Absolute and relative reliability of isokinetic and isometric trunk strength testing using the IsoMed-2000 dynamometer

Reproducibility of peak force for isometric and isokinetic multi-joint leg extension exercise

BACKGROUND

Isokinetic dynamometry is a common tool for evaluating muscle function and is used across various disciplines. Technical advancements have shifted focus towards multi-joint exercises such as the leg press, offering insights into practical human movement dynamics. However, previous reproducibility studies have focused predominantly on single-joint exercises, warranting investigations into the reliability of multi-joint exercises. This study aimed to assess the reproducibility of peak force (PF) during multi-joint leg press exercises using the IsoMed 2000 dynamometer.

METHODS

Thirty physically active subjects (mean: stature 179.4 cm; body mass 76.0 kg; age 30.6 years) participated in three testing sessions. Each session consisted of isometric and isokinetic leg press exercises. Knee angles for isometric exercises included 100° and 140°; velocities for isokinetic exercise included 30 mm/s and 600 mm/s. The first session served as the familiarization session. Statistical analysis included paired sample t-tests, Cohen's d effect sizes, intraclass correlation coefficients (ICC), standard errors of measurement (SEM), and Bland-Altman calculations, including corresponding plots.

RESULTS

Descriptive data revealed consistent PF across sessions, with a significant between-sessions difference observed only for isometric (100°) leg extension in the right leg (p < 0.001; d = 0.13). ICC calculations showed high relative reproducibility (ICC > 0.911), with SEM ranging from 37.6 to 294.7 N (SEM% 2.3-6.3%, respectively). Bland-Altman plots depicted minimal intersession disparities (-141.8-68.3 N, respectively - 3.02-1.26%), supporting high reliability.

CONCLUSIONS

This study highlights the reliability of assessing peak force during isometric and isokinetic leg press exercises using the IsoMed 2000 after a single familiarization session. These findings support its utility in muscular performance evaluation, urging practitioners to incorporate familiarization trials for accurate assessments.

Peak hip external rotation torque and single-rater reliability is influenced by measurement position in the ISOMED2000

Measurement of hip external rotation strength (ERS) is important for preventive and rehabilitative purposes. ERS can be measured in 3 different positions in the isokinetic dynamometer ISOMED2000. However, it is not clear whether these measurement positions effect ERS nor if these positions are reliable in the ISOMED2000. Hence, the purpose of this study was to compare ERS in these positions, the reliability and the agreement. A cross-sectional design was conducted to compare measurement positions and a test-retest design to assess intra-rater reliability and agreement. Twenty-four healthy, physically active athletes participated in the study. Peak isometric torque was measured in the ISOMED in prone, supine, and side-lying position across two sessions on one day. Differences between positions were evaluated with the Wilcoxon-signed-rank test and cliff's delta. Reliability was assessed via intraclass correlation. Agreement was determined using the standard error of measurement (SEM), minimal detectable change (MDC), and Bland-Altman analysis (BAA). Results indicated a significant influence of measurement position on ERS (p < 0.001) with high effect sizes (>0.74). Reliability and agreement were high in all positions, but highest for the side-lying position (ICC = 0.90 [0.78, 0.96]; SEM = 0.08; MDC = 0.23; BAA_bias = 3.4 %, BAA_loA = 37 %). There were only poor to moderate correlations between measurement positions. These findings suggest that measurement position significantly affects ERS. Furthermore, the effect varies across individuals indicating that normative values cannot be used interchangeably or be adapted across positions. In diagnostic testing ERS should be measured in the same position, but preferably in the side-lying position.

Intra-session reliability of isometric muscle strength of the bilateral standing press in female handball players

Background

Systematizing reliable protocols and procedures for strength assessment in handball has allowed for a more thorough kinetic analysis and increased precision in detecting training-induced changes in muscular strength. The evaluation of upper limb strength with a bilateral standing press (BSP) exercise in handball players approximates blocking actions in the defensive phase, pushing and fixation.

Aim

The aim of this study was to analyze the relative and absolute reliability of intra-session comparisons in an isometric peak muscle strength protocol in a bilateral standing press (BSP) exercise among female handball players.

Methods

Sixteen young female handball players at an international level, aged between 22 ± 4 years, with no prior experience in using functional electromechanical dynamometers (FEMD) participated in this study. The participants initiated the assessment of maximum isometric force in a bipedal stance with a forward projection of the dominant foot between 20 and 30 cm. The knees were kept semi-flexed, and the hip extension of the non-dominant limb ranged from 15 to 20°. Bilateral anterior push of the upper limb was performed with shoulder abduction and elbow flexion at 90°, maintaining a pronated hand position. Participants were instructed to exert three sets of maximal force for 5 s in BSP exercise. Relative reliability was assessed using the model intraclass correlation (ICC) and absolute reliability was assessed using the coefficient of variation (CV) and standard error of measurement (SEM). For this study, the parameters of maximum and mean muscle strength were considered.

Results

The results demonstrated high relative reliability (ICC 0.93-0.97) and absolute reliability (SEM 0.19-2.79) y (CV 4.78-9.03) for both mean force and peak force, with no significant differences between the sets (p > 0.05), indicating a negligible effect size (0.01-0.12).

Conclusion

The mean and peak isometric muscle strength for the BSP exercise controlled with FEMD in female handball players exhibits high relative and absolute reliability between series.

Research on design and control methods of a lightweight upper limb joint isokinetic rehabilitation training equipment

Introduction

Isokinetic exercise can improve joint muscle strength and stability, making it suitable for early rehabilitation of stroke patients. However, traditional isokinetic equipment is bulky and costly, and cannot effectively avoid external environmental interference.

Methods

This paper designed a lightweight upper limb joint isokinetic rehabilitation training equipment, with a control system that includes a speed planning strategy and speed control with disturbance rejection. Based on the established human-machine kinematic closed-loop model between the equipment and the user, a dynamic evaluation method of torque at the joint level was proposed.

Results

To validate the effectiveness of the equipment, experiments were conducted by manually applying random disturbances to the equipment operated at an isokinetic speed. The results showed that the root mean square error between the observed torque curve of the second-order linear extended state observer used in this paper and the actual disturbance curve was 0.52, and the maximum speed tracking error of the speed control algorithm was 1.27%. In fast and slow sinusoidal speed curve tracking experiments, the root mean square errors of the speed tracking results for this algorithm were 9.65 and 5.27, respectively, while the tracking errors for the PID speed control algorithm under the same environment were 19.94 and 12.11.

Discussion

The research results indicate that compared with traditional PID control method, the proposed control strategy demonstrates superior performance in achieving isokinetic control and suppressing external disturbances, thereby exhibiting significant potential in promoting upper limb rehabilitation among patients.

