Dynamic Strength Test Research Articles

Optimizing mechanical properties and pioneering biodegradable polymer blends for superior energy-absorbing structures used in sport helmets

Replacing elements made of conventional plastics (like polystyrene) with biodegradable substitutes is part of the trend of sustainable development and waste reduction. The manuscript covers issues related to the design, manufacturing and testing of sports helmet protective inserts made of biodegradable material. The FEM numerical simulations carried out by the authors allowed to determine the optimal desirable mechanical properties (Re = 8.5–65 MPa, E = 500–8000 MPa for 30 × 30 mm inserts; Re = 10.5–60 MPa, E = 500–7500 MPa for 48 × 48 mm inserts; Re = 13–95 MPa, E = 400–8500 MPa for 55 × 55 mm inserts) and geometric parameters (wall thickness equal to 0.2–0.5 mm, height of 20 mm), ensuring the formation of a plastic fold, which is the most effective energy-absorbing mechanism. The conducted quasi-static compression, bending and dynamic tensile strength tests allowed to determine blends with appropriate proportions of durable PLA with more plastic PBAT, PBS and TPS that meet the established criteria: PLA50PBAT50, PLA30PBAT70 and PLA30TPS70.

Developing Accurate Repetition Prediction Equations for Trained Older Adults with Osteopenia.

The aim of this study was to evaluate prediction equations to estimate 1RM in different exercises in older men and women with osteopenia/osteoporosis. Forty well-trained older women and men (73 ± 8 years) with osteopenia/osteoporosis performed 1RM dynamic and isometric maximum strength tests on resistance devices. In addition, each participant performed repetitions-to-fatigue (RTF) in the 5-8RM, 9-12RM, and 13-16RM zones. After evaluating the predictive performance of available 1RM prediction equations from the literature, new prediction equations were developed for all seven exercises. One of the available equations that focus on postmenopausal women already acceptably predicted 1RM from RTF for all but one exercise. Nevertheless, new exercise-specific prediction equations based on a cubic polynomial most accurately predict 1RM from RTF in the 5-8 reps range with mean absolute differences between predicted and actual 1RM of 3.7 ± 3.7% (leg-press) to 6.9 ± 5.5% (leg flexion) that is roughly within the acceptable coefficient of variation. For some exercises, the inclusion of the isometric maximum strength tests slightly increases the prediction performance of the 5-8RM. In conclusion, the present prediction equation accurately estimates 1RM in trained, older women and men with osteopenia/osteoporosis. Further evaluation of this new equation is warranted to determine its applicability to different age groups and populations.

Reliability of dynamic and isometric upper muscle strength testing in breast cancer survivors.

Breast cancer is the most common cancer in women worldwide, and its treatment usually involves a combination of many medical procedures, including surgery, chemotherapy, radiotherapy, and hormonal therapy. One of the detrimental effects on physical function is reduced upper limb muscle strength. This study aimed to evaluate upper body strength intra-day and inter-day (test-retest) reliability using the handgrip strength test (HGS) and the bilateral isometric bench press (BIBP) and the test-retest reliability of the one repetition maximum on the bench press (BP-1RM) in breast cancer survivors (BCS). Thirty-two (52.94 ± 8.99 yrs) BCS participated in this study. The muscle strength tests were performed in two different moments, three to seven days apart. Intraclass coefficient correlation (ICC) and coefficient of variation (CV) were used to assess the reliability. Standard error of measurement (SEM), typical error of measurement (TEM), and minimally detectable change (MDC) analyses were performed. The Bland-Altman analysis was used to assess the agreement between test-retest. We found a reliability that can be described as "high" to "very high" (ICC ≥ 0.88; CV ≤ 10%) for intra-day and test-retest. SEM% and MDC% were lower than 5% and 11%, respectively, for all intra-day testing. SEM% and TEM% ranged from 3% to 11%, and MDC% ranged from 9% to 23% in the test-retest reliability. The agreement demonstrated a systematic bias ranging from 2.3% to 6.0% for all testing, and a lower systematic bias may be presented in the non-treated side assessed by HGS and BIBP. HGS, BIBP, and BP-1RM assessments are reliable for measuring upper-body muscle strength in BCS.

Reliability of Dynamic Shoulder Strength Test Battery Using Multi-Joint Isokinetic Device.

