Healthy Young Male Volunteers Research Articles

Total body water percentage and 3rd space water are novel risk factors for training-related lower extremity muscle injuries in young males

PurposeTo identify the risk factors for training-related lower extremity muscle injuries in young males by a non-invasive method of body composition analysis. MethodsA total of 282 healthy young male volunteers aged 18 – 20 years participated in this cohort study. Injury location, degree, and injury rate were adjusted by a questionnaire based on the overuse injury assessment methods used in epidemiological studies of sports injuries. The occurrence of training injuries is monitored and diagnosed by physicians and treated accordingly. The body composition was measured using the BodyStat QuadScan 4000 multifrequency Bio-impedance system at 5, 50, 100 and 200 kHz to obtain 4 impedance values. The Shapiro-Wilk test was used to check whether the data conformed to a normal distribution. Data of normal distribution were shown as mean ± SD and analyzed by t-test, while those of non-normal distribution were shown as median (Q1, Q3) and analyzed by Wilcoxon rank sum test. The receiver operator characteristic curve and logistic regression analysis were performed to investigate risk factors for developing training-related lower extremity injuries and accuracy. ResultsAmong the 282 subjects, 78 (27.7%) developed training injuries. Lower extremity training injuries revealed the highest incidence, accounting for 23.4% (66 cases). These patients showed higher percentages of lean body mass (p = 0.001), total body water (TBW, p = 0.006), extracellular water (p = 0.020) and intracellular water (p = 0.010) as well as a larger ratio of basal metabolic rate/total weight (p = 0.006), compared with those without lower extremity muscle injuries. On the contrary, the percentage of body fat (p = 0.001) and body fat mass index (p = 0.002) were lower. Logistic regression analysis showed that TBW percentage > 65.35% (p = 0.050, odds ratio = 3.114) and 3rd space water > 0.95% (p = 0.045, odds ratio = 2.342) were independent risk factors for lower extremity muscle injuries. ConclusionTBW percentage and 3rd space water measured with bio-impedance method are potential risk factors for predicting the incidence of lower extremity muscle injuries in young males following training.

Is the Brainstem Activation Different Between Healthy Young Male and Female Volunteers at Initiation of Voiding? A High Definition 7-Tesla Magnetic Resonance Imaging Study.

Assessing brainstem function in humans through typical neuroimaging modalities has been challenging. Our objective was to evaluate brain and brainstem activation patterns during initiation of voiding in healthy males and females utilizing a 7 Tesla magnetic resonance imaging (MRI) scanner and a noninvasive brain-bladder functional MRI (fMRI) protocol. Twenty healthy adult volunteers (10 males and 10 females) with no history of urinary symptoms were recruited. Each volunteer underwent a clinic uroflow and postvoid residual assessment and was asked to consume water prior to entering the scanner. Anatomical and diffusion tensor images were obtained first, followed by a blood oxygenation level dependent (BOLD) resting-state fMRI (rs-fMRI) during the empty bladder. Subjects indicated when they felt the urge to void, and a full bladder rs-fMRI was obtained. Once completed, the subjects began 5 voiding cycles, where the first 7.5 seconds of each voiding cycle was identified as "initiation of voiding." BOLD activation maps were generated, and regions of interests with a t-value greater than 2.1 were deemed statistically significant. We present 5 distinct regions within the periaqueductal gray (PAG) and pontine micturition center (PMC) with statistically significant activation associated with an initiation of voiding in both men and women, 3 within the PAG and 2 within the PMC. Several additional areas in the brain also demonstrated activation as well. When comparing males to females, there was an overall lower BOLD activation seen in females throughout all regions, with the exception of the caudate lobe. Our study effectively defines regions within the PAG and PMC involved in initiation of voiding in healthy volunteers. To our knowledge, this is the first study investigating differences between male and female brainstem activation utilizing an ultra-high definition 7T MRI.