[Isokinetic strength testing with different biomechanical demands on core strength: a comparison of military competitive athletes and soldiers with high occupational physical strain]

It is known that anthropometric data (weight, height, BMI, waist circumference and WHtR) and male gender are positively correlated with greater core strength, while age is negatively correlated. For competitive athletes with no significant differences in the anthropometric data stated above, there have hardly been any studies in which isometric core strength in a seated position is quantitatively compared among athletes in different sports. This study aimed to analyse different sports in well-trained athletes using military competitive sports as an example with regard to possible differences in core strength. For this purpose, Parachuting (n=28), Military Pentathlon (n=34) and Ski Platoon (n=38) groups were compared with regard to isokinetic core strength using dynamometry in seated position. In addition to the comparison of anthropometry and isokinetic results with descriptive statistics, ANOVA and Welch-ANOVA were used to compare the means of absolute and weight-adjusted core strength. It was shown that the Ski Platoon group had significantly higher flexion peak torque values than the Military Pentathlon and Parachuting groups. Even when adjusted for weight, the values were significantly higher than those measured in the Military Pentathlon group but not significantly higher than those in the Parachuting group. For extension peak torque, it was found that the Military Pentathlon group had significantly lower values than the Ski Platoon group and, in the weight-adjusted analysis, significantly lower values than the Parachuters. Using the example of competitive military sports, this study was able to show that there are significant differences in isokinetic core strength even among professional competitive athletes.This knowledge should be used to carry out detailed quantitative analyses of core strength, even in well-trained professional athletes, to find applications for prevention or to coordinate compensating exercises.

Physiological Profiles of Male and Female CrossFit Athletes

OBJECTIVE

To (1) establish extensive physiological profiles of highly trained CrossFit® athletes using gold-standard tests and (2) investigate which physiological markers best correlate with CrossFit Open performance.

METHODS

This study encompassed 60 participants (30 men and 30 women), all within the top 5% of the CrossFit Open, including 7 CrossFit semifinalists and 3 CrossFit Games finalists. Isokinetic dynamometers were employed to measure maximum isometric and isokinetic leg and trunk strength. Countermovement-jump height and maximum isometric midthigh-pull strength were assessed on a force plate. Peak oxygen uptake (VO2peak) was measured by a cardiopulmonary exercise test, and critical power and W' were evaluated during a 3-minute all-out test, both on a cycle ergometer.

RESULTS

Male and female athletes' median (interquartile range) VO2peak was 4.64 (4.43, 4.80) and 3.21 (3.10, 3.29) L·min-1, critical power 314.5 (285.9, 343.6) and 221.3 (200.9, 238.9) W, and midthigh pull 3158 (2690, 3462) and 2035 (1728, 2347) N. Linear-regression analysis showed strong evidence for associations between different anthropometric variables and CrossFit Open performance in men and women, whereas for markers of cardiorespiratory fitness such as VO2peak, this was only true for women but not men. Conventional laboratory evaluations of strength, however, manifested minimal evidence for associations with CrossFit Open performance across both sexes.

CONCLUSIONS

This study provides the first detailed insights into the physiology of high-performing CrossFit athletes and informs training optimization. Furthermore, the results emphasize the advantage of athletes with shorter limbs and suggest potential modifications to CrossFit Open workout designs to level the playing field for athletes across different anthropometric characteristics.

Reproducibility of peak moment for isometric and isokinetic knee extension exercise

BACKGROUND

Accurate measurements of muscular performance are important for diagnostics, for example during rehabilitation after traumatic injuries but also in competitive sports. For these purposes, dynamometric devices are widely used and considered the gold standard for muscle strength testing. However, few previous studies have tested the reproducibility of peak moment (PM) at velocities close to the maximum device capability, and in general, reproducibility results cannot be transferred to other devices or test protocols. The purpose of this study was to evaluate the reproducibility of PM for different isometric and isokinetic knee extension exercises using the IsoMed 2000.

METHODS

Thirty subjects volunteered in three repeated test sessions, including isometric knee extension (100° and 140° knee angle) and isokinetic knee extension (30°/s and 400°/s). Statistical analysis for comparison of sessions two and three included paired sample t-test, calculation of intraclass correlation coefficient (ICC) and standard error of measurement (SEM). Additionally, Bland Altman statistics and corresponding plots were created.

RESULTS

A significant difference between sessions in PM was found for isometric knee extension in one leg (140° left). Reproducibility was high for all conditions with ICC ranging from 0.964 to 0.988 and SEM in the range of 7.6 to 10.5 Nm. Bland Altman statistics revealed a bias between - 7.3 and 0.7 Nm.

CONCLUSIONS

Reproducibility of PM using the IsoMed 2000 was good after an initial familiarization trial with high values of relative reproducibility. Absolute reproducibility can be interpreted as appropriate for most common practical applications.

Comprehensive Physical Work Capacity Evaluations for Korean Farmers Assessed in Healthy Volunteers

OBJECTIVE

To establish the lower limits of normative values of the physical work capacity for Korean farmers in healthy working individual.

METHODS

We developed a comprehensive set of physical work capacity evaluation items that encompass common farming tasks. These items include measurements of trunk flexion/extension angles, strength (hand grip, trunk flexion/extension, leg/back lifting, and pushing/pulling), and positional tolerances. We calculated the normative values for the items and defined the normal range in 124 healthy volunteers aged 20-79 years. We calculated the intraclass correlation coefficient (ICC) to validate the test-retest reliability of the measurements protocol.

RESULTS

The normal values for each measurement item were as follows: trunk flexion and extension angle (65.3°±11.6° and 29.6°±6.6°), dominant hand grip strength (32.2±10.5 kgf), trunk flexion and extension strength (288.4±119.0 N and 297.3±129.9 N), leg and back lifting strength (452.9±233.5 N and 349.2±166.7 N), pushing and pulling strength (214.7±75.1 N and 221.7±63.3 N), and positional tolerance time (squat: 76.8±9.0 seconds, front: 73.8±7.7 seconds, twist: 82.2±8.8 seconds, upward: 71.9±11.3 seconds). Regarding test-retest reliability, all strength measurements demonstrated excellent absolute agreement (ICC, 0.91-0.96). However, positional tolerance showed poor-to-moderate absolute agreement (ICC, 0.37-0.58).

CONCLUSION

We conducted measurements of muscle strength and positional tolerance in healthy participants of various ages, focusing on tasks commonly performed by Korean farmers. The outcomes hold significant value as they offer a pertinent instrument for assessing the appropriateness of workers, thereby carrying implications for rehabilitation objectives, legal evaluations, and work capacity assessments within the agricultural domain.