This study aimed to determine the absolute and relative reliability of concentric and eccentric flexion, extension, horizontal abduction, and adduction movements of the shoulder using a functional electromechanical dynamometer (FEMD). Forty-three active male university students (23.51 ± 4.72 years) were examined for concentric and eccentric strength of shoulder flexion, extension, horizontal abduction, and horizontal adduction with an isokinetic test at 0.80 m·s-1. Relative reliability was determined by intraclass correlation coefficients (ICCs) with 95% confidence intervals. Absolute reliability was quantified by the standard error of measurement (SEM) and coefficient of variation (CV). Reliability was very high to extremely high for all movements on concentric and eccentric strength measurements (ICC: 0.76-0.94, SEM: 0.63-6.57%, CV: 9.40-19.63%). The results of this study provide compelling evidence for the absolute and relative reliability of concentric and eccentric flexion, extension, horizontal abduction, and horizontal adduction shoulder isokinetic strength tests in asymptomatic adults. The mean concentric force was the most reliable strength value for all tests.

Menstrual cycle and strength levels in women: a pilot study

It is speculated that hormonal fluctuations during the different menstrual cycle (MC) phases can influence physiological systems, such as musculoskeletal, and can also impact physical performance and quality of life. The aimed to check and compare the effects of MC on women's strength levels. The sample was made up of 18-30 years old women, who were using (G1) or not (G2) Oral Contraceptives (OC). Hormonal concentrations were determined using blood extraction, while muscle strength (FM) was assessed through the maximal dynamic strength (1RM) and muscle power tests at 40%, 60%, and 80%. The data were processed using two-factor ANCOVA (group and time), at a significance level of p < 0.05. Hormonal values showed greater significant differences in almost all hormones and G1 phases. The results of the FM tests showed a significant reduction of 1 RM (day 21) in G1, with a moderate effect size on days 21 and 11. In the G1 muscle power (MP) test, on day 01 there was a significant increase in 60% concerning day 11 and day 21. It can be considered that the hormonal behavior of both groups was maintained throughout the evaluations. Regarding FM manifestations, it is suggested that regular MC, without the use of OC, induces a reduction in FM levels during days 11 and 21 in women. However, the group that used OC had a larger effect size on 40% on day 01 and 40% on day 21.

Assessing muscle strength following massive weight loss: a preliminary study in patients who desired body contouring surgery

Background Sarcopenia, which is commonly associated with ageing, is increasingly prevalent among individuals with significant obesity and massive weight loss (MWL). This study aimed to evaluate the muscle strength of MWL patients who desired body contouring surgery (BCS) due to the excess skin. Methods This prospective study enrolled 23 patients with MWL who were eligible for BCS. Participants underwent three distinct muscle strength tests with age- and gender-related references: the hand grip strength test (HGS), the squatting test, and the dynamic muscle strength of the body (DMSoB). Results The cohort comprised 18 (78.3%) women and five (21.8%) men with a mean age of 45.7 years and body mass index (BMI) of 26.9 kg/m2. Among the participants, 17 (73.9%) had previously undergone bariatric surgery (BS group), while six (26.1%) had achieved weight loss through the non-surgery method (non-BS-group). In the HGS test, 87% of the participants reached only the lowest (poor) or second lowest (fair) fitness levels. In the squatting test, 73.8% of the participants reached above the intermediate level or better. Only 8.7% of the participants had a lower fitness level. In the dynamic muscle strength test, 69.7% of the participants reached the lowest (poor) level. Conclusions This preliminary study showed that patients with prior MWL exhibited lower muscle strength than the age- and gender-matched general population. In particular, the HGS results suggested the possibility of sarcopenia.

Experimental study on the quasi-static and dynamic tensile behaviour of thermally treated Barakar sandstone in Jharia coal mine fire region, India