The effect of warm-up on postural sway in the dominant and non-dominant leg

Although the chronic effects of a long-term warm-up program have been widely studied, to our knowledge, the number of studies examining the acute effects of a single warm-up session on inter-limb balance asymmetries in symmetrical sports such as cycling is limited. The aim of this study was to examine the effect of warm-up on postural sway in the dominant and non-dominant leg in male bicycle athletes. Sixteen healthy young male volunteers who engage in cycling sports participated in the study. The participants' age was determined as 15.50±1.15 years, body weight as 56.06±7.79 kg, height as 169.87±4.98 cm, and sports experience as 4.31±1.25 years. The postural control performance on the dominant and non-dominant leg of the athletes was evaluated on Biodex Balance System balance device platform for 20 seconds before and after a 10-minute warm-up exercise performed at a constant pedaling frequency of 80 RPM on a bicycle ergometer. In the comparison of the pre-test to post-test dominant leg Overall Sway Index (t=3.456; p=0.004), Anterior-Posterior (Z=-3.160; p=0.002) and Medial-Lateral (Z=-2.428; p=0.015) postural control scores of the participants, a significant decrease was found in the post-test. It was determined that warm-up exercise can only improve acute postural control in the dominant leg. The effects of the study can be extended to different sports branches with symmetrical features in order to obtain comparable results.

Body weight reduction by exercise increases the urinary 3-methylhistidine excretion level with relatively positive nitrogen, sodium, and potassium balances when compared to dietary restriction

BackgroundRegarding changes in muscle mass, differences due to types of exercise and/or nutritional interventions, and associations with nutrient balances are still unclear. MethodsTo estimate changes in muscle mass during a body weight loss program using either a diet or exercise regimen, we investigated levels of muscle mass-related indices, and body contents of nitrogen, sodium, and potassium as measured by the balance method. Six healthy young adult male volunteers participated in two 10-day crossover experiments (20 days total). The first 5 days comprised an adjustment period (energy intake, 2656 ± 367 kcal/day (mean ± standard deviation)). During the second 5-day period, the participants either reduced their energy intake to 1770 ± 244 kcal/day (diet regimen) or exercised on a bicycle ergometer to expend 886 ± 122 kcal/day (exercise regimen). ResultsThe nitrogen, sodium, and potassium balances were significantly more positive during the exercise regimen than during the diet regimen. The urinary excretion levels of creatinine, 3-methylhistidine (3-MH), aldosterone, and catecholamines, and the 3-MH/creatinine ratio were significantly increased only during the exercise regimen. ConclusionsThe exercise regimen suppresses the decrease in muscle mass-related indices during body weight loss compared to the diet regimen with a relatively positive state of whole-body protein, sodium, and potassium balances, accompanied by an increase in sympathetic/adrenal cortical functions.

The atherosclerosis index during body weight reduction is improved with exercise

IntroductionBody weight reduction is often used for addressing lifestyle-related diseases, and for slimming down or improving the competitiveness of athletes. It is known that high-density lipoprotein-cholesterol (HDL-C) levels can be increased by habitual exercise, while low-density lipoprotein-cholesterol (LDL-C) levels may not always be decreased by dietary restriction or exercise. We hypothesized that the levels of not only HDL-C, but also LDL-C improve more with body weight reduction by a combined diet-and-exercise regimen than that by a diet-only regimen. Summary of facts and resultsSix healthy young adult male volunteers participated in two 10-day crossover experiments (20 days total). The first 5 days comprised an adjustment period (energy intake, 2521±304kcal/day (mean±standard deviation)). During the second 5-day period, participants either reduced their energy intake to 1261±152kcal/day, or reduced their energy intake to 1891±228kcal/day and exercised on a bicycle ergometer to consume 630±76kcal/day. Decreases in the serum total cholesterol (TC), LDL-C, and apolipoprotein (apo) B levels were significantly larger, and decreases in the HDL-C and apo A1 levels were significantly smaller with the diet-and-exercise regimen than with the diet-only regimen. Consequently, the atherosclerosis index (AI: (TC–HDL-C)/HDL-C ratio) was significantly lower, and the degree of its reduction was significantly larger, after the diet-and-exercise regimen than after the diet-only regimen. ConclusionThese results suggest that reducing the body weight by a combination of diet and exercise has more beneficial effects on cholesterol metabolism, including changes in apo levels, than diet alone in healthy young adults.

