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Biomedical subjects

E Van Praagh

Publications and source records attributed to E Van Praagh.

At least 19 recordsLinked to original sources
PubMed2007

Preserved bone health in adolescent elite rhythmic gymnasts despite hypoleptinemia.

BACKGROUND/AIMS: Leptin is linked to hormonal disturbances occurring in anorexia and positively linked with bone mineral density. The aim of this study was to determine whether hypoleptinemia occurring in rhythmic gymnasts may affect bone health. METHOD: Leptin, insulin, cortisol, IGF1 levels and bone markers were determined in 36 rhythmic gymnasts (EG) and 20 controls (C). Body composition, BMD at the whole body (WBBMD), lumbar spine (LSBMD) and bone ultrasound properties (SOS, BUA) were measured. RESULTS: The rhythmic gymnasts had lower fat mass and leptin level than the controls. There was no difference for IGF1, cortisol and insulin levels. Bone turnover rate was higher in elite gymnasts. The uncoupling index showed that remodeling favored the bone formation. LSBMD, WBBMD, SOS and BUA were higher in elite gymnasts after adjustment for fat mass. Leptin correlated positively with fat mass and negatively with physical activity. CONCLUSION: High impact training is able to counterbalance bone effects usually encountered in hormonally disturbed subjects. Our results suggest that hypoleptinaemia might be related to direct osteogenic effects and indirect hormonal mechanisms including preservation of IGF and cortisol levels.

Adolescent↗
PubMed2006

Longitudinal follow-up of fitness during childhood: interaction with physical activity.

Health-related fitness values during childhood (from age 11 to 16 years) were analyzed in relation to changes in physical activity level. One hundred fifty-eight children were monitored over a 4-year period. Twice a year, they performed six physical fitness tests: standing broad jump, 10 x 5-meter shuttle run, sit-and-reach, handgrip, number of sit-ups in 30 s, and 20-m shuttle run. Height was measured four times per year to assess age at peak height velocity. Physical activity was assessed with a self-administered questionnaire at baseline and at the end of the follow-up. The physical activity level was defined by the frequency and the time spent in moderate-to-vigorous physical activities. Two groups were constituted: regularly active and sedentary. A multiple linear multilevel regression analysis was used to analyze the longitudinal relationships between changes in physical activity and physical fitness levels. Corrections were made for both time-dependent (time) and time-independent (sex) variables. Except for flexibility, boys' fitness performances increased more than that for the girls. Positive and significant (P < 0.05) regression coefficients were found with the regularly active for standing broad jump, 20-m shuttle run, number of sit-ups, 10 x 5-m shuttle run in both sexes, and for the girls' sit-and-reach performance. Increasing or decreasing physical activity level was not associated with changes in fitness performances over time, except for flexibility for the girls and the 20-m shuttle run for the boys. From childhood to adolescence, increasing physical activity is not sufficient to be more fit. The children who are stayed the most active were the fittest, particularly the girls. Am. J. Hum. Biol. 18:51-58, 2006. (c) 2005 Wiley-Liss, Inc.

Adolescent↗
PubMed2005

Peak leg muscle power, peak VO2 and its correlates with physical activity in 57 to 70-year-old women.

The two aims of this study were first to measure short-term muscle power (STMP) by means of a cycling force-velocity test (cycling peak power: CPP) and a vertical jump test (jumping peak performance: JPP) and second, to examine the relationships between physical activity (PA) level, peak oxygen uptake (peak VO2) and STMP in healthy elderly women. Twenty-three independent community-dwelling elderly women (mean age: 64+/-4.4) performed on separate days, a peak oxygen uptake test on cycle ergometer, a cycling force-velocity test and a vertical jump test. A questionnaire (QUANTAP) was used to assess lifespan exercise habits. Four indices expressed in kJ day(-1) kg(-1) were calculated. Two indices represented average past PA level: 1/quantity of habitual physical activity (QHPA), 2/quantity of sports activities (QSA). Two indices represented the actual PA level: 3/actual quantity of habitual physical activity (AQHPA), 4/actual quantity of sports activities (AQSA). CPP (6.3+/-1.2 W kg(-1)) was closely correlated to JPP (14.8+/-3.4 cm) (r=0.80, P<0.001). AQHPA and AQSA were only positively associated with peak VO2 (ml min(-1) kg(-1)) (r=0.49; r=0.50, P<0.05, respectively). Past PA level was not related to fitness measurements. Results show that in this population: (1) jumping peak performance was closely related to CPP measured in the laboratory; (2) the cardio-respiratory fitness was related to the actual habitual physical activity level; (3) only age and anthropometric variables explained the actual performances in multivariate analysis.

