| 1. |
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| 2. |
- Barlow, Matthew J., et al.
(författare)
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The Effect of a Dietary Nitrate Supplementation in the Form of a Single Shot of Beetroot Juice on Static and Dynamic Apnea Performance
- 2018
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Ingår i: International Journal of Sport Nutrition & Exercise Metabolism. - : Human Kinetics. - 1526-484X .- 1543-2742. ; 28:5, s. 497-501
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present study was to assess the effects of acute nitrate (NO3-)-rich beetroot juice (BRJ) supplementation on peripheral oxygen saturation (SpO(2)), heart rate (HR), and pulmonary gas exchange during submaximal static and dynamic apnea. Methods: Nine (six males and three females) trained apneists (age: 39.6 +/- 8.2 years, stature: 170.4 +/- 11.5 cm, and body mass: 72.0 +/- 11.5 kg) performed three submaximal static apneas at 60%, 70%, and 80% of the participant's current reported personal best time, followed by three submaximal (similar to 75% or personal best distance) dynamic apneas following the consumption of either a 70-ml concentrated BRJ (7.7 mmol NO3-) or a NO3--depleted placebo (PLA; 0.1 mmol NO3-) in doubleblind randomized manner. HR and SpO(2) were measured via fingertip pulse oximetry at the nadir, and online gas analysis was used to assess pulmonary oxygen uptake ((V)over dotO2) during recovery following breath-holds. Results: There were no differences (p < .05) among conditions for HR (PLA = 59 +/- 11 bpm and BRJ = 61 +/- 12 bpm), SpO(2) (PLA = 83% +/- 14% and BRJ = 84% +/- 9%), or (V)over dotO2 (PLA = 1.00 +/- 0.22 L/min and BRJ = 0.97 +/- 0.27 L/min). Conclusion: The consumption of 7.7 mmol of beetroot juice supplementation prior to a series of submaximal static and dynamic apneas did not induce a significant change in SpO(2), HR, and (V)over dotO2 when compared with placebo. Therefore, there is no apparent physiological response that may benefit free divers as a result of the supplementation.
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| 3. |
- Beaven, Christopher, 1977-
(författare)
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Dose effect of caffeine on testosterone and cortisol responses to resistance exercise
- 2008
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Ingår i: International Journal of Sport Nutrition & Exercise Metabolism. - 1526-484X .- 1543-2742. ; 18:2, s. 131-141
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Interest in the use of caffeine as an ergogenic aid has increased since the International Olympic Committee lifted the partial ban on its use. Caffeine has beneficial effects on various aspects of athletic performance, but its effects on training have been neglected.Purpose: To investigate the acute effect of caffeine on the exercise-associated increases in testosterone and cortisol in a double-blind crossover study.Methods: 24 professional rugby-league players ingested caffeine doses of 0, 200, 400 and 800 mg in random order 1 h before a resistance-exercise session. Saliva was sampled at the time of caffeine ingestion, at 15-min intervals throughout each session, and at 15 and 30 min after the session. Data were log transformed to estimate percent effects with mixed modeling, and effects were standardized to assess magnitudes.Results: Testosterone concentration showed a small increase of 15% (90% confidence limits, ±19%) during exercise. Caffeine raised this concentration in a dose-dependent manner by a further small 21% (±24%) at the highest dose. The 800-mg dose also produced a moderate 52% (±44%) increase in cortisol. The effect of caffeine on the testosterone/cortisol ratio was a small decline (14; ±21%).Conclusion: Caffeine has some potential to benefit training outcomes via the anabolic effects of the increase in testosterone concentration, but this benefit may be counteracted by the opposing catabolic effects of the increase in cortisol and resultant decline in the testosterone/cortisol ratio.
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| 4. |
- Burke, Louise M, et al.
(författare)
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International Association of Athletics Federations Consensus Statement 2019 : Nutrition for Athletics.
- 2019
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Ingår i: International Journal of Sport Nutrition & Exercise Metabolism. - : Human Kinetics. - 1526-484X .- 1543-2742. ; 29:2, s. 73-84
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Tidskriftsartikel (refereegranskat)abstract
- The International Association of Athletics Federations recognizes the importance of nutritional practices in optimizing an Athlete's well-being and performance. Although Athletics encompasses a diverse range of track-and-field events with different performance determinants, there are common goals around nutritional support for adaptation to training, optimal performance for key events, and reducing the risk of injury and illness. Periodized guidelines can be provided for the appropriate type, amount, and timing of intake of food and fluids to promote optimal health and performance across different scenarios of training and competition. Some Athletes are at risk of relative energy deficiency in sport arising from a mismatch between energy intake and exercise energy expenditure. Competition nutrition strategies may involve pre-event, within-event, and between-event eating to address requirements for carbohydrate and fluid replacement. Although a "food first" policy should underpin an Athlete's nutrition plan, there may be occasions for the judicious use of medical supplements to address nutrient deficiencies or sports foods that help the athlete to meet nutritional goals when it is impractical to eat food. Evidence-based supplements include caffeine, bicarbonate, beta-alanine, nitrate, and creatine; however, their value is specific to the characteristics of the event. Special considerations are needed for travel, challenging environments (e.g., heat and altitude); special populations (e.g., females, young and masters athletes); and restricted dietary choice (e.g., vegetarian). Ideally, each Athlete should develop a personalized, periodized, and practical nutrition plan via collaboration with their coach and accredited sports nutrition experts, to optimize their performance.
