Jaak Jürimäe

University of Tartu, Dorpat, Tartu County, Estonia

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Publications (123)207.48 Total impact

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    ABSTRACT: The association of body fat mass (FM) with bone mineral mass (BMC) and bone mineral density (BMD) has been attributed to a mechanical load exerted on the skeleton by FM and by the effect of different hormones. The aim of the present study was to determine whether there is a relationship between ghrelin, adiponectin, and leptin with BMC and BMD in healthy postmenopausal women (n = 88; age, 68.9 +/- 6.8 years; body mass index, 27.4 +/- 3.6 kg/m(2)). Body composition, BMC, and BMD were derived by dual-energy X-ray absorptiometry. Waist-to-hip (WHR) and waist-to-thigh (WTR) ratios were also obtained. Ghrelin was associated with total BMC (beta = -0.945; P = 0.0001), total BMD (beta = -0.959; P = 0.0001), lumbar spine BMD (beta = -0.945; P = 0.0001), and femoral neck BMD (beta = -0.957; P = 0.0001), and remained associated (P < 0.041) in different analyses that controlled for measured body composition and hormonal and insulin resistance values. However, the associations between ghrelin and measured bone mineral values were no longer significant (P > 0.149) when adjusted for body fat distribution values (WHR, WTR). Adiponectin was significantly related to total BMC (beta = -0.931; P = 0.0001), total BMD (beta = -0.940; P = 0.0001), lumbar spine BMD (beta = -0.937; P = 0.0001), and femoral neck BMD (beta = -0.940; P = 0.0001) values, and these relationships remained significant (P < 0.019) after adjusting for measured body fat, hormonal, and insulin resistance values but not when adjusted for fat-free mass (FFM; P > 0.106). In addition, significant associations of leptin with total BMC (beta = 0.912; P = 0.0001), total BMD (beta = 0.907; P = 0.0001), lumbar spine BMD (beta = 0.899; P = 0.0001), and femoral neck BMD (beta = 0.906; P = 0.0001) were found. These associations remained significant (P < 0.010) in different analyses that controlled for hormonal and insulin resistance values, but the associations between leptin and bone mineral values were no longer significant (P > 0.145) when adjusted for specific body composition values (WHR, WTR, FM, and FFM). In conclusion, it appears that the influence of plasma ghrelin, adiponectin, and leptin levels on BMC and BMD values is mediated or confounded by the specific body composition parameters in healthy postmenopausal women.
    Journal of Bone and Mineral Metabolism 01/2008; 26(6):618-23. · 2.22 Impact Factor
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    ABSTRACT: We examined the effect of regular physical activity on plasma ghrelin concentration after onset of puberty in girls. In addition, we also examined the association of fasting plasma ghrelin concentration with various plasma biochemical, body composition, and aerobic capacity variables in healthy adolescent girls. Fifty healthy schoolgirls ages 11 to 16 yr were divided either into a physically active (N = 25) or a physically inactive (N = 25) group. The physically active group consisted of swimmers who had trained on an average of 6.2 +/- 2.0 h.wk(-1) for the last 2 yr, whereas the inclusion criterion for the physically inactive group was the participation in physical education classes only. The subjects were matched for age (+/- 1 yr) and body mass index (BMI; +/- 2 kg.m(-2)). Maturation I group (14 matched pairs) included pubertal stages 2 and 3, and maturation II group (11 matched pairs) included pubertal stages 4 and 5. Physically active girls had significantly higher (P < 0.05) mean plasma ghrelin levels than the physically inactive girls (maturation I: 1152.1 +/- 312.9 vs 877.7 +/- 114.8 pg.mL(-1); maturation II: 1084.0 +/- 252.5 vs 793.4 +/- 164.9 pg.mL(-1)). Plasma ghrelin concentration was negatively related to percent body fat, fat mass, peak oxygen consumption per kilogram of body mass, leptin, estradiol, insulin, and insulin-like growth factor-I (IGF-I) (r > -0.298; P < 0.05). Multivariate linear regression analysis to determine the predictors of ghrelin concentration using the variables that were significantly associated with ghrelin concentration demonstrated that plasma IGF-I was the most important predictor of plasma ghrelin concentration (beta = -0.396; P = 0.008). Regular physical activity influences plasma ghrelin concentrations in girls with different pubertal maturation levels. Plasma IGF-I concentration seems to be the main determinant of circulating ghrelin in healthy, normal-weight adolescent girls.