In the present study, the effect of mild to high-temperature regimes on the quasi-static and dynamic tensile behaviours of Barakar sandstone from the Jharia coal mine fire region has been experimentally investigated. The experimental work has been performed on Brazilian disk specimens of Barakar sandstone, which are thermally treated up to 800 °C. The quasi-static and dynamic split tensile strength tests were carried out on a servo-controlled universal testing machine and Split Hopkinson Pressure Bar (SHPB), respectively. Microscopic and mineralogical changes were studied through a petrographic investigation. The experimental results suggest the prevalence of both, static and dynamic loading scenarios after 400 °C. Up to 400 °C, the quasi-static and dynamic tensile strengths increased due to the evaporation of water, which suggests a strengthening effect. However, beyond 400 °C, both strengths decreased significantly as newly formed thermal microcracks became prevalent. The dynamic tensile strength exhibits strain rate sensitivity up to 400 °C, although it shows a marginal decline in this sensitivity beyond this temperature threshold. The Dynamic Increase Factor (DIF) remained constant up to 400 °C and slightly increased after 400 °C. Furthermore, the characteristic strain rate at which the dynamic strength becomes twice the quasi-static strength remains consistent until reaching 400 °C but steadily decreases beyond this temperature. This experimental study represents the first attempt to validate the Kimberley model specifically for thermally treated rocks. Interestingly, the presence of water did not have a significant impact on the failure modes up to 400 °C, as the samples exhibited a dominant tensile failure mode, breaking into two halves with fewer fragments. However, as temperature increased, the failure behaviours became more complex due to the combined influence of thermally induced microcracks and the applied impact load. Cracks initially formed at the centre and subsequently, multiple shear cracks emerged and propagated in the loading direction, resulting in a high degree of fragmentation. This study also demonstrates that shear failure is not solely dependent on the loading rate but can also be influenced by temperature, further affecting the failure mode of the sandstone.

Estimating dynamic compressive strength of rock subjected to freeze-thaw weathering by data-driven models and non-destructive rock properties

ABSTRACT The dynamic compressive strength (DCS) of frozen-thawed rock influences the stability of rock mass in cold regions, especially when rock masses are possibly disturbed by dynamic loads. Laboratory freeze-thaw weathering treatment is usually time-consuming, and the dynamic strength test is destructive. Therefore, this paper attempts to quickly predict the DCS of frozen-thawed sandstones using data-driven methods, non-destructive rock properties, and basic environmental parameters. The sparrow search algorithm (SSA), gorilla troops optimiser, and dung beetle optimiser were chosen to develop two hyperparameters in the random forest (RF). The classic RF, back propagation neural network, and support vector regression models were taken as the control group. These six models were developed to predict the DCS. Their prediction results were compared. Finally, the sensitivity analysis was carried out to assess the significance of all input variables. The results indicate that the SSA – RF model yields the best prediction result, and three optimised models have better performance than single machine-learning models. Strain rate, dry density, and wave velocity are found to be the three most important parameters in DCS prediction, which further indicates that there is also a strong correlation between the characteristic impedance of the rock and the DCS.

Optimization of Piezoresistive Response of Elastomeric Porous Structures Based on Carbon-Based Hybrid Fillers Created by Selective Laser Sintering.

Recently, piezoresistive sensors made by 3D printing have gained considerable interest in the field of wearable electronics due to their ultralight nature, high compressibility, robustness, and excellent electromechanical properties. In this work, building on previous results on the Selective Laser Sintering (SLS) of porous systems based on thermoplastic polyurethane (TPU) and graphene (GE)/carbon nanotubes (MWCNT) as carbon conductive fillers, the effect of variables such as thickness, diameter, and porosity of 3D printed disks is thoroughly studied with the aim of optimizing their piezoresistive performance. The resulting system is a disk with a diameter of 13 mm and a thickness of 0.3 mm endowed with optimal reproducibility, sensitivity, and linearity of the electrical signal. Dynamic compressive strength tests conducted on the proposed 3D printed sensors reveal a linear piezoresistive response in the range of 0.1-2 N compressive load. In addition, the optimized system is characterized at a high load frequency (2 Hz), and the stability and sensitivity of the electrical signal are evaluated. Finally, an application test demonstrates the ability of this system to be used as a real-time wearable pressure sensor for applications in prosthetics, consumer products, and personalized health-monitoring systems.

A numerical study based on GBM3D-DEM model: Multi-level force chain analysis in dynamic flexural tensile strength test

A numerical study based on GBM3D-DEM model: Multi-level force chain analysis in dynamic flexural tensile strength test

Performance evaluation of petroleum hard pitch modified with rice straw bio-oil

In this present study, bio-binder was made using the bio-oil obtained from rice straw and petroleum hard pitch to reduce the air pollution caused by the burning of waste rice straw in the field. The physical, rheological, and chemical tests were conducted on the viscosity-grade binders (VG30 and VG40), petroleum hard pitch, and bio-binders prepared with a blending of petroleum hard pitch with 20 and 30 wt.%. The performance of bituminous mixes made with viscosity-grade binders and bio-binder was evaluated by using the dynamic creep, resilient modulus, and tensile strength tests. The results of the frequency sweep and Fourier transform infrared tests indicate that bio-binders have poor resistance to aging. The rut resistance of the bio-binder modified mix was better than that of the VG30 mix. There is no significant difference in moisture resistance of bituminous mixes prepared with bio-binder and viscosity-grade binders.