Contribution of different strength determinants on distinct phases of Olympic rowing performance in adolescent athletes

Aerobic metabolism dominates Olympic rowing, but research on the relative contribution of strength and power demands is limited. This study aimed to identify the contribution of different strength determinants for distinct phases of rowing ergometer performance. The cross-sectional analysis comprised of 14 rowing athletes (4 female, 10 male, age: 18.8 ± 3.0y, 16.9 ± 2.2y). Measurements included anthropometrics, maximal strength of leg press, trunk extension and flexion, mid-thigh pull (MTP) and handgrip strength, VO2max, and a 2000 m time trial, where peak forces at the start, middle and end phase were assessed. Additionally, rate of force development (RFD) was assessed during the isometric leg press and MTP with intervals of 150, 350 ms and 150, 300 ms, respectively. Stepwise regression models for ergometer performance showed that the start phase was mainly explained by maximal trunk extension and RFD 300 ms of MTP (R2 = 0.91, p < 0.001) and the middle section by VO2max, maximal leg press strength and sitting height (R2 = 0.84, p < 0.001). For the end phase, a best fit was observed for trunk flexion, RFD 350 ms of leg press, body height and sex (R2 = 0.97 p < 0.001), whereas absolute VO2max, trunk flexion and sex explained variance over the entire 2000 m time trial (R2 = 0.98, p < 0.001). It appears that for the high acceleration in the start phase, force transmission through maximum strength for trunk extension is essential, while fast power production along the kinetic chain is also relevant. Additionally, the results support that maximal force complements the reliance on VO2max. Further intervention studies are needed to refine training recommendations.

Comparing the effect of intermittent blood flow restriction training and high-load resistance training in patients with patellofemoral pain: study protocol for a randomised trial

BACKGROUND

Patellofemoral pain (PFP) syndrome is a common knee joint functional disorder. Blood flow restriction (BFR) training has shown promise in improving PFP; however, the effectiveness of intermittent BFR (iBFR) training remains uncertain. This study aims to compare the rehabilitative effects of iBFR combined with low-load resistance training and high-load resistance training in PFP patients and to assess the effectiveness of iBFR combined with low-load resistance training for improving PFP.

METHODS AND ANALYSIS

This randomised, patient-assessor blinded, controlled trial will include 42 eligible PFP patients randomly allocated to an intervention group (iBFR combined with low-load resistance training) or a control group (high-load resistance training) in a 1:1 ratio. Participants will receive interventions three times per week for 8 weeks and will be followed up for 24 weeks. The primary outcome measure is pain, and the secondary outcomes include self-reported function, quality of life, muscle strength and muscle thickness. Assessments will be conducted at baseline, 8 weeks and 24 weeks during follow-up. Intention-to-treat analysis will be performed.Collectively, we expect that the findings of this randomised clinical trial will contribute to understanding the potential benefits of iBFR training and provide insightful guidance for developing more effective treatment strategies for patients with PFP.

ETHICS AND DISSEMINATION

This study was approved by the Sports Science Experiment Ethics Committee of Beijing Sport University (2022274H). Written informed consent will be obtained from all participants. Trial results will be disseminated through peer-reviewed publications.

TRIAL REGISTRATION NUMBER

Chinese Clinical Trial Registry (ChiCTR2300068281).

Which trunk muscle parameter is the best predictor for physical function in older adults?

Background

Despite preliminary evidence demonstrating the relevance of trunk muscle strength for physical function in older adults, it is not clear which muscle-related trunk parameter is the best predictor for physical functions. Therefore, this study aimed to compare trunk muscle morphology or strength parameters regarding their predictive ability for physical functions.

Methods

Seventy-four older adults (38 men, 36 women, mean age 76.85 years) were tested for maximum absolute and relative isokinetic trunk flexion and extension strength, trunk lean mass, and trunk muscle quality. Functional assessment included normal and fast walking speed, repeated sit-to-stand transfer, timed up and go, and postural sway during a closed-feet and a semi-tandem stance adjusted for body height. Pearson's correlations were used to compare relationship between trunk strength adjusted and unadjusted for body weight to physical functions. Linear regression analysis including sex and age as co-variables was performed between trunk muscle and functional test parameters.

Results

Relative back extension strength was the most consistent significant predictor for all physical function tests (p = 0.004-0.04) except for postural sway. Relative trunk flexion strength was related to normal walking speed (p = 0.024). Trunk lean mass was related to timed up and go performance (p = 0.024).

Conclusion

Relative back extension strength is associated with better performance in nearly all standard tests for physical function in older adults, while trunk flexion strength and lean mass seem to play a minor role. Our findings emphasize the importance of trunk muscle strength, especially the back extensor muscles, for physical function in older adults.

Isokinetic strength assessment of trunk muscle and its relationship with spinal-pelvic parameters in patients with degenerative spinal deformity

BACKGROUND

The incidence rate of degenerative spinal deformity (DSD) has gradually increased in the elderly. Currently, the relationship between the functional status of trunk muscle and the spinal-pelvic parameters of DSD patients remains unclear.

OBJECTIVE

This paper aims to explore the relationship between the two factors and provide new clues for exploring the mechanism of the occurrence and development of DSD.

METHODS

A total of 41 DSD patients treated in our hospital (DSD group) and 35 healthy volunteers (control group) were selected. Muscle strength was evaluated using an IsoMed-2000 isokinetic dynamometer, and the trunk flexor and extensor peak torque (PT) of subjects was measured at a low, medium, and high angular velocity of 30∘/s, 60∘/s, and 120∘/s, respectively. Hand grip strength (HGS) was assessed using an electronic grip dynamometer and Surgimap software was used to measure the spinal-pelvic parameters, including the sagittal vertical axis (SVA), thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence rate (PI), and PI-LL, and the relationship between trunk muscle function and various parameters was analyzed.

RESULTS

Under the three angular velocities, the flexor and extensor PT values in the DSD group were lower than those in the control group, and only the extensor PT showed a statistically significant difference (P< 0.05). There was no significant difference in HGS between the two groups (P> 0.05). In the DSD group, the extensor PT at 30∘/s was significantly negatively correlated with SVA (P< 0.05). At 60∘/s and 120∘/s, the extensor PT was significantly negatively correlated with SVA and PT (P< 0.05).

CONCLUSION

Trunk extensor strength is significantly lower in DSD patients than in normal controls. The decline in trunk extensor strength in DSD patients is a type of local muscle dysfunction more closely related to the deformity, which is likely involved in the compensatory mechanism of DSD and may reflect the overall imbalance of the trunk.

