The Impact of Physical Activity on Serum Inflammatory Markers in Overweight Pubertal Boys: 24-Month Follow-Up Study.

PURPOSE: To investigate the differences in the pattern of changes in serum inflammatory cytokines measured annually over a 24-month period, between less active and more active overweight boys. PARTICIPANTS/METHODS: In total, 25 pubertal overweight boys were divided by their moderate to vigorous physical activity (MVPA) levels into 2 groups: less active group (LAG; n = 10; MVPA < 60 min/d) and more active group (MAG; n = 15; MVPA > 60 min/d). Physical activity was measured by 7-day accelerometry. Serum concentration of 13 inflammatory cytokines [interleukin (IL)-2, IL-4, IL-6, IL-8, IL-10, IL-1α, IL-1ß, vascular endothelial growth factor, interferon-γ, tumor necrosis factor-α, monocyte chemotactic protein-1, epidermal growth factor, and C-reactive protein] was measured at baseline (T0), after 12 months (T1), and after 24 months (T2) from fasting blood samples. RESULTS: Serum IL-6 level was significantly higher [LAG: 1.27 (0.86, 1.98) pg/mL; MAG: 0.80 (0.52, 0.84) pg/mL] at T0 and IL-8 level [LAG: 10.26 (8.80, 11.64) pg/mL; MAG: 7.42 (6.10, 9.54) pg/mL] at T2 in LAG compared with MAG. The changes over the study period varied between different inflammatory markers. None of the slopes of any measured markers were statistically different between the LAG and MAG, although the slopes of interferon-γ and IL-10 tended to be different between the groups. CONCLUSIONS: The pattern of changes over the study period varied between different inflammatory markers, but these changes were not different between the MVPA groups. More longitudinal studies are needed to investigate whether IL-6, IL-8, IL-10, and interferon-γ would be the choice of inflammatory markers to study the associations between obesity and physical activity in future.

Extensive BMI Gain in Puberty is Associated with Lower Increments in Bone Mineral Density in Estonian Boys with Overweight and Obesity: A 3-Year Longitudinal Study.

The aim of this 3-year prospective study was to examine changes in bone mineral characteristics during pubertal maturation in boys with different BMI values at the beginning of puberty and with different BMI increments during puberty. 26 boys with overweight and obesity (OWB) and 29 normal weight boys (NWB) were studied yearly for 3 years from the age of 11 years to measure the changes in different bone mineral characteristics. The OWB group was further divided into two subgroups according to extensive or non-extensive BMI increment during 3-year period. OWB had higher (P < 0.01) baseline total body (TB) bone mineral density (BMD), TB bone mineral content (BMC), TB BMC for height, lumbar spine (LS) BMD, and LS BMC compared to NWB. Throughout the study period, OWB gained more TB BMD (P = 0.0001), TB BMC (P = 0.0048), TB BMC for height (P = 0.0124), LS BMD (P = 0.0029), and LS BMC (P = 0.0022) compared to NWB. Also during the study period, TB BMD (P = 0.0065), TB BMC (P = 0.0141), TB BMC for height (P = 0.0199), LS BMD (P = 0.0066), LS apparent volumetric BMD (BMAD) (P = 0.0075), and LS BMC (P = 0.017) increased significantly less in those OWB whose BMI increased more extensively. Extensive BMI gain is associated with lower increments in bone mineral characteristics in boys with overweight and obesity. Unfavorable increment in total body fat mass and percentage during pubertal years could be one reason for that.

Associations of serum leptin, ghrelin and peptide YY levels with physical activity and cardiorespiratory fitness in adolescent boys with different BMI values.

