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Wim Derave and Kevin D. Tipton

Many athletes use dietary supplements, with use more prevalent among those competing at the highest level. Supplements are often self-prescribed, and their use is likely to be based on an inadequate understanding of the issues at stake. Supplementation with essential micronutrients may be useful when a diagnosed deficiency cannot be promptly and effectively corrected with food-based dietary solutions. When used in high doses, some supplements may do more harm than good: Iron supplementation, for example, is potentially harmful. There is good evidence from laboratory studies and some evidence from field studies to support health or performance benefits from appropriate use of a few supplements. The available evidence from studies of aquatic sports is small and is often contradictory. Evidence from elite performers is almost entirely absent, but some athletes may benefit from informed use of creatine, caffeine, and buffering agents. Poor quality assurance in some parts of the dietary supplements industry raises concerns about the safety of some products. Some do not contain the active ingredients listed on the label, and some contain toxic substances, including prescription drugs, that can cause health problems. Some supplements contain compounds that will cause an athlete to fail a doping test. Supplement quality assurance programs can reduce, but not entirely eliminate, this risk.

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Weiliang Chung, Audrey Baguet, Tine Bex, David J. Bishop, and Wim Derave

Muscle carnosine loading through chronic oral beta-alanine supplementation has been shown to be effective for short-duration, high-intensity exercise. This randomized, placebo-controlled study explored whether the ergogenic effect of beta-alanine supplementation is also present for longer duration exercise. Subjects (27 well-trained cyclists/triathletes) were supplemented with either beta-alanine or placebo (6.4 g/day) for 6 weeks. Time to completion and physiological variables for a 1-hr cycling time-trial were compared between preand postsupplementation. Muscle carnosine concentration was also assessed via proton magnetic resonance spectroscopy before and after supplementation. Following beta-alanine supplementation, muscle carnosine concentration was increased by 143 ± 151% (mean ± SD; p < .001) in the gastrocnemius and 161 ± 56% (p < .001) in the soleus. Postsupplementation time trial performance was significantly slower in the placebo group (60.6 ± 4.4–63.0 ± 5.4 min; p < .01) and trended toward a slower performance following beta-alanine supplementation (59.8 ± 2.8–61.7 ± 3.0 min; p = .069). We found an increase in lactate/proton concentration ratio following beta-alanine supplementation during the time-trial (209.0 ± 44.0 (beta-alanine) vs. 161.9 ± 54.4 (placebo); p < .05), indicating that a similar lactate concentration was accompanied by a lower degree of systemic acidosis, even though this acidosis was quite moderate (pH ranging from 7.30 to 7.40). In conclusion, chronic beta-alanine supplementation in well-trained cyclists had a very pronounced effect on muscle carnosine concentration and a moderate attenuating effect on the acidosis associated with lactate accumulation, yet without affecting 1-h time-trial performance under laboratory conditions.

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Adam Mallett, Phillip Bellinger, Wim Derave, Eline Lievens, Ben Kennedy, Hal Rice, and Clare Minahan

Purpose: To determine the association between estimated muscle fiber typology and the start and turn phases of elite swimmers during competition. Methods: International and national competition racing performance was analyzed from 21 female (FINA points = 894 ± 39: 104.5 ± 1.8% world record ratio [WRR]) and 25 male (FINA points = 885 ± 54: 104.8 ± 2.1% WRR) elite swimmers. The start, turn, and turn out times were determined from each of the swimmers’ career best performance times (FINA points = 889 ± 48: 104.7 ± 2.0% WRR). Muscle carnosine concentration was quantified by proton magnetic resonance spectroscopy in the gastrocnemius and soleus and was expressed as a carnosine aggregate z score relative to an age- and gender-matched nonathlete control group to estimate muscle fiber typology. Linear mixed models were employed to determine the association between muscle fiber typology and the start and turn times. Results: While there was no significant influence of carnosine aggregate z score on the start and turn times when all strokes and distance events were entered into the model, the swimmers with a higher carnosine aggregate z score (ie, faster muscle typology) had a significantly faster start time in 100-m events compared with the swimmers with a lower carnosine aggregate z score (P = .02, F = 5.825). The start and turn times were significantly faster in the male compared with the female swimmers in the 100-m events compared with other distances, and between the 4 different swimming strokes (P < .001). Conclusion: This study suggests that start times in sprint events are partly determined (and limited) by muscle fiber typology, which is highly relevant when ∼12% of the overall performance time is determined from the start time.

