Dynamic Strength Test Research Articles

Strength, Endurance, Throwing Velocity and in-Water Jump Performance of Elite German Water Polo Players.

The purpose of this study was threefold: 1) to assess the eggbeater kick and throwing performance using a number of water polo specific tests, 2) to explore the relation between the eggbeater kick and throwing performance, and 3) to investigate the relation between the eggbeater kick in the water and strength tests performed in a controlled laboratory setting in elite water polo players. Fifteen male water polo players of the German National Team completed dynamic and isometric strength tests for muscle groups (adductor, abductor, abdominal, pectoralis) frequently used during water polo. After these laboratory strength tests, six water polo specific in-water tests were conducted. The eggbeater kick assessed leg endurance and agility, maximal throwing velocity and jump height. A 400 m test and a sprint test examined aerobic and anaerobic performance. The strongest correlation was found between jump height and arm length (p < 0.001, r = 0.89). The laboratory diagnostics of important muscles showed positive correlations with the results of the in-water tests (p < 0.05, r = 0.52–0.70). Muscular strength of the adductor, abdominal and pectoralis muscles was positively related to in-water endurance agility as assessed by the eggbeater kick (p < 0.05; r = 0.53–0.66). Findings from the current study emphasize the need to assess indices of water polo performance both in and out of the water as well as the relation among these parameters to best assess the complex profile of water polo players.

Effects of resistance training on neuromuscular characteristics and pacing during 10-km running time trial.

The purpose of this study was to analyze the impact of an 8-week strength training program on the neuromuscular characteristics and pacing adopted by runners during a self-paced endurance running. Eighteen endurance runners were allocated into either strength training group (STG, n = 9) or control group (CG, n = 9) and performed the following tests before and after the training period: (a) incremental test, (b) running speed-constant test, (c) 10-km running time trial, (d) drop jump test, (e) 30-s Wingate anaerobic test, (f) maximum dynamic strength test (1RM). During 1RM, the electromyographic activity was measured. In the STG, the magnitude of improvement for 1RM (23.0 ± 4.2 %, P = 0.001), drop jump (12.7 ± 4.6 %, P = 0.039), and peak treadmill speed (2.9 ± 0.8 %, P = 0.013) was significantly higher compared to CG. This increase in the 1RM for STG was accompanied by a tendency to a higher electromyographic activity (P = 0.080). The magnitude of improvement for 10-km running performance was higher (2.5 %) for STG than for CG (-0.7 %, P = 0.039). Performance was improved mainly due to higher speeds during the last seven laps (last 2800 m) of the 10-km running trial. There were no significant differences between before and after training period for maximal oxygen uptake, respiratory compensation point, running economy, and anaerobic performance for both groups (P > 0.05). These findings suggest that a strength training program offers a potent stimulus to counteract fatigue during the last parts of a 10-km running race, resulting in an improved overall running performance.

Development of Dynamic Load Strength Test Machine Based on Automotive BIW

The dynamic load strength test of automotive BIW is an important parameter for vehicle passive safety, but different test standards, different test requirements, which caused much trouble to the test authority. To solve the shortcomings of the traditional machines, such as low automation, poor universality and weak ability of data processing, this paper designs a new test machine for the dynamic load strength trials of automotive BIW on the basis of three typical standards. The test results indicated that this test machine embodies the characteristic of easy operation, stable function, and wide suitability, which improves the measurement accuracy and efficiency, at the same time, solves the problem of the database construction.