The aim of this study was to investigate the differences in associations of serum acylated and des-acylated ghrelin, peptide YY (PYY) and leptin levels with physical activity (PA) and cardiorespiratory fitness (CReF) in adolescent boys (mean age of 14.0 years) with overweight (OWB; n=55) and with normal weight (NWB; n=154). METHODS: Total PA was measured by 7-day accelerometry (counts/min) and CReF by peak oxygen consumption (VO2peak/kg). RESULTS: No differences were found in serum PYY, acylated ghrelin or des-acyl ghrelin levels, whereas mean leptin (11.6±10.6 vs. 2.0±2.7 ng/ml; p<0.05) and insulin (18.1±8.7 vs. 11.0±6.2 mU/l; p<0.05) levels were significantly higher in OWB compared to NWB. Mean CReF was significantly lower in OWB compared to NWB (39.7±8.7 vs. 50.5±6.8 ml/min/kg; p<0.05). Leptin was negatively correlated with CReF in both groups (r=-0.43; p<0.05), des-acylated ghrelin with CReF only in OWB (r =-0.36; p<0.05). In OWB leptin was negatively correlated with total PA (r=-0.32; p<0.05) and positively with sedentary time of PA (r=0.35; p<0.05). In NWB 28.1% of the variability of CReF was determined by leptin and insulin resistance index (HOMA-IR), whereas in OWB 71.9% was determined by trunk FM and BMI. CONCLUSIONS: Leptin concentration was inversely associated with CReF in adolescent boys independently of BMI in both groups, while des-acylated ghrelin was associated with CReF only in OWB. Low PA in OWB was associated with high serum leptin level.

Diet misreporting can be corrected: confirmation of the association between energy intake and fat-free mass in adolescents.

Subjective energy intake (sEI) is often misreported, providing unreliable estimates of energy consumed. Therefore, relating sEI data to health outcomes is difficult. Recently, Börnhorst et al. compared various methods to correct sEI-based energy intake estimates. They criticised approaches that categorise participants as under-reporters, plausible reporters and over-reporters based on the sEI:total energy expenditure (TEE) ratio, and thereafter use these categories as statistical covariates or exclusion criteria. Instead, they recommended using external predictors of sEI misreporting as statistical covariates. We sought to confirm and extend these findings. Using a sample of 190 adolescent boys (mean age=14), we demonstrated that dual-energy X-ray absorptiometry-measured fat-free mass is strongly associated with objective energy intake data (onsite weighted breakfast), but the association with sEI (previous 3-d dietary interview) is weak. Comparing sEI with TEE revealed that sEI was mostly under-reported (74 %). Interestingly, statistically controlling for dietary reporting groups or restricting samples to plausible reporters created a stronger-than-expected association between fat-free mass and sEI. However, the association was an artifact caused by selection bias - that is, data re-sampling and simulations showed that these methods overestimated the effect size because fat-free mass was related to sEI both directly and indirectly via TEE. A more realistic association between sEI and fat-free mass was obtained when the model included common predictors of misreporting (e.g. BMI, restraint). To conclude, restricting sEI data only to plausible reporters can cause selection bias and inflated associations in later analyses. Therefore, we further support statistically correcting sEI data in nutritional analyses. The script for running simulations is provided.

Cardiovascular fitness, physical activity, and metabolic syndrome risk factors among adolescent estonian boys: A longitudinal study.

OBJECTIVES: The aim was to examine the changes in metabolic syndrome risk factors over a 2-year period, and to investigate the independent influence of baseline physical activity (PA) and cardiovascular fitness (CVF) on these changes. METHODS: 120 Estonian boys (age at baseline 11.9 ± 0.1 years) were grouped according to baseline PA or CVF/kg (VO2max/kg ) and CVF/LBM (VO2max/LBM ). PA was assessed by 7-day accelerometry. Total cholesterol (TC), high-density lipoprotein (HDL), triglycerides (TRG), insulin and glucose were measured and assessment for insulin resistance (HOMA-IR) and TC/HDL ratio were calculated. RESULTS: In both CVF/kg and CVF/LBM , the low CVF groups had significantly higher values of HOMA-IR (P < 0.009) over time. In TRG and TC/HDL ratio values the only significant difference over time emerged between CVF/kg groups (P < 0.001). Participants in high metabolic risk CVF/kg group were 5.9 times more likely to have high HOMA-IR values, 2.9 times more likely to have high triglyceride values, and 3.5 times more likely to have high TC/HDL ratio values (P ≤ 0.045) in the second year follow-up compared to those who were in the low metabolic risk CVF/kg group. In moderate-to-vigorous PA groups there were no significant differences between HOMA-IR, TRG, and TC/HDL ratio values over time. CONCLUSIONS: The results of the study indicate that CVF has a stronger longitudinal prediction value compared to moderate to vigorous physical activity in terms of metabolic risk factors in adolescent boys. Fitness remained a significant predictor if the influence of body fatness was removed from the analysis. Am. J. Hum. Biol. 28:782-788, 2016. © 2016Wiley Periodicals, Inc.