Estimation of One-Repetition Maximum, Type, and Repetition of Resistance Band Exercise Using RGB Camera and Inertial Measurement Unit Sensors

Resistance bands are widely used nowadays to enhance muscle strength due to their high portability, but the relationship between resistance band workouts and conventional dumbbell weight training is still unclear. Thus, this study suggests a convolutional neural network model that identifies the type of band workout and counts the number of repetitions and a regression model that deduces the band force that corresponds to the one-repetition maximum. Thirty subjects performed five different exercises using resistance bands and dumbbells. Joint movements during each exercise were collected using a camera and an inertial measurement unit. By using different types of input data, several models were created and compared. As a result, the accuracy of the convolutional neural network model using inertial measurement units and joint position is 98.83%. The mean absolute error of the repetition counting algorithm ranges from 0.88 (seated row) to 3.21 (overhead triceps extension). Lastly, the values of adjusted r-square for the 5 exercises are 0.8415 (chest press), 0.9202 (shoulder press), 0.8429 (seated row), 0.8778 (biceps curl), and 0.9232 (overhead triceps extension). In conclusion, the model using 10-channel inertial measurement unit data and joint position data has the best accuracy. However, the model needs to improve the inaccuracies resulting from non-linear movements and one-time performance.

Correlations of strength, proprioception, and tactile sensation to return-to-sports readiness among patients with anterior cruciate ligament reconstruction

Objectives: Anterior cruciate ligament reconstruction (ACLR) is the most common surgery for anterior cruciate ligament (ACL) injuries, and the relationships between patients' return to sports (RTS) readiness and different physical functions are inconclusive among patients with ACLR. This study aimed to investigate the correlations of strength, proprioception, and tactile sensation to the RTS readiness among patients with ACLR. Methods: Forty-two participants who received ACLR for at least 6 months were enrolled in this study. Their strength, proprioception, and tactile sensation were tested, and their RTS readiness was measured with the Knee Santy Athletic Return to Sports (K-STARTS) test, which consists of a psychological scale [Anterior Cruciate Ligament Return to Sports after Injury scale (ACL-RSI)] and seven functional tests. Partial correlations were used to determine their correlations while controlling for covariates (age, height, weight, and postoperative duration), and factor analysis and multivariable linear regressions were used to determine the degrees of correlation. Results: Knee extension strength was moderately correlated with K-STARTS total, ACL-RSI, and functional scores. Knee flexion strength, knee flexion and extension proprioception, and tactile sensation at the fifth metatarsal were moderately correlated with K-STARTS total and functional scores. Strength has higher levels of correlation with functional scores than proprioception. Conclusion: Rehabilitation to promote muscle strength, proprioception and tactile sensation should be performed among patients with ACLR, muscle strength has the highest priority, followed by proprioception, with tactile sensation making the least contribution.

What are the optimum training parameters of progressive resistance exercise for changes in muscle function, activity and participation in people with cerebral palsy? A systematic review and meta-regression

OBJECTIVES

To explore the effect of progressive resistance exercise (PRE) on impairment, activity and participation of people with cerebral palsy (CP). Also, to determine which programme parameters provide the most beneficial effects.

DATA SOURCES

Electronic databases searched from the earliest available time.

ELIGIBILITY CRITERIA

Randomised controlled trials (RCTs) implementing PRE as an intervention in people with cerebral palsy were included.

STUDIES APPRAISAL & SYNTHESIS METHODS

Methodological quality of trials was assessed with the PEDro scale. Meta-analysis and meta-regression were completed.

RESULTS

We included 20 reports of 16 RCTs (n = 504 participants). Results demonstrated low certainty evidence that PRE improved muscle strength (pooled standardised mean difference (SMD)= 0.59 (95%CI: 0.16-1.01; I²=70%). This increase in muscle strength was maintained an average of 11 weeks after training stopped. Τhere was also moderate certainty evidence that it is inconclusive whether PRE has a small effect on gross motor function (SMD= 0.14 (95%CI: -0.09 to 0.36; I²=0%) or participation (SMD= 0.26 (95%CIs: -0.02 to 0.54; I²=0%). When PRE was compared with other therapy there were no between-group differences. Meta-regression demonstrated no effect of PRE intensity or training volume (frequency x total duration) on muscle strength (p > 0.5). No serious adverse events were reported. There is lack of evidence of the effectiveness of PRE in adults and non-ambulatory people with CP.

CONCLUSIONS

PRE is safe and increases muscle strength in young people with CP, which is maintained after training stops. The increase in muscle strength is unrelated to the PRE intensity or dose. CONTRIBUTION OF THE PAPER.

Reliability of trunk strength measurements with an isokinetic dynamometer in non-specific low back pain patients: A systematic review

BACKGROUND

Imbalance or decreased trunk strength has been associated with non-specific low back pain (NSLBP).

OBJECTIVE

This systematic review aimed (I) to evaluate the quality of evidence of studies evaluating the reliability of trunk strength assessment with an isokinetic dynamometer in NSLBP patients, (II) to examine the reliability of trunk strength assessment using an isokinetic dynamometer in NSLBP patients and (III) to determine the most reliable protocol for trunk strength assessment in NSLBP patients.

METHOD

PRISMA guidelines were followed. Three databases were used: PubMed, Scopus, and Web of Science with the following keywords: Isokinetic, Dynamometer, Trunk strength testing, Muscle testing, Isokinetic measurement, CORE, Abdominal muscles, Abdominal wall, Torso, Trunk, Spine, Reliability and, Reproducibility. We included only test-retest studies, focused on the reliability of isometric and isokinetic strength assessed with an isokinetic dynamometer in NSLBP adults' patients, published in English and from inception to March 30, 2021. The methodological quality was evaluated with the CAT scale and QAREL checklist.

RESULTS

Five hundred and seventy-seven articles were retrieved, of which five are included in this review. Three articles provide good quality of evidence, the reliability of trunk strength assessment in NSLBP patients is excellent, and the most reliable protocol for isometric assessment is in a seated position (ICC = 0.94-0.98) and for isokinetic strength in standing position, at 60∘/s and 120∘/s (ICC = 0.98).

CONCLUSION

There is good quality evidence regarding the trunk strength assessment's reliability. Reliability is excellent in NSLBP patients; however, a familiarization process should be considered to obtain clinically reliable data. The most reliable protocol is in a seated position for isometric strength and a standing position for isokinetic strength.

Verification of Shoulder External Rotators Strength Measurement Using a Suspension Scale

Background

Of the shoulder external rotators, the infraspinatus and teres minor are the key muscles that contribute to the dynamic stability of the shoulder. It is crucial to properly measure the strength values to evaluate muscle function and training load for shoulder external rotators. A suspension scale (SPS) can measure the mass of the suspended object, and it may be possible to apply it to measure strength. However, the utility of strength measurements using an SPS has not been clarified in previous studies. In this study, we aimed to investigate the intra-rater reliability of measuring the strength of shoulder external rotators using an SPS and the relationship between strength measurement using an SPS and a handheld dynamometer (HHD).