Thermo-mechanical performance of nanostructured electrospun composites produced from poly(vinyl alcohol) and cellulosic compounds for potential uses as wound dressings

The purpose of this research was to analyze the morphology, thermal and mechanical properties of poly(vinyl alcohol) (PVA)-based electrospun mats reinforced with cellulose acetate (CA) or cellulose nanocrystalline (CNC) for potential applications in wound dressings. Bead-free and water-stable electrospun nanofibers made of blends of PVA and CA or CNC were successfully produced and crosslinked with glutaraldehyde vapor. Crosslinking slightly increased the nanofibers' diameters in order of 43 and 13% for 80/20 PVA/CA and PVA/CNC electrospun mats, respectively, while maintaining their bead-free morphology. Thermogravimetry (TGA) and differential scanning calorimetry (DSC) evaluations were employed to determine the miscibility and the thermal response of the uncrosslinked and crosslinked mats, reporting a reduction in mass loss upon addition of CA and CNC and upon crosslinking process. Polymers' powder and mats (before and after crosslinking) crystallinity was assessed by X-ray diffraction analysis (XRD). Crosslinked mats experienced a slight reduction in crystallinity compared to the uncrosslinked. Static and dynamic tensile strength tests revealed that CA and CNC doped mats enhanced the Young's modulus and lowered deformation at failure compared to pristine PVA electrospun mats. Data from storage modulus (E′) demonstrated the strength of the physical interactions formed between PVA and the cellulosic derivatives (either before and after crosslinking), highlighting the stiffness of CA (231.58 MPa for the 80/20 mat) and, particularly, CNC (742.04 MPa for the 80/20 mat). This research uncovered important information concerning the chemical and physical relation between polymeric matrices and additives, essential for the proper selection of materials for wound dressings production.

Active brazing of cBN micro-particles with AISI 1045 steel using ceramic reinforced Ag-based fillers

cBN micro-particles have been brazed to medium carbon steel substrate using a new formulation of low-temperature, ceramic reinforced Ag-Cu-Ti alloy and evaluated for their wear resistance in developing cBN brazed tools. TiN and TiB2 microparticles were added as reinforcements independently in different proportions to Ag-Cu-2Ti (Ag-Cu-2wt%Ti) filler alloy and cBN tools were brazed. Wear characteristics of the ceramic reinforced alloys showed that the TiB2 added Ag-Cu-2Ti alloy exhibited excellent abrasion resistance with an improvement of 91–95 % over the commercial Ag-Cu-2Ti alloy. Conversely, the wear performance of the TiN added Ag-Cu-Ti alloys was poor owing to the weak bonding of TiN microparticles by the alloy matrix. The results were compared with 5 wt% TiB2 and TiN added Ag-Cu-5Ti alloys. However a significant improvement in the mechanical properties was not observed and the wetting on cBN was lower for reinforced Ag-Cu-5Ti alloy. Tensile tests showed that the Ag-Cu-2Ti-5TiB2 alloy demonstrated higher tensile strength (305.89 MPa) when compared to the Ag-Cu-2Ti and Ag-Cu-2Ti-5TiN filler materials. Low and high impact dynamic joint strength tests were further carried out on the 2 and 5 wt% reinforced Ag-Cu-2Ti and Ag-Cu-5Ti alloys. TiB2 added Ag-Cu-2Ti alloy displayed sufficient joint strength with TiN added Ag-Cu-2Ti alloys performing marginally better. Bearing in mind the excellent mechanical properties of the Ag-Cu-2Ti-5TiB2 filler and its appreciable joint strength, Ag-Cu-2Ti-5TiB2 filler can be used as an efficient filler material in developing cBN brazed tools for grinding applications.

