Evelin Lätt

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.

Elevated Serum IL-6, IL-8, MCP-1, CRP, and IFN-γ Levels in 10- to 11-Year-Old Boys with Increased BMI

Background/Aims: Many inflammation parameters are associated with obesity, but few comparable data are found in youth. This study aims to characterize the differences in serum levels of 13 biochemical inflammatory markers between boys with increased BMI and boys with normal BMI, and examine the relationships between inflammation markers, skinfold thicknesses, and body composition. Participants/Methods: The participants were 38 boys (BMI above 85th percentile) and 38 boys (normal BMI) at the age of 10–11 years. Measurements included BMI, 9 skinfold thicknesses, waist and hip circumferences, and total body and trunk fat mass and percentage as indices of obesity, fasting insulin, glucose, and serum concentrations of IL-2, IL-4, IL-6, IL-8, IL-10, VEGF, IFN-γ, TNF-α, IL-1α, IL-1β, monocyte chemoattractant protein-1 (MCP-1), epidermal growth factor, and CRP. Results: Overweight boys (OWB) were taller and more frequently in puberty than normal-weight boys (NWB). Skinfold thicknesses and body composition parameters were higher in OWB. They had significantly higher serum IL-6, IL-8, IFN-γ, MCP-1, and CRP values compared to NWB. Conclusions: Six of 13 measured biochemical markers were significantly increased in OWB, indicating that many low-grade inflammatory processes are already involved in the development of obesity in childhood.

Physical Activity and Bone Mineral Accrual in Boys with Different Body Mass Parameters during Puberty: A Longitudinal Study

The aim of our longitudinal study was to investigate the relationships between physical activity and bone mass in boys with different body mass status during the years surrounding pubertal growth spurt. Two hundred and six boys entering puberty took part in this study. The subjects were divided into underweight (), normal weight (), overweight () and obese () groups at baseline according to age related categories. Whole-body DXA scans were performed at baseline, after 12 and 24 months to assess body composition (lean body mass, fat mass), and total body (TB), lumbar spine (LS) and femoral neck (FN) bone mineral density (BMD) parameters. Physical activity was measured by 7- day accelerometry. For longitudinal analysis, multilevel fixed effects regression models were constructed. Biological age, height and lean body mass had an effect for explanation of TB BMD, FN BMD and LS BMD. Moderate to vigorous physical activity (MVPA), vigorous physical activity (VPA) and sedentary time (SED) had the significant effect only on FN BMD. Being an underweight boy at the baseline indicated greater chance (p<0.01) to have lower TB BMD in the future (2 years at follow up) development, compared to normal weight (estimates = −0.038), overweight (estimates = −0.061) and obese boys (estimates = −0.106).

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.

Relationships between finger-length ratios, ghrelin, leptin, IGF axis, and sex steroids in young male and female swimmers

The aim of this study was to investigate possible relationships between different right-hand finger-length ratios and different fasting hormone concentrations in young swimmers. Fifty-five young swimmers participated in this study (26 boys and 29 girls, aged 10–17 years). The original method of Visnapuu and Jürimäe (J Strength Cond Res 21:923–929, 2007) was used for the measurement of length parameters of the hand. The following finger-length ratios were calculated: 1D:2D, 1D:3D, 1D:4D, 1D:5D, 2D:3D, 2D:4D, 2D:5D, 3D:4D, 3D:5D, and 4D:5D. All finger-length ratios were significantly higher in girls compared with boys. Ghrelin, leptin, testosterone in boys, estradiol in girls, insulin-like growth-factor I (IGF-I), IGFBP-3, and insulin were analyzed. Leptin and insulin concentrations were lower in boys compared with girls. In both groups, the relationships between finger-length ratios and basic anthropometric parameters were not significant. In girls, estradiol correlated negatively with 2D:3D (r = −0.51) and 2D:4D (r = −0.49) finger ratios. In boys, ghrelin concentration correlated with most of the finger-length ratios (r = 0.37–0.40). In girls, the relationship of ghrelin with the 2D:3D (r = 0.45) and 2D:4D (r = 0.48) finger ratios was significant. In boys, but not in girls, IGF-I (r = 0.42) and IGFBP-3 (r = 0.44) correlated only with the 2D:4D finger ratio. Leptin and insulin did not correlate with the finger-length ratios. In boys, the most important hormone to characterize several finger-length ratios was ghrelin (13.7–15.6% variance accounted for). Ghrelin and testosterone together accounted for 20.3% (R2 × 100) of the variance in the 2D:4D ratio. In girls, estradiol was correlated with the 2D:3D ratio (25.7%) and estradiol in combination with ghrelin with the 2D:4D ratio (30.0%). In conclusion, ghrelin appears to be a further biochemical parameter in addition to the sex steroids which correlated with different digit-length ratios at least in boys.