Aged↗
PubMed2005

Gender differences in peak muscle performance during growth.

Gender-related differences in maximal leg muscle power were examined in 496 females and 426 males aged 8 to 20 years. Cycling peak power (CPP, including the force required to accelerate the flywheel of the cycle ergometer) was measured during three sprints. Optimal velocity (Vopt, velocity at CPP) was also determined. No gender-differences were observed in anthropometric characteristics and cycling performance between 8- and 14-year-old. From age 14, however, males showed a higher CPP than females, but also a higher lean leg volume (LLV, assessed by anthropometry). Allometric relationship between CPP and LLV (CPP = a . LLV ( b)) showed a clear gender-differentiation between 14- and 16-year-old: LLV exponent (b) was 1.05 in males vs. 0.74 in females. From 16 years onwards, analysis of covariance (ANCOVA) showed that the slopes of the CPP-LLV relationship were similar in both genders, but the intercepts differed. In other words, for a similar LLV, males showed greater CPP than females. It was suggested that this sex-related difference was due to total body fat increase, and more specifically lower-limb fat increase during puberty in girls, whilst the boys experienced increased lean body mass. Considering that the same gender-related difference was observed for optimal velocity adjusted for leg length, other factors such as fibre type variability or (and) neuromuscular activation might also be partly responsible for the higher peak muscle performance observed in males.

Adolescent↗
PubMed2005

Torque and power-velocity relationships in cycling: relevance to track sprint performance in world-class cyclists.

The aims of the present study were both to describe anthropometrics and cycling power-velocity characteristics in top-level track sprinters, and to test the hypothesis that these variables would represent interesting predictors of the 200 m track sprint cycling performance. Twelve elite cyclists volunteered to perform a torque-velocity test on a calibrated cycle ergometer, after the measurement of their lean leg volume (LLV) and frontal surface area (A(p)), in order to draw torque- and power-velocity relationships, and to evaluate the maximal power (P(max)), and both the optimal pedalling rate (f(opt)) and torque (T(opt)) at which P (max) is reached. The 200 m performances--i.e. velocity (V200) and pedalling rate (f 200)--were measured during international events (REC) and in the 2002 French Track Cycling Championships (NAT). P(max), f(opt), and T(opt) were respectively 1600 +/- 116 W, 129.8 +/- 4.7 rpm and 118.5 +/- 9.8 N . m. P(max) was strongly correlated with T(opt) (p < 0.001), which was correlated with LLV (p < 0.01). V200 was related to P(max) normalized by A(p) (p < or = 0.05) and also to f(opt) (p < 0.01) for REC and NAT. f 200 (155.2 +/- 3, REC; 149 +/- 4.3, NAT) were significantly higher than f(opt) (p < 0.001). These findings demonstrated that, in this population of world-class track cyclists, the optimization of the ratio between P(max) and A(p) represents a key factor of 200 m performance. Concerning the major role also played by f(opt), it is assumed that, considering high values of f 200, sprinters with a high value of optimal pedalling rate (i.e. lower f200-f(opt) difference) could be theoretically in better conditions to maximize their power output during the race and hence performance.

Adult↗
PubMed2004

High-intensity intermittent activities at school: controversies and facts.