Ultra-high-performance fiber-reinforced sustainable concrete modified with silica fume and wheat straw ash

Developing ultra-high fiber-reinforced concrete (UHPFRC) demands an immense quantity of ordinary Portland cement (OPC). Using a high percentage of cement in UHPFRC leads to uneconomic concrete and significant release of CO2 into the atmosphere. Therefore, it is critical to address this issue by substituting the part of cement with a sustainable material. The current research has tried to tackle this issue by assessing the impact of adding wheat straw ash (WSA) and silica fume (SF) as a partial substitute of cement on the properties of UHPFRC on the static and dynamic compressive strength test, among other strength and durability characteristics. Two different batches of mixes were developed. The OPC was substituted for up to 40% in the first batch, with combined WSA plus SF at 10% intervals. In the second batch, OPC was replaced up to 40% with only WSA at an interval of 10%. Polypropylene fibers (PPFs) at 2% (by vol.) were added to modified samples to improve the ductility of concrete. The dynamic compression strength was evaluated utilizing a Split Hopkinson pressure bar, and quasi-static compression strength was determined using the compression machine. Moreover, splitting and flexural strength were also assessed, and water permeability and sorptivity tests were carried out for durability. The test outcome showed that the sample with 15% WSA plus 15% SF had higher compressive strength (174.8 MPa at 90 days) and improved durability than the sample with only 30% WSA (170.2 MPa at 90 days) and the control sample. The assessed properties tend to decline at 40% of WSA and 20% WSA with 20% SF. In dynamic compression strength, it was observed that the WSA and SF, and fibers samples performed similarly to the control sample, and these modified samples were not sensitive to strain rates. Adding 15% plus 15% SF had an optimal effect in improving the durability properties of UHPFRC. Also, the thermogravimetric analysis (TGA) confirms the role of WSA and SF in densifying the matrix of UHPFRC, decreasing the porous pores and amount of calcium-hydroxide and developing additional gels of calcium-silicate-hydrate, which enhances the strength and durability of UHPFRC. The current study revealed that the modified samples (with WSA and SF) had a low embedded CO2 for the sustainability features compared to the control sample.

Muscle typology influences the number of repetitions to failure during resistance training

This study examined whether muscle typology (muscle fiber type composition) is related to maximal strength and whether it can explain the high inter-individual variability in number of repetitions to failure during resistance training. Ninety-five resistance training novices (57 males) were assessed for their maximal isometric knee extension strength and muscle typology. Muscle typology was estimated by measuring carnosine in the soleus, gastrocnemius and/or vastus lateralis using proton magnetic resonance spectroscopy. Forty-four subjects (22 males) performed dynamic strength tests (1RM) and 3 sets of leg extensions and curls to failure (60%1RM) to determine the association between muscle typology and (total) number of repetitions. Twenty-one subjects performed additional biceps curls and triceps extensions (60%1RM) to assess influence of exercise, 23 subjects performed additional leg extensions and curls at 80% and 40%1RM to evaluate influence of training load. There was a weak but significant relationship between muscle typology and maximal isometric strength (r = 0.22, p = 0.03) favoring the fast typology individuals. Slow and fast typology individuals did not differ in upper arm and upper leg 1RM. Total number of repetitions was related to muscle typology at 80% (r = -0.42; p = 0.04) and 60% (p = -0.44; p = 0.003) but not at 40%1RM. Slow typology individuals performed more repetitions to failure at 60%1RM in the leg extension (p = 0.03), leg curl (p = 0.01) and biceps curl (p = 0.02). In conclusion, muscle typology has a small contribution to maximal isometric strength but not dynamic strength and partly determines the number of repetitions to failure during resistance training. This insight can help individualizing resistance training prescriptions.

The relationship between judo specific test performances and physical fitness in prepubescent male judo athletes

The aim of this study was to investigate the relationship between judo specific test performances and physical fitness of prepubescent judo athletes. Forty male judo athletes aged 10-13 voluntarily participated. Athletes completed special judo fitness test (SJFT), hikisdashi uchi-komi test (HUT), judogi grip strength tests, and performance-related physical fitness components tests (aerobic power, strength, agility, explosive power, body composition). Correlation coefficients were used to analyze the relationship between the judo specific tests and physical fitness performances. Significant correlations were found between total throw numbers during SJFT, HUT performance, isometric and dynamic judogi grip strength test performance and general performance-related physical fitness tests. Also, negative correlations were found between judo specific tests performances and body fat percent. It can be concluded from the study that total throws in SJFT, 20 s HUT and dynamic judogi grip strength tests can be used to monitor performances of prepubescent judo athletes as these tests present large significant correlations with performance related physical fitness tests.