Experimental Study on the Dynamic Characteristic of Soft Soil under Cyclic Loads

To study the change law of the dynamic characteristics of soft soil, particularly the inadequate bearing capacity of highway and railway roadbeds induced by traffic loads, the soft soil in Yingkou area was taken as the research object. A series of dynamic strength and dynamic modulus tests were performed under different dynamic stress amplitude amplitudes, consolidation ratios, confining pressures, dynamic stress amplitudes, consolidation confining pressures, consolidation ratios, vibration frequencies, soft soil dynamic strains, dynamic strengths, dynamic backbone curves, dynamic moduli, and dynamic damping ratios. The results show that (1) Yingkou soft soil has a significant structural property. A strain turning point was found in the εd-N and dynamic curves. The deformation of soil increases rapidly when the strain is larger than this turning point. (2) Dynamic strength increases as consolidation confining pressures increase, but the influence of consolidation ratio and vibration frequencies on soft soil dynamic strength is not limited to an increase or decrease. (3) The dynamic modulus increases as consolidation confining pressure, consolidation ratio, and vibration frequencies increase, whereas dynamic damping ratio decreases with increasing pressure and ratio but increases with increasing vibrational frequency. The above results provide a theoretical basis for studying the insufficient bearing capacity of highway and rail roadbeds caused by long-term cyclic loads.

Pacing Strategy Determinants During a 10-km Running Time Trial

The purpose of this study was to identify the main determinants of the self-selected pacing strategy during a 10-km running time trial. Twenty eight male long-distance runners performed the following tests: (a) maximal incremental treadmill test, (b) economy running test, (c) maximum dynamic strength test, and (d) 10-km running time trial on an outdoor track. A stepwise multiple regression model was used to identify the contribution of rating of perceived exertion (RPE), physiological, and muscular parameters on the pacing strategy adopted by athletes. In the start phase (first 400 m), RPE accounted for 72% (p = 0.001) of the pacing variance. Peak treadmill speed (PTS) measured during a maximal incremental test explained 52% (p = 0.001) of the pacing variance during the middle phase (400-9,600 m), whereas maximal oxygen uptake and maximum dynamic strength accounted for additional 23% (p = 0.002) and 5% (p = 0.003), respectively. In the end phase (last 400 m), PTS accounted alone for 66% (p = 0.003) of the pacing variance. These data suggest that predictors of the pacing strategy during a 10-km running time trial have a transitional behavior from perceptive (start phase) to muscular and physiological factors (middle and end phases).

Thermo-mechanical and hydrophilic properties of polysaccharide/gluten-based bioplastics

The influence of adding different polysaccharides (locust bean gum, LBG; methyl cellulose, MC; and carboxymethyl cellulose, CMC) to gluten-based biodegradable polymeric materials was assessed in this work. Gluten/polysaccharide/plasticiser bioplastics were prepared at different polysaccharide concentrations (0–4.5%) and pH values by mixing in a two-blade counter-rotating batch mixer (at 25°C under adiabatic conditions) and thermomoulding at 9MPa and 130°C. Bioplastic probes were evaluated through dynamic mechanical thermal analysis, tensile strength and water absorption capacity tests. Results pointed out that a moderate enhancement of the network structure may be achieved by adding polysaccharide at a pH close to the protein isoelectric point (pH 6), which also conferred a further thermosetting capacity to the system. Moreover, the addition of MC and CMC was found to significantly enhance material elongation properties. However, the presence of charges induced by pH leaded to a higher incompatibility between the polysaccharide and protein domains forming the composite. The pH value played a relevant role in the material water absorption, which significantly increased under acidic or basic conditions (particularly at pH 3).

Influence of Coupling Agent on the Performance of Epoxy Molding Compound

Coupling agent, which acts as the bridge of epoxy resin and silica filler as well as the adhesion promoter of the Epoxy Molding Compound (EMC) and metal leadfream, is one of the most important ingredients in EMC manufacture. Here, the influences of the incorperation mannner of coupling agent agent, different types and content of coupling agent on the performance of EMC have been screened. Dynamic Mechanical Analyzer (DMA) modulus, impact strength, water absorption and adhesion test on copper, silver and PPF have been introduced to characterize the performance of EMC. Test results showed that for the incorperation manners, 85% coupling agent hydrolysate directly added in the high speed mixing process show hgiher adhesion strength on the silver, when coupling agent is used to pretreat silica, all the pretreated batches show a little lower DMA modulus than that non treated one. For different coupling agent types, normal epoxy group silane show higher adhesion on copper as well as other silanes, special silane A show higher adhesion on silver while special silane B show higher adeshion on PPF, meanwhile composite silane C show lower water absorption. For the content of the coupling agent, when the perportion of the siliane is more than 1%, the impact strength significantly decreased.

