Neglected problem: Influence of school bag on lumbar segment in children.

Background and Objectives: School bag (SB) load causes significant changes in the height and symmetry of the intervertebral discs at each level of the spine from T12-L1 to L5-S1. This study aims to determine the change in the size of the lumbar segment angle at a particularly critical point L3-L4 of the spine in relation to the load of the average weight of SB in healthy male children (students) at standing and after 2-minute gait. Methods: 47 boys, aged 12.2 ± 0.92 years, underwent photogrammetric measurements in the sagittal plane in statics and dynamics, walking on a laboratory treadmill. Measurements were repeated with the weight of SB with a constant load of 6,251 kg, which represents 13.78% of the average body weight of our sample. The lumbar angle (LA) connecting the point of the big toe, the lumbar point L3-L4 and the processus spinosus C7 was measured. In gait, LA was measured in the phases of the middle support and the initial contact of the heel. Results: T-test of paired samples was used to estimate the change in LA at standing from 4.953° and walking phases from 6.295° to 7.332° in relation to the unloaded state, and the value of the effect size (ES) indicates that the impact of SB load is significant. Conclusions: Cumulatively, microtraumas caused by SB load significantly affect the increase in intervertebral pressure at the L3-L4 point, which is susceptible to degenerative processes and which can be the cause of lumbar syndrome (LS). Preventive measures are needed in order to lighten SB in this population and introduce up to 10% of students' body weight into the safe zone.

Trends in Morphological Characteristics among 7- and 11-Year-Old Serbian Children: A Comparison between 1990 and 2020.

Since knowledge possession about the morphological characteristics trend is important to understand, it is necessary to monitor the physical growth and children's development. We have aimed to examine the current state, dynamics, and direction of changes in morphological characteristics, over a 30-year period in Serbian children and adolescents. Morphological characteristics measured in 2020 (n = 304; age 7 ± 6 and 11 ± 6) were compared with the results of same-age children and adolescents from 1990 (n = 1789). The following characteristics were measured: body height, body mass, body mass index, forearm circumference, and upper arm skinfold. The average height (95% IP) of 7-year-old boys was significantly lower in all morphological variables in 1990, compared to their 2020 peers, while in forearm circumference was opposite. As for the 11-year-old boys, body mass (p = 0.02) and BMI (p = 0.009) had significantly better average values in 2020 than 1990, whereas forearm circumference (1.6-2.5 cm) and upper arm skinfold (2.7-4.9 cm) results were opposite. Seven-year-old girls from a 1990 sample also had significantly lower average values for morphological characteristics, compared to their 2020 peers. All morphological characteristic variables of 11-year-old girls have significantly better average values in 1990 sample than in 2020, except for body mass (p = 0.47) and BMI (p = 0.55). The current results have presented a true "picture" of the trends in morphological characteristics status among 7- and 11-year-old Serbian children by comparing them with the already obtained results 30 years ago.

Redox balance in elite female athletes: differences based on sport types.

BACKGROUND: The aim of the present study was to analyze changes in redox balance throughout parameters of oxidative stress and activities of antioxidant enzymes in elite female water polo (N.=15) and football players (N.=19) aged between 20 and 23. Fourteen age-matched sedentary women were also included in the study. METHODS: Blood sampling was performed to measure levels of lipid peroxidation (MDA), total antioxidant status (TAS), superoxide anion radical (O2-), hydrogen peroxide (H2O2), reduced glutathione (GSH), oxidized glutathione (GSSG), nitrites, superoxide dismutase activity (SOD), catalase activity (CAT) and glutathione-peroxidase activity (GPx). RESULTS: Levels of MDA, TAS, GSSG and H2O2 were significantly higher in athletes than in the control women. Football players had higher levels of O2- than the other two groups. Activity of SOD was higher in water polo players when compared with the football and control groups, CAT was increased in all athletes, while GPx did not differ among groups. CONCLUSIONS: Therefore, prolonged intensive training markedly increases oxidative stress in women, which depends on the type of sport. Lower concentration of O2- and increased activity of SOD in water polo players compared to football players suggest that mechanisms of adaptation of antioxidative defense are related to the type of exercise.

Biphasic response of cardiodynamic adaptations to swimming exercise in rats.