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| 5. |
- Burke, Louise M., et al.
(författare)
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Pitfalls of Conducting and Interpreting Estimates of Energy Availability in Free-Living Athletes
- 2018
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Ingår i: International Journal of Sport Nutrition & Exercise Metabolism. - : Human Kinetics. - 1526-484X .- 1543-2742. ; 28:4, s. 350-363
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Forskningsöversikt (refereegranskat)abstract
- The human body requires energy for numerous functions including, growth, thermogenesis, reproduction, cellular maintenance, and movement. In sports nutrition, energy availability (EA) is defined as the energy available to support these basic physiological functions and good health once the energy cost of exercise is deducted from energy intake (EI), relative to an athlete's fat-free mass (FFM). Low EA provides a unifying theory to link numerous disorders seen in both female and male athletes, described by the syndrome Relative Energy Deficiency in Sport, and related to restricted energy intake, excessive exercise or a combination of both. These outcomes are incurred in different dose-response patterns relative to the reduction in EA below a "healthy" level of similar to 45 kcal.kg FFM-1.day(-1). Although EA estimates are being used to guide and monitor athletic practices, as well as support a diagnosis of Relative Energy Deficiency in Sport, problems associated with the measurement and interpretation of EA in the field should be explored. These include the lack of a universal protocol for the calculation of EA, the resources needed to achieve estimates of each of the components of the equation, and the residual errors in these estimates. The lack of a clear definition of the value for EA that is considered "low" reflects problems around its measurement, as well as differences between individuals and individual components of "normal"/"healthy" function. Finally, further investigation of nutrition and exercise behavior including within-and between-day energy spread and dietary characteristics is warranted since it may directly contribute to low EA or its secondary problems.
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| 6. |
- Carr, Amelia, et al.
(författare)
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Nutritional Intake in Elite Cross-Country Skiers During Two Days of Training and Competition
- 2019
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Ingår i: International Journal of Sport Nutrition & Exercise Metabolism. - Birmingham : Human Kinetics. - 1526-484X .- 1543-2742. ; 29:3, s. 273-281
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the energy, macronutrient, and fluid intakes, as well as hydration status (urine specific gravity), in elite cross-country skiers during a typical day of training (Day 1) and a sprint skiing competition the following day (Day 2). A total of 31 (18 males and 13 females) national team skiers recorded their food and fluid intakes and urine specific gravity was measured on Days 1 and 2. In addition, the females completed the Low Energy Availability in Females Questionnaire to assess their risk of long-term energy deficiency. Energy intake for males was 65 ± 9 kcal/kg on Day 1 versus 58 ± 9 kcal/kg on Day 2 (p = .002) and for females was 57 ± 10 on Day 1 versus 55 ± 5 kcal/kg on Day 2 (p = .445). Carbohydrate intake recommendations of 10-12 g·kg-1·day-1 were not met by 89% of males and 92% of females. All males and females had a protein intake above the recommended 1.2-2.0 g/kg on both days and a postexercise protein intake above the recommended 0.3 g/kg. Of the females, 31% were classified as being at risk of long-term energy deficiency. In the morning of Day 1, 50% of males and 46% of females were dehydrated; on Day 2, this was the case for 56% of males and 38% of females. In conclusion, these data suggest that elite cross-country skiers ingested more protein and less carbohydrate than recommended and one third of the females were considered at risk of long-term energy deficiency. Furthermore, many of the athletes were dehydrated prior to training and competition.
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| 7. |
- Cermak, NM, et al.
(författare)
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No improvement in endurance performance after a single dose of beetroot juice
- 2012
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Ingår i: International journal of sport nutrition and exercise metabolism. - : Human Kinetics. - 1543-2742 .- 1526-484X. ; 22:6, s. 470-478
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Tidskriftsartikel (refereegranskat)abstract
- Dietary nitrate supplementation has received much attention in the literature due to its proposed ergogenic properties. Recently, the ingestion of a single bolus of nitrate-rich beetroot juice (500 ml, ~6.2 mmol NO3−) was reported to improve subsequent time-trial performance. However, this large volume of ingested beetroot juice does not represent a realistic dietary strategy for athletes to follow in a practical, performancebased setting. Therefore, we investigated the impact of ingesting a single bolus of concentrated nitrate-rich beetroot juice (140 ml, ~8.7 mmol NO3−) on subsequent 1-hr time-trial performance in well-trained cyclists.Methods:Using a double-blind, repeated-measures crossover design (1-wk washout period), 20 trained male cyclists (26 ± 1 yr, VO2peak 60 ± 1 ml · kg−1 · min−1, Wmax 398 ± 7.7 W) ingested 140 ml of concentrated beetroot juice (8.7 mmol NO3−; BEET) or a placebo (nitrate-depleted beetroot juice; PLAC) with breakfast 2.5 hr before an ~1-hr cycling time trial (1,073 ± 21 kJ). Resting blood samples were collected every 30 min after BEET or PLAC ingestion and immediately after the time trial.Results:Plasma nitrite concentration was higher in BEET than PLAC before the onset of the time trial (532 ± 32 vs. 271 ± 13 nM, respectively; p < .001), but subsequent time-trial performance (65.5 ± 1.1 vs. 65 ± 1.1 s), power output (275 ± 7 vs. 278 ± 7 W), and heart rate (170 ± 2 vs. 170 ± 2 beats/min) did not differ between BEET and PLAC treatments (all p > .05).Conclusion:Ingestion of a single bolus of concentrated (140 ml) beetroot juice (8.7 mmol NO3−) does not improve subsequent 1-hr time-trial performance in well-trained cyclists.
