| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
- 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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| 8. |
- 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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| 9. |
- 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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| 10. |
- 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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