Isokinetic trunk flexion-extension protocol to assess trunk muscle strength and endurance:Reliability,learning effect,and sex differences

Purpose:The purpose of this study was to examine the reliability and the learning effect of an isokinetic trunk flexion-extension protocol designed to simultaneously assess trunk muscle strength and endurance.In addition,the effect of the participants’sex on the reliability data was examined.Methods:Fifty-seven healthy and physically active young men(n=28)and women(n=29)performed the isokinetic protocol 5 times,separated by a week between each of the first 4 sessions and by a month between the last 2 sessions.The protocol consisted of performing 4 trials of 15 maximum flexion-extension concentric exertions at 120°/s(range of trunk motion=50°).The absolute and relative peak torque and total work were calculated to assess trunk flexion and extension strength.In addition,endurance ratio,modified endurance ratio,fatigue final ratio,recovery ratio,and modified recovery ratio variables were used for the assessment of trunk muscle endurance in both directions.Results:Regarding the absolute reliability,no relevant changes were found between paired-comparison sessions for most strength and endurance variables,except for total work and relative total work variables in the flexion movement in both sexes.In addition,the typical error of the isokinetic variables was lower than 10%in both males and females,and minimum detectable changes ranged from 7%to 20%,with a tendency to be higher in females and in endurance variables.The strength variables showed high-to-excellent intraclass correlation coefficients(ICCs;>0.74);however,for the endurance variables only the endurance ratio and the modified endurance ratio obtained moderate-to-high ICC values(0.57<ICC<0.82).In addition,the analysis of the variance reported no significant differences between consecutive pairs of sessions for most variables in both sexes.Conclusion:Overall,these findings provide clinicians,trainers,and researchers with a 10-min single-session protocol to perform a reliable muscle strength and endurance evaluation of trunk flexor and extensor muscles,all within the same protocol.

Isokinetic Strength of Trunk Flexors and Extensors Muscles in Adult Men with and without Nonspecific Back Pain: A Comparative Study

Background: There is no proven relationship between back pain and trunk muscle strength, researches in this field yielded conflicting results: some found significant weakness of trunk muscles in back pain patients compared with healthy subjects, however many researches did not show any relationship. Objectives: The focus of this study is to assess the trunk muscles strength using isokinetic dynamometer then tries to find a relation between back pain and trunk muscles strength. Materials and Methods: Fifty patients with back pain (BP) and 50 healthy subjects were recruited in this study. The flexors and extensors of the trunk muscles were evaluated by Isokinetic dynamometer and compared with control groups. Results: Patients with acute back pain show a significant reduction of the trunk muscles strengths at 120°/s velocities (p value < 0.05) with reversed flexor/extensor ration in comparison with sound subjects. Such a relationship does not show in subacute or chronic back pain patients. Conclusions: Acute back pain associated with decreased the strength of the trunk flexors and extensors at 120°/s. The trunk muscle reinforcement programs must be considered in-patients with acute back pain.

Bio-signal based elbow angle and torque simultaneous predictionduring isokinetic contraction

It is of great importance to decode motion dynamics of the human limbs such as the joint angle and torque in order to improve the functionality and provide more intuitive control in human-machine collaborative systems. In order to achieve feasible prediction,both the surface electromyography(sEMG) and A-mode ultrasound were applied to detect muscle deformation and motor intent.Six abled subjects were recruited to perform five trails elbow isokinetic flexion and extension, and each trail contained five repetitions, with muscle deformation and s EMG signals recorded simultaneously. The experimental datasets were categorized as:the ultrasound-EMG combined datasets, ultrasound-only datasets and EMG-only datasets. The support vector machine(SVM)regression model was developed for both elbow joint angle and torque prediction, based on the above three kinds of datasets. The root-mean-square error(RMSE) and the correlation coefficients(R) were applied to evaluate the prediction accuracy. The results across all the subjects for different datasets indicated that the combined datasets and the ultrasound datasets were superior to the sEMG datasets both on elbow joint angle and torque prediction, and there were no significant differences between the combined datasets and the ultrasound datasets. It turns out that elbow angle and torque can be reconstructed by A-mode ultrasound, and the significant findings pave the way towards the application of musculature-driven human-machine collaborative systems.

Isokinetic correlation analysis of the series of electrophilic substitution reactions of o-substituted phenylmercurials

Isokinetic relationships of the series of electrophilic substitution reactions of o-substi- tuted phenylmercurials are studied, and the results show, for the first time, that isokinetic correlation analysis can reveal the dominant factor in the system of the reactions. The analysis of SE2 of o-substituted phenylmercuric chlorides indicates that the steric effect of o-substituents is the pre-dominant factor when I2 is used as electrophilic agent, however, the electronic effect of o-substituents would become the predominant factor when HCl is used as the electrophilic agent. In SE1 of o-substituted phenylmercuric chlorides, the results of the analysis display that the predomi-nant factor is the field effects of o-substituents. The determination of predominant factors in those reactions would provide further scientific basis for those reaction mechanisms.