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| 8. |
- Cook, C, et al.
(författare)
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Acute caffeine ingestion increases voluntarily chosen resistance training load following limited sleep
- 2012
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Ingår i: International Journal of Sport Nutrition & Exercise Metabolism. - 1526-484X .- 1543-2742. ; 22:3, s. 157-164
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION:This study aimed to determine whether caffeine ingestion would increase the workload voluntarily chosen by athletes in a limited sleep state.METHODS:In a double-blind, crossover study, sixteen professional rugby players ingested either a placebo or 4 mg·kg-1 caffeine 1 h before exercise. Athletes classified themselves into non-deprived (8 h+) or sleep-deprived states (6 h or less). Exercise comprised four sets of bench press, squats, and bent rows at 85% 1-RM. Athletes were asked to perform as many repetitions on each set as possible without failure. Saliva was collected prior to administration of placebo or caffeine, and again prior to and immediately after exercise and assayed for testosterone and cortisol.RESULTS:Sleep deprivation produced a very large decrease in total load (p = 1.98 x 10-7).Caffeine ingestion in the non-deprived state resulted in a moderate increase in total load with a larger effect in the sleep deprived state resulting in total load similar to those observed in the non-deprived placebo condition.Eight of the sixteen athletes were identified as caffeine responders.Baseline testosterone was higher (p < 0.05) and cortisol trended lower in non-sleep deprived states.Changes in hormones from pre-dose to pre-exercise correlated to individual workload responses to caffeine.Testosterone response to exercise increased with caffeine compared to placebo, as did cortisol response.CONCLUSIONS:Caffeine increased voluntary workload in professional athletes, emphasised further under conditions of self-reported limited sleep. Caffeine may prove worthwhile when athletes are perceived as tired, especially in individuals identified as responders.
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| 9. |
- Fagerberg, P
(författare)
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Negative Consequences of Low Energy Availability in Natural Male Bodybuilding: A Review
- 2018
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Ingår i: International journal of sport nutrition and exercise metabolism. - : Human Kinetics. - 1543-2742 .- 1526-484X. ; 28:4, s. 385-402
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Tidskriftsartikel (refereegranskat)abstract
- Energy availability (EA) is a scientific concept describing how much energy is available for basic metabolic functions such as reproduction, immunity, and skeletal homeostasis. Carefully controlled studies on women have shown pathological effects of EA < 30 kcal/kg fat-free mass (FFM), and this state has been labeled low EA (LEA). Bodybuilding is a sport in which athletes compete to show muscular definition, symmetry, and low body fat (BF). The process of contest preparation in bodybuilding includes months of underfeeding, thus increasing the risk of LEA and its negative health consequences. As no well-controlled studies have been conducted in natural male bodybuilders on effects of LEA, the aim of this review was to summarize what can be extrapolated from previous relevant research findings in which EA can be calculated. The reviewed literature indicates that a prolonged EA < 25 kcal/kg FFM results in muscle loss, hormonal imbalances, psychological problems, and negatively affects the cardiovascular system when approaching the lower limits of BF (∼4%–5%) among males. Case studies on natural male bodybuilders who prepare for contest show muscle loss (>40% of total weight loss) with EA < 20 kcal/kg FFM, and in the study with the lowest observed BF (∼4 kg), major mood disturbance and hormonal imbalances co-occurred. Studies also underline the problem of BF overshoot during refeeding after extremes of LEA among males. A more tempered approach (EA > 25 kcal/kg FFM) might result in less muscle loss among natural male bodybuilders who prepare for contest, but more research is needed.
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| 10. |
- Gross, M, et al.