    Medicine &amp Science in Sports &amp Exercise 11/2007; 39(10):1736-41. · 4.48 Impact Factor
  • International Journal of Sports Medicine 11/2007; · 2.27 Impact Factor
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    ABSTRACT: The purpose of the present study was to investigate the use of electromyographic signals (EMG), to determine the EMG threshold (EMGT) in four lower extremity muscles and to compare these thresholds with the second ventilatory threshold (VT2) in subjects participating in different sports and at different performance levels. Forty-nine subjects (23.8 +/- 5.7 years, 182.7 +/- 5.3 cm, 79.1 +/- 8.6 kg) including eleven cyclists, ten team-handball players, nine kayakers, eight power lifters and eleven controls were investigated utilizing a cycle ergometer. Respiratory gas exchange measures were collected and EMG activity was continuously recorded from four muscles (vastus lateralis, vastus medialis, biceps femoris and gastrocnemius lateralis). The VO(2)max averaged 56.1 +/- 11.1 ml kg(-1) min(-1), the average aerobic power was 348.5 +/- 61.0 W and the corresponding VT2 occurred at 271.4 +/- 64.0 W. The EMGT ranged from 80 to 98% of power output for the different muscles. The VT2 and EMG thresholds from four different muscles were not different. When thresholds were analyzed among different groups of subjects, no significant difference was observed between VT2 and EMGT despite threshold differences between the groups. All four EMGT were significantly related to maximal aerobic power (r = 0.73-0.83) and were highly correlated to each other (r = 0.57-0.88). In conclusion, EMGT can be used to determine the VT2 for individuals independent of sport specificity or performance level.
    Arbeitsphysiologie 11/2007; 101(3):341-6. · 2.66 Impact Factor
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    ABSTRACT: The use of the heart rate turn point (HRTP) to set target heart rate (THR) for prolonged rowing ergometer (E) and single scull rowing (R) was evaluated. Ten trained subjects (age 21.3 +/- 4.0 yrs; VO (2max) 4.77 +/- 0.62 l . min-1) performed incremental exercise tests and 30-min prolonged E and R. Expired air and heart rate (HR) were measured continuously. During E and R, blood lactate concentration (La) was measured at rest and after 5, 10, 20, and 30 min. HRTP and V (E)TP (2) were determined as the deflection point of the heart rate performance curve and the second TP in minute ventilation (V. (E)). No significant differences were found for work rate (W), HR, and VO (2) between HRTP and V. (E)TP (2) and they were significantly related (r = 0.94, p < 0.001; r = 0.96, p < 0.001). Mean HR, VO (2), VCO (2), and V. (E) were not significantly different between E and R. La remained at a steady state in both E and R but was slightly higher in E. Tidal volume (V (T)) was found to be lower and breathing rate (BR) was significantly higher in R. HR at HRTP from an incremental rowing ergometer exercise test is valid to establish a THR consistent with constant metabolic training intensity in prolonged ergometer and single scull rowing.
    International Journal of Sports Medicine 11/2007; 28(11):964-9. · 2.27 Impact Factor
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    J Jürimäe, T Jürimäe
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    ABSTRACT: Adipose-modulated biochemical signal that explains some of the association between fat mass and bone mineral density (BMD) is adiponectin. The results demonstrated an independent association between adiponectin and BMD, while the influence of adiponectin on bone mineral content is mediated by fat free mass in middle-aged women. Positive association between fat mass (FM) and bone mineral density (BMD) is mediated by biochemical factors. The relationship between plasma adiponectin concentration and BMD in 98 sedentary premenopausal women aged 38-49 years with a body mass index range of 20.0-42.1 kg/m(2) was examined. Different body composition and blood biochemical parameters were measured to adjust for possible confounding variables. The association between adiponectin and BMD values (total BMD: beta = -0.919; p = 0.0001, femoral neck BMD: beta = -0.925; p = 0.0001 and lumbar spine BMD: ss = -0.912; p = 0.0001) was independent of the influences that measured body composition, hormonal and insulin resistance factors may exert on BMD (p < 0.02). However, adiponectin explained only 3-12% of the variations in measured BMD variables. Similarly, adiponectin was associated with total bone mineral content (BMC; beta = -0.911; p = 0.0001) and remained associated in different analyses that controlled for possible confounding parameters (p < 0.01). However, the association between adiponectin and total BMC was no longer significant when adjusted for fat free mass (FFM; p > 0.21). Adiponectin is an independent predictor of BMD, while its independent contribution to the interindividual variance in measured values is only modest. The influence of adiponectin on total BMC is mediated or confounded by FFM in middle-aged premenopausal women.