In comparison to continuous aerobic type activity, little is known about high-intensity intermittent physical activity in children. Repeated short-term high-intensity activities (> maximal aerobic speed and <10 s) are more characteristic of the spontaneous physical activity of children. Recent studies have shown during repetitive bouts of sprints separated by short recovery intervals, that prepubescent children compared with adults are more able to maintain their performance without substantial fatigue. Moreover, repetitive runs at high velocities (near and higher than the maximal aerobic speed) separated by short recovery periods may elicit a high oxygen consumption in children. Several studies using interval training programmes for 7 weeks, twice a week for 30 min in physical education lessons showed that children's aerobic performance (maximal O2 uptake, maximal aerobic speed) could be enhanced. Training based on these repeated short-term high-intensity exercises could also improve children's anaerobic performance (short-term muscle power, strength and speed). Current evidence suggests that recovery from high-intensity exercises is faster in children than in adults and that repeated runs at high velocities separated by short recovery intervals can improve both aerobic and anaerobic performance. Although continuous aerobic type activity is more scientifically established as a training mode, repeated short-term high-intensity exercises in physical education programmes should be considered to enhance aerobic, as well as, anaerobic fitness in children.

Child↗
PubMed2002

Acid-base balance during repeated cycling sprints in boys and men.

The aim of this study was to investigate the acid-base balance during repeated cycling sprints in children and adults. Eleven boys (9.6 +/- 0.7 yr) and ten men (20.4 +/- 0.8 yr) performed ten 10-s sprints on a cycle ergometer separated by 30-s passive recovery intervals. To measure the time course of lactate ([La]), hydrogen ions ([H(+)]), bicarbonate ions ([HCO(3)(-)]), and base excess concentrations and the arterial partial pressure of CO(2), capillary blood samples were collected at rest and after each sprint. Ventilation and CO(2) output were continuously measured. After the 10th sprint, concentrations of boys vs. men were as follows: [La], 8.5 +/- 2.1 vs. 15.4 +/- 2.0 mmol/l; [H(+)], 43.8 +/- 1.3 vs. 66.9 +/- 9.9 nmol/l (P < 0.001). Significant correlations showed that, for a given [La], [H(+)] was lower in the boys compared with the men (P < 0.001). Significant relationships also indicated that, for a given [La], [HCO(3)(-)] and base excess concentration were similar in the boys compared with the men. Moreover, significant relationships revealed that, for a given [H(+)] or [HCO(3)(-)], arterial partial pressure of CO(2) was lower in the boys compared with the men (P < 0.001). The ventilation-to-CO(2) output ratio was higher in the boys during the first five rest intervals and was then higher in the men during the last five sprints. To conclude, during repeated sprints, the ventilatory regulation related to the change in acid-base balance induced by lactic acidosis was more important during the first rest intervals in the boys compared with the men.

Acid-Base Equilibrium↗
PubMed2001

Anaerobic cycling performance characteristics in prepubescent, adolescent and young adult females.

The purpose of this study was to determine whether the relationships between short-term power and body dimensions in young females were similar whatever the age of the individuals. A cohort of 189 prepubescent (mean age 9.5 years), adolescent (mean age 14.4 years) and young adult (mean age 18.2 years) females performed three all-out sprints on a friction-loaded cycle ergometer against three braking forces corresponding to applied loads of 25, 50 and 75 g.kg-1 body mass (BM). For each sprint, peak power including flywheel inertia was calculated. Results showed that a braking load of 75 g.kg-1 BM was too high for prepubescent and adolescent girls. Therefore, when measuring short-term cycling performance in heterogeneous female populations, a braking load of 50 g.kg-1 BM (0.495 N.kg-1 BM) is recommended. During growth, cycling peak power (CPP; defined as the highest peak power obtained during the three sprints) increased, as did total BM, fat-free mass (FFM) and lean leg volume (LLV) (P < 0.001). Analysis of covariance revealed that the slopes of the linear relationships between CPP and biometric characteristics were similar in the three groups (P > 0.7 for the CPP/BM and CPP/FFM relationships, and P > 0.2 for the CPP/LLV relationship). However, the adjusted means were always significantly higher in young women (P < 0.001) compared with both of the other groups. Although differences in performance during anaerobic cycling in growing females are primarily dependent upon body dimensions, other as yet undetermined factors may be involved during late adolescence.

