Context:Dietary supplements are widely used across all levels of sport. While the 'food first but not food only' approach remains central to sports nutrition, selected supplements may support performance, recovery or health when used appropriately. However, variable regulation, product contamination, mislabelling and inappropriate decision-making may expose athletes to inadvertent antidoping rule violations (ADRVs). Evidence Acquisition:This structured narrative review searched PubMed and Scopus for literature published between January 2000 and December 2025. Evidence from primary studies, randomised controlled trials, systematic reviews, meta-analyses, mechanistic studies, contamination analyses, behavioural research, consensus statements and official guidance documents from major sports and antidoping organisations was critically evaluated and synthesised. A PRISMA-style literature identification and evidence-selection diagram is provided as Supporting Table S1; the review was not designed as a systematic review or meta-analysis. Study Design:Narrative clinical review. Level of Evidence:Level V for the overall narrative framework, with supplement-specific strength of recommendation reported separately. Results:Evidence supporting supplementation varies substantially across categories. Creatine and caffeine have the most consistent evidence for selected performance outcomes, whereas beta-alanine, dietary nitrate and sodium bicarbonate show context-specific benefits. Iron and vitamin D have clearer clinical indications when deficiency is present, but limited evidence supports routine use in replete athletes. Many recovery- or health-oriented supplements rely on smaller, heterogeneous studies or indirect outcomes. Contamination risk is also heterogeneous and is highest for multi-ingredient products, preworkout supplements, weight-loss products, muscle-building products, 'testosterone boosters', selective androgen receptor modulators (SARMs) and other substances positioned as supplements despite pharmacological or prohibited profiles. Effective risk reduction requires individual nutritional assessment, evidence-based selection, third-party certification, product verification, education of athletes and Athlete Support Personnel, and systematic documentation. Conclusions:Supplement use in athletes should be considered a controlled, individualised and documented intervention rather than routine practice. The proposed framework integrates efficacy, evidence quality, mechanisms of action, contamination pathways, behavioural determinants, strict liability and antidoping risk to support safer supplementation decisions. Protecting athlete health and the integrity of clean sport requires a shift from performance-driven to risk-aware supplementation.Strength-of-Recommendation Taxonomy (SORT): Overall framework: B/C, based on consensus statements, position stands, limited controlled studies and expert-informed synthesis. Supplement-specific ratings are provided in Table 2.

Technological innovations can provide cyclists and their support team additional data. These data have potential to improve understanding of performance determinants and could be used to identify and tailor nutritional strategies to improve cycling performance. This potential, however, is dependent on the quality, interpretation, and practical use of the data generated. In this review, several technologies that are used or have some potential for use, in professional cycling are discussed. These include power meters, continuous glucose monitors, portable sweat and lactate analyzers, noninvasive estimation of muscle fiber typology, ultrasound for muscle glycogen concentrations and subcutaneous fat quantification, noninvasive core body temperature sensors, and portable substrate metabolism analyzers. The evidence regarding the validity of these technologies is critically evaluated, alongside a discussion of the potential rationale (or lack thereof) for their use in guiding nutritional strategies. Some of these technologies have sufficient validity and reliability to provide data of sufficient quality and, combined with appropriate rationale, can inform some nutritional strategies (e.g., energy expenditure from power meters). In contrast, other technologies either have insufficient rationale to inform a nutritional strategy or currently lack the validity and/or reliability to provide data of sufficient quality to inform nutritional strategies. Practitioners working with athletes are recommended to consider whether there is any practical value in each metric and, if so, then consider the validity and reliability of a method to measure such a metric before implementation.

Continuous glucose monitoring (CGM) is an emerging tool for dietary counseling in athletes. This study aimed to explore blood glucose profiles in Para cyclists and evaluate CGM accuracy at rest and during exercise. Thirteen Para cyclists, comprising eight hand bikers and five cyclists, wore a CGM sensor (Abbott) for 2 weeks. Participants recorded the timing of meals and regular training sessions and executed one standardized training session. Fifteen capillary blood glucose reference values (seven at rest and eight during the standardized training) were obtained by finger pricks. Mean glucose concentrations and time spent in hypoglycemia (<3.9 mmol/L), euglycemia (3.9-7.8 mmol/L), and hyperglycemia (>7.8 mmol/L) were calculated over 24 hrs and during daytime, nighttime, exercise, and 2 hrs postprandial periods. Mean absolute relative differences (MARD) were calculated between the CGM and capillary blood glucose. The mean glucose concentration over the 24 hr-period was 5.7 (5.6-5.8) mmol/L. Athletes were in the euglycemia range 91% of the time. Hyperglycemia was almost exclusively observed postprandially and during exercise. Hypoglycemia was restricted to the night and was particularly observed in athletes with a spinal cord injury. CGM accuracy was acceptable at rest (MARD: 12%) but markedly lower during exercise (MARD: 34%; p = 0.01), especially for hand bikers (MARD: 41%) compared with cyclists (MARD: 24%; p = 0.01). Para cyclists generally do not display signs of disturbed glucose regulation. However, the increased risk for nocturnal hypoglycemia in athletes with a spinal cord injury warrants attention. Furthermore, CGM accuracy is compromised during exercise, especially if the sensor is in proximity to highly active muscles.

