H Kuipers's research while affiliated with Maastricht University and other places

Publications (163)

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Hemoglobin concentration and percent reticulocytes (%retics) were analyzed in blood samples taken pre-competition, post-competition, and during out of competition testing in elite speed skaters. Percent reticulocytes during screening was not different from the values obtained post-race, and no significant gender difference was found. Mean hemoglobi...
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This systematic review summarizes the research of previous studies that used resistance training in the post-treatment phase of cancer patients with a focus on methodological quality, training methods and physical outcome measures. We found twenty-four studies (10 RCTs, 4 controlled clinical trials and 10 uncontrolled trials) that met all inclusion...
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Het doel van training is het verbeteren van het fysieke prestatievermogen en te pieken tijdens belangrijke wedstrijden. Ofschoon het prestatievermogen van ieder mens voor 60-70 procent door aangeboren eigenschappen (talent) wordt bepaald, blijft er 25-30 procent ruimte voor prestatieverbetering door middel van training. Om het volledige potentieel...
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Structured exercise is considered a cornerstone in type 2 diabetes treatment. However, adherence to combined resistance and endurance type exercise or medical fitness intervention programmes is generally poor. Group-based brisk walking may represent an attractive alternative, but its long-term efficacy as compared with an individualised approach su...
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Cardiac remodelling is commonly defined as a physiological or pathological state that may occur after conditions such as myocardial infarction, pressure overload, idiopathic dilated cardiomyopathy or volume overload. When training excessively, the heart develops several myocardial adaptations causing a physiological state of cardiac remodelling. Th...
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To assess possible ergogenic properties of corticosteroid administration. A balanced, double-blind, placebo-controlled design was used. 28 well-trained cyclists and rowers. 4 weeks' daily inhalation of 800 microg budesonide or placebo. The subjects performed three incremental cycle ergometer tests until exhaustion, before and after 2 and 4 weeks of...
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To determine the feasibility and the benefits of combined resistance and interval exercise training on phenotype characteristics and skeletal muscle function in deconditioned, type 2 diabetes (T2D) patients with polyneuropathy. Short-term, single-arm intervention trial. Eleven male T2D patients (age: 59.1+/-7.5 years; body mass index: 32.2+/-4.0 kg...
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We studied the mean hemoglobin (Hb) concentration in elite male and female long track junior and senior speed skaters from 2000 to 2005. In addition, the number of abnormal hematological findings observed over this period of time was investigated. We also studied whether there were differences in Hb concentration between top ranked and lower ranked...
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Skeletal muscle mitochondrial function in type 2 diabetes (T2D) is currently being studied intensively. In vivo (31)P magnetic resonance spectroscopy ((31)P MRS) is a noninvasive tool used to measure mitochondrial respiratory function (MIFU) in skeletal muscle tissue. However, microvascular co-morbidity in long-standing T2D can interfere with the (...
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It has been suggested that minimally invasive surgery (MIS) in total hip replacement (THR) is less traumatic than standard techniques. This study was designed to address the question of whether an anterior MIS approach generates less inflammation and muscle damage than the standard posterolateral (PL) approach. Inflammation parameters such as inter...
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After recent scandals in cycling involving doping, it has been asserted that top-level cycling is impossible without pharmacological support. An important prerequisite for successfully completing the Tour de France is maintaining energy balance. To compensate for the daily caloric expenditure of 23-25 MJ, conventional food must be supplemented with...
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The average length of hospital stay after Total Hip Replacement (THR) has been decreasing over time. Recently, many hospitals have commenced rapid recovery programs such as Joint Care. In Joint Care the patients are usually discharged on the fifth post-operative day with relatively fresh surgical wounds. The aim of this study is to evaluate the Joi...
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Synchronized skating is a relatively new competitive sport and data about injuries in this discipline are lacking. Therefore the purpose of this study was to investigate the frequency and pattern of acute and overuse injuries in synchronized skaters. Before and during the World Synchronized Skating Championship 2004, a questionnaire inquiring about...