Methodology

The participants were 10 healthy males with 20 shoulders (24.5 ± 2.5 years old; height = 172.8 ± 5.4 cm; weight = 69.6 ± 8.1 kg). Upper extremity strength was measured at 90° shoulder abduction, 90° external rotation, 0° horizontal adduction/abduction, 90° elbow flexion, and 0° forearm pronation/supination in the prone position. The isometric strength of shoulder external rotation was measured with the SPS and HHD, and one examiner measured the maximum strength value. The intra-rater reliability of the two methods using SPS and HHD was evaluated using the intraclass correlation coefficient (ICC_1,2), standard error of measurement (SEM), minimum detectable change (MDC), and Bland-Altman analysis. The relationship between the SPS and HHD was calculated as the correlation coefficient between the strength values of SPS and HHD.

Results

The intra-rater reliability of the strength measurement of shoulder external rotators using SPS was ICC_1,2 0.98 (95% confidence interval = 0.95-0.99), and SEM and MDC were 0.3 and 0.9, respectively. The measurements using SPS had no fixed and proportional biases. A significant positive correlation was observed between SPS and HHD (r = 0.94, p < 0.01).

Conclusions

The SPS is an alternative to the HHD for measuring the strength of shoulder external rotators. Thus, measuring the strength of shoulder external rotators using an SPS may be applied as a cost-effective and portable assessment method for shoulder function.

Practicable performance-based outcome measures of trunk muscle strength and their measurement properties: A systematic review and narrative synthesis

Introduction

The evaluation of muscle strength is frequently used as part of the physical examination process, with decreased trunk muscle strength reported in individuals with spinal disorders (e.g., low back pain). Access to practicable performance-based outcome measures (PBOM) to monitor patients’ progress in spinal rehabilitation is essential. Knowledge of the psychometric properties of the available practicable PBOM for trunk strength evaluation is therefore needed to inform practitioners and further research.

Objective

To synthesise evidence on the measurement properties of practicable measures of trunk muscle strength in adults with and without musculoskeletal pain.

Methods

Following a published and registered protocol [PROSPERO CRD42020167464], databases were searched from the database inception date up to 30th of June 2021. Citations and grey literature were also searched. Eligibility criteria comprised: 1) studies which examined the psychometric properties of the trunk strength outcome measures, 2) included adults ≥ 18 years, either asymptomatic or with spinal musculoskeletal pain. Non-English language studies were excluded. Two independent reviewers evaluated the quality and synthesized the data from included studies according to the COnsensus-based Standards for the selection of health Measurement Instruments (COSMIN) checklist. The overall quality of evidence was evaluated using a modified Grading of Recommendations Assessment Development and Evaluation (GRADE).

Results

From 34 included studies, 15 different PBOMs were identified that have been investigated for reliability and validity, none evaluated responsiveness. In asymptomatic individuals, high quality evidence supports intra-rater reliability of digital-loading cells and moderate quality evidence supports the criterion validity of the hand-held dynamometer. Very low quality evidence exists for the reliability and validity estimates of testing tools among individuals with spinal pain.

Conclusions

Findings underpin a cautious recommendation for the use of practicable PROMs to evaluate muscle strength in individuals with spinal pain in clinical practice due to the level of evidence and the heterogeneity of the protocols used. Further high quality research to explore the psychometric properties of the practicable PBOMs with detailed methodology is now needed.

Hamstring and ACL injuries impacts on hamstring-to-quadriceps ratio of the elite soccer players: A retrospective study

This study aimed to compare the angle-specific (AS) and non-angle-specific (NAS) hamstring to quadriceps conventional and functional ratios between healthy, hamstring- and ACL-injured elite soccer players. One hundred and eleven players (27.42 ± 8.01 years, 182.11 ± 6.79 cm, 75.93 ± 7.25 kg) completed a series of concentric knee flexor and extensor strength in addition to eccentric knee flexor strength was measured at an angular velocity of 60°.s^-1. Normalized and raw peak torque values, and the torque-angle profiles were extracted for analysis. Conventional and functional NAS (peak values) and AS (waveform ratios) hamstring to quadriceps ratios were calculated and compared between the groups. Healthy players produced greater functional and conventional ratios compared to players with either ACL or hamstring injury. Players with hamstring injury produced a lower AS functional ratios between 46° and 54° of knee flexion. Players suffering from ACL injury depicted a lower value for the AS functional ratio between 33° and 56° of knee flexion. Although NAS can identify soccer players with previous hamstring or ACL injury, the range where there is a strength deficiency is eluded. With the use of AS the range where the deficiency is present can be identified, and clinicians can benefit from this analysis to design robust rehabilitation protocols.

Isokinetic trunk muscle performance in adolescents with different body mass indices

Objective

This study aims to evaluate the isokinetic performance for the peak torque and average power of the spinal flexor and extensor muscles in adolescents aged 12 to 18 years. The study also analyses the differences between the trunk muscle peak torque and average power with body mass index (BMI).

Method

The peak torque and average power of the trunk flexor and extensor muscles were measured in 180 adolescents (aged 12–18 years). The participants were classified into four groups according to BMI. The Biodex isokinetic dynamometer in concentric mode at speeds of 60° and 120°/sec was used for assessment.

Results

One-way multivariate analysis of variance MANOVA results demonstrated a significant difference in trunk muscle peak torque and average power with different BMI (F = 14.692, p = 0.0005). A Pearson's correlation analysis demonstrated a significantly negative correlation between weight and peak torque of trunk flexors and extensors (r = - 0.43, p = 0.0001; r = −0.31, p = 0.007, respectively). Finally, the results showed a negative correlation between weight and average power of trunk flexors and extensors (r = −0.54, p = 0.0001; r = −0.31, p = 0.007).

Conclusion

In this study, overweight and obese adolescents are found to be correlated with decreased trunk muscle torque and power. Thus, therapeutic interventions for overweight and obese adolescents, along with exercise training programmes, may help improve muscle performance including peak torque and power. Finally, these measures may enhance the quality of life of such adolescents.