Der Zusammenhang von dynamischen und isometrischen Maximalkraftparametern und Muskelquerschnitt bzw. Muskelvolumen

The aim of the study was the evaluation of the correlation between maximal strength and muscle mass depending on the kind of analysis which was used. Two different methods of strength evaluation and several morphological parameters were used. 77 male participants (age: 27,2 ± 6,6 years; body height: 179,9 ± 4,0 cm; body weight: 82,5 ± 10,4 kg) joined the study. Maximal strength was tested by measuring the isometric force (MIF) and analysing the one repetition maximum (1RM). The morphological data was captured by magnetic resonance imaging. The volume of the muscle (VOL), the biggest cross sectional area (QSMAX), the cross sectional area of the upper (QS30), middle (QS60) and lower (QS90) third of the scanned area of the arm flexors were examined. After analysing the data for normal distribution with the Kolmogorov-Smirnov-Test, the Pearson product moment correlation was used to quantify the correlation of the parameters. Significance level was set at 1%. The results of the study showed high correlations between the dynamic strength test and the morphological parameters (r = 0,77-0,82; p &lt; 0,01) and moderate correlations between the isometric strength test and the morphological data (r = 0,46-0,53; p &lt; 0,01). In addition, the two different parameters for maximal strength correlated moderately (r = 0,55; p &lt; 0,01). The results of the study show that different morphological parameters can be used to describe the correlation between maximal strength and muscle mass. It should be recognised that the way of measuring maximal strength seems to be a substantial variable, which influences the apparent correlations.

Fracture of Metal Ring Samples Caused by Magnetic Pulse Loading in a Wide Time Range of Durations

On the basis of previously developed magnetic pulse method for short durations developed and implemented in [1] tests of thin metal ring samples of aluminum and copper in the range 10-5 −10-8s were conducted. The developed method allows us to measure the time to the fracture that is principally important for dynamic strength testing. A mathematical model describing the process of expansion of samples is suggested. A comparison of experimental and calculated data is performed.Structural-time approach based on the notion of incubation time [2] can be used to describe temporal dependence of critical tensile stress observed in experiments.

Development of albumen/soy biobased plastic materials processed by injection molding

Biobased plastics from renewable polymers constitute a highly interesting field for relevant industrial applications such as packaging, agriculture, etc., in which thermomechanical techniques (i.e. extrusion, compression molding, etc.) are increasingly being used. In spite of the potentials of injection molding in the manufacture of shaped products it is still scarcely used with biopolymers. This study evaluates injection molding as an alternative to produce biobased materials from blends prepared in a mixing rheometer, using different albumen/soy ratios and glycerol as the plasticizer. Viscoelastic measurements and DSC of protein/glycerol blends were used to select suitable processing conditions. Physicochemical properties of injection-molded probes were characterized through dynamic mechanical thermal analysis, tensile strength, water uptake and transmittance tests. Occurrence of shear-induced effects over mixing was confirmed by extractability analysis of protein concentrates and blends, particularly for soy-based systems. Both proteins and their mixtures yield injection-molded bioplastics, although showing lower mechanical properties than LDPE standards.