Relative energy deficiency in sport (REDs) is a widely adopted model, originally proposed by an International Olympic Committee (IOC) expert panel in 2014 and recently updated in an IOC 2023 consensus statement. The model describes how low energy availability (LEA) causes a wide range of deleterious health and performance outcomes in athletes. With increasing frequency, sports practitioners are diagnosing athletes with “REDs,” or “REDs syndrome,” based largely upon symptom presentation. The purpose of this review is not to “debunk” REDs but to challenge dogmas and encourage rigorous scientific processes. We critically discuss the REDs concept and existing empirical evidence available to support the model. The consensus (IOC 2023) is that energy availability, which is at the core of REDs syndrome, is impossible to measure accurately enough in the field, and therefore, the only way to diagnose an athlete with REDs appears to be by studying symptom presentation and risk factors. However, the symptoms are rather generic, and the causes likely multifactorial. Here we discuss that (1) it is very difficult to isolate the effects of LEA from other potential causes of the same symptoms (in the laboratory but even more so in the field); (2) the model is grounded in the idea that one factor causes symptoms rather than a combination of factors adding up to the etiology. For example, the model does not allow for high allostatic load (psychophysiological “wear and tear”) to explain the symptoms; (3) the REDs diagnosis is by definition biased because one is trying to prove that the correct diagnosis is REDs, by excluding other potential causes (referred to as differential diagnosis, although a differential diagnosis is supposed to find the cause, not demonstrate that it is a pre-determined cause); (4) observational/cross-sectional studies have typically been short duration (< 7 days) and do not address the long term “problematic LEA,” as described in the IOC 2023 consensus statement; and (5) the evidence is not as convincing as it is sometimes believed to be (i.e., many practitioners believe REDs is well established). Very few studies can demonstrate causality between LEA and symptoms, most studies demonstrate associations and there is a worrying number of (narrative) reviews on the topic, relative to original research. Here we suggest that the athlete is best served by an unbiased approach that places health at the center, leaving open all possible explanations for the presented symptoms. Practitioners could use a checklist that addresses eight categories of potential causes and involve the relevant experts if and when needed. The Athlete Health and Readiness Checklist (AHaRC) we introduce here simply consists of tools that have already been developed by various expert/consensus statements to monitor and troubleshoot aspects of athlete health and performance issues. Isolating the purported effects of LEA from the myriad of other potential causes of REDs symptoms is experimentally challenging. This renders the REDs model somewhat immune to falsification and we may never definitively answer the question, “does REDs syndrome exist?” From a practical point of view, it is not necessary to isolate LEA as a cause because all potential areas of health and performance improvement should be identified and tackled.