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Phillip Bellinger, Eline Lievens, Ben Kennedy, Hal Rice, Wim Derave, and Clare Minahan

Purpose: To examine whether the muscle typology of elite and world-class swimmers could discriminate between their best distance event, swimming stroke style, or performance level. Methodology: The muscle carnosine content of 43 male (860 [76] FINA [Fédération Internationale de Natation] points) and 30 female (881 [63] FINA points) swimmers was measured in the soleus and gastrocnemius by proton magnetic resonance spectroscopy and expressed as a carnosine aggregate Z score (CAZ score) to estimate muscle typology. A higher CAZ score is associated with a higher estimated proportion of type II fibers. Swimmers were categorized by their best stroke, distance category (sprinters, 50–100 m; middle distance, 200–400 m; or long distance, 800 m–open water), and performance level (world-class, world top 10, or elite and world top 100 swimmers outside of the world top 10). Results: There was no significant difference in the CAZ score of sprint- (−0.08 [0.55]), middle- (−0.17 [0.70]), or long-distance swimmers (−0.30 [0.75], P = .693). World-class sprint swimmers (all strokes included) had a significantly higher CAZ score (0.37 [0.70]) when compared to elite sprint swimmers (−0.25 [0.61], P = .024, d = 0.94). Breaststroke swimmers (0.69 [0.73]) had a significantly higher CAZ score compared to freestyle (−0.24 [0.54], P < .001, d = 1.46), backstroke (−0.16 [0.47], P = .006, d = 1.42), and butterfly swimmers (−0.39 [0.53], P < .001, d = 1.70). Furthermore, within the cohort of breaststroke swimmers, there was a significant positive correlation between FINA points and CAZ score (r = .728, P = .011); however, this association was not evident in other strokes. Conclusion: While there was no clear association between muscle typology and event distance specialization, world-class sprint swimmers possess a greater estimated proportion of type II fibers compared to elite sprint swimmers, as well as breaststroke swimmers compared to freestyle, backstroke, and butterfly swimmers.

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Peter Peeling, Linda M. Castell, Wim Derave, Olivier de Hon, and Louise M. Burke

Athletes are exposed to numerous nutritional products, attractively marketed with claims of optimizing health, function, and performance. However, there is limited evidence to support many of these claims, and the efficacy and safety of many products is questionable. The variety of nutritional aids considered for use by track-and-field athletes includes sports foods, performance supplements, and therapeutic nutritional aids. Support for sports foods and five evidence-based performance supplements (caffeine, creatine, nitrate/beetroot juice, β-alanine, and bicarbonate) varies according to the event, the specific scenario of use, and the individual athlete’s goals and responsiveness. Specific challenges include developing protocols to manage repeated use of performance supplements in multievent or heat-final competitions or the interaction between several products which are used concurrently. Potential disadvantages of supplement use include expense, false expectancy, and the risk of ingesting banned substances sometimes present as contaminants. However, a pragmatic approach to the decision-making process for supplement use is recommended. The authors conclude that it is pertinent for sports foods and nutritional supplements to be considered only where a strong evidence base supports their use as safe, legal, and effective and that such supplements are trialed thoroughly by the individual before committing to use in a competition setting.