Methodology for nanoindentation-assisted prediction of macroscale elastic properties of high performance cementitious composites

This paper describes a methodology applied for determination of macroscale elastic properties of high performance cementitious composites (HPCC) based on nanoindentation measurements. For that, the elastic properties of HPCC mixtures with quartz filler and fly ash were evaluated at different length scales by nanoindentation (microscale) and the static and dynamic elastic moduli and compressive strength tests (macroscale). The nanoindentation results, obtained from a representative microlevel area by grid indentation with subsequent phase deconvolution, were complemented by an independent porosimetry test and inserted into a two-step analytical homogenization scheme to predict the overall macroscale properties. The final results indicate that the presented methodology allows a reliable advanced prediction of HPCC elastic properties, which is promising for the concrete industry since it would allow for reducing the number of large scale experiments and producing of a more predictable composite in an easier and experimentally less expensive way.

Efeitos do treinamento concorrente sobre aspectos da saúde de idosas

3 Abstract - Training programs that include aerobics and strength exercises, either at the same session or alternate days are defined as concurrent training (CT). The objective of this study was to verify the effects of a CT program on biochemical parameters, cardiovas- cular fitness, body composition and neuromuscular aspects. Twenty two elderly women physically active were randomly allocated to one of the five groups: AS (aerobic exercises followed by strength training; n=5), SA (strength activities followed by aerobics exercises; n=5), AG (aerobics exercise only; n=5), SG (strength activities only; n=4), CG (control group; n=3). The program lasted 12 weeks. Tests of dynamic and static strength, flexibility, aerobic power, body composition and biochemical parameters were conducted. In the aerobics power test, AS and SA groups showed differences in the post-test compared to the CG. In dynamic strength test of upper limbs, the groups S, SA, AS showed statistical differences from the CG in the post-test (p=0.009, 0.006 and 0.002 respectively). Only the AS group presented some difference from the pre to post-tests (P=003). AG, SG, SA, AS showed differences in the post-test in relation to the CG for the lower limbs strength test (p<0.001). From pre to post-test within the same group, the groups SG, SA and AS showed differences (p=0.001, 0.03, 0.02). Stretching, static strength, biochemical factors and body composition showed no association with any of the groups. We concluded that CT was equivalent to the strength and aerobics exercises performed exclusively.

Electrical Insulation Breakdown Strength in Epoxy/Spherical Alumina Composites for HV Insulation

In order to develop high voltage (HV) insulation materials, epoxy/spherical alumina composites with two different particle sizes (in <TEX>${\mu}m$</TEX>) were prepared and a dynamic mechanical analysis (DMA) and electrical insulation breakdown strength test were carried out in sphere-sphere electrodes and the data were estimated using Weibull statistical analysis. Alumina content varied from 50 to 70 wt%. The electrical insulation breakdown strength for epoxy/alumina (50 wt%) was 44.0 kV/1 mm and this value decreased with increasing alumina content. The effects of insulation thickness and alumina particle size on the insulation breakdown strength were also studied. The insulation thickness varied from 1 mm to 3 mm, and the particle sizes were 7.3 or <TEX>$40.3{\mu}m$</TEX>.

Strength-Training with Whole-Body Vibration in Long-Distance Runners: A Randomized Trial

A parallel group randomized trial was designed to analyze the impact of 6 weeks of strength training programs performed with or without whole-body vibration on muscular and endurance performance parameters in long-distance runners. 22 endurance runners were allocated into strength with whole-body vibration (n=8), without (n=8), and control (n=6) groups. Before and after the experimental period the subjects performed the following tests: a) maximum dynamic strength test, b) maximal incremental treadmill test, and c) time to exhaustion at velocity corresponding to maximal oxygen uptake. The fractions of the aerobic and anaerobic contribution in time to exhaustion test were also calculated. Both strength trained groups showed a similar increase in maximum dynamic strength (~18%). The aerobic contribution was enhanced for strength training group without whole-body vibration (~25%) after experimental period. No statistical differences were observed in any other variable. These results suggest that 6 weeks of strength training performed with or without whole-body vibration improve similarly the maximum dynamic strength in long-distance runners. In addition, both training modes studied had no deleterious effects on the traditional parameters of endurance performance, traditional strength training program results in increased aerobic contribution during high-intensity aerobic exercise.