ViewpointFragile bones of elite cyclists: to treat or not to treat?Luuk Hilkens, Pim Knuiman, Mathieu Heijboer, Robert Kempers, Asker E. Jeukendrup, Luc J.C van Loon, and Jan-Willem van DijkLuuk HilkensSchool of Sport and Exercise, HAN University of Applied Sciences, Nijmegen, The NetherlandsDepartment of Human Biology, School of Nutrition and Translational Research in Metabolism (NUTRIM), Maastricht University Medical Centre, Maastricht, The Netherlands, Pim KnuimanSchool of Biomedical Sciences, University of Leeds, Leeds, United Kingdom, Mathieu HeijboerTeam Jumbo-Visma (Professional Cycling Team), Den Bosch, The Netherlands, Robert KempersRoyal Dutch Cycling Union (KNWU), Arnhem, The Netherlands, Asker E. JeukendrupTeam Jumbo-Visma (Professional Cycling Team), Den Bosch, The NetherlandsSchool of Sport, Exercise, and Health Sciences, Loughborough University, Loughborough, United Kingdom, Luc J.C van LoonSchool of Sport and Exercise, HAN University of Applied Sciences, Nijmegen, The NetherlandsDepartment of Human Biology, School of Nutrition and Translational Research in Metabolism (NUTRIM), Maastricht University Medical Centre, Maastricht, The Netherlands, and Jan-Willem van DijkSchool of Sport and Exercise, HAN University of Applied Sciences, Nijmegen, The NetherlandsPublished Online:28 Jun 2021https://doi.org/10.1152/japplphysiol.01034.2020This is the final version - click for previous versionMoreSectionsPDF (233 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Accumulating evidence suggests that most elite cyclists have lower bone mineral density (BMD) values when compared with their nonelite counterparts (1) or sedentary young males (2, 3). This raises the question whether these ostensibly healthy athletes have a higher acute bone fracture risk and a higher risk of osteoporosis and associated comorbidities later in life. Although treatment of low BMD seems warranted in elite cyclists, the benefits of treatment for health and performance in this population remain to be established. In this viewpoint, we describe the etiology and consequences of impaired bone health in elite cyclists and discuss the need for interventions to optimize bone health in this unique population.IMPAIRED BONE HEALTH IN ELITE CYCLISTS: WHAT ARE THE CAUSES?The cause of impaired bone health in elite cyclists is likely multifactorial. Lack of mechanical loading of the skeleton is an important factor contributing to impaired bone health in elite cyclists (4). Elite cyclists perform extremely high volumes of exercise training and competition (20–30 h/wk; 500–1,000 km/wk), spending a large part of their days on a bike. As the recovery periods are largely spent in a seated or supine position, these cyclists generally obtain insufficient robust osteogenic stimuli throughout daily life.Low energy availability (LEA) and low body mass are also implicated in the compromised bone health of elite cyclists. Indeed, male and female elite cyclists have been identified as a population at risk for LEA (5, 6), which may eventually lead to the relative energy deficiency in sport (RED-S) syndrome. LEA can be partly attributed to extremely high energy demands for long periods, which may even exceed 30 MJ/day during multistage races (7). Energy intake may also be purposely low when aiming to reduce body mass to enhance the power-to-mass ratio (8). Furthermore, LEA has a major impact on the endocrine system, affecting key hormones that regulate bone metabolism (9).Another factor that may be involved in low BMD in elite cyclists is dermal calcium loss through sweating, which can be as high as ∼150 mg/h (10). In response to dermal calcium losses, the parathyroid gland will release the parathyroid hormone (PTH), which activates demineralization of bone tissue to prevent or attenuate a decline in serum calcium levels. Chronic activation of this mechanism may contribute to low BMD in elite cyclists (11), although the impact of dermal calcium loss in calcium homeostasis has also been challenged recently (12).It can also be speculated that chronic exercise stress is implicated in impaired bone health in elite cyclists. Although research on this topic is lacking, there is some evidence to suggest that chronic inflammation (13) and elevated cortisol levels (14) are related to bone loss, albeit in nonathletes.It can be argued that the use of glucocorticoids, as a treatment for musculoskeletal injuries, asthma, and exercise-induced bronchoconstriction, may also contribute to low BMD. However, it should be noted that the use of systemic glucocorticoids seems rare in modern elite cycling, which is also evidenced by a steady decline in "adverse analytical findings" due to glucocorticoid use over the past 2 decades (15). Although inhaled glucocorticoids may be used by some elite cyclists for the treatment of asthma or exercise-induced bronchoconstriction (16), their systemic bioavailability (17) and impact on BMD (18, 19) seem rather limited. Taken together, we believe that the potential contribution of glucocorticoids to the decreased BMD in the current generation of elite cyclists is likely to be negligible.IMPAIRED BONE HEALTH IN ELITE CYCLISTS: WHAT ARE THE CONSEQUENCES?Short-term consequences of low BMD in athletes include an increased risk of stress fractures and traumatic bone fractures (5). Stress fractures, however, seem very uncommon among elite cyclists due to the minimal bone stress during cycling. Traumatic bone fractures, on the other hand, are highly prevalent among elite cyclists due to the considerable risk of crashes during training and competition. In this regard, Haeberle and coworkers (20) showed that fractures as a result of crashes were the most common reason for withdrawal during the Tour de France between 2010 and 2017. Moreover, half of the cyclists with fractures underwent surgery (20), emphasizing the importance of this problem. Crashes, however, are inherent to cycling races, and it remains to be established whether stronger bones reduce the risk of bone fractures due to crashes.An important long-term consequence of low peak bone mass in elite cyclists could be an increased risk of bone fractures later in life. It has been proposed that a high peak bone mass during early adulthood is the single most important factor for the prevention of osteoporosis with aging (21). An increase in peak bone mass of 10% has been estimated to delay the onset of osteoporosis by 13 years (22), thereby emphasizing the necessity for healthy bones in young adulthood. However, the progression and/or regression of impaired bone status during and after the cyclists' active career remain(s) to be established, and no (anecdotal) evidence is available that indicates a higher prevalence of bone fractures in retired elite cyclists.The implications of poor bone health for performance should be considered as well. RED-S syndrome, which is often associated with low BMD, has been linked to impaired exercise performance (5). However, when low BMD occurs without other features of RED-S syndrome, there is no direct evidence to assume that cycling performance will be affected. Nevertheless, given the function of bone in