The Effect of Familiarization on the Reliability of Isokinetic Assessment in Breast Cancer Survivors

Purpose To determine the amount of familiarization sessions required by breast cancer survivors to achieve a reliable meas-urement of muscle function assessed using isokinetic dynamometry.Methods Twenty-six breast cancer survivors performed three isokinetic knee extension tests separated by,at least,48 h.The isokinetic testing protocol included one warm-up set of 10 submaximal knee extensions at 120°/s,followed by two sets of four maximal knee extensions at 60°/s,with 2-min rest interval between sets.Peak torque(PT),time to peak torque(TPT),angle of peak torque(APT),and average power(AP)of each trial was used for the assessment of testing reliability.Percentage change in the mean,typical error,coefficient of variation and intraclass correlation coefficients(ICC2.1)were calculated to determine test-retest reliability.Results For PT,change in mean was lower between trials 2 and 3 than between trials 1 and 2(4.18% and 13.18%,respec-tively),and ICC was greater between trials 2 and 3 than between trials 1 and 2(0.962 and 0.818,respectively).For TPT and APT,ICC was clinically acceptable only between trials 2 and 3(0.757 and 0.803,respectively).For AP,change in mean was clinically acceptable between trials 2 and 3(9.84%),while ICC met acceptable reliability between both,trials 1 and 2 and,trials 2 and 3(0.756 and 0.891,respectively).Conclusion At least one familiarization session is adequate to achieve reliable measurements of muscle function using isokinetic dynamometry,while avoiding the impact of learning effect of the measurements in breast cancer survivors.

Relationship of Isokinetic Leg Press Force with Jumping Performance and 1RM in the Squat

Purpose Muscle strength and power are important requirements in many sports.The correlation of jumping performance as manifestation of muscle power and squatting one-repetition maximum(1RM)has been shown in several investigations.Correlations with maximum force in a linear isokinetic leg press are still pending.Since different testing devices produce different relationships and rotational isokinetic measurements show conflicting results,further evidence is needed.Methods We investigated the correlation of isokinetic leg press force at 0.1 m/s and 0.7 m/s with squat 1RM and jumping performance in different vertical jumps.Results The results show medium to strong,significant correlations for isokinetic force at 0.1 m/s with squat-and counter-movement-jump performance,whereas isokinetic force at 0.7 m/s showed strong,significant correlations for both jumping tests.Drop jump performance(dropping heights:20,30,40,and 50 cm,respectively)reveals weak to medium,significant correlations with isokinetic force at 0.1 m/s and weak,significant correlations with isokinetic force at 0.7 m/s.Squat 1RM displays strong relationships to isokinetic force with greater coefficients regarding higher movement speed in the isokinetic condition.Conclusion The maximum strength of the leg extensors displays a basic requirement for vertical jumping with great motion in knee-and hip-joints and should be considered in training programs.For vertical jumps that are mainly generated via ankle motion,maximum strength of knee-and hip-extensors plays an indirect role to guarantee for performance-enhancing mechanisms.Additionally,in strength testing,different manifestations of strength performance should carefully be taken into account.

Is hamstrings-to-quadriceps torque ratio useful for predicting anterior cruciate ligament and hamstring injuries?A systematic and critical review

Background:For the past 30 years,the hamstring(H)-to-quadriceps(Q)(H:Q)torque ratio has been considered an important index of muscle strength imbalance around the knee joint.The purpose of this systematic review was to examine the value of H:Q torque ratio as an independent risk factor for hamstring and anterior cruciate ligament(ACL)injuries.Methods:Database searches were performed to identify all relevant articles in PubMed,MEDLINE,Cochrane Library,and Scopus.Prospective studies evaluating the conventional(concentric H:Q),functional(eccentric H:concentric Q),and mixed(eccentric H at 300/s:concentric Q at2400/s)H:Q ratios as risk factors for occurrence of hamstring muscle strain or ACL injury were considered.Risk of bias was assessed using the Quality In Prognosis Studies tool.Results:Eighteen included studies reported 585 hamstrings injuries in 2945 participants,and 5 studies documented 128 ACL injuries in 2772participants.Best evidence synthesis analysis indicated that there is very limited evidence that H:Q strength ratio is an independent risk factor for hamstring and ACL injury,and this was not different between various ratio types.Methodological limitations and limited evidence for ACL injuries and some ratio types might have influenced these results.Conclusion:The H:Q ratio has limited value for the prediction of ACL and hamstring injuries.Monitoring strength imbalances along with other modifiable factors during the entire competitive season may provide a better understanding of the association between H:Q ratio and injury.