(författare)
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Beta-alanine supplementation improves jumping power and affects severe-intensity performance in professional alpine skiers
- 2014
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Ingår i: International journal of sport nutrition and exercise metabolism. - : Human Kinetics. - 1543-2742 .- 1526-484X. ; 24:6, s. 665-673
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Tidskriftsartikel (refereegranskat)abstract
- Supplementation with beta-alanine may have positive effects on severe-intensity, intermittent, and isometric strength-endurance performance. These could be advantageous for competitive alpine skiers, whose races last 45 to 150 s, require metabolic power above the aerobic maximum, and involve isometric muscle work. Further, beta-alanine supplementation affects the muscle force-frequency relationship, which could influence explosiveness. We explored the effects of beta-alanine on explosive jump performance, severe exercise energy metabolism, and severe-intensity ski-like performance.Methods:Nine male elite alpine skiers consumed 4.8 g/d beta-alanine or placebo for 5 weeks in a double-blind fashion. Before and after, they performed countermovement jumps (CMJ), a 90-s cycling bout at 110% VO2max (CLT), and a maximal 90-s box jump test (BJ90).Results:Beta-alanine improved maximal (+7 ± 3%, d = 0.9) and mean CMJ power (+7 ± 2%, d = 0.7), tended to reduce oxygen deficit (-3 ± 8%, p = .06) and lactate accumulation (-12 ± 31%) and enhance aerobic energy contribution (+1.3 ± 2.9%, p = .07) in the CLT, and improved performance in the last third of BJ90 (+7 ± 4%, p = .02). These effects were not observed with placebo.Conclusions:Beta-alanine supplementation improved explosive and repeated jump performance in elite alpine skiers. Enhanced muscle contractility could possibly explain improved explosive and repeated jump performance. Increased aerobic energy production could possibly help explain repeated jump performance as well.
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| 11. |
- Hahn, Robert, et al.
(författare)
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An Aggregate Urine Analysis Tool to Detect Acute Dehydration
- 2013
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Ingår i: International Journal of Sport Nutrition & Exercise Metabolism. - : Human Kinetics. - 1526-484X .- 1543-2742. ; 23:4, s. 303-311
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE:Urine sampling has previously been evaluated for detecting dehydration in young male athletes. The present study investigated whether urine analysis can serve as a measure of dehydration in men and women of a wide age span.METHODS:Urine sampling and body weight measurement were undertaken before and after recreational physical exercise (median time: 90 minutes) in 57 volunteers aged between 17 and 69 years (mean age: 42). Urine analysis included urine color, osmolality, specific gravity, and creatinine.RESULTS:The volunteers' body weight decreased 1.1% (mean) while they exercised. There were strong correlations between all four urinary markers of dehydration (r = 0.73 to 0.84, P < 0.001). Researchers constructed a composite dehydration index graded from 1 to 6 based on these markers. This index changed from 2.70 before exercising to 3.55 after exercising, which corresponded to dehydration of 1.0% as given by a preliminary reference curve based on seven previous studies in athletes. Men were slightly dehydrated at baseline (mean: 1.9%) compared to women (mean: 0.7%; P < 0.001), while age had no influence on the results. A final reference curve that considered both the present results and the seven previous studies was constructed in which exercise-induced weight loss (x) was predicted by the exponential equation x= 0.20 dehydration index.CONCLUSION:Urine sampling can be used to estimate weight loss due to dehydration in adults up to the age of 70 years. A robust dehydration index based on four indicators reduces the influence of confounders.
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| 12. |
- Hahn, RG, et al.
(författare)
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An aggregate urine analysis tool to detect acute dehydration
- 2013
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Ingår i: International journal of sport nutrition and exercise metabolism. - : Human Kinetics. - 1543-2742 .- 1526-484X. ; 23:4, s. 303-311
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Tidskriftsartikel (refereegranskat)abstract
- Urine sampling has previously been evaluated for detecting dehydration in young male athletes. The present study investigated whether urine analysis can serve as a measure of dehydration in men and women of a wide age span.Methods:Urine sampling and body weight measurement were undertaken before and after recreational physical exercise (median time: 90 min) in 57 volunteers age 17–69 years (mean age: 42). Urine analysis included urine color, osmolality, specific gravity, and creatinine.Results:The volunteers’ body weight decreased 1.1% (mean) while they exercised. There were strong correlations between all 4 urinary markers of dehydration (r = .73–.84, p < .001). Researchers constructed a composite dehydration index graded from 1 to 6 based on these markers. This index changed from 2.70 before exercising to 3.55 after exercising, which corresponded to dehydration of 1.0% as given by a preliminary reference curve based on 7 previous studies in athletes. Men were slightly dehydrated at baseline (mean: 1.9%) compared with women (mean: 0.7%; p < .001), though age had no influence on the results. A final reference curve that considered both the present results and the 7 previous studies was constructed in which exercise-induced weight loss (x) was predicted by the exponential equation x = 0.20 dehydration index1.86.Conclusion:Urine sampling can be used to estimate weight loss due to dehydration in adults up to age 70. A robust dehydration index based on four indicators reduces the influence of confounders.
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| 13. |
- Hall, Ulrika Andersson, et al.
(författare)
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Metabolism and Whole-Body Fat Oxidation Following Post-Exercise Carbohydrate or Protein Intake.
