Optimizing Field Body Fat Percentage Assessment in Professional Soccer Players

Body composition is a determinant of performance in soccer. To estimate the body fat percentage (%BF), dual energy X-ray absorptiometry (DXA) is effective though this method is expensive and not readily accessible. This study examines the validity of widely used field methods based on anthropometric data and bioelectrical impedance analysis (BIA). Participants were 21 male Spanish First Division soccer players aged between 22 and 35 years. In each participant, body fat mass was determined by BIA and using 18 anthropometric equations including skinfold (SKF) measurements. DXA was used as reference. Correlation with DXA measurements was excellent for all equations and separate SKF measurements yet only moderate for BIA. However, only the equation recently developed for use in soccer players based on iliac crest and triceps SKFs showed no significant or standardized differences with DXA-derived %BF and these measurements also had the lowest bias. Our findings suggest that when DXA is not available, the best field method for %BF assessment in footballers is the equation based on iliac crest and triceps SKF. As another good option, we propose the sum of triceps, subscapular, supraspinal, and abdominal SKFs, as this combination also showed good correlation with DXA.

Transmission Line Model Impedance Analysis of Lithium Sulfur Batteries: Influence of Lithium Sulfide Deposit Formed During Discharge and Self-Discharge

The effect of Li2S deposition on the impedance response of Li-S battery cells is investigated using a simplified cell design, systematic impedance spectroscopy measurements combined with transmission line modeling, and a complementary microscopy analysis. Glassy carbon cathodes are employed to build and validate the proposed transmission line model, which is later on employed to investigate the effect of various parameters of Li2S deposit (coverage, thickness, porosity) on cell’s impedance. Among others, the model is applied to study the effect of discharge and self-discharge. Finally, the simplified planar cathode is exchanged with a more conventional mesoporous carbon cathode to determine the effect of Li2S deposition on the impedance of a commercially viable cell design. We have found that Li2S deposit has little effect on the impedance response, owing to its porous structure. The most noticeable change stemming from the process of Li2S deposition is due to the depletion of polysulfide species concentration in the electrolyte, which decreases the chemical capacitance and increases the tail height in the low frequency region of the impedance spectra.

A novel method for diagnosing rolling bearing surface damage by electric impedance analysis

This paper presents a novel condition monitoring method for rolling bearings, based on measuring the electric bearing impedance. The method can diagnose the presence of damage by frequency-domain analysis, and its extension along the raceway by time-domain analysis. The latter enables the assessment of the severity and the progression of bearing damage. A fatigue test shows that the occurrence of pittings in the bearing raceways causes characteristic peaks in the impedance signal, and that the duration of the peaks increases during damage progression. A second test series with artificial damage shows that the duration of the peaks depends on the bearing load and the length of the damage along the raceway and confirms the explanation hypothesis.

Association Between Body Fat Percentage and Level of Physical Activity Among Adolescents in Kuala Nerus, Terengganu

Lack of physical activity among adolescents is one of the factors which lead to the accumulation of body fat and increase prevalence of obesity among Malaysian population. Therefore, this study was aimed to determine the association between body fat percentage and physical activity level among adolescents in Kuala Nerus, Terengganu. This cross-sectional study involved 300 participants consists of 44.7% male and 55.3% female aged between 10 to 16 years old. Anthropometric measurements included body weight, height and waist circumference. Body fat percentage (%BF) was assessed using bioelectrical impedance analysis (BIA). Physical activity was assessed by physical activity questionnaire (PAQ-C) and pedometers in a subsample (n = 50). The result shows that the mean body fat percentage and BMI of the participants were 23.02±9.41% and 20.03±4.77 kg/m2, respectively. Mean PAQ-C score and pedometer steps count for both genders were 1.9±0.42 and 6079±1878, respectively. Male has higher PA level compared to female in their daily life based on PAQ-C score and pedometer steps count. PAQ-C score and pedometer step counts were negatively associated with %BF however there is no significant association between screen time and %BF. As a conclusion, the problems of obesity can be solved by providing strategies to promote active living among adolescents in Malaysia not only focus on increasing physical activity but also emphasise reduction in sedentary behaviours.

Redox Cycling for SOFC Accelerated Degradation

This work aims at development of Accelerated Stress Tests for SOFC via artificial aging of the fuel electrode applying chemical and electrochemical (hydrogen starvation) redox cycling. In principle the degradation processes follows that of calendar aging (Ni coarsening and migration), but in addition it can bring to irreversible damages caused by the development of cracks at the interface anode/electrolyte due to the expansion/shrinkage of the Ni network. The challenge is to introduce conditions which will prevent the formation of cracks which can be done by partial oxidation. The advantage of the proposed methodology is that a mild level of oxidation can be regulated by direct impedance monitoring of the Ni network resistance changes during oxidation/reduction. Once the redox cycling conditions are fixed on bare anode and checked on anode/electrolyte sample for eventual cracks, the procedure can be introduced for AST in full cell configuration. The developed methodology is evaluated by comparative impedance analysis of artificially aged and calendar aged button cells. The results for 20 redox cycles which can be performed for 24 hours are comparable with those obtained for about 1600 hours operation in standard conditions which ensures more than 50 times acceleration.

Rapid Differentiation of Unfrozen and Frozen-Thawed Tuna with Non-Destructive Methods and Classification Models: Bioelectrical Impedance Analysis (BIA), Near-Infrared Spectroscopy (NIR) and Time Domain Reflectometry (TDR)

The performances of three non-destructive sensors, based on different principles, bioelectrical impedance analysis (BIA), near-infrared spectroscopy (NIR) and time domain reflectometry (TDR), were studied to discriminate between unfrozen and frozen-thawed fish. Bigeye tuna (Thunnus obesus) was selected as a model to evaluate these technologies. The addition of water and additives is usual in the fish industry, thus, in order to have a wide range of possible commercial conditions, some samples were injected with different water solutions (based on different concentrations of salt, polyphosphates and a protein hydrolysate solution). Three different models, based on partial least squares discriminant analysis (PLS-DA), were developed for each technology. This is a linear classification method that combines the properties of partial least squares (PLS) regression with the classification power of a discriminant technique. The results obtained in the evaluation of the test set were satisfactory for all the sensors, giving NIR the best performance (accuracy = 0.91, error rate = 0.10). Nevertheless, the classification accomplished with BIA and TDR data resulted also satisfactory and almost equally as good, with accuracies of 0.88 and 0.86 and error rates of 0.14 and 0.15, respectively. This work opens new possibilities to discriminate between unfrozen and frozen-thawed fish samples with different non-destructive alternatives, regardless of whether or not they have added water.