded crossover design study consuming either placebo or 15 g of vitamin C–enriched gelatin or hydrolyzed collagen (HC), or gummy containing equal parts of gelatin and HC. Supplements were consumed 1 hr before 6 min of jump rope. Blood samples were collected immediately prior to supplement consumption and 4 hr after jump rope. A subset of blood samples (n = 4) was collected for amino acid analysis 1 hr after ingestion. Consumption of an equivalent dose of each supplement increased amino acids in the circulation similarly across all interventions. N-terminal peptide of procollagen levels tended to increase ∼20% from baseline in the gelatin and HC interventions but not the placebo or gummy. These results suggest that vitamin C–enriched gelatin and HC supplementation may improve collagen synthesis when taken 1 hr prior to exercise. However, large variability was observed, which precluded significance for any treatment.