    Osteoporosis International 09/2007; 18(9):1253-9. · 4.04 Impact Factor
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    ABSTRACT: The aim of the study was to investigate the relationships between handgrip and pinch strength values with basic body (body height, body mass, BMI) and with specific hand anthropometric parameters (fingers spans, lengths and perimeters) in prepubertal children. Body height, body mass and five fingers spans, lengths and perimeters were measured in 461 6-10 year old Estonian children according to Visnapuu & Jürimäe (2007). BMI was calculated (kg/m2). The maximal handgrip strength of the right and left hand was measured with hand dynamometer. The right and left key and tip pinch were measured with a pinch gauge. Body height, as a rule, in combination with BMI, was the strongest predictor of handgrip strength, especially in older children (about 40-60 % of the total variance, R2 x 100). From the hand anthropometry, the most important span parameter was FS2 (see explanations in the methods), which explained about 10-50% (R2 x 100) of the total variance. In older groups, the FS1 and FS3 were added to the models. From the length parameters, the most important was IFL, which in younger groups together with MFL explained 10-30% of the total variance, and in older groups the addition of RFL increased the influence to 45% (R2 x 100). From the perimeters, the most important one was P2 which explained the variability of the handgrip strength in younger groups by 15-30% (R2 x 100) and in older groups together with P3 and P4 even 30-40%. In children, the basic anthropometric parameters (body height and BMI) contribute more to the prediction of handgrip strength than the specific anthropometric parameters. With increasing age the contribution of basic and specific hand anthropometry increases and the relation between anthropometry and handgrip strength is stronger in boys compared with girls. The relation of basic and hand anthropometry to the tip and key pinch strength is relatively low.
    Anthropologischer Anzeiger 09/2007; 65(3):293-302. · 0.54 Impact Factor
  • J Jürimäe, P Purge, T Jürimäe
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    ABSTRACT: Adiponectin is secreted by adipocytes and has been implicated in the regulation of energy homeostasis. Vigorous training program represents a physical stress condition in which heavy changes in energy expenditure might increase adiponectin concentration in athletes. Therefore, the aim of the present study was to investigate if there are changes in fasting adiponectin concentration during preparatory period in elite male rowers. Twelve rowers (mean and SD; age: 20.8+/-3.0 years; height: 192.9+/-4.7 cm; body mass: 91.9+/-5.3 kg; body fat percentage: 11.9+/-1.4%) were tested seven times over a 24-week training season. In addition to adiponectin, leptin, insulin, growth hormone, and glucose values were evaluated. Maximal oxygen consumption (VO (2 max)) and aerobic power (Pa (max)) were determined before and after the training period. Training was mainly organized as low-intensity prolonged training. Significant increases in VO (2 max) (by 3.2+/-1.8%; from 6.2+/-0.5 to 6.4+/-0.4 l/min), VO (2 max/kg) (by 2.2+/-2.0%; from 67.9+/-3.0 to 69.4+/-3.0 ml/min/kg) and Pa (max) (by 4.6+/-6.3%; from 444.6+/-39.1 to 465.8+/-25.0 W) were observed after the 24-week period. All measured body compositional values were similar to pretraining values after the training period. Fasting adiponectin did not change during the preparatory period. Likewise, leptin, insulin, growth hormone, and glucose values were not significantly changed after the training period. Adiponectin concentration was significantly correlated (all p<0.05) with body mass (r=-0.40), body fat mass (r=-0.33), body fat free mass (r=0.38), and leptin (r=-0.31) values. In conclusion, fasting adiponectin does not change throughout the prolonged training period in elite male rowers despite substantial changes in training volume. Further studies are needed to clarify possible mechanisms by which adiponectin might influence energy homeostasis during heavy training in elite athletes.