The aim of research was to assess exercise-induced changes in mechanics of hearts isolated from rats, as well as time-course of those changes. Wistar rats (n = 42) were divided into control, moderately trained (swimming 1 hour, 5 days a week for 9 or 12 weeks) and strenuously trained (swimming 2, 3 and 4 times a day for an hour in weeks 10, 11 and 12, respectively) groups. After sacrificing, hearts (weight: 1480.82 ± 145.38 mg) were isolated and perfused on a Langendorff apparatus. Coronary perfusion pressure (CPP) was gradually increased (from 40 to 120 cm H(2)O) in order to establish coronary autoregulation. Parameters of cardiac contractility were recorded: maximum and minimum rate of change of pressure in the left ventricle (dp/dt max and dp/dt min), systolic and diastolic left ventricular pressure (SLVP and DLVP), heart rate (HR) and coronary flow (CF). Nine weeks of moderate exercise induced slight depression of coronary function (decrease of dp/dt max, dp/dt min, SLVP and DLVP), while 3 additional weeks of moderate training improved hearts function, but not to the extent that the strenuous training program did. The results of our study add evidence about beneficial effects of regular moderate exercise on heart, and furthermore, show that exercising frequently, if the intensity stays within moderate range, may not have detrimental effects on cardiodynamics.

[Vertical jump as a tool in assessment of muscular power and anaerobic performance].

Muscular strength and anaerobic power could be assessed by single and multiple vertical jump testing procedures. Anaerobic capacity measured by vertical jump testing is highly correlative with athletic performance, as compared to other anaerobic testing procedures. The most frequently used protocol with contact mat or force platform consists of single jump (i.e., squat jump, drop jump, countermovement jump) and serial jump testing with different duration. Measured variables include jump height and duration along with absolute and relative peak muscular power. Several investigators have clearly shown superior jump performance variables in elite athletes as compared to non-elite subjects. Differences obtained could be due to genetic factors and acute or prolonged effects of training regimen. with

The effect of 4 weeks treatment with a 2-gram daily dose of pyruvate on body composition in healthy trained men.

The principal aim of this study was to determine the effects of short-term (28 days) pyruvate supplementation on body composition in young healthy men. Twenty-two young (mean age, 22.2 +/- 2.7 years) male soccer players were allocated to two randomly assigned groups in a placebo-controlled, double-blind design. Subjects in the pyruvate group orally ingested tablets that contained pyruvate at a dose of 2 g per day in two equal doses for 4 weeks. There were no statistically significant changes in weight and body-mass index (BMI) within or between groups (p>0.05) after the supplementation protocol. Percentage of body fat decreased similarly in both pyruvate and placebo groups after the supplementation protocol (p>0.05). There were no changes in waist-to-hip ratio (WHR), arm fat index (AFI), and total or regional muscle mass within or between groups (p>0.05). No subject reported any side effects from pyruvate or placebo treatment. The results of the present study indicate that supplementation with pyruvate during training does not significantly alter the body mass, fat, and muscle mass in healthy trained men. Pyruvate supplementation appears to be ineffective as a fat loss strategy in young athletes.

Gastrointestinal distress after creatine supplementation in athletes: are side effects dose dependent?

The main aim of the present study was to investigate the effects of two different creatine-supplementation protocols on incidence of gastrointestinal (GI) distress in top-level athletes. Data were collected from 59 top-level male soccer players who were allocated in a double-blind design to three randomly assigned trials: ingesting creatine supplement (C5: 2 x 5-g doses, and C10: 1 x 10-g dose) or placebo (P) for 28 days. In order to assess potential side effects of the supplementation regimen, all subjects were instructed to report any adverse effects of supplementation on their GI system. Survey questions covered perceived side effects on GI system linked with creatine supplementation. In all three treatment groups, the most frequent GI complaints were diarrhoea (39.0%), stomach upset (23.8%), and belching (16.9%). We did not find a significant difference between incidence of GI distress symptoms between C5 and the placebo group after the survey. Yet, significant differences were found for incidence of diarrhoea between the C5 and C10 groups (28.6% vs. 55.6%, respectively, p < 0.05). Moreover, diarrhoea was more frequent in the C10 group as compared with the placebo group (55.6% vs. 35.0%, p < 0.05). There is no reason to believe that short-term oral creatine supplementation for 28 days has any detrimental effect on the GI tract if taken in a recommended amount (10 g per day in two equal doses). The risk of diarrhoea may be increased, however, following intake of 10 grams of creatine per single serving.