Publications by authors named "Olivier de Hon"

Background: Anabolic androgenic steroids (AAS) are thought to increase venous thromboembolism (VTE) risk.

Objectives: We investigated whether AAS influence coagulation parameters associated with VTE by assessing their changes during and after AAS use.

Methods: The HAARLEM study enrolled 100 male amateur athletes voluntarily starting an AAS cycle between 2015 and 2018.

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Androgen abuse is associated with unfavourable changes in blood pressure, lipid metabolism and erythrocytosis. Most knowledge is based on cross-sectional studies sensitive to bias. We assessed the magnitude of these effects and their recovery in a prospective cohort study which included 100 men (≥18 years) performing an androgen cycle.

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Tools for reliable assessment of socially sensitive or transgressive behavior warrant constant development. Among them, the Crosswise Model (CM) has gained considerable attention. We systematically reviewed and meta-analyzed empirical applications of CM and addressed a gap for quality assessment of indirect estimation models.

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Sports nutrition supplements have previously been reported to contain undeclared doping substances. The use of such supplements can lead to general health risks and may give rise to unintentional doping violations in elite sports. To assess the prevalence of doping substances in a range of high-risk sports nutrition supplements available from Dutch web shops.

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Background: The prevalence of doping in competitive sport, and the methods for assessing prevalence, remain poorly understood. This reduces the ability of researchers, governments, and sporting organizations to determine the extent of doping behavior and the impacts of anti-doping strategies.

Objectives: The primary aim of this subject-wide systematic review was to collate and synthesize evidence on doping prevalence from published scientific papers.

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An estimated 4-6% of fitness center visitors uses anabolic-androgenic steroids (AAS). Reliable data about adverse reactions of AAS are scarce. The HAARLEM study aimed to provide insight into the positive and negative effects of AAS use.

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Background: The use of anabolic androgenic steroids (AAS) is common among visitors of fitness centers. Knowledge about health risks of AAS use is limited due to lack of clinical studies.

Methods: One hundred men, at least 18 years old, intending to start a cycle of AAS were recruited.

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Recombinant human erythropoietin (rHuEPO) is used as doping a substance. Anti-doping efforts include urine and blood testing and monitoring the athlete biological passport (ABP). As data on the performance of these methods are incomplete, this study aimed to evaluate the performance of two common urine assays and the ABP.

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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.

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The present study investigates the applicability of the chemical analysis of wastewater to assess the use of doping substances by the general population and amateur athletes. To this end, an analytical methodology that can identify and quantify a list of 15 substances from the groups of anabolic steroids, weight loss products, and masking agents in wastewater has been developed. The method uses solid phase extraction to increase the detection sensitivity of the target analytes, expected to be present at very low concentrations (ng L range), and decrease possible matrix interferences.

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Background: The sanction that an athlete receives when an anti-doping rule violation has been committed depends on the specific circumstances of the case. Anti-doping tribunals decide on the final sanction, following the rules of the World Anti-Doping Code.

Objectives: To assess the athletes' degree of fault based on the length of sanctions imposed on them to feed policy-related discussions.

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Background: Substances that potentially enhance performance (eg, recombinant human erythropoietin [rHuEPO]) are considered doping and are therefore forbidden in sports; however, the scientific evidence behind doping is frequently weak. We aimed to determine the effects of rHuEPO treatment in well trained cyclists on maximal, submaximal, and race performance and on safety, and to present a model clinical study for doping research on other substances.

Methods: We did this double-blind, randomised, placebo-controlled trial at the Centre for Human Drug Research in Leiden (Netherlands).

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The prevalence of doping in elite sports is relevant for all those involved in sports, particularly for evaluating anti-doping policy measures. Remarkably, few scientific articles have addressed this subject so far, and the last review dates back to 1997. As a consequence, the true prevalence of doping in elite sports is unknown.

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Background: To improve anti-doping efforts in sports, the World Anti-Doping Agency (WADA) introduced the World Anti-Doping Program, in which (among others) regulations for providing athletes' whereabouts are described. Because the effectiveness and efficiency of this system depends on the co-operation and compliance of athletes, the perspective of elite athletes is important. This paper answers the following research questions: What is the perspective of Dutch elite athletes on the current whereabouts system in general and how important is their privacy in providing whereabouts in particular? In addition, this study explores how far the whereabouts system can be developed in the future.

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Studies on the use of performance enhancing drugs (PED) in fitness centres rely predominately on conventional survey methods using direct questioning. However, research indicates that direct questioning of sensitive information is characterized by under-reporting. The aim of the present study was to contrast direct questioning of different types of PED use by Dutch fitness centre members with results obtained with the Randomized Response Technique (RRT).

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Physicians should possess specific diagnostic and pharmacotherapeutic skills in order to recognize symptoms associated with doping use. It is important to be on the alert in athletes and fitness enthusiasts for physical and psychological changes due to use of anabolic steroids such as acne, stretch marks, gynecomastia, signs of acromegaly, irascibility and lethargy. Stimulants such as amphetamines, ephedrine and cocaine lead to fat loss and increased alertness; their main side effects are cardiac problems, behavioural changes and addiction.

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The possibility of gene doping, defined as the transfer of nucleic acid sequences and/or the use of normal or genetically modified cells to enhance sport performance, is a real concern in sports medicine. The abuse of knowledge and techniques gained in the area of gene therapy is a form of doping, and is prohibited for competitive athletes. As yet there is no conclusive evidence that that gene doping has been practiced in sport.

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Inhaled β₂-agonists are commonly used as bronchodilators in the treatment of asthma. Their use in athletes, however, is restricted by anti-doping regulations. Controversies remain as to whether healthy elite athletes who use bronchodilators may gain a competitive advantage.

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In the Netherlands an estimated 20,000 people use anabolic androgenic steroids (AAS). The use of AAS is particularly common in regular visitors to gyms and fitness centres. AAS are usually synthetic derivatives of testosterone with both an anabolic and an androgenic effect.

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Nutritional supplements can be a source of positive doping cases as some supplements contain prohibited substances without showing this on their label. This problem has existed for some time and has been extensively studied in the past 8 years. The sport of tennis has played a particular role in this problem because of some peculiar doping cases within its community.

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