Effects of nature-adapted lighting solutions ("Virtual Sky") on subjective and objective correlates of sleepiness, well-being, visual and cognitive performance at the workplace.

Exposure to natural daylight benefits human well-being, alertness, circadian rhythms and sleep. Many workplaces have limited or no access to daylight. Thus, we implemented a light-panel ("Virtual Sky"), which reproduced nature-adapted light scenarios. In a laboratory office environment, three lighting scenarios were presented during the day: two lighting conditions with nature-adapted spectral light distributions, one with static and one with dynamic clouds, and a standard office lighting condition. We compared the impact of the three lighting scenarios on subjective and objective measures of alertness, cognitive performance, wellbeing, visual comfort, contrast sensitivity, and cortisol levels in 18 healthy young male volunteers in a within-participant cross-over study design. We found no evidence that an 8-h lighting scenario with static or dynamic clouds during the waking day (9am-5pm) was associated with any significant effect on objective and/or subjective alertness, cognitive performance and morning cortisol concentrations compared to standard workplace lighting. However, the dynamic light scenario was accompanied with lower levels of perceived tensionafter completing cognitive tasks and less effort to concentrate compared to the static lighting scenarios. Our findings suggest that apart from smaller effects on tension and concentration effort, nature-adapted lighting conditions did not improve daytime alertness and cognitive performance in healthy well-rested young participants, as compared to standard office lighting.

Imaging evaluation of physical activity effect on knee articular cartilage

IntroductionHyaline cartilage is a complex tissue with great load absorbing-function. Studies showed that moderate exercise can have a positive effect on chondral matrix composition but excessive can be harmful to cartilage. ObjectivesEvaluate knee cartilage thickness before and after physical activity (running) in healthy young individuals. MethodsTen healthy young adult male volunteers aged between 18 and 21 years old were selected to undergo magnetic resonance imaging examination of the right knee to measure the cartilage thickness of the anterior, medial, and lateral compartments before and after 1 hour of continuous running. Cartilage thickness measurements were performed by a radiologist who did not know the identity of the volunteers or the moment of the evaluation (before or after the exercise). ResultsThe subjects' mean age, height, and weight were 19.5 years, 1.80 m, and 75.2 kg, respectively, with a mean body mass index of 23.14. There was a decrease in chondral thickness after running on all surfaces evaluated. The changes that were relevant (P < .05) were all the medial femoral condyle, the anterior portion of the lateral femoral condyle, the anterior portion of the lateral plateau, the entire surface of the patella and trochlea. The greatest difference in thickness between before and after exercise was observed in the lateral facet of the patella (−0.224 mm) followed by the anterior surface of the medial femoral condyle (−0.186 mm). In proportional values, the highest decrease occurred in the anterior portion of the medial femoral condyle (−11.42%). ConclusionThere was a decrease in knee chondral thickness after 60 minutes of running, being statistically significant in the medial femoral condyle, anterior surface of the lateral femoral condyle, and lateral plateau and patellofemoral joint (patella and trochlea). Level of evidenceIV (Case Series).