- 2018
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Ingår i: International journal of sport nutrition and exercise metabolism. - : Human Kinetics. - 1543-2742 .- 1526-484X. ; 28:1, s. 37-45
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated how post-exercise intake of placebo (PLA), protein (PRO) or carbohydrate (CHO) affected fat oxidation (FO) and metabolic parameters during recovery and subsequent exercise.In a cross-over design, 12 moderately trained women (VO2max 45 ± 6 ml·min(-1)·kg(-1)) performed three days of testing. A 23 min control (CON) incremental FO bike test (30-80% VO2max) was followed by 60 min exercise at 75% VO2max. Immediately post-exercise, subjects ingested PLA, 20 g PRO or 40 g CHO followed by a second FO bike test 2h later.Maximal fat oxidation (MFO) and the intensity at which MFO occurs (Fatmax) increased at the second FO test compared to the first following all three post-exercise drinks (MFO for CON=0.28±0.08, PLA=0.57±0.13, PRO=0.52±0.08, CHO=0.44±0.12 g fat·min(-1); Fatmax for CON=41±7, PLA=54±4, PRO=55±6, CHO=50±8 %VO2max, P<0.01 for all values compared to CON). Resting FO, MFO and Fatmax were not significantly different between PLA and PRO, but lower for CHO. PRO and CHO increased insulin levels at 1h post-exercise, though both glucose and insulin were equal with PLA at 2h. Increased post-exercise ketone levels only occurred with PLA.Protein supplementation immediately post-exercise did not affect the doubling in whole body fat oxidation seen during a subsequent exercise trial 2 hours later. Neither did it affect resting fat oxidation during the post-exercise period despite increased insulin levels and attenuated ketosis. Carbohydrate intake dampened the increase in fat oxidation during the second test, though a significant increase was still observed compared to the first test.
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| 14. |
- Hansen, Mette, et al.
(författare)
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Effect of Whey Protein Hydrolysate on Performance and Recovery of Top-Class Orienteering Runners.
- 2015
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Ingår i: International Journal of Sport Nutrition & Exercise Metabolism. - : Human Kinetics. - 1526-484X .- 1543-2742. ; 25:2
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Tidskriftsartikel (refereegranskat)abstract
- This trial aimed to examine the effect of whey protein hydrolysate intake before and after exercise sessions on endurance performance and recovery in elite orienteers during a training camp. Eighteen elite orienteers participated in a randomized controlled intervention trial during a 1-week training camp (13 exercise sessions). Half of the runners (PRO-CHO) ingested a protein drink before (0.3 g kg−1) and a protein-carbohydrate drink after (0.3 g protein kg−1 and 1 g carbohydrate kg−1) each exercise session. The others ingested energy and timematched carbohydrate drinks (CHO). A 4-km run-test with 20 control points was performed before and on the last day of the intervention. Blood and saliva were obtained in the mornings, before and after run-tests, and after the last training session. During the intervention, questionnaires were fulfilled regarding psychological sense of performance capacity and motivation. PRO-CHO and not CHO improved performance in the 4-km run-test (interaction p < .05). An increase in serum creatine kinase was observed during the week, which was greater in CHO than PRO-CHO (interactionp < .01). Lactate dehydrogenase (p < .001) and cortisol (p = .057) increased during the week, but the change did not differ between groups. Reduction in sense of performance capacity during the intervention was greater in CHO (p < .05) than PRO-CHO. In conclusion, ingestion of whey protein hydrolysate before and after each exercise session improves performance and reduces markers of muscle damage during a strenuous 1-week training camp. The results indicate that protein supplementation in conjunction with each exercise session facilitates the recovery from strenuous training in elite orienteers.
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| 15. |
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| 16. |
- Melin, Anna K., Assistant Professor, 1965-, et al.
(författare)
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Disordered Eating and Eating Disorders in Aquatic Sports
- 2014
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Ingår i: International Journal of Sport Nutrition & Exercise Metabolism. - : Human Kinetics. - 1526-484X .- 1543-2742. ; 24:4, s. 450-459
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Tidskriftsartikel (refereegranskat)abstract
- Disordered eating behavior (DE) and eating disorders (EDs) are of great concern because of their associations with physical and mental health risks and, in the case of athletes, impaired performance. The syndrome originally known as the Female Athlete Triad, which focused on the interaction of energy availability, reproductive function, and bone health in female athletes, has recently been expanded to recognize that Relative Energy Deficiency in Sport (RED-S) has a broader range of negative effects on body systems with functional impairments in both male and female athletes. Athletes in leanness-demanding sports have an increased risk for RED-S and for developing EDs/DE. Special risk factors in aquatic sports related to weight and body composition management include the wearing of skimpy and tight-fitting bathing suits, and in the case of diving and synchronized swimming, the involvement of subjective judgments of performance. The reported prevalence of DE and EDs in athletic populations, including athletes from aquatic sports, ranges from 18 to 45% in female athletes and from 0 to 28% in male athletes. To prevent EDs, aquatic athletes should practice healthy eating behavior at all periods of development pathway, and coaches and members of the athletes' health care team should be able to recognize early symptoms indicating risk for energy deficiency, DE, and EDs. Coaches and leaders must accept that DE/EDs can be a problem in aquatic disciplines and that openness regarding this challenge is important.