Acute Leg and Trunk Muscle Fatigue Differentially Affect Strength, Sprint, Agility, and Balance in Young Adults

ABSTRACT

Roth, R, Donath, L, Zahner, L, and Faude, O. Acute leg and trunk muscle fatigue differentially affect strength, sprint, agility, and balance in young adults. J Strength Cond Res 35(8): 2158-2164, 2021-How important leg or trunk muscles are for balance and sprint performance is still unexplored. Therefore, we separately fatigued the leg and trunk musculature and examined their contribution to strength, balance, sprint, and agility performance. Twenty-four healthy adults (12 women; age 22.9 [SD: 2.6] years; body mass 59 [10] kg; height 1.65 [0.09] m; and 12 men; age 22.7 [3.0] years; body mass 78 [9] kg; height 1.81 [0.06] m; at least 3 training sessions/week for at least 90 minutes) underwent a leg and a trunk fatigue procedure, each of 20-minute duration and a control condition at rest in a randomized order. Each condition was conducted individually on 3 separate days. Isokinetic leg and trunk strength, as well as static and dynamic balance, sprint, agility, and prone plank endurance, were assessed before and after each fatiguing protocol. Before assessment, a familiarization was conducted. Pairwise magnitude-based inference analyses showed likely relevant deterioration in leg (probability >87%; 0.36 < standardized mean differences [SMDs] < 0.92) and trunk (>88%, 0.28 < SMD < 0.74) fatigue procedures for all motor test parameters compared with the control condition, except for the 20-m sprint after the trunk fatigue procedure. Isokinetic strength testing revealed a large loss of strength in leg fatigue (particularly knee extension, 78%, SMD = 0.24) and trunk fatigue (trunk flexion, 100%, SMD = 1.36). Acute fatigue of leg and trunk muscles decreases performance in relevant measures of strength, balance, sprint, and agility. The impact of leg fatigue compared with trunk fatigue was larger in almost all measurements.

Adaptive Force and emotionally related imaginations - preliminary results suggest a reduction of the maximal holding capacity as reaction to disgusting food imagination

The link between emotions and motor control has been discussed for years. The measurement of the Adaptive Force (AF) provides the possibility to get insights into the adaptive control of the neuromuscular system in reaction to external forces. It was hypothesized that the holding isometric AF is especially vulnerable to disturbing inputs. Here, the behavior of the AF under the influence of positive (tasty) vs. negative (disgusting) food imaginations was investigated. The AF was examined in n = 12 cases using an objectified manual muscle test of the hip flexors, elbow flexors or pectoralis major muscle, performed by one of two experienced testers while the participants imagined their most tasty or most disgusting food. The reaction force and the limb position were measured by a handheld device. While the slope of force rises and the maximal AF did not differ significantly between tasty and disgusting imaginations (p > 0.05), the maximal isometric AF was significantly lower and the AF at the onset of oscillations was significantly higher under disgusting vs. tasty imaginations (both p = 0.001). A proper length tension control of muscles seems to be a crucial functional parameter of the neuromuscular system which can be impaired instantaneously by emotionally related negative imaginations. This might be a potential approach to evaluate somatic reactions to emotions.

Residual force enhancement in humans: Is there a true non-responder?

When an active muscle is stretched and kept isometrically active, the resulting force is enhanced compared to a purely isometric reference contraction at the same muscle length and activity; a generally accepted muscle property called residual force enhancement (rFE). Interestingly, studies on voluntary muscle action regularly identify a significant number of participants not showing rFE. Therefore, the aim was to unmask possible confounders for this non-responsive behavior. Ten participants performed maximum voluntary isometric plantarflexion contractions with and without preceding stretch. Contractions were accompanied by the assessment of voluntary activation using the twitch-interpolation technique. The same test protocol was repeated four additional times with a least on day rest in-between. Additionally, at the first and fifth sessions, a submaximal tetanic muscle-stimulation condition was added. At both muscle-stimulation sessions mean rFE higher 10% (p < 0.028) was found. In contrast, during voluntary muscle action, individual participants showed inconsistent rFE across sessions and only one session (#3) had significant rFE (5%; p = 0.023) in group means. As all participants clearly had rFE in electrical stimulation conditions, structural deficits cannot explain the missing rFE in voluntary muscle action. However, we also did not find variability in voluntary activation levels or muscle activity as the confounding characteristics of "non-responders."

Isometric and isokinetic muscle strength measurements of the lumbar flexors and extensors with BioniX Sim3 Pro in patients with chronic low back pain: A pilot study

BACKGROUND

The World Health Organization states that low back pain is the leading cause for disability worldwide. Patients with chronic low back pain (CLBP) show important decreases in lumbar strength and can now be assessed by using the new isokinetic dynamometer BioniX Sim3 Pro which offers very detailed measurements.

OBJECTIVE

To compare lumbar flexion and extension strength values, as well as extension-flexion ratio (EFR) based on isokinetic velocity and gender, for patients with CLBP on the BioniX Sim3 Pro.

METHODS

A retrospective analysis was performed on data from 20 men and 22 women with CLBP. Maximum torque in flexion and extension was measured isometrically and isokinetically. Statistical analysis was performed on these parameters.

RESULTS

EFR shows a downward trend with increasing speed of measurement (isometric to isokinetic 30∘/s and isokinetic 30∘/s to isokinetic 90∘/s, respectively): in men from 1.21 to 1.04 (p< 0.001) and from 1.04 to 0.93 (p= 0.207). In women, EFR decreased from 1.41 to 1.13 (p< 0.001) and from 1.13 to 1.00 (p= 0.144).

CONCLUSIONS

Patients with CLBP have a decreased strength in lumbar extension and flexion compared to the age-corrected normal values of Bionix Sim3 Pro. With increasing speed of testing protocol, a decrease in EFR is observed in this population.

Age-Related Changes in Concentric and Eccentric Isokinetic Peak Torque of the Trunk Muscles in Healthy Older Versus Younger Men

This study investigated age-related changes in trunk muscle function in healthy men and the moderating effect of physical activity. Twelve older (67.3 ± 6.0 years) and 12 younger (24.7 ± 3.1 years) men performed isokinetic trunk flexion and extension tests across a range of angular velocities (15°/s-180°/s) and contractile modes (concentric and eccentric). For concentric trunk extension, mixed-effects analysis of covariance revealed a significant interaction between Angular velocity × Age group (p = .026) controlling for physical activity. Follow-up univariate analysis of covariance revealed that the younger group produced significantly greater peak torque for all concentric extension conditions. Eccentric trunk strength was somewhat preserved in the older group. Age-related changes in trunk strength were independent of physical activity. The normal loss of trunk muscle strength in older age is muscle- and contractile-mode specific. These findings provide guidance for effective intervention strategies to offset adverse health outcomes related to trunk strength loss in older adults.

Intrasession and Intersession Reliability of Isometric Trunk and Hip Strength Measurements Using the Portable Tension Dynamometer

CONTEXT

The trunk/pelvis is an important link between the upper- and lower-extremities. Therefore, assessing strength of the trunk and hip muscles that control the segments is clinically meaningful. While an isokinetic dynamometer can be used to measure trunk strength, the equipment is expensive and not portable.