Mechanical analysis of structural adhesive for marine joints

A structural adhesive from I.C.R., X07 Extreme®, was fully characterised through tensile test, static and dynamic lap-shear strength test, cleavage peel test and DSC. Lap-shear tests were performed by using either aluminium, stainless steel and glass fibre reinforced polymer as substrate and after aging the specimen under extreme environmental conditions. The performance of this novel adhesive was compared to that of a structural adhesive of a competitor. The work summarises the typical procedures intended for the qualification of a structural adhesive for marine joints.

Feasible method, utilizing density changes, for estimating in situ dynamic strength and deformation properties of sand samples

Laboratory tests and design reliability are directly controlled by sample quality. The frozen sampling (FS) method is useful for dynamic strength and deformation tests of undisturbed clean sand. However, it is very expensive and requires considerable equipment. The sample quality of Toyoura sands obtained from 48mm and 75mm samplers are scrutinized based on void ratio, dynamic strength and deformation properties through model and cyclic undrained triaxial tests. A conventional method for estimating in-situ dynamic strength and deformation properties of sand samples utilizing density changes is examined and the applicability of the proposed method is discussed for the samples obtained from Niigata sand deposits.The main conclusions obtained from this study are summarized as follows:(1) A conventional method for estimating in-situ void ratio (e0), Dr, stress ratio (RL20) in a 20 cyclic time frame and the initial modulus of rigidity (G0) of sand samples utilizing density changes is proposed.(2) The in-situRL20 and G0 estimated from the proposed method for sand samples from tube samplers were similar to those of frozen sampling and the in-situ modulus of initial rigidity was calculated from the secondary wave velocity for Niigata sand deposits.Therefore, dynamic strength and deformation properties changes, caused by sampling, can be modified appropriately to an in-situ condition by this proposed method.

切欠きをもつGF/PP板の高速引張試験による破壊

The effects of notch geometry on the tensile strength of notched fiber-reinforced polymer (FRP) plates in dynamic tensile strength tests were investigated. A short-glass-fiber-reinforced polypropylene (GF/PP) plate containing 30% E-glass fiber by weight was prepared by injection molding. The notch-root radii were 0.5, 1, and 2mm, while the notch depth ranged from 2 to 5mm. Dynamic tensile strength tests were carried out at room temperature of 23°C and a tensile speed of 1000mm/s. The validity of the fracture criterion based on the concept of the severity near the notch root was previously confirmed for notched FRP plates under static loading. In other words, the maximum elastic stress at fracture is determined only by the notch-root radius. This is accomplished by the experimental data of the static tensile test at a constant cross-head speed of 0.5mm/min (= 0.008mm/s). When the time to a fracture was the same, the results of the dynamic tensile strength tests showed that the maximum elastic stress at fracture is determined by the notch-root radius but is independent of the notch depth. Thus, the concept of the severity near the notch root could be applicable to the fracture of notched FRP plates in dynamic tensile tests. On the other hand, the fracture strength of FRP is time-dependent, and this dependence is called viscoelastic behavior. Therefore, when the tensile speed is varied, the maximum elastic stress at fracture would be determined by the notch-root radius and time.

Novel poly(hydroxyalkanoates)-based composites containing Bioglass® and calcium sulfate for bone tissue engineering