    Hormone and Metabolic Research 07/2007; 39(7):519-23. · 2.15 Impact Factor
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    Jaak Jürimäe, Toivo Jürimäe, Priit Purge
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    ABSTRACT: The aim of the present investigation was to investigate plasma ghrelin response to acute maximal exercise in elite male rowers. Eight elite male rowers performed a maximal 6000-m rowing ergometer test (mean performance time: 19 mins 52 secs; 1192.1 +/- 16.4 secs), and venous blood samples were obtained before, immediately after, and after 30 mins of recovery. In addition to ghrelin concentration, leptin, insulin, growth hormone, insulin-like growth factor-1 (IGF-1), testosterone, cortisol, and glucose values were measured. Ghrelin was significantly increased immediately after the exercise (+24.4%; P < 0.05) and was not significantly different than baseline after 30 mins of recovery. Leptin was significantly decreased immediately after the exercise (- 15.8%; P < 0.05) and remained significantly decreased after the first 30 mins of recovery. No changes occurred in insulin concentrations. Growth hormone, IGF-1, and testosterone values were significantly increased and decreased to the pre-exercise level immediately after the exercise and after the first 30 mins of recovery, respectively. Cortisol and glucose values were significantly increased immediately after the exercise and remained significantly increased during the first 30 mins of recovery. There were no relationships between plasma ghrelin and other measured blood parameters after the exercise, nor were changes in ghrelin related to changes in other measured blood biochemical values after the exercise. In conclusion, these results suggest that acute negative energy balance induced by specific maximal short-term exercise elicits a metabolic response with opposite changes in ghrelin and leptin concentrations in elite male athletes.
    Experimental Biology and Medicine 07/2007; 232(7):904-9. · 2.80 Impact Factor
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    ABSTRACT: The aim of this study was to examine the relationships between body fat measured by DXA and subcutaneous adipose tissue layers (SAT-layers) measured by LIPOMETER in adult males (n=28) and females (n=53). Body height and mass were measured and BMI was calculated (kg/m2). Measurements of the thicknesses of SAT-layers by LIPOMETER were performed at 15 original body sites. Body composition was measured using DXA. Total body fat % measured by DXA was highly dependent on the SAT-layers in the upper back and inner thigh in males (87.1%, R(2)x100) and the lateral chest, biceps, and calf in females (78.5%, R(2)x100). There were gender differences in trunk fat mass and right hand and leg fat mass calculation using specific SAT-layers. In conclusion, our results indicate that there are close relationships between SAT-layers and body fat measured by DXA. However, there are big differences between genders.
    Journal of PHYSIOLOGICAL ANTHROPOLOGY 07/2007; 26(4):513-6. · 0.63 Impact Factor
  • Jaak Jürimäe, Toivo Jürimäe
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    ABSTRACT: The aim of the current investigation was to determine the possible relationships of fasting adiponectin level with body composition, bone mineral, insulin sensitivity, leptin, and cardiorespiratory fitness parameters in 153 women. Subjects were classified as premenopausal (n = 42; 40.8 +/- 5.7 yr) if they had regular menstrual periods, early postmenopausal (n = 49; 56.7 +/- 3.6 yr) if they had been postmenopausal for more than >1 yr but <7 yr (5.5 +/- 1.3 yr), and postmenopausal (n = 62; 72.2 +/- 4.5 yr) if they had been postmenopausal for >7 yr. All women studied had a body mass index (BMI) <30 kg/m(2). Adiponectin values were higher (P < 0.05) in middle-aged (12.0 +/- 5.1 microg/ml) and older (15.3 +/- 7.3 microg/ml) postmenopausal women compared with middle-aged premenopausal women (8.4 +/- 3.2 microg/ml). Mean plasma adiponectin concentration in the total group of women (n = 153) was 12.2 +/- 6.3 microg/ml and was positively related (P < 0.05) to age, indexes of overall obesity (BMI, body fat mass), and cardiorespiratory fitness (PWC) values. In addition, a negative association (P < 0.05) between adiponectin with central obesity (waist-to-hip and waist-to-thigh ratio), fat-free mass, bone mineral (bone mineral content, total and lumbar spine bone mineral density), and leptin and insulin resistance (insulin, fasting insulin resistance index) values was observed. However, multivariate regression analysis revealed that only age, fasting insulin resistance index, and leptin were independent predictors of adiponectin concentration. In conclusion, circulating adiponectin concentrations increase with age in normal-weight middle-aged and older women. It appears that adiponectin is independently related to age, leptin, and insulin resistance values in women across the age span and menstrual status.