Longitudinal associations between bone and adipose tissue biochemical markers with bone mineralization in boys during puberty.

BACKGROUND: We investigated longitudinal relationships between the biochemical markers of bone and adipose tissue with bone mineral content (BMC), bone mineral density (BMD), moderate-to-vigorous physical activity (MVPA) and sedentary time (SED) in pubertal boys. METHODS: Ninety-six boys (11.9 ± 0.6 years old) were measured at baseline, after 12 and 24 months. Body composition (fat mass [FM], lean body mass [LBM]), and whole body (WB), lumbar spine (LS) and femoral neck (FN) BMD and BMC were assessed. Additionally, serum leptin, adiponectin, osteocalcin (OC) and C-terminal telopeptide of type I collagen (CTX) were measured. RESULTS: OC had a strong longitudinal inverse effect on changes in WB_BMD (p < 0.001) and LS_BMD (p = 0.021), while CTX had an inverse effect only on changes in FN_BMD (p = 0.011). Leptin had an inverse effect on changes in WB_BMC/WB_BMD (p = 0.001), FN_BMD (p = 0.002) and LS_BMD (p = 0.001). MVPA showed a longitudinal inverse effect on changes in leptin (p = 0.030), however no longitudinal effect of SED to biochemical markers of bone and adipose tissue was found. CONCLUSIONS: Bone metabolism markers have negative effect on bone mineral accrual during puberty. Increases in MVPA affect leptin, suggesting a positive link of MVPA through leptin metabolism on increases in bone mineralization during puberty.

Sedentary time has a negative influence on bone mineral parameters in peripubertal boys: a 1-year prospective study.

One of the key determinants of adult skeletal health is the maximization of bone mass during the growth period. Physical activity (PA) in combination with lean mass and fat mass contribute to a great extent to bone mineral accrual; however, PA changes significantly during puberty. The aim of the present study was to examine PA exposure relative to bone mass acquisition during a longer observation period. Daily PA was measured with 7-day accelerometry and bone mineral parameters by DXA in 11- to 13-year-old peripubertal boys (n = 169). Similar testing was done after 1 calendar year. Changes in sedentary time were negatively related to changes in whole-body bone mineral density (BMD), lumbar spine bone mineral content (BMC), lumbar spine bone area (BA), femoral neck (FN) BMD, and FN BMC (r > -0.157; p < 0.05). Sedentary time emerged as the main PA level in predicting changes in FN BMC (p = 0.027) and in combination with vigorous PA predicting changes in FN BMD (p < 0.024). In addition to the effect of body composition on the skeleton, increase in sedentary time emerged as one main physical activity predictor (in addition to vigorous PA) of bone mineral acquisition during a 12-month period in peripubertal boys.

Vigorous physical activity rather than sedentary behaviour predicts overweight and obesity in pubertal boys: a 2-year follow-up study.