BTE康复训练和评估系统功能简介

本文主要介绍了美国BTE公司生产的康复系统的评估和治疗功能,并对临床和科研意义进行探讨。

Can infrared thermography be used to monitor fatigue during exercise? A case study

Background: Infrared thermographic imaging(IRTG) is a safe and reliable technology used to monitor skin temperature. The main aim of our study was to evaluate the relationship between skin temperature changes and muscle fatigue in order to answer the main research question if IRTG can be used to monitor muscle fatigue.Methods: This was a case study performed on a 23-year-old trained middle distance runner. After warm-up the subject was exercising on the dynamometer for 7.5 min at 120?/s performing only concentric contractions of quadriceps. At the same time IRTG recording of both(exercising and non-exercising) quadriceps was performed.Results: A correlational analysis that was performed in order to quantify the relationship between power and temperature change over time has shown that there is a significant negative correlation between skin temperature increase and power decrease(r = -0.543, p = 0.036) of exercising quadriceps. In linear regression model the exercising quadriceps power could be predicted from skin temperature. No such relationships were noted for the non-exercising limb that served as a control.Conclusion: We believe that correlation between skin temperature change and muscle power output as described in this case study deserves further analysis on the larger sample including subjects of the different ages, health status, and physical abilities in order to create a new tool for monitoring the muscle fatigue.

Various performance-enhancing effects from the same intensity of whole-body vibration training

Purpose:The purpose of this study was to compare the effects of an 8-week whole-body vibration training program in various frequency and amplitude settings under the same acceleration on the strength and power of the knee extensors.Methods:Sixty-four young participants were randomly assigned to 1 of 4 groups with the same acceleration(4 g):high frequency and low amplitude(n = 16,32 Hz,1 mm) group,medium frequency and medium amplitude(n = 16,18 Hz,3 mm) group,low frequency and high amplitude(n = 16,3 Hz,114 mm) group,and control(n = 16,no vibration) group.All participants underwent 8 weeks of training with body mass dynamic squats,3 sessions a week.Results:The results showed that the high frequency and low amplitude group increased significantly in isometric contraction strength and 120°/s isokinetic concentric contraction strength;the medium frequency and medium amplitude group increased significantly in 60°/s and 120°/s isokinetic strength of both concentric and eccentric contraction;and the low frequency and high amplitude group increased significantly in 60°/s and 120°/s isokinetic eccentric contraction strength.Conclusion:All frequency and amplitude settings in the 8-week whole-body vibration training increased muscle strength,but different settings resulted in various neuromuscular adaptations despite the same intensity.

Skeletal muscle stiffness as measured by magnetic resonance elastography after chronic spinal cord injury:a cross-sectional pilot study

Skeletal muscle stiffness is altered after spinal cord injury(SCI).Assessing muscle stiffness is essential for rehabilitation and pharmaceutical interventions design after SCI.The study used magnetic resonance elastography to assess the changes in stiffness after chronic SCI compared to matched able-bodied controls and determine its association with muscle size,spasticity,and peak torque in persons with SCI.Previous studies examined the association between muscle stiffness and spasticity,however,we are unaware of other studies that examined the effects of muscle composition on stiffness after SCI.Ten participants(one female)with chronic SCI and eight(one female)matched able-bodied controls participated in this cross-sectional study.Magnetic resonance elastography was utilized to monitor stiffness derived from shear waves propagation.Modified Ashworth scale was used to evaluate spasticity scores in a blinded fashion.Peak isometric and isokinetic torques were measured using a biodex dynamometer.Stiffness values were non-significantly lower(12.5%;P=0.3)in the SCI group compared to able-bodied controls.Moreover,stiffness was positively related to vastus lateralis whole muscle cross-sectional area(CSA)(r2=0.64,P<0.005)and vastus lateralis absolute muscle CSA after accounting for intramuscular fat(r2=0.78,P<0.0007).Stiffness was also positively correlated to both isometric(r2=0.55-0.57,P<0.05)and isokinetic peak(r2=0.46-0.48,P<0.05)torques.Our results suggest that larger clinical trial is warranted to confirm the preliminary findings that muscle stiffness is altered after SCI compared to healthy controls.Stiffness appeared to be influenced by infiltration of intramuscular fat and modestly by the spasticity of the paralyzed muscles.The preliminary data indicated that the relationship between muscle stiffness and peak torque is not altered with changing the frequency of pulses or angular velocities.All study procedures were approved by the Institutional Review Board at the Hunter Holmes McGuire VA Medical Center,USA(IRB#:02314)on May 3,2017.