    AJP Endocrinology and Metabolism 07/2007; 293(1):E42-7. · 4.51 Impact Factor
  • T Sööt, T Jürimäe, J Jürimäe
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    ABSTRACT: The aim of this study was to find possible relationships between plasma leptin and bone mineral density (BMD) in weight bearing and non-weight bearing sites in young females with different physical activities and body composition parameters. In 33 strength-trained, 32 endurance-trained, 41 sedentary normal weight and 23 sedentary overweight females, fasting plasma leptin and BMD of the total body, antero-posterior lumbar spine L2-L4, dominant arm distal radius and femoral neck were measured. Endurance-trained females had lower values in L2-L4 when compared to strength-trained (P<0.01) and overweight (P<0.01) females. Normal weight sedentary females had lower (P<0.01) BMDs in sites L2-L4, femoral neck and total BMD when compared to strength-trained females. Overweight sedentary females had higher BMD values in sites L2-L4 (P<0.01) and total BMDs (P<0.05) when compared to normal weight sedentary females. No significant relationships (P>0.05) were found between plasma leptin and any measured BMD parameters in strength-trained and overweight sedentary females. In endurance-trained and normal weight sedentary females, leptin was correlated only with L2-L4 (r=0.461 and r=0.456, respectively). In normal weight sedentary females, distal radius BMD correlated significantly with leptin concentration (r=0.388). Our findings indicate that plasma leptin concentrations, as a rule, are not directly related to areal BMD in young females. However, only in endurance-trained and normal weight sedentary groups, in L2-L4 sites and also in normal weight sedentary group at distal radius, leptin concentrations are related to areal BMD via body fat mass.
    The Journal of sports medicine and physical fitness 04/2007; 47(1):65-9. · 0.73 Impact Factor
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    ABSTRACT: The regulatory effect of ghrelin on growth hormone (GH) is limited in describing ghrelin response to acute submaximal exercise intensities in elite athletes. We investigated the effects of a single sculling exercise performed above and below the individual anaerobic threshold (IAT) on total ghrelin concentration in highly trained male rowers. Nine elite male rowers (20.1 +/- 3.7 years; 190.0 +/- 5.2 cm; 89.6 +/- 4.6 kg; %body fat: 9.9 +/- 2.5%) volunteered for this study. Single scull rowing was performed below and above IAT using a mean of 5 bpm above and below the heart rate of the IAT during graded exercise test. Ghrelin, leptin, GH, insulin, and glucose were measured before, immediately after, and after 30 min of recovery. Plasma ghrelin concentration did not increase significantly in either exercise but was approaching significance after 30 min of recovery (P = 0.051) when the constant load sculling was performed at the intensity above the IAT. There were no changes in plasma leptin levels. GH increased significantly immediately after exercise and remained elevated during the 30 min of recovery in both exercise conditions, while insulin decreased significantly immediately after exercise and remained significantly lower after the 30 min of recovery in both exercise intensities. Baseline ghrelin was not correlated with the body composition, physical performance, or blood biochemical data. There was no significant relationship between plasma ghrelin and other blood variables immediately after the 30 min of recovery in both exercise tests and changes in ghrelin were not related to blood biochemical variables after the exercise tests. The acute constant load sculling exercise above or below IAT that increased GH concentrations did not significantly increase the circulating plasma ghrelin levels.
    Arbeitsphysiologie 04/2007; 99(5):467-74. · 2.66 Impact Factor
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    ABSTRACT: The purpose of this study was to examine the influence of the energy cost of swimming, body composition, and technical parameters on swimming performance in young swimmers. Twenty-nine swimmers, 15 prepubertal (11.9 +/- 0.3 years; Tanner Stages 1-2) and 14 pubertal (14.3 +/- 1.4 years; Tanner Stages 3-4) boys participated in the study. The energy cost of swimming (Cs) and stroking parameters were assessed over maximal 400-m front-crawl swimming in a 25-m swimming pool. The backward extrapolation technique was used to evaluate peak oxygen consumption (VO2peak). A stroke index (SI; m2 . s(-1) . cycles(-1)) was calculated by multiplying the swimming speed by the stroke length. VO2peak results were compared with VO2peak test in the laboratory (bicycle, 2.86 +/- 0.74 L/min, vs. in water, 2.53 +/- 0.50 L/min; R2 = .713; p = .0001). Stepwise-regression analyses revealed that SI (R2 = .898), in-water VO2peak (R2 = .358), and arm span (R2 = .454) were the best predictors of swimming performance. The backward-extrapolation method could be used to assess VO2peak in young swimmers. SI, arm span, and VO2peak appear to be the major determinants of front-crawl swimming performance in young swimmers.