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| 17. |
- Melin, Anna K., Assistant Professor, 1965-, et al.
(författare)
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Energy Availability in Athletics : Health, Performance, and Physique
- 2019
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Ingår i: International Journal of Sport Nutrition & Exercise Metabolism. - : Human Kinetics. - 1526-484X .- 1543-2742. ; 29:2, s. 152-164
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Forskningsöversikt (refereegranskat)abstract
- The reported prevalence of low energy availability (LEA) in female and male track and field athletes is between 18% and 58% with the highest prevalence among athletes in endurance and jump events. In male athletes, LEA may result in reduced testosterone levels and libido along with impaired training capacity. In female track and field athletes, functional hypothalamic amenorrhea as consequence of LEA has been reported among 60% of elite middle- and long-distance athletes and 23% among elite sprinters. Health concerns with functional hypothalamic amenorrhea include impaired bone health, elevated risk for bone stress injury, and cardiovascular disease. Furthermore, LEA negatively affects recovery, muscle mass, neuromuscular function, and increases the risk of injuries and illness that may affect performance negatively. LEA in track and field athletes may occur due to intentional alterations in body mass or body composition, appetite changes, time constraints, or disordered eating behavior. Long-term LEA causes metabolic and physiological adaptations to prevent further weight loss, and athletes may therefore be weight stable yet have impaired physiological function secondary to LEA. Achieving or maintaining a lower body mass or fat levels through long-term LEA may therefore result in impaired health and performance as proposed in the Relative Energy Deficiency in Sport model. Preventive educational programs and screening to identify athletes with LEA are important for early intervention to prevent long-term secondary health consequences. Treatment for athletes is primarily to increase energy availability and often requires a team approach including a sport physician, sports dietitian, physiologist, and psychologist.
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| 18. |
- Mishima, T, et al.
(författare)
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Chicken breast attenuates high-intensity-exercise-induced decrease in rat sarcoplasmic reticulum Ca2+ handling
- 2008
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Ingår i: International journal of sport nutrition and exercise metabolism. - : Human Kinetics. - 1526-484X .- 1543-2742. ; 18:4, s. 399-411
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Tidskriftsartikel (refereegranskat)abstract
- This study was conducted to determine whether dietary chicken-breast extract (CBEX), a rich source of histidine-containing dipeptides, could modify exerciseinduced changes in sarcoplasmic reticulum (SR) function. After 5 weeks of dietary CBEX, SR Ca2+-handling ability was examined in the vastus lateralis muscles of rats subjected to high-intensity running for 2.5 min. Dietary CBEX caused an approximately 15% and 45% increase (p < .01) in muscle carnosine and anserine concentrations, respectively. In resting muscles, depressions in SR Ca2+–ATPase activity were evoked by dietary CBEX without concomitant changes in SR Ca2+ uptake and release rates. The data confirm that high-intensity exercise depresses SR Ca2+ handling. In spite of the same run time, SR Ca2+ handling was reduced to a lesser degree in muscles of CBEX-containing-chow-fed rats than in standard-chow-fed rats (p < .05). These results suggest that dietary CBEX might attenuate deteriorations in SR Ca2+-handling ability that occur with high-intensity exercise.
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| 19. |
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| 20. |
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| 21. |
- Pettersson, Stefan, 1972, et al.
(författare)
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Dietary Intake at Competition in Elite Olympic Combat Sports.
- 2014
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Ingår i: International journal of sport nutrition and exercise metabolism. - : Human Kinetics. - 1543-2742 .- 1526-484X. ; 24:1, s. 98-109
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the current study was to investigate elite female (n=21) and male (n=47) combat sports athletes' (n=68; mean age (± SD) 21.3 ± 3.8 years; mean height 177 ± 10.2 cm) dietary intake between weigh-in and the first bout in Olympic combat sports. The data were collected at 6 separate tournaments and measurements included estimated food records, time for recovery, and body weight (BW) at weigh-in and first match. In total, 33 athletes participated in wrestling and taekwondo, sports with extended recovery times, and 35 athletes in judo and boxing, sports with limited recovery time. The results displayed that despite a mean consumption of food and drinks corresponding to 4.2 kg, the athletes only regained an average of 1.9 kg BW during recovery. Water accounted for 86% of the total intake. For each litre of water consumed, athletes gained 0.57 kg BW, when excluding heavy weight athletes (n=5). Carbohydrate consumption was 5.5 g/kg BW, compared to the recommended 8-10 g/kg BW. In total, one-quarter of the consumed water originated from carbohydrate-rich drinks. Given the average recovery time of 18 (wrestling, taekwondo) versus 8 hours (judo, boxing), the former group consumed twice the amount of water, carbohydrates, protein, and fat as the latter group. In conclusion, a large proportion of the participants did not meet the recovery nutrition guidelines for carbohydrates. Also, the discrepancy between nutrient intake and weight gain points to the physiological barriers to retaining fluids during a limited recovery time after engaging in weight making practices.