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Creatine supplementation is popular among tennis players but it is not clear whether it actually enhances tennis performance. To examine the effects of creatine supplementation on tennis specific performance indices. In a randomised, double blind design, 36 competitive male tennis players (24 creatine, mean (SD) age, 22.5 (4.9) years; 12 placebo, 2...
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During the world junior speed skating championship 2002 all athletes (60 males, 56 females) were subjected to hematologic blood testing one day before the competition as requested by International Skating Union--ISU. This study aimed to obtain hematological reference values for junior athletes, whilst the influence of endurance training on hematolo...
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This study examined the effects of visual distractors on reaching performance in 7, 9 and 13 year-old children. The task was to reach for a green target appearing either with or without a red distractor stimulus on a computer screen. Results showed that the presence of a distractor lengthened movement times in all age groups, but, importantly, this...
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Background: The pattern of cortisol secretion is influenced by surgery. As cortisol can adversely affect neuronal function, this may be an important factor in the development of post-operative cognitive dysfunction (POCD). We hypothesized that the incidence of POCD would be related to changes in cortisol level. Methods: We studied 187 patients a...
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To identify educational needs of elite sportspeople with respect to the doping laws. A questionnaire survey of 196 Olympic level sportspeople from the fields of athletics, cycling, rowing, and sailing. The questionnaire addressed the date and source of the last doping educational update, the usefulness of current resources, sources of help, and pos...
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This study attempted to contribute to standardization of blood testing in sport, and to investigate the effect of artificial dilution with saline. In 10 healthy, physically active males and 3 healthy physically active females hemoglobin (Hb), hematocrit (Ht), and % reticulocytes (%retics) were measured at different time points to look for possible...
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We investigated the temporal effects of sepsis on muscle wasting and function in order to study the contribution of wasting to the decline in muscle function; we also studied the fiber-type specificity of this muscle wasting. Sepsis was induced by injecting rats intraperitoneally with a zymosan suspension. At 2 h and at 2, 6, and 11 days after inje...
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The purpose of the study was to investigate whether severe fatigue, possibly leading to overreaching, could be diagnosed at an early stage by a combination of parameters. Seven well-trained male subjects (age [mean +/- SD]: 25.3 +/- 4.7 yr; body mass: 76 +/- 6.6 kg; VO2max: 61.1 +/- 7 ml.kg(-1).min(-1)) increased their training load by doubling the...
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Assessment of postprandial glycaemic response to four nutritional feeds with different macronutrient and fibre composition. A randomized, double-blind, crossover study. University of Maastricht, the Netherlands. A total of 10 healthy volunteers and 10 patients with type II diabetes. Subjects received 200 kcal of four enteral nutrition products (two...
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Parents of children treated with growth hormone (GH) frequently report to the paediatrician that their children have become more physically active. In the present study, activity patterns of GH-treated children were measured and compared to those of healthy controls. Subjects were 25 children at the start of GH treatment (age 8.4 +/- 2.6 y) and 19...
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Beta(2)-adrenergic agonists are important therapeutic agents for the prevention and treatment of (exercise-induced) asthma in athletes, but may have ergogenic effects. In this study we investigated whether inhalation of a supra-therapeutic dose of 800 microg salbutamol before exercise affects endurance performance during a cycling trial in non-asth...
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Accelerometry was used to assess the relationship between the physical activity level (PAL) and time spent on activities of various intensities in children. A total of 20 children aged 8.6+/-3.3 y wore a triaxial accelerometer (Tracmor2) for 2 weeks. PAL was calculated with Tracmor2 output data. The fraction of time spent on activities with a given...
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To investigate the effects of two different regimens of androgenic-anabolic steroid (AAS) administration on serum lipid and lipoproteins, and recovery of these variables after drug cessation, as indicators of the risk for cardiovascular disease in healthy male strength athletes. In a non-blinded study (study 1) serum lipoproteins and lipids were as...
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Major surgery is frequently associated with postoperative cognitive dysfunction (POCD) in elderly patients. Type of surgery and hospitalization may be important prognostic factors. The aims of the study were to find the incidence and risk factors for POCD in elderly patients undergoing minor surgery. We enrolled 372 patients aged greater than 60 ye...