hematopoiesis, and the emerging evidence regarding bone-muscle cross talk (23), it should be realized that the importance of healthy bones may extend well beyond bone fracture risk alone.IMPAIRED BONE HEALTH IN ELITE CYCLISTS: CONSIDERATIONS FOR TREATMENTAlthough oral bisphosphonates are effective in increasing BMD and reducing the risk of bone fractures in men with osteoporosis (24), we feel that pharmacological treatment should be the last line of defense, especially in young athletes. The impact of exercise and nutritional interventions to increase BMD has been reported extensively, particularly for older adults and postmenopausal women (25, 26). To our knowledge, no exercise and/or nutritional interventions aimed at increasing BMD have been documented in elite cyclists. Possible interventions should result in clinically relevant increments in BMD, without interfering with training targets and cycling performance.Resistance exercise training and impact training (e.g., jumping or bounding) are generally prescribed as the more effective exercise strategies to increase BMD (27). Although resistance exercise training may support cycling performance, many elite cyclists are afraid of potential negative effects of resistance-type exercise training on body mass and cycling performance (8). Impact training is likely more effective than resistance exercise training (28) and may interfere less with the adaptation to endurance training (29). In support, daily short bouts of high-impact jumping exercise have been shown to increase BMD (30), making this a possible intervention to integrate into an elite cyclist's training program. It is unknown, however, if such a low-dose osteogenic stimulus outweighs the deleterious effects of elite cycling on bone health.Energy availability, calcium, vitamin D, and protein are among the major nutritional factors that should be considered (31). Careful assessment of nutritional intake and regular blood testing (for vitamin D) are needed to assess whether cyclists have an inadequate energy and calcium intake and/or vitamin D status. An adequate calcium intake is needed for bone mineralization, with adequate serum 25-hydroxyvitamin D levels promoting the absorption of calcium from the gut. Deficiencies should be addressed, whereas supplementation above intake recommendations seems to provide little (32) or no (33) benefit for bone health. Being the most abundant protein in the bone matrix, collagen could be an interesting target for novel nutritional strategies as well. Indeed, 12 mo of daily supplementation with collagen has been shown to positively affect BMD and markers of bone metabolism in postmenopausal women (34), whereas a combination of gelatin supplementation with jumping exercise has been shown to increase the (bone) collagen synthesis marker N-terminal propeptide of type I collagen (P1NP) in young males (35).It is clear that both exercise and nutrition have the potential to increase BMD in elite cyclists, but more work is needed to establish their efficacy and effectiveness in this specific population.IMPAIRED BONE HEALTH IN ELITE CYCLISTS: TO TREAT OR NOT TO TREAT?The answer to the question whether low BMD in elite cyclists should be treated may not be as clear-cut as initially thought. It is concerning that elite cyclists have a low bone mass at an age where peak bone mass is normally achieved. However, the potential short- and long-term consequences of impaired bone health in terms of health and performance are unclear in this specific population. Although BMD can generally be increased by exercise and/or nutritional interventions, the feasibility, effectiveness, and potential side effects of such interventions remain to be established in this population. The ultimate piece of evidence would reveal the relationship between bone health and the incidence of traumatic bone fractures during and after the active career of elite cyclists. Until more evidence becomes available, all elite cyclists and their supporting staff should at least be aware of this issue and carefully consider the available treatment options for low BMD.GRANTSThe work of L. Hilkens and J. W. van Dijk on this topic is part of the Eat2Move project and sponsored by a grant from the Province of Gelderland, the Netherlands.DISCLOSURESNo conflicts of interest, financial or otherwise, are declared by the authors.AUTHOR CONTRIBUTIONSL.H. and J.W.v.D conceived and designed research; L.H. and J.W.v.D. drafted manuscript; L.H., P.K., M.H., R.K., A.E.J., L.J.v. and J.W.v.D. edited and revised manuscript; L.H., P.K., M.H., R.K., A.E.J., L.J.v. and J.W.v.D. approved final version of manuscript.REFERENCES1. Mojock CD, Ormsbee MJ, Kim JS, Arjmandi BH, Louw GA, Contreras RJ, Panton LB. Comparisons of bone mineral density between recreational and trained male road cyclists. Clin J Sport Med 26: 152–156, 2016. doi:10.1097/JSM.0000000000000186.Crossref | ISI | Google Scholar2. Campion F, Nevill AM, Karlsson M, Lounana J, Shabani M, Fardellone P, Medelli J. Bone status in professional cyclists. Int J Sports Med 31: 511–515, 2010. doi:10.1055/s-0029-1243616.Crossref | ISI | Google Scholar3. 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Shaw G, Lee-Barthel A, Ross ML, Wang B, Baar K. Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis. Am J Clin Nutr 105: 136–143, 2017. doi:10.3945/ajcn.116.138594. Crossref | PubMed | ISI | Google ScholarAUTHOR NOTESCorrespondence: Dr. J.-W. van Dijk (JanWillem.[email protected]nl). Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation Related ArticlesCommentaries on Viewpoint: Fragile bones of elite cyclists: to treat or not to treat? 28 Jun 2021Journal of Applied PhysiologyLast Word on Viewpoint: Fragile bones of elite cyclists: to treat or not to treat? 28 Jun 2021Journal of Applied PhysiologyCited ByCommentaries on Viewpoint: Do we need to change the guideline values for determining low bone mineral density in athletes?19 May 2022 | Journal of Applied Physiology, Vol. 132, No. 5Do we need to change the guideline values for determining low bone mineral density in athletes?Kristin L. Jonvik, Monica K. Torstveit, Jorunn Sundgot-Borgen, and Therese Fostervold Mathisen19 May 2022 | Journal of Applied Physiology, Vol. 132, No. 5Site-Specific Bone Differences and Energy Status in Male Competitive Runners and Road CyclistsJournal of Clinical Densitometry, Vol. 25, No. 2Commentaries on Viewpoint: Fragile bones of elite cyclists: to treat or not to treat?28 June 2021 | Journal of Applied Physiology, Vol. 131, No. 1Last Word on Viewpoint: Fragile bones of elite cyclists: to treat or not to treat?Luuk Hilkens, Pim Knuiman, Mathieu Heijboer, Robert Kempers, Asker E. Jeukendrup, Luc J.C. van Loon, and Jan-Willem van Dijk28 June 2021 | Journal of Applied Physiology, Vol. 131, No. 1 More from this issue > Volume 131Issue 1July 2021Pages 26-28 Crossmark Copyright & PermissionsCopyright © 2021 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.01034.2020PubMed33703944History Received 3 December 2020 Accepted 8 March 2021 Published online 28 June 2021 Published in print 1 July 2021 Keywordsboneelite cyclistsexercisenutritionosteoporosis Metrics