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

Abstract 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.

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

Abstract 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 (VO2peak and VO2peak/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-1β, 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 VO2peak was significantly higher (2.1±0.3 vs. 1.8±0.3 L/min; p<0.05) and mean VO2peak/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 VO2peak/kg (r=–0.37; p<0.05) and TNF-α with VO2peak (r=0.41; p<0.01) in OWB. BMI and IL-6 together explained 44.5% of the variability of VO2peak/kg in the OWB group. Conclusions: Overweight boys had lower cardiorespiratory fitness level measured by VO2peak/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.

Effect of pubertal development and physical activity on plasma ghrelin concentration in boys

The aim of the present study was to assess the influence of regular physical activity on plasma ghrelin concentration in pre-pubertal and pubertal boys. In addition, the impact of ghrelin concentration on bone mineral density (BMD) was examined. In total, 56 healthy schoolboys aged between 10 and 16 yr were divided into the swimming (no.=28) and the control (no.=28) groups. The subjects were matched by age and body mass index (BMI), generating 9 matched pairs in pubertal group I (Tanner stage 1), 11 pairs in group II (Tanner stages 2 and 3), and 8 pairs in group III (Tanner stages 4 and 5). Swimmers in pubertal groups II and III had significantly (both p<0.05) higher mean ghrelin levels than the controls (group II: 1126.8±406.0 vs 868.3±411.2 pg/ml; group III: 1105.5±337.5 vs 850.8±306.0 pg/ml, respectively), whereas no difference was seen in the pubertal group I (1230.8±386.0 vs 1272.7±424.4 pg/ml). Ghrelin was the most important hormonal determinant for total BMD and lumbar apparent volumetric BMD (BMAD) (R2=27.2% and R2=19.8%, respectively) in swimmers, whereas in control boys, plasma IGF-I was the most important hormonal predictor accounting for 41.8% of the variability of total BMD and 20.4% of the variability of lumbar BMAD. In conclusion, ghrelin concentration decreased during puberty in physically inactive boys, while in regularly physically active boys it remained relatively unchanged. Ghrelin appears to be an important hormonal predictor for BMD in physically active boys, while BMD is mostly determined by IGF-I in physically inactive boys.

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.

Osteocalcin is inversely associated with adiposity and leptin in adolescent boys.

Abstract Background/Aims: Recently, osteocalcin (OC), an osteoblast-derived hormone, has been found to correlate with adiposity, adipocytokines and insulin resistance in adults, but few studies have investigated this in children. The aim of this study was to investigate these associations in adolescent boys, for whom it is a time of significant bone mineral accrual, taking into account possible confounders related to adipose and bone tissues. Participants/Methods: Participants were 141 adolescent boys (mean age 13.9±0.7 years), who were divided into tertiles according to OC levels. Across these groups, differences in total body fat mass (FM), body fat distribution, adiponectin, leptin and insulin resistance values were examined with relation to age, pubertal stage, daily energy and calcium intakes, and physical activity. Results: Mean body mass index (BMI), FM, body fat% and leptin differed significantly between subjects in the three OC tertiles after adjustment for age, pubertal stage, energy and calcium intakes, and physical activity. There were no differences in fat free mass (FFM), bone mineral content, energy and calcium intakes, physical activity, adiponectin and insulin resistance values between study groups. For the entire cohort, mean serum OC was 130.2±45.2 ng/mL and was related to body mass, BMI, FM, body fat distribution and leptin. Circulating OC was not associated with FFM, daily energy and calcium intakes, physical activity, adiponectin or insulin resistance (insulin, glucose, homeostasis model assessment-insulin resistance) values. Conclusions: In male adolescents, OC is inversely related to body adiposity and leptin values, even after consideration of several factors that may affect bone and adipose tissues.