AIM: Current physical activity (PA) recommendations indicate that children should get involved in 60 minutes of moderate-to-vigorous PA (MVPA), and should include vigorous-intensity PA at least three days a week. However, it is not known how many minutes of vigorous PA they should do. Using objective methods and a longitudinal design, this study aimed to examine how different PA intensities and sedentary behaviour relate with the risk of being overweight and obese during puberty over a two-year period. METHODS: A sample of 136 10-12-year-old (at baseline) boys participated. PA was measured by seven-day accelerometry. RESULTS: From MVPA thresholds, only 90 minutes per day of MVPA had important odds ratios (OR) for being overweight at baseline (OR=8.14, 95% confidence interval [CI] 1.03-64.04). A significant cut-off point for being overweight was indicated by 59 minutes per day of MVPA with at least 14 minutes per day of vigorous PA, and 55 minutes per day MVPA with at least 10 minutes per day of vigorous PA for those who were obese. Sedentary behaviour did not have any significant ORs for being overweight or obese. Subjects who did not meet the thresholds of 5 and 20 minutes per day of vigorous PA at baseline had an increased risk of being overweight (OR=4.05, 95% CI 1.41-11.59, and OR=4.14, 95% CI 1.35-12.73, respectively) and obese (OR=6.54, 95% CI 1.97-21.69, and OR=8.75, 95% CI 1.12-68.51, respectively) two years later. CONCLUSIONS: The results indicate that vigorous PA in particular predicts overweight and obesity in boys. They should aim to do at least 60 minutes per day of MVPA. These results contribute to the recommendations suggesting that a minimum of 15 minutes per day of vigorous PA is desired to reduce the risk of developing overweight/obesity in later puberty.

Tracking of physical activity in pubertal boys with different BMI over two-year period.

We examined the tracking of physical activity (PA) measured by accelerometers and subjective self- and parental reports in normal weight and overweight and obese pubertal boys over two-year period. In total, 156 boys with mean (±SD) age of 11.53 ± 0.76 at baseline and with mean age of 13.94 ± 0.74 at 2 year follow-up were studied. At baseline and approximately two years later, the boys completed self-report questionnaire and wore an accelerometer for seven consecutive days. On the basis of first year assessment's body mass index (BMI), the children were grouped as normal weight and overweight and obese groups according to BMI cut-offs. Tracking correlations of objectively measured PA and subjectively measured PA were fairly similar across the 12-14 year-old-boys weight groups over two year period. Tracking correlations of objectively measured PA and subjectively measured PA were not significantly different over two-year period between both BMI groups. The results of the study show that pubertal boys objectively measured PA decreased over two-year period and so the boys started to be less active in their pubertal period.

Caliper vs. Lipometer--Comparing Two Methods of Subcutaneous Body Fat Measurement by Bland-Altman Diagrams.

Skinfold Calipers are widely used to obtain subcutaneous adipose tissue thickness because of its non-invasive, simple and inexpensive technique. Nevertheless, Caliper skinfold thicknesses have the disadvantage of measuring compressed adipose tissue and double layers of skin, which might reduce the precision of these results. In contrast, the computerized optical device Lipometer was developed to permit a quick, precise and non-invasive determination of non-compressed mono layers of subcutaneous adipose tissue thickness. In the present paper we investigate the hypothesis that Caliper skinfold thicknesses are significantly different from subcutaneous adipose tissue thicknesses in mm, which can be measured by Lipometer. Caliper and Lipometer results were obtained from 371 Estonian boys aged between 9.0 and 12.8 years. Measurements were performed at six different body sites: triceps, biceps, upper back, upper abdomen, hip and front thigh. Caliper measurements were systematically higher than Lipometer results in a range between 1.2 mm (hip) and 11.08 mm (front thigh). The limits of agreement analysis provided intervals from 7.5 mm (biceps) up to 30.14 mm (front thigh). Comparing Caliper and Lipometer results very low measurement agreement was found. The two methods provided very poor interchangeability.

ASSOCIATION OF SUBJECTIVE RATINGS TO OBJECTIVELY ASSESSED PHYSICAL ACTIVITY IN PUBERTAL BOYS WITH DIFFERING BMI.

The associations between subjective ratings and objectively measured moderate-to-vigorous physical activity (MVPA) were examined in normal, and overweight and obese, pubertal boys and compared with their parents' reports. In total, 224 boys (M age=12.2 yr.) completed the self-report questionnaire and wore an accelerometer for 7 consecutive days. Questionnaire-based indexes of physical activity (PA) were weakly associated with the accelerometer PA data. Correlations between subjective and objective assessments were significantly higher in overweight and obese groups. Parent reports predicted sedentary time better than boys' self-reports but no difference was found for MVPA. Future studies must consider that the source of rating, season, and weight status may be possible sources of confounding when using subjective assessments of PA.