Infographic 1: UEFA 2020 expert group statement in elite football: Training day. Infographic 2: UEFA 2020 expert group statement in elite football: match-day. Infographic 3: UEFA 2020 expert group statement in elite football: Best of the rest—8 other key take-home messages. UEFA commissioned an expert group statement on nutrition in elite football.1 Gathering 32 global experts in football and nutrition research …

Hypohydration increases physiological strain and reduces physical and technical soccer performance, but there are limited data on how fluid balance responses change between different types of sessions in professional players. This study investigated sweat and fluid/carbohydrate intake responses in elite male professional soccer players training at low and high intensities in cool and hot environments. Fluid/sodium (Na+) losses and ad-libitum carbohydrate/fluid intake of fourteen elite male soccer players were measured on four occasions: cool (wet bulb globe temperature (WBGT): 15 ± 7 °C, 66 ± 6% relative humidity (RH)) low intensity (rating of perceived exertion (RPE) 2–4, m·min−1 40–46) (CL); cool high intensity (RPE 6–8, m·min−1 82–86) (CH); hot (29 ± 1 °C, 52 ± 7% RH) low intensity (HL); hot high intensity (HH). Exercise involved 65 ± 5 min of soccer-specific training. Before and after exercise, players were weighed in minimal clothing. During training, players had ad libitum access to carbohydrate beverages and water. Sweat [Na+] (mmol·L−1), which was measured by absorbent patches positioned on the thigh, was no different between conditions, CL: 35 ± 9, CH: 38 ± 8, HL: 34 ± 70.17, HH: 38 ± 8 (p = 0.475). Exercise intensity and environmental condition significantly influenced sweat rates (L·h−1), CL: 0.55 ± 0.20, CH: 0.98 ± 0.21, HL: 0.81 ± 0.17, HH: 1.43 ± 0.23 (p =0.001), and percentage dehydration (p < 0.001). Fluid intake was significantly associated with sweat rate (p = 0.019), with no players experiencing hypohydration > 2% of pre-exercise body mass. Carbohydrate intake varied between players (range 0–38 g·h−1), with no difference between conditions. These descriptive data gathered on elite professional players highlight the variation in the hydration status, sweat rate, sweat Na+ losses, and carbohydrate intake in response to training in cool and hot environments and at low and high exercise intensities.

Football is a global game which is constantly evolving, showing substantial increases in physical and technical demands. Nutrition plays a valuable integrated role in optimising performance of elite players during training and match-play, and maintaining their overall health throughout the season. An evidence-based approach to nutrition emphasising, a 'food first' philosophy (ie, food over supplements), is fundamental to ensure effective player support. This requires relevant scientific evidence to be applied according to the constraints of what is practical and feasible in the football setting. The science underpinning sports nutrition is evolving fast, and practitioners must be alert to new developments. In response to these developments, the Union of European Football Associations (UEFA) has gathered experts in applied sports nutrition research as well as practitioners working with elite football clubs and national associations/federations to issue an expert statement on a range of topics relevant to elite football nutrition: (1) match day nutrition, (2) training day nutrition, (3) body composition, (4) stressful environments and travel, (5) cultural diversity and dietary considerations, (6) dietary supplements, (7) rehabilitation, (8) referees and (9) junior high-level players. The expert group provide a narrative synthesis of the scientific background relating to these topics based on their knowledge and experience of the scientific research literature, as well as practical experience of applying knowledge within an elite sports setting. Our intention is to provide readers with content to help drive their own practical recommendations. In addition, to provide guidance to applied researchers where to focus future efforts.