Experimental and Numerical Evaluation and Optimization of a Non Standard Pitot/Sampling Probe

An isokinetic sampling probe is designed and constructed to measure entrained liquid droplet fluxes in separated gasliquid pipe flows. This probe also has the capability of working as a non-standard Pitot tube when the sampling is stopped. CFD simulations using the commercial software Ansys CFX were carried out for single phase gas flow to analyze the non-standard design. Pitot tube velocity calculations and isokinetic sampling conditions were studied. The predicted results were compared against theoretical velocity profiles from the literature and with gas single phase experimental data acquired in a horizontal 49 m long steel pipeline with an internal diameter of 69 mm. The experiments were done by using a dense gas (SF6) at 7 bara. An asymmetry of the experimental velocity profiles reproduced with the numerical simulations. The CFD simulations made it possible to verify the design and predict and correct an installation problem.

Vitamin C Supplementation Reduces Exercise-Induced Oxidative Stress and Increases Peak Muscular Force

Vitamin C is a popular supplement in exercise and sport for its chemical properties i.e.v antioxidant capabilities. However, no clear role has been established for vitamin C supplementation (VCS) within these areas despite nearly a century’s worth of ongoing research. This study examined peak muscular pushing force (PMF) before and after a VCS intervention, 250 mg every 12 hrs for 28 days, in nine participants whom were naive to VCS and resistance exercise (RE). A dynamometer was used to perform two RE bouts, pre- and post-intervention, that quantified PMF during a state of exercise-induced oxidative stress (EI-OS). Saliva was collected for EIOS analysis from each participant before and after each RE bout;salivary vitamin C (VC) and free salivary malondialdehyde (MDA) were the examined biomarkers. PMF increased significantly post-intervention (405.48 ± 92.75 m·kg·s-2) from baseline (368.31 ± 76.36 m·kg·s-2, p < 0.05). MDA elevated significantly after the pre-intervention RE bout (0.385 ± 0.017 μg/mL) and the post-intervention RE bout (0.373 ± 0.014 μg/mL) compared to the baseline measures (0.373 ± 0.014 μg/mL, 0.359 ± 0.008 μg/mL;p < 0.01);a significant reduction in MDA was observed post-intervention, confirming vitamin C’s ability to reduce oxidative stress (p < 0.05). VC increased post-intervention (1.22 ± 0.73 μg/mL) from baseline (0.47 ± 0.51 μg/mL, p < 0.001). The results from this study suggest VCS is capable of increasing PMF by reducing EIOS in untrained individuals, and can be possibly used for enhancing resistance-exercise performance.

Optimization of an axial coarse powder separator for low-density lignite based on the optimal seeking method

As a major equipment for thermal power plants,the main function of coarse powder separators is to separate particles into size groups according to particle diameter.With the rising coal prices,power plants are using more low-density lignite.Consequently,the original equipment does not operate under normal conditions.Therefore,to return the equipment to normal operating conditions,the isokinetic sampling method,computational fluid dynamics(CFD),and discrete phase model(DPM)based on the Euler-Lagrange method are applied in this research to analyze the effect of baffle shapes,baffle numbers,and centrifugal blades on the equipment performance index,like R90.The shape of the baffle plate was optimized and improved.Preferential method was applied to determine the optimal number of baffles to ensure normal working conditions.Results show that curved baffles can suppress the axial negative gradient field below themselves better than rectangular baffles.The curved baffles selected by the optimal seeking method make full use of the negative axial gradient field and provide the particles entering the separation zone at tangential velocity in advance with the addition of centrifugal blades.Thus,pre-separation can be realized.The R90 is 5 at the separator outlet and 95 at the powder return port,indicating that the output capacity of the separator returned to a reasonable operating performance.

Training Effect of Isotonic Concentric and Eccentric Contraction of Elbow Flexors in Different Combinations

In order to determine a rational protocol for isotonic training from macroscopic angle, five training protocols were designed, particularly protocols composed of pure eccentric contraction with heavy resistance in different propotions. The study results indicated that the protocol mixed with faster speed eccentric training,being more rational than traditional isotonic training and pure isotonic eccentric training, had the most all - round effects(including change of musle size, isotonic strength, musle power and et al. ). The protocol principle mixed with faster speed eccentric training may be widely used in rehabilitation and sports training,especially in the sports events of strength resistance. The significance to study the ratio of eccentric contaction to concentic contraction was suggested.