Maturity-related differences in moderate, vigorous, and moderate-to-vigorous physical activity in 10-14-year-old boys.

The goal of this study was to investigate differences in physical activity (PA) levels between early, average, and late maturing boys and the effect of chronological age, body mass index, and fat mass. PA was measured by accelerometry in 10-14-yr.-old boys (N=265) during seven consecutive days. Biological maturation groups (early, average, and late) were created. Average and late maturing boys had significantly higher moderate PA and moderate-to-vigorous PA compared to early maturing boys. Late maturers also had higher vigorous PA compared to early maturers. Differences in moderate PA and moderate-to-vigorous PA remained significant after controlling for chronological age; however, after controlling for Body Mass Index or fat mass the differences were no longer significant. Mean differences in PA between early, average, and late maturing boys are not independent of Body Mass Index or fat mass. Vigorous PA differences between maturity groups were not independent of chronological age.

Role of physical activity in bone health in peripubertal boys.

BACKGROUND: The aim of the present cross-sectional study was to investigate the relationship of physical activity level to bone mineral parameters in 11-13-year-old boys. METHODS: In total, 264 boys, divided into normal weight (n = 154) and overweight (n = 110), participated in this study. Physical activity was measured via 7 day accelerometry and bone mineral parameters using dual-energy X-ray absorptiometry. RESULTS: In overweight boys, vigorous physical activity was associated with total bone mineral density (BMD), total bone mineral content (BMC), while moderate-vigorous physical activity MVPA was associated with femoral neck BMD. In normal weight boys, however, only vigorous physical activity was associated with femoral neck BMD. When the normal weight group was divided into tertiles according to MVPA, femoral neck BMD was higher in the highest tertile compared to the lowest tertile. No other significant differences were found in bone mineral parameters according to the tertiles of MVPA. CONCLUSIONS: In overweight peripubertal boys, physical activity is more associated with bone mineral parameters compared to normal weight subjects. In addition to vigorous physical activity, moderate physical activity has a significant impact on bone mineral parameters in overweight subjects.

Adipocytokine and ghrelin levels in relation to body composition in rhythmic gymnasts entering into puberty: a 3-year follow-up study.

The aim of this study was to describe longitudinal changes in body composition, leptin, adiponectin, and ghrelin over a 36-month period in prepubertal rhythmic gymnasts (RG) and their age-matched untrained controls (UC) entering into puberty. Thirty-five RG (8.0 ± 0.6 yrs) and 33 UC (8.2 ± 0.6 yrs) were followed at 12-month intervals for the next 3 years. Height, weight, pubertal stage, body composition, leptin, adiponectin, and ghrelin were measured at each time points. The pubertal development over the next 36 months was slower in the RG compared with UC. Leptin was increased in UC and remained unchanged in RG over 3-year study period (3.7 ± 3.6 vs. 0.2 ± 1.1 ng/ml; p < .05). In RG, baseline leptin was negatively correlated with the change in body fat percentage over a 36-month period (r = -0.34; p < .05). The change in adiponectin over the study period was negatively correlated with the change in BMI (r = -0.43; p < .05). RG had relative leptin deficiency per body fat mass. In conclusion, relatively high leptin concentration at the beginning of puberty may predict those girls who do not increase their body fat percentage through coming years and therefore may have increased risk for delayed puberty.

Correlations of skinfold thicknesses and circumferences at exactly defined body sites with leptin in 10-12-year-old boys with different BMIs.

The aim of this study was to investigate the correlations of leptin with values of skinfold thicknesses and circumferences in 10-12-year-old boys (N = 248) and these correlations were additionally studied in boys with different BMI subgroups (normal N = 190, overweight N = 34 and obese N = 24). In total, 9 skinfolds and 13 circumferences were measured using the recommendations of ISAK. Fasting leptin concentrations were also determined. No significant differences emerged between the three subgroups in age and Tanner stage. Skinfold thicknesses, circumferences and leptin concentrations were significantly higher in overweight and obese groups. In the total group, the correlation (partial correlation, eliminating age and Tanner stage) between separate skinfold thicknesses and leptin was higher than r = 0.70. The sum of 9 skinfold thicknesses correlated significantly to leptin in all groups (r = 0.558-0.779). In the obese group, triceps, biceps and front thigh skinfold thicknesses did not correlate (p > 0.05) with leptin. In the total group, all measured circumferences correlated significantly to leptin concentration (r = 0.328-0.724). However, in the obese group, the measured circumferences did not correlate to leptin (p > 0.05). Waist-to-hip ratio correlated with leptin only in the total group of boys. It was concluded that as a rule, close correlations emerged between leptin and skinfold thicknesses and circumferences. The strongest correlation with leptin was found with the sum of 9 skinfolds and waist-to-hip ratio.