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To study the effect of stage duration on some physiological variables in an incremental running test, 8 well-trained runners underwent 3 running tests, with stage durations of 1, 3 and 6 min. To study maximal lactate steady state (maxLASS) and its corresponding speed, every subject underwent a 4th test with three 15-min stages at three speeds, base...
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To investigate in glycolytic and oxidative muscles of trained (nine weeks) and untrained hyperglycaemic female rats the effect of hyperandrogenicity and/or endurance training on energy metabolic properties. Glycogen content and activity of muscle enzymes with regulatory functions in glycogen synthesis were examined. Testosterone treatment increased...
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Since the abuse of androgenic-anabolic steroids (AAS) has been associated with the occurrence of serious cardiovascular disease in young athletes, we performed two studies to investigate the effects of short-term AAS administration on heart structure and function in experienced male strength athletes, with special reference to dose and duration of...
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The data of the present case demonstrate that the abuse of androgenic anabolic steroids (AAS) may lead to serious health effects. Although most clinical attention is usually directed towards peripheral side effects, the most serious central side effect, hypothalamic-pituitary-dysfunction, is often overlooked in severe cases. Although this latter ce...
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An important feature of human motor behaviour is anticipation and preparation. We report a functional magnetic resonance imaging study of the neuronal activation patterns in the human brain that are associated with the rapid visuomotor preparation of discrete finger responses. Our imaging results reveal a large-scale distributed network of neural a...
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The aim of the study was to determine the effects of creatine supplementation on tennis performance and various health parameters. This was an experimental, double blind study that was placebo-controlled. A total of 36 competitive tennis players (24 with creatine supplementation, 12 with placebo) of International Tennis No. 3 status or higher were...
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Postoperative cognitive dysfunction (POCD) is a common complication after cardiac and major non-cardiac surgery with general anaesthesia in the elderly. We hypothesized that the incidence of POCD would be less with regional anaesthesia rather than general. We included patients aged over 60 years undergoing major non-cardiac surgery. After giving wr...
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To study the effect of stage duration on heart rate, ventilatory variables, and lactate in an incremental cycle exercise test, ten trained cyclists underwent three incremental exercise tests with stage duration of 1, 2.5 and 5 minutes. To determine maximal lactate steady state, based on the power output at 4 mmol.L-1 blood lactate (W4) from the 5 m...
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The purpose of this review is to describe the current status of knowledge regarding the prevalence and causes of exercise-related anaemia. Intravascular haemolysis is a rare cause of exercise-induced haematuria and anaemia. The causes are thought to be mechanical, osmotic and oxidative injury to erythrocytes. Treatment is not usually necessary, and...
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The purpose of this study was to monitor general and individual changes in hematological variables during long-term endurance training, detraining and altitude training in elite Olympic distance triathletes. Over a period of three years, a total of 102 blood samples were collected in eleven (7-male and 4 female) elite Olympic distance triathletes (...
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Postoperative cognitive dysfunction (POCD) after noncardiac surgery is strongly associated with increasing age in elderly patients; middle-aged patients (aged 40-60 yr) may be expected to have a lower incidence, although subjective complaints are frequent. The authors compared the changes in neuropsychological test results at 1 week and 3 months in...
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The objective of this investigation was to study the effects of androgenic-anabolic steroid (AAS) misuse on deltoid muscle fiber characteristics in experienced, male strength-trained athletes. In a double-blind study, 15 volunteers were administered nandrolone decanoate (ND) for 8 weeks (200 mg/week, intramuscularly). In an additional study, 12 sub...
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(a) To investigate the effects of reduced training on physical condition and performance in well trained cyclists; (b) to study whether an intermittent exercise programme would maintain physiological training adaptations more effectively than a continuous exercise programme during a period of reduced training. Twelve male cyclists participated in a...
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In general, physical activity benefits health. However, long-term intensive physical training may have detrimental effects on the health of some individuals. In cyclists, changes in the femoral arteries may occur leading to stenoses that are manifested in claudication type symptoms. Some endurance athletes may experience atrial fibrillations that a...