Lightweight Optimization Design and Fatigue Lifetime Analysis for Anti-rolling Torsion Bar of Rail Vehicle

Based on the fatigue strength assessment method in the FKM standard, the lightweight design of a type of anti-rolling torsion bar is studied by using the finite element method. Firstly, the finite element model of the torsion bar structure is constructed by using the Creo software and the HyperMesh software, and then the finite element analysis is carried out by using the ABAQUS software. The numerical simulation results indicate that under the condition of ultimate load 29.2kN, the static strength, anti-rolling stiffness and fatigue strength of the torsion bar are all satisfy with the design requirements. Secondly, the orthogonal numerical test method is utilized to investigate the influence of geometric parameters on the anti-rolling stiffness and Factor of Strength (FOS) value of the torsion bar. Taking the structural geometric parameters as variables and the FOS value as the objective function, a second-order response surface model is established. The single objective and multi-factor optimization design for the torsion bar under the condition of stiffness constraint is conducted by using the Isight software and multi-island genetic algorithm. The results show that, comparing with the original structure, the weight of the optimized structure is reduced by 20.89%, and the static and dynamic strength, and anti-rolling stiffness of the optimized structure are match with the design requirements. Finally, the static and dynamic strength tests for the optimized torsion bar are individually operated at the ultimate load and under two-stage cyclic loading with amplitude 18.0kN and 29.2kN. the results show that the calculated stiffness coefficient is consistent with the test one, and the service lifetime of the torsion bar is satisfy with the design requirement.

Validity and Reliability of an Isometric Row in Quantifying Maximal Force Production in Collegiate Rowers.

Pineda, D, Hudak, J, Bingham, GE, and Taber, CB. Validity and reliability of an isometric row in quantifying maximal force production in collegiate rowers. J Strength Cond Res 37(8): e462-e465, 2023-The objective of this study was to examine the relationship between a maximal isometric strength test with a maximal dynamic strength test. The main outcome was to evaluate the isometric test to determine if it was a valid and reliable measurement tool for testing and monitoring of rowing athletes. Collegiate Division 1 rowers were tested on measures of maximal dynamic and isometric strength on 2 occasions separated by 14 days. Thirty-two female athletes (age: 19.9 11.0 years; height: 168.2 ± 7.6 cm; body mass: 71.3 as13.2 kg) participated in this study. Although the isometric test had greater reliability, both tests displayed good-to-excellent reliability (intraclass correlation coefficient = 0.79-0.92). Strong correlations were present for the relationship between isometric and dynamic strength tests ( r = 0.76-0.82, p = <0.001). The data indicate that the isometric row test is valid and reliable compared with dynamic testing and may be used in conjunction with dynamic testing in the evaluation of collegiate rowers.

Chronic Effects of Inter-Set Static Stretching on Morphofunctional Outcomes in Recreationally Resistance-Trained Male and Female

ABSTRACT Purpose: The purpose of this study was to compare the effects of resistance training (RT) with inter-set static stretching (IS) versus traditional RT (TRT) on morphofunctional outcomes in recreationally resistance-trained male and female. Methods: Twenty-two recreationally-trained subjects were allocated to IS group (n = 12) or TRT (n = 10) and completed eight weeks of RT. The only difference between the groups was that IS group included static stretching between sets, while the TRT rested between the sets. Ultrasound images, dynamic and isometric strength tests for the elbow flexors and elbow extensors were evaluated pre- and post-intervention period. Results: Total training volume (TTV) was greater in TRT than IS (p = .031). TRT and IS caused similar increases in maximal dynamic and isometric strength. Fascicle length of the brachialis increased following TRT (p = .033); muscle thickness and the pennation angle of the distal portion of the triceps brachii increased following IS (p = .035 and p = .007, respectively). There were no significant changes in thickness and architecture for biceps brachii in either group. There were no significant differences between groups for any muscle strength and morphology outcome. Conclusion: IS negatively affects TTV but does not affect muscle strength and architecture of recreationally resistance-trained male and female.

Effect of Molding Methods on Free-Thaw Durability of Pervious Concrete

Pervious concrete is one of the most important new materials in the sustainable development of infrastructure construction, and has been widely studied and developed by the industry. Through freeze-thaw test, dynamic elastic modulus test, mass test and strength test, the durability of pervious concrete with different molding methods was studied. The test results show that the mass loss rate and strength decline rate of the pervious concrete controlled by the pervious rate are the lowest after 25 cycles of freezing and thawing, marshall compacted pervious concrete has the lowest loss rate of dynamic elastic modulus, and plug-in concrete has the lowest durability. Finally, the mix proportion of pervious concrete with optimal target porosity by rotary compaction is suggested.