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| 22. |
- Pettersson, Stefan, 1972, et al.
(författare)
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Hydration Status in Elite Wrestlers, Judokas, Boxers and Taekwondo Athletes on Competition Day.
- 2014
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Ingår i: International journal of sport nutrition and exercise metabolism. - : Human Kinetics. - 1543-2742 .- 1526-484X. ; 24:3
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Tidskriftsartikel (refereegranskat)abstract
- Weight category athletes are known for practicing rapid weight loss prior to competition weigh-in. After weigh-in, athletes strive to restore euhydration and body mass through food and fluid intake. The aim of the present study was to assess prevalence of hypohydration at competition time among elite athletes' in four different combat sports, and how water intake and timing of official weigh-in were related to hydration status. Participants were 31 taekwondo practitioners and wrestlers who performed evening weigh-in (EWI) the night before competition day and had thus time for rehydration, and 32 boxers and judokas conducting competition day morning weigh-in (MWI). In total, 32% were female. Urine specific gravity (USG) was measured by refractometry on the competition day's first morning urine sample. Hypohydration was defined as USG ≥1.020 and serious hypohydration as USG>1.030. Water intake was measured by means of dietary records. The prevalence of hypohydration was 89% in the morning of competition day. Serious hypohydration was also prevalent. This was found in over 50% of MWI athletes and was also present in 42% of the EWI group. A higher water intake, from both fluids and solid foods, in the evening before competition day was not associated with a more favourable hydration status the following morning. In conclusion, neither weigh-in close to competition nor evening weigh-in with more time for rehydration seems to prevent hypohydration prior to competition.
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| 23. |
- Podlogar, T., et al.
(författare)
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Addition of Fructose to a Carbohydrate-Rich Breakfast Improves Cycling Endurance Capacity in Trained Cyclists
- 2022
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Ingår i: International Journal of Sport Nutrition & Exercise Metabolism. - : Human Kinetics. - 1526-484X .- 1543-2742. ; 32:6, s. 439-445
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Tidskriftsartikel (refereegranskat)abstract
- It was previously demonstrated that postexercise ingestion of fructose-glucose mixtures can lead to superior liver and equal muscle glycogen synthesis as compared with glucose-based carbohydrates (CHOs) only. After an overnight fast, liver glycogen stores are reduced, and based on this we hypothesized that addition of fructose to a glucose-based breakfast would lead to improved subsequent endurance exercise capacity. In this double-blind cross-over randomized study (eight males, peak oxygen uptake: 62.2 ± 5.4 ml·kg-1·min-1), participants completed two experimental trials consisting of two exercise bouts. In the afternoon of Day 1, they completed a cycling interval training session to normalize glycogen stores after which a standardized high-CHO diet was provided for 4 hr. On Day 2, in the morning, participants received 2 g/kg of CHOs in the form of glucose and rice or fructose and rice, both in a CHO ratio of 1:2. Two hours later they commenced cycling exercise session at the intensity of the first ventilatory threshold until task failure. Exercise capacity was higher in fructose and rice (137.0 ± 22.7 min) as compared with glucose and rice (130.06 ± 19.87 min; p = .046). Blood glucose and blood lactate did not differ between the trials (p > .05) and neither did CHO and fat oxidation rates (p > .05). However, due to the duration of exercise, total CHO oxidation was higher in fructose and rice (326 ± 60 g vs. 298 ± 61 g, p = .009). Present data demonstrate that addition of fructose to a glucose-based CHO source at breakfast improves endurance exercise capacity. Further studies are required to determine the mechanisms and optimal dose and ratio.
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| 24. |
- Staal, Sarah, et al.
(författare)
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Low RMRratio as a Surrogate Marker for Energy Deficiency, the Choice of Predictive Equation Vital for Correctly Identifying Male and Female Ballet Dancers at Risk
- 2018
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Ingår i: International Journal of Sport Nutrition & Exercise Metabolism. - : Human Kinetics. - 1526-484X .- 1543-2742. ; 28:4, s. 412-418
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Tidskriftsartikel (refereegranskat)abstract
- Ballet dancers are reported to have an increased risk for energy deficiency with or without disordered eating behavior. A low ratio between measured ((m)) and predicted ((p)) resting metabolic rate (RMRratio < 0.90) is a recognized surrogate marker for energy deficiency. We aimed to evaluate the prevalence of suppressed RMR using different methods to calculate pRMR and to explore associations with additional markers of energy deficiency. Female (n = 20) and male (n = 20) professional ballet dancers, 19-35 years of age, were enrolled. mRMR was assessed by respiratory calorimetry (ventilated open hood). pRMR was determined using the Cunningham and Harris-Benedict equations, and different tissue compartments derived from whole-body dual-energy X-ray absorptiometry assessment. The protocol further included assessment of body composition and bone mineral density, blood pressure, disordered eating (Eating Disorder Inventory-3), and for females, the Low Energy Availability in Females Questionnaire. The prevalence of suppressed RMR was generally high but also clearly dependent on the method used to calculate pRMR, ranging from 25% to 80% in males and 35% to 100% in females. Five percent had low bone mineral density, whereas 10% had disordered eating and 25% had hypotension. Forty percent of females had elevated Low Energy Availability in Females Questionnaire score and 50% were underweight. Suppressed RMR was associated with elevated Low Energy Availability in Females Questionnaire score in females and with higher training volume in males. In conclusion, professional ballet dancers are at risk for energy deficiency. The number of identified dancers at risk varies greatly depending on the method used to predict RMR when using RMRratio as a marker for energy deficiency.