Adolescent↗
PubMed2001

High-intensity aerobic training during a 10 week one-hour physical education cycle: effects on physical fitness of adolescents aged 11 to 16.

The aim of this study was to analyse the effects of a high-intensity aerobic training program on different components of physical fitness in adolescents aged 11 to 16 years. The subjects were divided into a high intensity (HI) group (243 girls and 260 boys) and a control (C) group (21 girls and 27 boys). HI and C completed a weekly 3 hour physical education (PE) session. Before and after a 10-week period, the two groups performed the European physical fitness test battery (EUROFIT). During these 10 weeks HI spent one hour out of three at a specific PE session. These specific sessions consisted of short intermittent exercises (10 seconds) at 100 to 120% of maximal aerobic speed. They showed a significant influence on standing broad jump (2.9 %, P<0.05, F=4.85), 20 meter shuttle run (3.8%, p0.001, F=23.21) and on the maximal distance covered over 7 min (7.6 %, P< 0.001, F= 14.48). For C there was no improvement in EUROFIT performances. It was concluded that training at high intensity improves not only children's aerobic fitness but also performance of standing broad jump. Well-monitored, adequate intensive training is necessary for a more desirable functional development.

Adolescent↗
PubMed2001

Effects of plyometric training followed by a reduced training programme on physical performance in prepubescent soccer players.

BACKGROUND: In adult population, stretch-shortening cycle exercise (plyometric exercise) is often used to improve leg muscle power and vertical jump performance. In children, limited information regarding this type of exercise is available. The purpose of this study was to examine the effectiveness of plyometric training and maintenance training on physical performances in prepubescent soccer players. METHODS: Twenty boys aged 12-13 years was divided in two groups (10 in each): jump group (JG) and control group (CG). JG trained 3 days/week during 10 weeks, and performed various plyometric exercises including jumping, hurdling and skipping. The subsequent reduced training period lasted 8 weeks. However, all subjects continued their soccer training. Maximal cycling power (Pmax) was calculated using a force-velocity cycling test. Jumping power was assessed by using the following tests: countermovement jump (CMJ), squat jump (SJ), drop jump (DJ), multiple 5 bounds (MB5) and repeated rebound jump for 15 seconds (RRJ15). Running velocities included: 20, 30 and 40 m (V20, V30, V40 m). Body fat percentage (BF percent) and lean leg volume were estimated by anthropometry. RESULTS: Before training, except for BF percent, all baseline anthropometric characteristics were similar between JG and CG. After the training programme, Pmax (p<0.01), CMJ (p<0.01), SJ (p<0.05), MB5 (p<0.01), RRJ15 (p<0.01) and V20 m (p<0.05), performances increased in the JG. During this period no significant performance increase was obtained in the CG. After the 8-week of reduced training, except Pmax (p<0.05) for CG, any increase was observed in both groups. CONCLUSIONS: These results demonstrate that short-term plyometric training programmes increase athletic performances in prepubescent boys. These improvements were maintained after a period of reduced training.

Adolescent↗
PubMed2000

Dimensional changes cannot account for all differences in short-term cycling power during growth.

The purpose of this study was to determine to what extent anthropometric characteristics account for cycling peak power during growth. Five hundred and six male subjects aged 7.5-18 years performed three brief maximal sprints on a friction-loaded cycle ergometer. Cycling peak power (CPP) was calculated including the flywheel inertia of the device. Fat-free mass (FFM) and lean leg volume (LLV) were assessed by anthropometry. Anthropometric characteristics increased significantly during growth (p<0.001) but plateaued from about 16 years of age (p > 0.3). The same pattern was observed for CPP, while the time to reach CPP decreased during growth. CPP correlated as highly with LLV as with FFM and both parameters may therefore be interchanged. However, in non weight-bearing exercises, such as cycling, it seems more relevant to "normalise" leg power for LLV. Multiple stepwise regression, using an allometric model, showed that a large part of the variance of CPP was explained by LLV (88.2%, p<0.001). However, age and time to reach peak power also contributed significantly (approximately 3 %, p < 0.001). The prediction of CPP revealed that FFM and age contributed to 92.2% of the total variance of CPP. Because of its practicability, fat-free mass is particularly useful in prospective studies. Although the effects of dimensional changes in CPP during growth are obvious, undetermined qualitative changes of muscle function during maturation must be considered.