OBJECTIVE

To test the reliability of simple trunk and hip strength measures that utilize a bar, straps, and a portable tension dynamometer.

DESIGN

Test-retest reliability study.

SETTING

Biomechanics research laboratory. Patients (or Other Participants): Twenty college-age individuals (10 males/10 females, age = 20.9 [3.7] y) participated.

INTERVENTION(S)

The participants attended 2 testing sessions, 1 week apart. The participants' trunk-flexion, rotation, and hip abduction strength were measured at each session.

MAIN OUTCOME MEASURES

Peak trunk flexion, rotation, and hip abduction forces were normalized to the participant's body weight (BW). In addition, hip-abduction torque was calculated by multiplying the force times the leg length and normalized to BW. The trial data from both sessions were used to calculate the intrasession reliability, and the averages from the 2 sessions were used to calculate the intersession reliability. Intraclass correlation coefficients, SEM, and minimal detectable change were calculated to evaluate reliability of measures.

RESULTS

The intrasession intraclass correlation coefficients (SEM) for trunk flexion, rotation, hip abduction, and hip abduction torque were .837 (5.2% BW), .978 (1.3% BW), .955 (1.0% BW), and .969 (5.8 N·m/BW), respectively. The intersession reliability for trunk flexion, rotation, hip abduction, and hip abduction torque were .871 (4.3% BW), .801 (3.8% BW), .894 (1.5% BW), and .968 (5.9 N·m/BW), respectively.

CONCLUSIONS

The measures of trunk and hip abduction strength are highly repeatable within a session. The reliability of the measures between sessions was also good/excellent with relatively small SEM and minimal detectable change. The tests described in this study can be used to assess changes in trunk/hip strength over time.

Contribution of lower limb muscle strength to walking, postural sway and functional performance in elderly women

BACKGROUND: Aging-related deterioration of the lower limb muscle strength could highly influence the functional performance of elderly individuals. OBJECTIVE: To investigate how advancing age impacts the lower limb muscle strength and consequently affects the balance and walking performance. METHODS: Twenty-seven community-dwelling elderly females underwent isokinetic ankle dorsi/plantar flexion (ADF/APF), inversion/eversion (AIN/AEV), knee flexion/extension (KFL/KEX), hip flexion/extension (HFL/HEX), and abduction/adduction (HAB/HAD) tests, the six-minute walk test, open-eyed biped balance test on foam rubber and the performance-oriented mobility assessment (POMA). RESULTS: The Pearson’s product-moment correlation coefficients demonstrated that advancing age negatively influenced the relative work and moment produced in all the muscle groups, the POMA score (r=-0.51), walking speed (r=-0.62), and the vertical (r= 0.55) and anteroposterior (r= 0.54) postural sway velocities. The peak moment and work values of AINs and APFs; KFLs and KEXs; and HABs, HFLs, and HEXs showed a significantly positive correlation with the walking speed (α⩽ 0.05). CONCLUSION: The strength of HFLs, HEXs and HABs, as the important contributors to the walking performance, underwent attenuation as the age increased, consequently resulting in impairments of stepping profiles of elderly females. Elderly females are needed to be trained to reach the optimum levels of lower limb muscular strength to overcome premature incapacitation and have control over their independence in daily activities.

Assessment of isokinetic trunk muscle strength and its association with health-related quality of life in patients with degenerative spinal deformity

Background

A considerable portion of the elderly population are increasingly afflicted by degenerative spinal deformity (DSD), which seriously affects patient health-related quality of life (HRQoL). HRQoL index is used across many studies to show correlations between radio-graphical alignment, disability, and pain in patients with DSD. However, imaged structural deformity represents only one aspect for consideration, namely, the disability effect of DSD. We assessed the isokinetic strength of trunk muscle in patients with degenerative spinal deformity (DSD), and investigated its relationship with HRQoL.

Methods

In total, 38 patients with DSD (DSD group) and 32 healthy individuals (control group) were recruited. Both groups were homogeneous for age, weight, height and body mass index (BMI). Assessments were performed using the isokinetic dynamometer IsoMed-2000; trunk extensor, flexor strength and flexion/extension (F/E) ratios were explored concentrically at speeds of 30°, 60° and 120° per second. The grip strength of both hands was measured using a hand-held dynamometer. Visual analogue scale (VAS) scores, the Oswestry Disability Index (ODI), a Roland-Morris disability questionnaire (RDQ), and a 36-item Short Form Health Survey (SF-36) evaluated patient HRQoL. Correlations between trunk strength and HRQoL were analyzed.

Results

When compared with the control group, the DSD group showed lower trunk extensor strength at three velocity movements, and higher F/E ratios at 60° and 120°/s (p < 0.05). Both groups exhibited similar trunk flexor strength and grip strength (p > 0.05). In DSD group, trunk extensor strength at 60°/s was negatively associated with ODI and RDQ (p < 0.05). A negative relationship between trunk flexor strength at 120°/s and ODI was also recorded (p < 0.05). In addition, trunk extensor strength at 60°/s and trunk flexor strength at 120°/s were positively correlated with physical functioning and role-physical scores according to the SF-36 (p < 0.05).

Conclusions

We identified isolated trunk extensor myopathy in DSD, which causes an imbalance in trunk muscle strength. Isokinetic trunk extensor strength at 60°/s and trunk flexor strength at 120°/s can predict disability, and decrease physical HRQoL in DSD patients.

Kinematic Calibration of a Parallel 2-UPS/RRR Ankle Rehabilitation Robot

In order to better perform rehabilitation training on the ankle joint complex in the direction of dorsiflexion/plantarflexion and inversion/eversion, especially when performing the isokinetic muscle strength exercise, we need to calibrate the kinematic model to improve its control precision. The ankle rehabilitation robot we develop is a parallel mechanism, with its movements in the two directions driven by two linear motors. Inverse solution of positions is deduced and the output lengths of the two UPS kinematic branches are calibrated in the directions of dorsiflexion, plantarflexion, inversion, and eversion, respectively. Motion of each branch in different directions is fitted in high-order form according to experimental data. Variances, standard deviation, and goodness of fit are taken into consideration when choosing the best fitting curve, which ensures that each calibration can match the most appropriate fitting curve. Experiments are conducted to verify the effectiveness of the kinematic calibration after finishing the calibration, and the errors before and after calibration of the two kinematic chains in different directions are compared, respectively, which shows that the accuracy after calibration has been significantly improved.

Evaluation isometric and isokinetic of trunk flexor and extensor muscles with isokinetic dynamometer: A systematic review

OBJECTIVE

To systematically review the literature analyzing the reliability and characteristics of the protocols of isokinetic and isometric evaluation of the trunk flexor and extensor muscles with isokinetic dynamometer.