ViewpointLast Word on Viewpoint: Fragile bones of elite cyclists: to treat or not to treat?Luuk Hilkens, Pim Knuiman, Mathieu Heijboer, Robert Kempers, Asker E. Jeukendrup, Luc J.C. van Loon, and Jan-Willem van DijkLuuk HilkensSchool of Sport and Exercise, HAN University of Applied Sciences, Nijmegen, The NetherlandsDepartment of Human Biology, School of Nutrition and Translational Research in Metabolism (NUTRIM), Maastricht University Medical Centre, Maastricht, The Netherlands, Pim KnuimanSchool of Biomedical Sciences, University of Leeds, Leeds, United Kingdom, Mathieu HeijboerTeam Jumbo-Visma, Den Bosch, The Netherlands, Robert KempersRoyal Dutch Cycling Union, Arnhem, The Netherlands, Asker E. JeukendrupTeam Jumbo-Visma, Den Bosch, The NetherlandsSchool of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, United Kingdom, Luc J.C. van LoonSchool of Sport and Exercise, HAN University of Applied Sciences, Nijmegen, The NetherlandsDepartment of Human Biology, School of Nutrition and Translational Research in Metabolism (NUTRIM), Maastricht University Medical Centre, Maastricht, The Netherlands, and Jan-Willem van DijkSchool of Sport and Exercise, HAN University of Applied Sciences, Nijmegen, The NetherlandsPublished Online:28 Jun 2021https://doi.org/10.1152/japplphysiol.00375.2021MoreSectionsPDF (186 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat to the editor: We thank the authors of the Commentaries (1) on our Viewpoint (2). Most authors seem to agree with our view that impaired bone health in elite (road-race) cyclists is an issue of concern. Nevertheless, Beck and Sipp (1) propose a performance benefit of low bone mineral density (BMD) as a result of a lower body weight. We argue, however, that this effect is negligible. The difference in whole body bone mineral content in cyclists with normal versus low BMD seems to be only ∼100 to 300 g. Irrespective of the impact on cycling performance, Beck and Kipp’s view touches the sensitive ethical dilemma of whether athletes should be willing to win at the expense of a potentially irreversible medical condition.Regarding the treatment of low BMD in elite cyclists, we read with interest the suggestions by many authors to include high-impact jump training as part of the training program of elite cyclists (1). Indeed, there is some evidence to suggest that high-impact training is effective in increasing BMD (3), although this has not been established in elite cyclists. The latter is of particular importance because large volumes of endurance training potentially affects the osteogenic stimulus of high-impact training. In this regard, the preferred training characteristics to maximize the osteogenic stimulus of high-impact training (i.e., mode, load, volume, and frequency) are currently unknown, particularly when combined with endurance training. We should also consider the notion that high-impact exercise may increase the risk of stress fractures, especially in populations characterized with osteopenic or osteoporotic BMD values (3, 4). Therefore, we agree with Gibbs and Churchward-Venne (1) that treatment strategies should ideally be initiated during young adulthood to prevent impaired bone health during later stages of the cycling career.Along with the efficacy of treatment options, we feel that feasibility and compliance are the major factors determining the value of interventions for elite cyclists. Even a high-impact workout of just 5 min per day may not be feasible for an elite cyclist throughout an entire year, as the competitive season is characterized by periodized training and nutrition schedules, congested race schedules, and a lot of traveling. Future research should establish whether strategically timed periods of high-impact training (e.g., high frequency of high-impact exercise sessions during the preparatory phase, with a lower frequency of sessions during the competitive phase) are effective in improving and/or maintaining bone health over time.We agree with Greeves and O’Leary (1) that BMD is just one aspect of bone health, whereas bone microarchitecture is at least as important with regard to bone quality, mechanical strength, and subsequent fracture risk (5). Indeed, even when BMD values are within a normal range, bone microarchitecture may be (irreversible) impaired (6). To the best of our knowledge, it is currently unknown whether low BMD in elite cyclist is accompanied by an impaired bone microarchitecture and bone strength. This might be associated with the limited availability of high-resolution peripheral computed tomography (HR-pQCT) as an instrument to monitor bone microarchitecture on a regular basis. Nevertheless, such information would be highly valuable to better understand the bone health of elite cyclists and to evaluate the need and effectiveness of treatment strategies in this population.DISCLOSURESNo conflicts of interest, financial or otherwise, are declared by the authors.AUTHOR CONTRIBUTIONSL.H. and J-W.v.D. drafted manuscript; L.H., P.K., M.H., R.K., A.E.J., L.J.C.v.L., and J-W.v.D. edited and revised manuscript; L.H., P.K., M.H., R.K., A.E.J., L.J.C.v.L., and J-W.v.D. approved final version of manuscript.REFERENCES1. Brocherie F, Camacho-Cardenosa M, Timon R, Debevec T, Rittweger J, Hutson MJ, O'Donnell E, Brooke-Wavell K, Blagrove RC, Beck ON, Kipp S, Fernandes RJ, Conceição F, Abraldes JA, Greeves JP, O'Leary TJ, Vagula M, Gibbs JC, Churchward‐Venne TA, Dolan E, Pintos RS, Oliveira LF, Sale C, Saunders B. Commentaries on Viewpoint: Fragile bones of elite cyclists: to treat or not to treat? J Appl Physiol (1985). doi:10.1152/japplphysiol.00335.2021.Link | Google Scholar2. Hilkens L, Knuiman P, Heijboer M, Kempers R, Jeukendrup AE, van Loon LJC, van Dijk J-W. Fragile bones of elite cyclists: to treat or not to treat? J Appl Physiol (1985). doi:10.1152/japplphysiol.01034.2020. Link | ISI | Google Scholar3. Hutson MJ, O’Donnell E, Brooke-Wavell K, Sale C, Blagrove RC. Effects of low energy availability on bone health in endurance athletes and high-impact exercise as a potential countermeasure: a narrative review. Sports Med 51: 391–403, 2021. doi:10.1007/s40279-020-01396-4. Crossref | PubMed | ISI | Google Scholar4. Myburgh KH, Hutchins J, Fataar AB, Hough SF, Noakes TD. Low bone density is an etiologic factor for stress fractures in athletes. Ann Intern Med 113: 754–759, 1990. doi:10.7326/0003-4819-113-10-754. Crossref | PubMed | ISI | Google Scholar5. Cheung AM, Adachi JD, Hanley DA, Kendler DL, Davison KS, Josse R, Brown JP, Ste-Marie LG, Kremer R, Erlandson MC, Dian L, Burghardt AJ, Boyd SK. High-resolution peripheral quantitative computed tomography for the assessment of bone strength and structure: a review by the Canadian Bone Strength Working Group. Curr Osteoporos Rep 11: 136–146, 2013. doi:10.1007/s11914-013-0140-9. Crossref | PubMed | ISI | Google Scholar6. Kazakia GJ, Burghardt AJ, Link TM, Majumdar S. Variations in morphological and biomechanical indices at the distal radius in subjects with identical BMD. J Biomech 44: 257–266, 2011. doi:10.1016/j.jbiomech.2010.10.010. Crossref | PubMed | ISI | Google ScholarAUTHOR NOTESCorrespondence: J-W. van Dijk (JanWillem.[email protected]nl). Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation Collections Related ArticlesFragile bones of elite cyclists: to treat or not to treat? 28 Jun 2021Journal of Applied PhysiologyCommentaries on Viewpoint: Fragile bones of elite cyclists: to treat or not to treat? 28 Jun 2021Journal of Applied Physiology More from this issue > Volume 131Issue 1July 2021Pages 34-35 Crossmark Copyright & PermissionsCopyright © 2021 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.00375.2021PubMed34181488History Received 28 May 2021 Accepted 28 May 2021 Published online 28 June 2021 Published in print 1 July 2021 Keywordsboneelite cyclistsexercisenutritionosteoporosis Metrics