Adolescent↗
PubMed2000

Testing peak cycling performance: effects of braking force during growth.

The purpose of this study was to investigate the relationship between cycling peak power (CPP; flywheel inertia included) and the applied braking force (F(B)) on a friction-loaded cycle ergometer in male children, adolescents, and adults. A total of 520 male subjects aged 8-20 yr performed three brief maximal sprints against three F(B): 0.245, 0.491, and 0.736 N x kg(-1) body mass (BM) (corresponding applied loads: 25 [F(B)25], 50 [F(B)50], and 75 [F(B)75] g x kg(-1) BM). For each F(B), peak power (PP) was measured (PP25, PP50 and PP75). For each subject, the highest PP was defined as CPP. Results showed that PP was dependent on F(B). In young adults PP25 underestimated CPP by more than 10%, and consequently, F(B)25 seemed to be too low for this population. However, in children, PP75 underestimated CPP by about 20%. A F(B) of 0.736 N x kg(-1) BM was definitively too high for the pediatric population. Therefore, the optimal F(B), even corrected for BM, was lower in children than in adults. The influence of growth and maturation on the force-generating capacity of the leg muscles may explain this difference. In this study, however, it was shown that the difference between PP50 and CPP was independent of age for the whole population investigated. Consequently, when flywheel inertia is included, one cycling sprint with a F(B) of 0.495 N x kg(-1) BM (corresponding applied load: 50 g x kg(-1) BM) is a feasible method for testing both children, adolescents, or young adults.

Adolescent↗
PubMed2000

Endurance exercise training in the elderly: effects on cardiovascular function.

Among many arguments for encouraging the maintenance of an active lifestyle into old age is that those who exercise regularly may anticipate a reduced risk of chronic disease. In earlier studies, because of insufficient training stimuli, no improvement in maximal oxygen consumption (VO(2)max) was observed in individuals over 60 years of age. However, in more recent studies, after sufficient training, the VO2max response of the older individual was the same as that in younger persons. It is well documented that maximal cardiac output is the main component of the age-related decline in VO(2)max. The underlying mechanisms of the impairment of maximal cardiac function and the beneficial effect of regular endurance exercise training are discussed in the present review.

Adaptation, Physiological↗
PubMed2000

Physiological issues surrounding the performance of adolescent athletes.

More than ever, many young athletes are being encouraged to train intensely for sporting competitions from an early age. Compared with studies in adults, less is known about the physiological trainability of adolescents. The velocity of physical growth during the adolescent years makes research with a group of young athletes particularly difficult. The purpose of this review is to discuss a number of physiological issues that surround the performances of the adolescent athlete. Research has highlighted the role of growth hormone (GH) in the abrupt acceleration of linear growth that occurs during adolescence. In addition, GH has been shown to be sensitive to exercise following short term intervention studies. The reduced anaerobic power of the adolescent athlete compared with that of an adult athlete has been attributed to the intrinsic properties of the muscle that are yet to be fully understood. Resistance training studies in male adolescents, and to a lesser extent female adolescents, highlight the substantial relative strength gains that can be obtained. Aerobic trainability in young boys appears to improve markedly during the adolescent years. One of the most plausible explanations for this observation is the 'trigger hypothesis' which links increased aerobic improvements in adolescence with hormonal changes and substantial growth of the cardiorespiratory and musculoskeletal systems. Studies of aerobic trainability in adolescent girls are too scarce to be conclusive. An understanding of the impact of long term intensive training on adolescent athletes is difficult to ascertain because physical stresses vary both between and within sports. There is, however, limited evidence to suggest that 'intense' training does not impair normal growth, development or maturation. Adolescent athletes who experience rapid growth as well as large increases in training volumes may be vulnerable to overuse injuries.