Incidence of G6pd Deficiency in Young Asymptomatic Males in Pakistan

Background: NADPH is crucial for glutathione reduction. Deficiecy of G6PD leads to excessive oxidised glutathione that denatures hemoglobin and forms Heinz bodies. Heinz bodies damages RBC membrane and cause premature removal of cells by spleen. G6PD deficiency is the most common X-linked inherited red cell enzymopathy that leads to hemolytic anemia and neonatal jaundice in enzyme deficient patients under oxidative stress. G6PD is the rate limiting enzyme in pentose phosphate pathway, a dominant form of glycolysis in RBCs. G6PD converts glucose-6 phosphate into 6-phosphonogluconolactone and reduces NADP to NADPH. Objective: To determine incidence of G6PD deficiency in young healthy males in Pakistan. Study design: A descriptive cross sectional study Place and duration: Study was carried out at PAF Hospital Sargodha from Jan 2021 to Feb 2023 Methodology: G6PD levels were checked in young healthy male volunteers of 12 to 18 years of age, after taking informed consent from subjects and their parents. Results: Out of 1493 volunteers, only 61 were G6PD deficient and rest all had normal levels. This shows an incidence of 4.08% in our population. Conclusion: Comparing with previous studies suggests 2-4% incidence of G6PD deficiency in Pakistani population. A larger study including females and studying variants of disease is needed. Patients with lab confirmed P.Vivax should get screened for G6PD deficiency, so that they receive Primaquine. Keywords: Incidence, G6PD deficiency, Malaria, Primaquine.

Second to Fourth Digit Ratio and Exercise Performance in Untrained Adult Males

This study was based on a random sample from a Prospective Cohort study including one hundred healthy young untrained male volunteers, with mean age ± standard deviation (SD) of 22.820 ± 2.271 years. The aim of this study was to evaluate the role of the digit ratio as an indicator for the performance of untrained adult males in endurance sports. The parameters that have been measured were: Index and ring fingers length of both right and left hand, body weight, height, waist and hip circumferences, body composition (including: fat, muscle and water percents) and exercise performance (including: distance and time). The descriptive analyses of this study showed that normative values of male 2D:4D ratio vary between 0.912-1.036. and it also revealed that there is a strong inverse relation-ship between digit ratio of the subjects and exercise performance according to the distance and time; as the subject briskly walked on the treadmill at fasting state

Second to Fourth Digit Ratio and Exercise Performance in Untrained Adult Males

This study was based on a random sample from a Prospective Cohort study including one hundred healthy young untrained male volunteers, with mean age ± standard deviation (SD) of 22.820 ± 2.271 years. The aim of this study was to evaluate the role of the digit ratio as an indicator for the performance of untrained adult males in endurance sports. The parameters that have been measured were: Index and ring fingers length of both right and left hand, body weight, height, waist and hip circumferences, body composition (including: fat, muscle and water percents) and exercise performance (including: distance and time). The descriptive analyses of this study showed that normative values of male 2D:4D ratio vary between 0.912-1.036. and it also revealed that there is a strong inverse relation-ship between digit ratio of the subjects and exercise performance according to the distance and time; as the subject briskly walked on the treadmill at fasting state

The Self-Rated Effects of Alcohol Are Related to Presystemic Metabolism of Alcohol.

A high number of alcohol units required to feel a subjective effect of alcohol predicts future alcohol use disorders (AUDs). The subjective response to alcohol can be measured using the validated retrospective self-rated effects of alcohol (SRE) questionnaire. Few studies have investigated the specific relationship between SRE and blood alcohol concentration (BAC) in an experimental setting. Twenty healthy young adult male volunteers who had experience with binge drinking, but did not have AUD, filled out the SRE-questionnaire and were served with a fixed amount of alcohol per body weight. BACs were measured throughout a 12-hour period, reaching a maximum BAC of ~0.13%. Median split of SRE-scores was utilized to compare BACs among participants with relatively high effects (low SRE) and relatively low effects (high SRE) of alcohol. Participants reporting a relatively low SRE-score had a statistically significant higher measured BAC at all time points until alcohol was eliminated. This was especially pronounced during the first 2 hours after alcohol (P = 0.015) without a significant difference in the alcohol elimination rate being detected. The study indicates that a self-ated SRE-score is related to BACs after the ingestion of a standardized amount of alcohol per body weight. Reporting a higher number of alcohol units before feeling an effect was related to a lower BAC. As the differences in BAC between relatively high and low self-rated effects appeared rapidly after intake, this could be interpreted as an effect of presystemic metabolism of alcohol.