There has been substantial progress in the knowledge of exercise and type 1 diabetes, with the development of guidelines for optimal glucose management. In addition, an increasing number of people living with type 1 diabetes are pushing their physical limits to compete at the highest level of sport. However, the post-exercise recovery routine, particularly with a focus on sporting performance, has received little attention within the scientific literature, with most of the focus being placed on insulin or nutritional adaptations to manage glycaemia before and during the exercise bout. The post-exercise recovery period presents an opportunity for maximising training adaption and recovery, and the clinical management of glycaemia through the rest of the day and overnight. The absence of clear guidance for the post-exercise period means that people with type 1 diabetes should either develop their own recovery strategies on the basis of individual trial and error, or adhere to guidelines that have been developed for people without diabetes. This Review provides an up-to-date consensus on post-exercise recovery and glucose management for individuals living with type 1 diabetes. We aim to: (1) outline the principles and time course of post-exercise recovery, highlighting the implications and challenges for endurance athletes living with type 1 diabetes; (2) provide an overview of potential strategies for post-exercise recovery that could be used by athletes with type 1 diabetes to optimise recovery and adaptation, alongside improved glycaemic monitoring and management; and (3) highlight the potential for technology to ease the burden of managing glycaemia in the post-exercise recovery period.

PRESENT 2020: Texto que desarrolla la lista de verificación para el adecuado informe de la evidencia en ensayos clínicos de deporte y nutrición del ejercicio (Traducción Inglés-Español). Traducido por: ME Da Silva-Grigoletto Grupo de entrenamiento funcional. Universidad Federal de Sergipe. São Cristovão. Brasil F Boscolo Del Vecchio Escuela de Educación Física. Universidad Federal de Pelotas. Pelotas. Brasil Juan de Dios Beas Jiménez Centro Andaluz de Medicina del Deporte. Sevilla. España.

© 2020 Human Kinetics, Inc. Some readers may not have access to the full paper, so a properly formatted and well-written abstract is imperative. Authors should give priority to information about the current study rather than using the abstract for an extensive background or rationale. 2a Methods: Key information regarding the study design, methods, and population should be summarized to enable broad understanding of the study from the abstract. 2b Results: Readers are interested in extracting key data that reflect the main findings of the study. The abstract should present data (e.g., the absolute magnitude of values and the size/precision of effects—specifying which measures of central tendency and variability are stated) rather than simply stating the presence, absence, or direction of effects. The presentation of p values or similar inferential statistics is no substitute for reporting actual data (Maughan, 2004). 2c Conclusion: Priority should be given to the reporting of results as per the previous section, with only a brief concluding statement thereafter. A concise conclusion based on what was actually measured in the study is preferred to speculative interpretations, with cautious use of language to avoid hyperbole or improper inference of causality (Brown et al., 2013). It is not appropriate or necessary to identify further research priorities here.

Distance events in Athletics include cross country, 10,000-m track race, half-marathon and marathon road races, and 20- and 50-km race walking events over different terrain and environmental conditions. Race times for elite performers span ∼26 min to >4 hr, with key factors for success being a high aerobic power, the ability to exercise at a large fraction of this power, and high running/walking economy. Nutrition-related contributors include body mass and anthropometry, capacity to use fuels, particularly carbohydrate (CHO) to produce adenosine triphosphate economically over the duration of the event, and maintenance of reasonable hydration status in the face of sweat losses induced by exercise intensity and the environment. Race nutrition strategies include CHO-rich eating in the hours per days prior to the event to store glycogen in amounts sufficient for event fuel needs, and in some cases, in-race consumption of CHO and fluid to offset event losses. Beneficial CHO intakes range from small amounts, including mouth rinsing, in the case of shorter events to high rates of intake (75-90 g/hr) in the longest races. A personalized and practiced race nutrition plan should balance the benefits of fluid and CHO consumed within practical opportunities, against the time, cost, and risk of gut discomfort. In hot environments, prerace hyperhydration or cooling strategies may provide a small but useful offset to the accrued thermal challenge and fluid deficit. Sports foods (drinks, gels, etc.) may assist in meeting training/race nutrition plans, with caffeine, and, perhaps nitrate being used as evidence-based performance supplements.

PURPOSE Large inter-individual variation exists in maximal fat oxidation rates (MFO) and the exercise intensity at which it occurs (FATMAX). However, there is no data describing the shape of the fat oxidation curve or, if individual differences exist when tested on separate occasions. Furthermore, there is limited data on fat metabolism in professional team sport athletes. Therefore, the aim of this study was to test-retest the concavity (shape) and intercept (height) of fat oxidation curves within a group of professional soccer players. METHOD On two occasions 16 professional male soccer players completed a graded exercise test in a fasted state (≥5 h). Rates of fat oxidation were determined using indirect calorimetry. Maximal oxygen uptake (VO2max) was measured to calculate FATMAX (%VO2max). The shape of the fat oxidation curves were modelled on an individual basis using third degree polynomial. Test-by-test differences, in the shape and vertical shift of the fat oxidation curves, were established to assess within-individual variability. RESULTS Average absolute MFO was 0.69 ± 0.15 g[BULLET OPERATOR]min (range 0.45 - 0.99g[BULLET OPERATOR]min). On a group level, no significant differences were found in MFO between the two tests. No differences were found (p>0.05) in the shape of the fat oxidation curves in 13/16 players (Test1 vs. Test2). There were also no differences (p>0.05) in the vertical shift of the fat oxidation curves in 10 players. CONCLUSION In general, the shape of the fat oxidation curve does not change within an individual however the vertical shift is more susceptible to change, which may be due to training status and body composition. Understanding a player's metabolism may be of value to practitioners working within sport, with regards to personalising nutrition strategies.