    Pediatric exercise science 03/2007; 19(1):70-81. · 1.57 Impact Factor
  • European Journal of Applied Physiology and Occupational Physiology 03/2007;
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    ABSTRACT: Both Estonia and Lithuania have a long history of pediatric fitness testing, but due to a lack of standardized test batteries spanning a substantial number of years, secular changes in fitness test performance have not been previously reported. Using the Eurofit test battery, the aim of this study was to quantify the secular changes in fitness test performance of Estonian and Lithuanian children and adolescents during the first ten years of independence. Two cross-sectional surveys of Estonian and Lithuanian 11- to 17-year-old tested on the Eurofit in 1992 and 2002 were compared. Secular changes were calculated by first, expressing mean values (at the country x age x sex x test level) in 2002 as a percentage of mean values in 1992, and second, by subtracting 100 from the resultant and then dividing 10 to express the changes as percentage changes per annum (p.a.). Negative values indicated secular declines, and positive values secular improvements. Secular changes in Eurofit test performance were calculated for 12,226 Estonian and Lithuanian children and adolescents over the 10-year period. Across all Eurofit tests, secular changes ranged on average from -0.98 to +0.49% p.a., with performances less variable for Estonian children than for Lithuanian children. Secular changes were strikingly consistent across age and sex groups. This is the first study to have described the secular changes in Eurofit test performance of children and adolescents from the Baltic states. It shows that between 1992 and 2002, changes in Eurofit performance varied among tests and were not always in line with European and global changes.
    Medicine and sport science 02/2007; 50:129-42.
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    Aire Leppik, Toivo Jürimäe, Jaak Jürimäe
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    ABSTRACT: The aim of this study was to investigate the anthropometric parameters and body impedance once per year during four years of the pubertal period in Estonian children. In total, 81 boys and 86 girls aged 10-11 years at the beginning of the study were investigated. Pubertal status was self-assessed by sexual maturation stages according to Tanner and physical activity index (PAI) according to Telama et al.. Body height and weight were measured and body mass index (BMI) calculated. In total, 9 skinfolds, 13 girths, 8 lengths and 8 breadths/lengths were measured according to the protocol of the International Society for the Advancement of Kinanthropometry. Somatotype components were estimated according to the method of Carter and Heath. Body impedance was measured using Multiscan 5000 (Bodystat, UK) and the impedance index (height/impedance) was calculated. The tracking of body height, weight, BMI, skinfolds, girths, lengths, breadth/lengths and body impedance was high (as a rule r> or =0.9). By increasing the time period, the correlation slightly decreased. In contrast, tracking correlations for PAI and Tanner stages were significant but quite low. Increase in mean body height was highest between 12-13 years of age (6.9 cm per year) in boys and in girls between 11-12 years of age (6.3 cm per year). In boys and girls, the peak increase in body weight was between 11 and 12 years of age, 5.7 kg and 5.2 kg, respectively. With the increasing age, body impedance decreased and impedance index increased. In conclusion, our results indicate that during puberty the detailed anthropometric parameters and body impedance tracked highly. However, the tracking of PAI and Tanner stages was significant but relatively low.
    Collegium antropologicum 01/2007; 30(4):753-60. · 0.61 Impact Factor
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    ABSTRACT: The aim of our study was to examine the relationship between bone mineral density (BMD) and serum ghrelin, insulin-like growth factor-1 (IGF-1), IGF-binding protein 3 (IGFBP-3), and testosterone levels in boys at different stages of puberty. The study included 60 healthy nonobese Estonian schoolboys at the age of 10-18 years. Subjects were divided in three groups (20 boys in each) based on the results of self-assessment using illustrated questionnaire of pubertal stage (G1, I; G2-G3, II; G3-G4, III). Morning fasting blood samples were collected for analysis of ghrelin, testosterone, IGF-1, and IGFBP-3. Total body BMD, lumbar BMD, lumbar apparent volumetric BMD (BMAD), and bone mineral content (BMC) were measured by DXA. Serum testosterone concentration was the most important biochemical predictor of BMD in the total group, explaining 48.8% of variability in total body BMD, 51.4% in lumbar BMD, and 36.8% in lumbar BMAD. Body mass and height were both related to BMD and BMC throughout puberty. The serum IGF-1/IGFBP-3 ratio was correlated with serum testosterone (r = 0.69) and ghrelin (r = -0.58) levels, but also with total BMD (r = 0.39), lumbar BMD (r = 0.42; P < 0.001 in all cases), BMAD (r = 0.29; P < 0.01), and total BMC (r = 0.48; P < 0.001). We conclude that serum testosterone concentration and serum IGF-1/IGFBP-3 molar ratio are the major determinants of bone mineral density in boys at different pubertal stages. Serum ghrelin concentration did not appear to have a direct independent effect on BMD. If present, the association may be mediated through sex hormones and the GH-IGF-I axis.