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Adam Mallett, Phillip Bellinger, Wim Derave, Katie McGibbon, Eline Lievens, Ben Kennedy, Hal Rice, and Clare Minahan

Purpose: To determine the influence of muscle fiber typology (MFT) on the pacing strategy of elite swimmers competing in the 200-m freestyle event. Method: The top 3 career-best performances from 25 elite 200-m freestyle swimmers were analyzed—12 women (1:58.0 [0:01.3] min:s) and 13 men (1:48.4 [0:02.5]). Muscle carnosine concentration was quantified by proton magnetic resonance spectroscopy in the gastrocnemius and soleus muscles and expressed as a carnosine aggregate z score (CAZ score) relative to an age- and gender-matched nonathlete control group to estimate MFT. Linear regression models were employed to examine the influence of MFT on the percentage of overall race time spent in each 50-m lap. Results: Swimmers with a higher CAZ score spent a greater percentage of race time in lap 3 compared with swimmers with a lower CAZ score (0.1%, 0.0% to 0.2%; mean, 90% confidence interval, P = .02). For every 1% increase in the percentage of race time spent in lap 1, the percentage of race time spent in lap 3 decreased by 0.4% for swimmers with a higher CAZ score (0.2% to −0.5%, P = .00, r = −.51), but not for swimmers with a lower CAZ score (−0.1%, −0.3% to 0.1%, P = .28, r = −.18). The percentage of race time spent in lap 4 decreased by 0.8% for higher-CAZ-score swimmers (−0.5% to −1.0%, P = .00, r = −.66) and by 0.9% for lower-CAZ-score swimmers (−0.6% to −1.3%, P = .00, r = −.65) when lap 1 percentage increased by 1%. Conclusion: MFT may influence the pacing strategy of swimmers in the 200-m freestyle event, which provides an avenue for maximizing individualized pacing strategies of elite swimmers.

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Erik A. Richter, Jørgen F.P. Wojtaszewski, Søren Kristiansen, Jens R. Daugaard, Jakob N. Nielsen, Wim Derave, and Bente Kiens

In the present short review some factors affecting glucose utilization during exercise in skeletal muscle will be briefly described. Special focus will be put on the glucose transport step across the sarcolemma. Glucose transporters (GLUT4) are expressed at a surprisingly similar level in the different muscle fiber types in human skeletal muscle in contrast to findings in the rat. When working at the same absolute work load muscle glucose transport is decreased in trained compared with untrained muscle in part due to a decrease in GLUT4 translocation to the sarcolemma in trained muscle. However, when trained and untrained muscle are stressed severely by a workload taxing 100% of their peak oxygen uptake in a glycogen-depleted state, then glucose uptake is larger in trained than in untrained muscle and correlates with muscle GLUT4 content. Finally, the possible role of the AMP-activated protein kinase (AMPK) in regulating glucose uptake during exercise is discussed. It is indicated that at present no experiments definitively link activation of AMPK to activation of muscle glucose transport during exercise.

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Sarah de Jager, Stefaan Van Damme, Siegrid De Baere, Siska Croubels, Ralf Jäger, Martin Purpura, Eline Lievens, Jan G. Bourgois, and Wim Derave

Carnosine (β-alanyl-L-histidine) and its methylated analogues anserine and balenine are highly concentrated endogenous dipeptides in mammalian skeletal muscle that are implicated in exercise performance. Balenine has a much better bioavailability and stability in human circulation upon acute ingestion, compared to carnosine and anserine. Therefore, ergogenic effects observed with acute carnosine and anserine supplementation may be even more pronounced with balenine. This study investigated whether acute balenine supplementation improves physical performance in four maximal and submaximal exercise modalities. A total of 20 healthy, active volunteers (14 males; six females) performed cycling sprints, maximal isometric contractions, a 4-km TT and 20-km TT following either preexercise placebo or 10 mg/kg of balenine ingestion. Physical, as well as mental performance, along with acid–base balance and glucose concentration were assessed. Balenine was unable to augment peak power (p = .3553), peak torque (p = .3169), time to complete the 4 km (p = .8566), nor 20 km time trial (p = .2660). None of the performances were correlated with plasma balenine or CN1 enzyme activity. In addition, no effect on pH, bicarbonate, and lactate was observed. Also, the supplement did not affect mental performance. In contrast, glucose remained higher during and after the 20 km time trial following balenine ingestion. In conclusion, these results overall indicate that the functionality of balenine does not fully resemble that of carnosine and anserine, since it was unable to elicit performance improvements with similar and even higher plasma concentrations.