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The aim of the study was to validate a new, fast metabolic measurement system (the Oxycon-Pro) during low and high exercise intensities against the Douglas bag method. For this purpose twelve highly trained subjects performed an incremental cycle ergometer test. In the third minute of each exercise step simultaneous measurements of the Douglas bag...
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To obtain more insight in the aetiology of deep pressure sores, an animal model was developed to relate controlled external loading to local muscle damage. The tibialis anterior muscle (TA) and overlying skin of a rat were compressed between indentor and tibia. Loads of 10, 70 and 250kPa at skin surface were applied for 2 or 6h. During half of the...
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The purpose of the present study was to investigate regional changes in body composition and anthropometric variables induced by nandrolone decanoate in bodybuilders. In a randomized, double blind, placebo controlled design 16 subjects received weekly intramuscular injections containing 200 mg nandrolone decanoate (ND) or placebo. Composition of to...
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The purpose of the present study was to investigate regional changes in body composition and anthropometric variables induced by nandrolone decanoate in bodybuilders. In a randomized, double blind, placebo controlled design 16 subjects received weekly intramuscular injections containing 200 mg nandrolone decanoate (ND) or placebo. Composition of to...
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To study the hypothesis that more severe damage, caused by controlled lengthening (L) contractions, results in greater myofiber hypertrophy compared to increase in fiber size followed shortening (S) contractions, tibialis anterior muscles of anesthesized male Wistar rats were subjected to 240 either L or S contractions. The highest increase in musc...
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To study the occurrence and contributing factors of transient hypoglycemia after pre-exercise ingestion of glucose after a 4-hour fast, 19 well-trained cyclists ingested 50 grams of glucose dissolved in water around noon after having a normal breakfast. The ingestion of the glucose solution was followed by 30 minutes rest after which the subjects c...
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Skeletal muscle has the ability to adapt as result of dietary, hormonal or pharmacological interventions affecting energy metabolism. The aim of the present study was to investigate the effects of energy restriction on skeletal muscle metabolic characteristics in obese women. The effects of 8 weeks' energy restriction on body composition, energy ex...
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In this study, it is assumed that the parameters of the distribution-moment (DM) model are distributed homogeneously in the muscle tissue. A simplified 1D model of the muscle-tendon complex is used to identify the unknown parameters. These parameters are important since they provide reasonable description of the isometric muscle torque's of the tib...
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Animal experiments were performed to study the relationship between strictly controlled external mechanical loads and the onset of tissue damage. The finite element model was used to determine the local stresses and strains within the tissues during the experiments. By comparison of the results of the animal experiments with the results of the fini...
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A stepwise increasing exercise protocol to measure the maximal aerobic power output of the quadriceps muscle is proposed for use in rehabilitation medicine. Sixteen healthy volunteers performed isokinetic knee extension/flexion exercises at an angular velocity of 180 degrees x s(-1). The protocol consisted of stages of 200 knee movements from 100 f...
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In sports, medical drugs are applied for supposedly ergogenic effects. Forbidden drug use (doping) implies that the drug enhances performance, which is not always the case. Amphetamines are ergogenic particularly during short-term, explosive exercise. Amphetamines exert an ergolytic effect on high-intensity endurance exercise. Caffeine has an ergog...
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The purpose of this study was to investigate in a cross-sectional design body composition, muscle fiber characteristics, cardiovascular risk factors and liver enzymes in long-term androgenic-anabolic steroids (AAS) using bodybuilders three months after drug withdrawal (AAS group; n = 16) and in non-users (CO group; n = 12). Training and dietary dat...
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Exercise-induced muscle damage is characterized by histological changes, like Z-line streaming, inflammatory response and decreased muscle function reflected in a prolonged decline in maximal isometric muscle strength after eccentric work. It is assumed that force decrement is mainly related to the amount of structural damage. However, the relation...
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This prospective non blind study in nine male experienced androgenic-anabolic steroid (AAS) users shows that AAS use is significantly associated with enhanced fibrinolytic activity compared with confirmed non using male bodybuilders as controls. Venous occlusion does not seem to have additional value in documenting this enhanced activity. It remain...