    Journal of Bone and Mineral Metabolism 01/2007; 25(3):193-7. · 2.22 Impact Factor
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    ABSTRACT: The aim of this study was to investigate the relationships between fasting serum ghrelin concentration, anthropometrical and body composition data in boys at different pubertal stages. Sixty healthy non-obese Estonian schoolboys (10 to 18 yr) were divided into 3 groups based on Tanner classification--group I was prepubertal, group II included stages 2 and 3, and group III stages 4 and 5. Additionally, we analyzed subjects as a total group. Fasting ghrelin, leptin, testosterone, insulin and glucose were collected between 08:00 and 10:00 h. Body fat % and lean body mass (LBM) were determined by dual-energy X-ray absorptiometry. Fasting ghrelin decreased, while leptin and insulin did not change and testosterone increased during puberty. There was a negative correlation between serum ghrelin and testosterone concentrations in group II (r=-0.51, p<0.05) and in the total group (r=-0.59, p<0.001). Ghrelin was also related to body height, body mass and LBM in group II and total group also with body mass index in total group. Stepwise multiple regression analysis showed that body height from auxological, LBM from body composition and testosterone from biochemical data explained 38.1, 41.7 and 33.7% of the ghrelin variance in the total group, respectively. In conclusion, body height, LBM and serum testosterone are the major determinants of serum ghrelin among parameters studied. Negative correlation between serum ghrelin and testosterone concentrations indicates that ghrelin may also have a role in male pubertal development.
    Journal of endocrinological investigation 12/2006; 29(11):962-7. · 1.65 Impact Factor
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    ABSTRACT: The aim of this study was to investigate the changes in serum ghrelin and leptin concentrations during acute aerobic cycle ergometer test in 60 boys at different pubertal stages. Boys were divided according to their pubertal status as group I (Tanner stage 1, n=20), group II (Tanner stages 2 and 3, n=20) and group 3 (Tanner stages 4 and 5, n=20). Maximal oxygen consumption and individual ventilatory threshold of the subjects were measured directly using stepwise increasing loads on cycle ergometer. Second exercise test consisted of a 30 minute constant load exercise on the same ergometer at the level of approximately 95% of the individual ventilatory threshold. Venous blood samples were obtained before, immediately after and after 30 minutes of recovery for the measurement of serum ghrelin, leptin, testosterone and insulin. At baseline, prepubertal children had significantly higher values for serum ghrelin compared to the groups II and III. Acute exercise altered significantly only insulin concentration. In all the groups, the maximal oxygen consumption/kg correlated positively with basal levels of testosterone (r=0.60, p<0.001) and insulin (r=0.34), and negatively to ghrelin (r=-0.35) and leptin (r=-0.32) (p<0.05). We conclude that moderate acute aerobic exercise does not change serum ghrelin or leptin level in boys at different pubertal stages.
    Hormone and Metabolic Research 11/2006; 38(11):752-7. · 2.15 Impact Factor

Publication Stats

1k Citations
207.48 Total Impact Points

Institutions

  • 1998–2014
    • University of Tartu
      • • Faculty of Exercise and Sports Sciences
      • • Faculty of Medicine
      • • Institute of Sport Pedagogy and Coaching
      Dorpat, Tartu County, Estonia
  • 2007–2010
    • University of Bologna
      • • School of Pharmacy, Biotechnology, and Sport Sciences
      • • Department of Experimental Evolutionary Biology BES
      Bologna, Emilia-Romagna, Italy
    • Karl-Franzens-Universität Graz
      Gratz, Styria, Austria
  • 2009
    • Medical University of Graz
      • Institute of Physiological Chemistry
      Gratz, Styria, Austria