Harmonic-to-noise ratio as speech biomarker for fatigue: K-nearest neighbour machine learning algorithm

BackgroundVital information about a person's physical and emotional health can be perceived in their voice. After sleep loss, altered voice quality is noticed. The circadian rhythm controls the sleep cycle, and when it is askew, it results in fatigue, which is manifested in speech. Using MATLAB statistical techniques and the k-nearest neighbour (KNN) machine learning algorithm, this study assessed the efficacy of the harmonic-to-noise ratio (HNR) as a speech biomarker in differentiating fatigued and normal voice after sleep deprivation of one night. MethodsAfter one night of sleep deprivation, acoustic samples for sustained vowel/a/and visual reaction time were recorded from n = 32 healthy young Indian male volunteers (20–40 yrs). One-way ANOVA established significant changes in voice characteristics with progressive sleep deprivation. The effectiveness of speech HNR as a biomarker for the detection of healthy and fatigued voice was researched, using the KNN classifier in a machine learning algorithm. ResultsThe HNR voice feature was taken from an acoustic sample for three times: baseline (Time 1), 3 AM (Time 2), and 7 AM (Time 3) towards an incremental one-night sleep loss. At 3AM, the HNR changed significantly p<0.05. Utilizing an iterative signal extrapolation approach, the KNN classifier divided the submitted voice signal sample into normal and fatigued categories. ConclusionThe findings imply that the HNR can be used to link fatigue from sleep deprivation with vocal alterations by classifying voice samples in a KNN classifier. Along with the multimodal diagnostic features, this method may also offer an additional acoustic biomarker for the diagnosis of fatigue post sleep loss.

Steroid Hormones in Seminal Plasma: the Relationship with Sperm Quality.

The purpose of this study was to find out whether the seminal testosterone and/or estradiol levels could serve as prognostic criteria for normal spermatogenesis and whether they are able to characterize the sperm pathology. The study involved healthy young male volunteers (n=269); serum and seminal steroid hormones were measured; the sperm concentration, mobility, and morphology were evaluated. The results indicate that the seminal testosterone concentration is lower (p<0.05) and the seminal estradiol is higher than the corresponding parameters in the serum (p<0.05). The seminal testosterone and estradiol concentrations negatively correlated with the sperm concentration, and the seminal estradiol concentration was higher in pathozoospermic than in normospermic men (p<0.05). It is assumed that the seminal estradiol level can be an indicator of sperm quality and serve as a biological predictor of normal spermatogenesis; in addition, this parameter can be used for diagnostic purposes in patients with impaired spermatogenesis induced by excess of estrogens.

Short-term head-down bed rest microgravity simulation alters salivary microbiome in young healthy men.

Microgravity influences are prevalent during orbital flight and can adversely affect astronaut physiology. Notably, it may affect the physicochemical properties of saliva and the salivary microbial community. Therefore, this study simulates microgravity in space using a ground-based -6° head-down bed rest (HDBR) test to observe the effects of microgravity on oral salivary secretion function and the salivary microbiome. Sixteen healthy young male volunteers were recruited for the 15-day -6° HDBR test. Non-stimulated whole saliva was collected on day 1 (pre-HDBR), on days 5, 10, and 15 of HDBR, and day 6 of recovery. Salivary pH and salivary flow rate were measured, and the V3-V4 region of the 16S rRNA gene was sequenced and analyzed in 80 saliva samples. The results showed that there were no significant differences in salivary pH, salivary flow rate, and alpha diversity between any two time points. However, beta diversity analysis revealed significant differences between pre-HDBR and the other four time points. After HDBR, the relative abundances of Actinomyces, Parvimonas, Peptostreptococcus, Porphyromonas, Oribacterium, and Capnocytophaga increased significantly, whereas the relative abundances of Neisseria and Haemophilus decreased significantly. However, the relative abundances of Oribacterium and Capnocytophaga did not recover to the pre-HDBR level on day 6 of recovery. Network analysis revealed that the number of relationships between genera decreased, and the positive and negative correlations between genera changed in a complex manner after HDBR and did not reach their original levels on day 6 of recovery. PICRUSt analysis demonstrated that some gene functions of the salivary microbiome also changed after HDBR and remained significantly different from those before HDBR on day 6 of recovery. Collectively, 15 days of -6° HDBR had minimal effect on salivary secretion function but resulted in significant changes in the salivary microbiome, mainly manifested as an increase in oral disease-related bacteria and a decrease in oral health-related commensal bacteria. Further research is required to confirm these oral microbial changes and explore the underlying pathological mechanisms to determine the long-term effects on astronauts embarking on long-duration voyages to outer space.