Adolescent↗
PubMed1999

Motion analysis of an articulated locomotion model by video and telemetric data.

Traditional techniques of human motion analysis use markers located on body articulations. The position of each marker is extracted from each image. Temporal and kinematic analysis is given by matching these data with a reference model of the human body. However, as human skin is not rigidly linked with the skeleton, each movement causes displacements of the markers and induces uncertainty in results. Moreover, the experiments are mostly conducted in restricted laboratory conditions. The aim of our project was to develop a new method for human motion analysis which needs non-sophisticated recording devices, avoids constraints to the subject studied, and can be used in various surroundings such as stadiums or gymnasiums. Our approach consisted of identifying and locating body parts in image, without markers, by using a multi-sensory sensor. This sensor exploits both data given by a video camera delivering intensity images, and data given by a 3D sensor delivering in-depth images. Our goal, in this design, was to show up the feasibility of our approach. In any case the hardware we used could facilitate an automated motion analysis. We used a linked segment model which referred to Winter's model, and we applied our method not on a human subject but on a life size articulated locomotion model. Our approach consists of finding the posture of this articulated locomotion model in the image. By performing a telemetric image segmentation, we obtained an approximate correspondence between linked segment model position and locomotion model position. This posture was then improved by injecting segmentation results in an intensity image segmentation algorithm. Several tests were conducted with video/telemetric images taken in an outdoor surrounding with the articulated model. This real life-size model was equipped with movable joints which, in static positions, described two strides of a runner. With our fusion method, we obtained relevant limbs identification and location for most postures.

Algorithms↗
PubMed1997

Leg cycling tracking by dynamic vision.

This study describes a method of tracking of human body limbs from a monocular sequence of perspective images. These objects and the associated articulations must be modelled. The principle of the method is based on the interpretation of image features as the three-dimensional perspective projections points of the object model and an iterative process method to compute the model position in accordance with the analysed image. This attitude is filtered (Kalman filter) to predict the model position relative to the next image of the sequence. The image features are extracted locally according to the computed prediction. Tracking experiments, illustrated in this study by a leg cycling sequence, have been conducted to demonstrate the viability of the approach.

Bicycling↗
PubMed1994

Evaluation of physical fitness from field tests at high altitude in circumpubertal boys: comparison with laboratory data.

Field tests of running and laboratory tests were performed in La Paz [high altitude (HA), 3700 m] and in Clermont-Ferrand [low altitude (LA), 300 m] to investigate their validity at HA. Prepubertal boys of mean ages 10.6 years (HA1, n = 16; LA1, n = 28) and pubertal boys of 13.7 years (HA2, n = 12; LA2, n = 41) took part in the study. All the boys performed a 30-m sprint (V30m), a 30-s shuttle run (V30s) and a progressive shuttle run test until their maximal aerobic velocity (VmaxSRT). Maximal oxygen consumption was extrapolated from the last test (VO2maxSRT). In the laboratory, the boys performed a force-velocity test (Pmax), a Wingate test (PWing) and a graded test to measure maximal oxygen consumption (VO2maxB; direct method) on a cycle ergometer. At similar ages, there was no significant difference between HA and LA boys for V30m and Pmax. The V30s of HA boys was 3%-4% lower than those of LA boys (P < 0.05); there was no significant difference for PWing. Significant relationships were observed at both altitudes between Pmax (watts per kilogram) and V30m (HA: r = 0.76; LA: r = 0.84) and between PWing and V30s (HA: r = 0.67; LA: r = 0.77); the slopes and the origins were the same at HA and LA. The VO2max, VmasSRT and VO2maxB were lower by 9%, 12% and 20%, respectively, at HA than at LA (P < 0.05). However, the relationships between VO2maxB and VO2maxSRT (litres per minute) at HA (r = 0.88) and at LA (r = 0.93) were identical.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