Bone mineral density in 11-13-year-old boys: relative importance of the weight status and body composition factors.

This study was aimed to investigate the influence of being overweight on bone mineral status in 11-13-year-old boys, who were divided into overweight (OW; n = 110) and normal weight (NW; n = 154) groups. Bone mineral density (BMD) at the whole body (WB), lumbar spine (LS) and femoral neck (FN), bone mineral content (BMC) at the WB, and body composition were assessed. Calculation of the bone mineral apparent density (BMAD) was completed for the WB, LS and FN. The BMC/height ratio was also computed. OW boys displayed similar values (P > 0.05) for LS and FN BMAD and lower (P < 0.05) WB BMAD, despite significantly higher values (P < 0.05) for more widely used WB and LS BMD, WB BMC and WB BMC/height in comparison with NW boys. Fat-free mass index (FFMI; kg/m(2)) had the highest correlation coefficients from the calculated body composition indices with all bone mineral values in NW boys. In OW boys, the FFMI had the highest correlation only with FN BMD, while other measured bone mineral values had highest correlations with either BMI or FMI indices. In conclusion, OW boys have higher crude WB BMD, BMC and BMC/height ratio in comparison with NW boys. However, the bone growth appears to be insufficient to compensate for the higher mechanical load applied on the bone by higher FM and also FFM values in OW boys. Excessive adiposity does not have a protective effect on the development of BMAD in growing boys reaching puberty.

Negative correlation between serum IL-6 level and cardiorespiratory fitness in 10- to 11-year-old boys with increased BMI.

BACKGROUND/AIMS: Some markers of inflammation have been found to be associated with cardiorespiratory fitness levels, but only few studies have studied this in overweight children. The aim of this study was to investigate associations between markers of inflammation and the fitness levels measured by peak oxygen consumption (VO(2peak) and VO(2peak)/kg) in boys with increased body mass index (BMI) and with normal BMI. PARTICIPANTS/METHODS: Subjects were 38 boys with BMI above 85th percentile (OWB) and 38 boys with normal BMI (NWB) at the age of 10 to 11 years. Serum concentrations of IL-2, IL-4, IL-6, IL-8, IL-10, VEGF, IFNγ, TNF-α, IL-1α, IL-1ß, MCP-1, EGF, CRP and associations with measured cardiorespiratory fitness levels were studied. High-sensitive chips were used to measure 13 markers of inflammation. RESULTS: Mean VO(2peak) was significantly higher (2.1±0.3 vs. 1.8±0.3 L/min; p<0.05) and mean VO(2peak)/kg significantly lower (33.7±4.7 vs. 48.9±6.4 mL/min/kg; p<0.05) in OWB than in NWB group. Out of 13 measured biochemical markers IL-6 correlated with VO(2peak)/kg (r=-0.37; p<0.05) and TNF-α with VO(2peak) (r=0.41; p<0.01) in OWB. BMI and IL-6 together explained 44.5% of the variability of VO(2peak)/kg in the OWB group. CONCLUSIONS: Overweight boys had lower cardiorespiratory fitness level measured by VO(2peak)/kg and this was negatively correlated with serum IL-6 level. Measurement of serum IL-6 level in overweight boys may help to identify subjects who need specific exercise formats to achieve maximal beneficial health effects and to reduce their risk for the development of type 2 diabetes and atherosclerosis later in life.

Physiological, biomechanical and anthropometrical predictors of sprint swimming performance in adolescent swimmers.