Remote ischemic preconditioning improves cognitive control in healthy adults: Evidence from an event-related potential study.

It is suggested that remote ischemic preconditioning (RIPC) may be a promising treatment for improving healthy adults’ cognitive control. However, direct empirical evidence was absent. Therefore, this study aims to provide evidence for the impact of RIPC on cognitive control. Sixty healthy young male volunteers were recruited, and 30 of them received 1-week RIPC treatment (RIPC group), while the rest did not receive RIPC (control group). Their cognitive control before and after RIPC treatment was evaluated using the classic Stroop task, and the scalp electricity activity was recorded by event-related potentials (ERPs). The behavioral results showed a conventional Stroop interference effect of both reaction times (RTs) and the accuracy rate (ACC), but the Stroop interference effect of RTs significantly decreased in the posttest compared to the pretest. Furthermore, at the electrophysiological level, ERP data showed that N450 and SP for incongruent trials were larger than that for congruent trials. Importantly, the SP differential amplitude increased after RIPC treatment, whereas there was no significant change in the control group. These results implied that RIPC treatment could improve cognitive control, especially conflict resolving in the Stroop task.

The Effect of Static Stretching Exercises at Different Times on Heart Rate Variability Before Anaerobic Capacity Test

This study aimed to examine the acute effect of different durations of static stretching on heart rate variability (HRV) and, the anaerobic capacity of moderately physically active men during the Wingate anaerobic test (WAnT) at two different pre-exercise periods. Sixty-five healthy young male volunteers performed 10 s static stretching (STS) and 30 s static stretching (LTS) consisting of five static stretching exercises before WAnT on two non-consecutive days. HRV was measured pre (60 s), during (30 s) and post (60 s) WAnT after two different periods of static stretching. Anaerobic capacity variables were also measured during WAnT. STS and LTS had similar effects on other HRV parameters except for Mean-RR during the WAnT. There was no significant difference between the protocols applied in any of the anaerobic capacity test values. But there was a negatively significant relationship between the average power output of 30 s static stretching and pNN50. This result has shown that STS and LTS exercises have a similar effect during maximal exercise, so if the practitioners carry out static stretching exercises before maximal or high-intensity exercise, it is recommended to perform the STS exercise in terms of the economy of the exercise.

Adiposity: Determinant of Peak Expiratory Flow Rate in Young Indian Adults Male

Although several factors such as respiratory muscle strength, lung compliance, resistance to airflow, and even obesity affect the lung functions, the nature of relationship with markers of adiposity is not clear. We hypothesised that central pattern of fat distribution is a significant predictor of decreased peak expiratory flow rate (PEFR). The present study was designed with the aim to examine the effects of adiposity on PEFR in males. One hundred young healthy male volunteers were analysed in the study. They were classified into non-obese, and obese groups based on body mass index (BMI) (obese > or = 30 Kg/m2 and non-obese < 30 Kg/m2). The PEFR was measured by using Wright's peak flow meter. Data was analysed using unpaired 't' test for statistical significance of differences between the non-obese and the obese, stratified into age groups of 20 to 30 years and 30 to 40 years. A partial correlation adjusted to age, height and BMI followed by regression analysis was conducted using adiposity markers as a predictor of PEFR. The model adjusted to age, height, weight and BMI revealed waist hip ratio (WHR) as the only parameter which shows significant variance in PEFR with a Pearson's r=-0.59, F (1, 100)=12.23, p=0.04. The resulting linear regression equation is y=-388.72xWHR+850.68. Our findings suggest that obesity itself and especially the pattern of body fat distribution have independent effects on PEFR. These results suggest that abdominal adiposity, measured as WHR, is a better predictor of expiratory flow than weight or BMI.