From the breakthrough studies of dietary carbohydrate and exercise capacity in the 1960s through to the more recent studies of cellular signaling and the adaptive response to exercise in muscle, it has become apparent that manipulations of dietary fat and carbohydrate within training phases, or in the immediate preparation for competition, can profoundly alter the availability and utilization of these major fuels and, subsequently, the performance of endurance sport (events >30min up to similar to 24 hr). A variety of terms have emerged to describe new or nuanced versions of such exercise-diet strategies (e.g., train low, train high, low-carbohydrate high-fat diet, periodized carbohydrate diet). However, the nonuniform meanings of these terms have caused confusion and miscommunication, both in the popular press and among the scientific community. Sports scientists will continue to hold different views on optimal protocols of fuel support for training and competition in different endurance events. However, to promote collaboration and shared discussions, a commonly accepted and consistent terminology will help to strengthen hypotheses and experimental/experiential data around various strategies. We propose a series of definitions and explanations as a starting point for a more unified dialogue around acute and chronic manipulations of fat and carbohydrate in the athlete's diet, noting philosophies of approaches rather than a single/definitive macronutrient prescription. We also summarize some of the key questions that need to be tackled to help produce greater insight into this exciting area of sports nutrition research and practice.

INTRODUCTION:The aim of this study was to describe maximal fat oxidation (MFO) rates in an athletic population. METHOD:In total, 1121 athletes (933 males and 188 females), from a variety of sports and competitive level, undertook a graded exercise test on a treadmill in a fasted state (≥5 h fasted). Rates of fat oxidation were determined using indirect calorimetry. RESULTS:The average MFO was 0.59 ± 0.18 g·min, ranging from 0.17 to 1.27 g·min. Maximal rates occurred at an average exercise intensity of 49.3% ± 14.8% V˙O2max, ranging from 22.6% to 88.8% V˙O2max. In absolute terms, male athletes had significantly higher MFO compared with females (0.61 and 0.50 g·min, respectively, P < 0.001). Expressed relative to fat-free mass (FFM), MFO were higher in the females compared with males (MFO/FFM: 11.0 and 10.0 mg·kg·FFM·min, respectively, P < 0.001). Soccer players had the highest MFO/FFM (10.8 mg·kg·FFM·min), ranging from 4.1 to 20.5 mg·kg·FFM·min, whereas American Football players displayed the lowest rates of MFO/FFM (9.2 mg·kg·FFM·min). In all athletes, and when separated by sport, large individual variations in MFO rates were observed. Significant positive correlations were found between MFO (g·min) and the following variables: FFM, V˙O2max, FATMAX (the exercise intensity at which the MFO was observed), percent body fat, and duration of fasting. When taken together these variables account for 47% of the variation in MFO. CONCLUSION:MFO and FATMAX vary significantly between athletes participating in different sports but also in the same sport. Although variance in MFO can be explained to some extent by body composition and fitness status, more than 50% of the variance is not explained by these variables and remains unaccounted for.

Peak exogenous carbohydrate oxidation rates typically reach ~1 g∙min−1 during exercise when ample glucose or glucose polymers are ingested. Fructose co‐ingestion has been shown to further increase exogenous carbohydrate oxidation rates. The purpose of this study was to assess the impact of fructose co‐ingestion provided either as a monosaccharide or as part of the disaccharide sucrose on exogenous carbohydrate oxidation rates during prolonged exercise in trained cyclists. Ten trained male cyclists (VO2peak: 65 ± 2 mL∙kg−1∙min−1) cycled on four different occasions for 180 min at 50% Wmax during which they consumed a carbohydrate solution providing 1.8 g∙min−1 of glucose (GLU), 1.2 g∙min−1 glucose + 0.6 g∙min−1 fructose (GLU + FRU), 0.6 g∙min−1 glucose + 1.2 g∙min−1 sucrose (GLU + SUC), or water (WAT). Peak exogenous carbohydrate oxidation rates did not differ between GLU + FRU and GLU + SUC (1.40 ± 0.06 vs. 1.29 ± 0.07 g∙min−1, respectively, p = 0.999), but were 46% ± 8% higher when compared to GLU (0.96 ± 0.06 g∙min−1: p < 0.05). In line, exogenous carbohydrate oxidation rates during the latter 120 min of exercise were 46% ± 8% higher in GLU + FRU or GLU + SUC compared with GLU (1.19 ± 0.12, 1.13 ± 0.21, and 0.82 ± 0.16 g∙min−1, respectively, p < 0.05). We conclude that fructose co‐ingestion (0.6 g∙min−1) with glucose (1.2 g∙min−1) provided either as a monosaccharide or as sucrose strongly increases exogenous carbohydrate oxidation rates during prolonged exercise in trained cyclists.