The purpose of this study was to analyze the relationships between 100-m front crawl swimming performance and relevant biomechanical, anthropometrical and physiological parameters in male adolescent swimmers. Twenty five male swimmers (mean ± SD: age 15. 2 ± 1.9 years; height 1.76 ± 0.09 m; body mass 63.3 ± 10.9 kg) performed an all-out 100-m front crawl swimming test in a 25-m pool. A respiratory snorkel and valve system with low hydrodynamic resistance was used to collect expired air. Oxygen uptake was measured breath-by-breath by a portable metabolic cart. Swimming velocity, stroke rate (SR), stroke length and stroke index (SI) were assessed during the test by time video analysis. Blood samples for lactate measurement were taken from the fingertip pre exercise and at the third and fifth minute of recovery to estimate net blood lactate accumulation (ΔLa). The energy cost of swimming was estimated from oxygen uptake and blood lactate energy equivalent values. Basic anthropometry included body height, body mass and arm span. Body composition parameters were measured using dual-energy X-ray absorptiometry (DXA). Results indicate that biomechanical factors (90.3%) explained most of 100-m front crawl swimming performance variability in these adolescent male swimmers, followed by anthropometrical (45.8%) and physiological (45.2%) parameters. SI was the best single predictor of performance, while arm span and ∆La were the best anthropometrical and physiological indicators, respectively. SI and SR alone explained 92.6% of the variance in competitive performance. These results confirm the importance of considering specific stroke technical parameters when predicting success in young swimmers. Key pointsThis study investigated the influence of different anthropometrical, physiological and biomechanical parameters on 100-m swimming performance in adolescent boys.Biomechanical factors contributed most to sprint swimming performance in these young male swimmers (90.3% of variability in performance), followed by anthropometrical (45.8%) and physiological (45.2%) parameters.Two selected variables (stroke index and stroke rate) explained 92.6% of the variance in competitive performance in these adolescent swimmers.

Physical development and swimming performance during biological maturation in young female swimmers.

The present study analyzed the development of physiological, biomechanical and anthropometrical parameters in young female swimmers and assessed the effect of these parameters on swimming performance during biological maturation. In total, 26 female swimmers participated in the study in which data were annually collected for two consecutive years. Body composition, basic anthropometrical parameters and biological age were measured. During the 400-m front-crawl swimming, the energy cost of swimming and stroking parameters were assessed. Peak oxygen consumption (VO2(peak)) was assessed by means of the backward-extrapolation technique recording VO2 during the first 20 sec of the recovery period after a maximal trial of 400-m distance. During the 2-year follow-up study period, age, height, body mass, body fat %, fat free mass, bone mineral mass, total bone mineral density, arm span and biological maturation values significantly increased during each year (p < 0.05). The tracking of the physical characteristics measured over the 2-year study period was relatively high (r > 0.694), except for the body fat% (r > 0.554). The tracking of the Tanner stages was also high (r = 0.759-0.780). Stepwise regression analyses showed that biomechanical factors (R2 > 0.322; p < 0.05) best characterized the 400-metre swimming performance in young female swimmers, followed by bioenergetical (R2 > 0.311; p < 0.05) and physical (R2 > 0.203; p < 0.05) factors during all three measurement times.

Longitudinal development of physical and performance parameters during biological maturation of young male swimmers.

The aim of the study was to examine the development of specific physical, physiological, and biomechanical parameters in 29 young male swimmers for whom measurements were made three times for two consecutive years. During the 400-m front-crawl swimming, the energy cost of swimming, and stroking parameters were assessed. Peak oxygen consumption (VO2 peak) was assessed by means of the backward-extrapolation technique recording VO2 during the first 20 sec. of recovery period after a maximal trial of 400-m distance. Swimming performance at different points of physical maturity was mainly related to the increases in body height and arm-span values from physical parameters, improvement in sport-specific VO2 peak value from physiological characteristics, and improvement in stroke indices on biomechanical parameters. In addition, biomechanical factors characterised best the 400-m swimming performance followed by physical and physiological factors during the 2-yr. study period for the young male swimmers.