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| 25. |
- Stenqvist, Thomas Birkedal, et al.
(författare)
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Prevalence of Surrogate Markers of Relative Energy Deficiency in Male Norwegian Olympic-Level Athletes
- 2021
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Ingår i: International Journal of Sport Nutrition & Exercise Metabolism. - : Human Kinetics. - 1526-484X .- 1543-2742. ; 31:6, s. 497-506
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Tidskriftsartikel (refereegranskat)abstract
- The syndrome of Relative Energy Deficiency in Sport (RED-S) includes wide-ranging effects on physiological and psychological functioning, performance, and general health. However, RED-S is understudied among male athletes at the highest performance levels. This cross-sectional study aimed to investigate surrogate RED-S markers prevalence in Norwegian male Olympic-level athletes. Athletes (n = 44) aged 24.7 +/- 3.8 years, body mass 81.3 +/- 15.9 kg, body fat 13.7% +/- 5.8%, and training volume 76.1 +/- 22.9 hr/month were included. Assessed parameters included resting metabolic rate (RMR), body composition, and bone mineral density by dual-energy X-ray absorptiometry and venous blood variables (testosterone, free triiodothyronine, cortisol, and lipids). Seven athletes (16%) grouped by the presence of low RMR (RMRratio < 0.90) (0.81 +/- 0.07 vs. 1.04 +/- 0.09, p <.001, effect size 2.6), also showed lower testosterone (12.9 +/- 5.3 vs. 19.0 +/- 5.3 nmol/L, p =.020) than in normal RMR group. In low RMRratio individuals, prevalence of other RED-S markers (-subclinical-low testosterone, low free triiodothyronine, high cortisol, and elevated low-density lipoprotein) was (N/number of markers): 2/0, 2/1, 2/2, 1/3. Low bone mineral density (z-score < -1) was found in 16% of the athletes, all with normal RMR. Subclinical low testosterone and free triiodothyronine levels were found in nine (25%) and two (5%) athletes, respectively. Subclinical high cortisol was found in 23% of athletes while 34% had elevated low-density lipoprotein cholesterol levels. Seven of 12 athletes with two or more RED-S markers had normal RMR. In conclusion, this study found that multiple RED-S markers also exist in male Olympic-level athletes. This highlights the importance of regular screening of male elite athletes, to ensure early detection and treatment of RED-S.
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| 26. |
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| 27. |
- Torstveit, Monica Klungland, et al.
(författare)
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Within-Day Energy Deficiency and Metabolic Perturbation in Male Endurance Athletes
- 2018
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Ingår i: International Journal of Sport Nutrition & Exercise Metabolism. - : Human Kinetics. - 1526-484X .- 1543-2742. ; 28:4, s. 419-427
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Tidskriftsartikel (refereegranskat)abstract
- Endurance athletes are at increased risk of relative energy deficiency associated with metabolic perturbation and impaired health. We aimed to estimate and compare within-day energy balance in male athletes with suppressed and normal resting metabolic rate (RMR) and explore whether within-day energy deficiency is associated with endocrine markers of energy deficiency. A total of 31 male cyclists, triathletes, and long-distance runners recruited from regional competitive sports clubs were included. The protocol comprised measurements of RMR by ventilated hood and energy intake and energy expenditure to predict RMR-ratio (measured RMR/predicted RMR), energy availability, 24-hr energy balance and within-day energy balance in 1-hr intervals, assessment of body composition by dual-energy X-ray absorptiometry, and blood plasma analysis. Subjects were categorized as having suppressed (RMRratio < 0.90, n = 20) or normal (RMRratio > 0.90, n = 11) RMR. Despite there being no observed differences in 24-hr energy balance or energy availability between the groups, subjects with suppressed RMR spent more time in an energy deficit exceeding 400 kcal (20.9 [18.8-21.8] hr vs. 10.8 [2.5-16.4], p =.023) and had larger single-hour energy deficits compared with subjects with normal RMR (3,265 +/- 1,963 kcal vs. -1,340 +/- 2,439, p =.023). Larger single-hour energy deficits were associated with higher cortisol levels (r = -.499, p =.004) and a lower testosterone: cortisol ratio (r =.431, p =.015), but no associations with triiodothyronine or fasting blood glucose were observed. In conclusion, within-day energy deficiency was associated with suppressed RMR and catabolic markers in male endurance athletes.
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