Association of Neck Circumference with Body Composition and Cardiovascular Parameters in Young Healthy Adult Males

Background and Aim: Increased Neck circumference is the marker of upper body obesity and identified as an indicator of future cardiovascular disease risk (CVD). Hence, in this study, we assessed the relationship of Neck circumference (NC) with basal cardiovascular and body composition (BC) parameter in young adult males. Methods: Sixty three healthy young adult male volunteers of age between 18 to 25 years were enrolled for this study and they were divided into two groups based on neck circumference (NC). Control group (n = 32) comprises of individuals with normal neck circumference of ≤ 35.5 cm and study group (n = 31) includes individuals with increased neck circumference of ≥ 35.5 cm. The, BC parameters was assessed by Bioimpedance Analysis (BIA) method using Quadscan 4000. And the basal cardiovascular parameters such as systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR) was measured by automated sphygmomanometer and the pulse pressure (PP), mean arterial pressure (MAP) and the rate pressure product (RPP) were derived. Results: Data was expressed in Mean ± SD. The groups were compared using Independent Student’s t test. The association between NC and various study parameters were assessed by Pearson’s correlation analysis. Our study, revealed increased body fat and reduced muscle mass in individuals with increased NC. Further, we observed a positive correlation of NC with body fat (%) and negative correlation with Lean Body Mass. Cardiovascular parameters SBP, DBP, MAP and PP were elevated in subjects with increased NC. Further, positive correlation is seen with SBP, DBP, RPP and NC. Conclusion: Neck circumference is a readily measurable screening tool of upper-body adiposity and increased NC is associated with CVD risk.

Relationship between Eccentric-Exercise-Induced Loss in Muscle Function to Muscle Soreness and Tissue Hardness.

It is well-known that unusual exercise, especially eccentric contraction (ECC), could cause delayed-onset muscle soreness. However, the factors related to the loss of muscle strength and range of motion (ROM) caused by eccentrically damaged muscle, such as increases in muscle soreness, tissue hardness, and pain threshold, have not been investigated in detail. Thus, this study was conducted to investigate the factors related to the loss of muscle strength and ROM caused by eccentrically damaged muscle in a large sample. Fifty-six sedentary healthy young male volunteers were instructed to perform 60 repetitions of ECC exercise. The outcome variables were measured before and 48 h after the ECC exercise. The results showed that a decrease in ROM was correlated to an increase in tissue hardness, whereas a decrease in muscle strength was correlated to an increase in muscle soreness. Our results suggested that tissue hardness must be controlled for ROM loss, and muscle soreness must be controlled for muscle-strength loss.

Effects of Magneto Active Compensation of Geomagnetic Field on Heart Rate Variability of Healthy Males

Geomagnetic field (GMF) is characterized by a strength of a few nT; however, during geomagnetic storms (GMSs), it can be sharply increased hundreds of times and pose a serious threat to magneto-sensitive people. A key scientific question is: How to compensate the possible negative influence of GMSs. The objective of the study was to determine the effects of magneto-active compensation (MAC) of GMF for its future use for protection from the negative influence of GMSs. The measurement of heart rate variability (HRV) on 25 healthy young male volunteers was carried out in the laboratory using the MAC at different levels of outdoor geomagnetic activity (GMA). The geomagnetic K-index was used to characterize the magnitude of GMSs; volunteers were tested during quiet magnetic days (K=1-3), during days with K=4 and during days with GMSs (K≥5). During quiet magnetic days, the comparison between HRV initial values with values measured under GMS compensation mode (CM) did not reveal any changes. On days with K=4 some HRV indices shifted from their initial values, but it was statistically not significant. However, on days with GMSs statistically significant changes in SDNN (p=0.033) and LF/HF (p=0.034) indices of HRV were observed in the GMS CM compared to their initial values. The experiments showed that GMSs cause a sensitive reaction of the heart rate regulatory mechanism, the effect of which can be cancelled in the GMS CM. The efficiency of the used MAC technology is supported by the results presented in this paper.