Three different poly(hydroxyalkanoates) (PHAs), copolymers of poly(3-hydroxybutyrate) (P3HB), have been used to make composites using two different fillers, bioactive glass (type 45S5 Bioglass®) and calcium sulfate dihydrate. The PHAs used were poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [PHBHV] and two copolymers of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [PHBHHx]. The aim of the study was the fabrication and characterization of the new composites and the assessment of the influence of the particular filler combination on the physical properties and bioactivity of the films. The thermal behaviour was studied using differential scanning calorimetry while mechanical properties were evaluated using dynamic mechanic thermal analysis and tensile strength test. The mechanical and thermal properties were affected by particles addition. The distribution of the particles in the polymer matrix, observed by scanning electron microscopy, was directly related to the mechanical properties. The surface characteristics were investigated by contact angle measurements and Raman spectroscopy. The extent of formation of hydroxyapatite (HA) upon immersion in simulated body fluid (SBF) depended on the polymer used, the amount of fillers employed and the time of immersion in SBF. Bioactivity was enhanced in the composites with a rise of hydrophilicity. The HA formation was controllable with time in the case of PHBHHx composites.

Effects of resisted physical training on muscle strength gain, body composition and metabolic repercussions in women with polycystic ovary syndrome

Analyze muscle strength (MS) gain, body composition (BC) and the metabolic changes in women with polycystic ovary syndrome (PCOS) after linear periodization of resisted physical training (RPT). Experimental study. 39 volunteers sedentary, who did not smoke or use any hormonal medications, aged 18 to 37 years, with BMI of 18 to 39.9 kg/m2, were divided in PCOS group (n=20) and control (CO) (n=19). After a period of adaptation, all volunteers were submitted to RPT for 16 weeks. Before and after RPT, handgrip isometric strength (HIS) tests were performed with dynamometer and 1RM maximum dynamic strength tests of trunk and lower and upper limbs were performed in the Bench press (BP), Leg extension (LE) and Arm Curl (AC) exercises. We determined serum total testosterone, SHBG, FAI, fasting insulin and glucose and HOMA index, lipid profile, characterization of the menstrual cycle and BC evaluated by DXA. Data were analyzed statistically by mixed effects linear regression. The results are reported as mean±standard deviation. The level of significance was set at P<0.05. After RPT, an increase in MS was observed in both groups, with the PCOS group showing the greater gain: HIS of the dominant limb (5079.61 × 5501.44, P=0.03), BP (31.20±4.75 × 40.00±5.61, P<0.01), LE (27.90±6.23 × 37.50±7.56, P<0.01), AC (19.07±3.40 × 23.35±4.00, P=0.01). Testosterone levels were reduced in the PCOS group (87ng/dl x 67ng/dl, P=0.01). The remaining variables did not change after RPT. Nine PCOS volunteers with amenorrhea presented menstrual bleeding. In the BC, the lean mass/height ratio in the DXA was higher in the PCOS group (PCOS 18.67±3.28 x CO 15.36±1.76, P=0.01). Comparing to CO, in short-time RPT, PCOS women gained more MS and lean mass. Although both groups did not present changes in glucide and lipid metabolism, PCOS women presented a decrease in testosterone levels and a return of menstrual cycle.

Bioenergetics and Neuromuscular Determinants of the Time to Exhaustion at Velocity Corresponding to V[Combining Dot Above]O2max in Recreational Long-Distance Runners

The purpose of this study was to investigate the main bioenergetics and neuromuscular determinants of the time to exhaustion (T(lim)) at the velocity corresponding to maximal oxygen uptake in recreational long-distance runners. Twenty runners performed the following tests on 5 different days: (a) maximal incremental treadmill test, (b) 2 submaximal tests to determine running economy and vertical stiffness, (c) exhaustive test to measured the T(lim), (d) maximum dynamic strength test, and (e) muscle power production test. Aerobic and anaerobic energy contributions during the T(lim) test were also estimated. The stepwise multiple regression method selected 3 independent variables to explain T(lim) variance. Total energy production explained 84.1% of the shared variance (p = 0.001), whereas peak oxygen uptake (V(O2)peak) measured during T(lim)and lower limb muscle power ability accounted for the additional 10% of the shared variance (p = 0.014). These data suggest that the total energy production, V(O2)peak, and lower limb muscle power ability are the main physiological and neuromuscular determinants of T(lim)in recreational long-distance runners.