METHODS

This is a systematic review using PubMed, CENTRAL, LILACS, PEDro and SCOPUS databases, searching the oldest records up to December 2019. The risk of bias, the methodological quality and the level of evidence were evaluated using the COSMIN checklist.

RESULTS

Fourteen articles have met the criteria and have been included in this study. All the articles performed an isometric or isokinetic evaluation of the trunk muscles with the isokinetic dynamometer and presented an analysis of the protocol's reliability using the intraclass correlation coefficient. Five articles had excellent reliability (0.93-0.98). Most of the studies presented doubtful and inconsistent psychometric values for reliability, because they used a short period between tests. The level of evidence to the fourteen selected articles for reliability was moderate.

CONCLUSIONS

Although the studies present limitations in methodological quality, it was possible to identify highly reliable patterns in the parameters employed and to present recommendations for the assessment of trunk flexor and extensor muscles in the isokinetic dynamometer, both for assessment in the sitting position and orthostatic.

Reliability and validity of three isometric back extensor strength assessments with different test postures

Objective

To compare the test-retest reliability and validity of three simple maximal isometric back extensor strength (BES) assessment protocols with different test postures, and to recommend an optimal clinical protocol to quantify BES.

Methods

Asymptomatic adults, aged over 45 years, were assessed for maximal isometric BES using external fixation of dynamometers, with the subject in standing, prone and sitting positions, respectively. Measurements were repeated at a one-week interval to examine test-retest reliability. Validation was performed by comparing with results obtained from isokinetic dynamometer assessments.

Results

Out of a total of 60 included participants, intra-class correlation coefficients (ICC) were 0.92, 0.93 and 0.90 in standing, prone and sitting positions, respectively. Correlation analyses revealed acceptable convergent validity in the standing and prone position (r = 0.50 and 0.54, respectively), whereas tests conducted in the sitting position showed a relatively low validity (r = 0.32). Among the three protocols, measurement error was lowest in the prone position.

Conclusions

Maximal isometric BES assessment in the prone position was shown to be the most reliable and valid protocol, and may be considered the preferred option for assessing BES in clinical practice.

Reliability of isometric and isokinetic trunk flexor strength using a functional electromechanical dynamometer

Aim

To determine the absolute and relative reliability of functional trunk tests, using a functional electromechanical dynamometer to evaluate the isokinetic strength of trunk flexors and to determine the most reliable assessment condition, in order to compare the absolute and relative reliability of mean force and peak force of trunk flexors and to determine which isokinetic condition of evaluation is best related to the maximum isometric.

Methods

Test-retest of thirty-seven physically active male student volunteers who performed the different protocols, isometric contraction and the combination of three velocities (V₁ = 015 m s⁻¹ , V₂ = 0.30 m  s⁻¹, V₃ = 0.45 m s⁻¹) and two range of movement (R₁ = 25% cm ; R₂ = 50% cm) protocols.

Results

All protocols to evaluate trunk flexors showed an absolute reliability provided a stable repeatability for isometric and dynamic protocols with a coefficient of variation (CV) being below 10% and a high or very high relative reliability (0.69 < intraclass correlation coefficient [ICC] > 0.86). The more reliable strength manifestation (CV = 6.82%) to evaluate the concentric contraction of trunk flexors was mean force, with 0.15 m  s⁻¹ and short range of movement (V₁R₁) condition. The most reliable strength manifestation to evaluate the eccentric contraction of trunk flexors was peak force, with 0.15 m  s⁻¹ and a large range of movement (V₁R_2; CV = 5.07%), and the most reliable way to evaluate isometric trunk flexors was by peak force (CV = 7.72%). The mean force of eccentric trunk flexor strength with 0.45 m  s⁻¹ and short range of movement (V₃R₁) condition (r = 0.73) was best related to the maximum isometric contraction.

Conclusion

Functional electromechanical dynamometry is a reliable evaluation system for assessment of trunk flexor strength.

Reliability of a Test for Assessment of Isometric Trunk Muscle Strength in Elderly Women

Objective

The aim of this study was to analyze the reproducibility of a protocol using the maximal isometric strength test of the trunk in elderly women aged above 60 years, without low back pain.

Methods

Twenty-one physically inactive elderly women, who had not engaged in any activity or exercise program in the past three months, participated in the cross-sectional study that consisted of two days of evaluations for the maximal isometric strength of the extensor and flexor muscles of the trunk, with a 48 h interval between the sessions. A platform with fixed seating was used, which allowed the fixation of the hip and lower limbs, with a load cell connected to a linear encoder. To verify the reliability of the test, the interclass correlation coefficient, variation coefficient, minimum detectable difference (MDD), standard error of measurement, and Bland–Altman graphs were calculated.

Results

No statistical difference was observed between the first and second evaluation, which indicates that there was no learning effect. Interclass correlation coefficient values were classified as very high and high for extensor (0.98) and flexor (0.86) muscles, respectively, besides low variation (9% for both muscle groups) and acceptable values for minimum detectable difference (extensors = 51.1 N, flexors = 48.9 N). In addition, the Bland–Altman analysis revealed low bias and values within the limits of agreement.

Conclusion

It is concluded that the test of maximum isometric strength of the trunk in healthy and trained elderly people presents high reliability. These values proved to be reliable if performed in at least two evaluation sessions, which confirms the hypothesis of the authors by the consistency of the measurement test.

Reliability and agreement of isometric functional trunk and isolated lumbar strength assessment in healthy persons and persons with chronic nonspecific low back pain

OBJECTIVES

to assess intra/inter-operator reliability and agreement of maximum isometric abdominal and back muscle strength in a functional trunk and isolated lumbar protocol, using an isokinetic dynamometer, in healthy persons and persons with chronic nonspecific low back pain (CNSLBP).

DESIGN

Test-retest.

SETTING

Participants performed two assessments consisting of two protocols on the Biodex 3 system, evaluating maximum isometric back and abdominal strength in a functional trunk and isolated lumbar position. During the first assessment, each protocol was executed twice, supported by different operators.

PARTICIPANTS

Healthy persons (n = 20) and persons with CNSLBP (n = 20).

MAIN OUTCOME MEASURES

Intraclass Correlation (ICC), Standard Error of Measurement (SEM and %SEM), and Minimal Detectable Change (MDC) of muscle strength outcomes and seat positioning characteristics were calculated.

RESULTS

Intra/inter reliability of muscle strength outcomes was excellent (ICC: 0.94-0.98), while seat positioning characteristics varied from low to high (ICC: 0-0.94). For muscle strength outcomes, %SEM ranged from 4.7 to 9.2% and MDC ranged from 14.3 to 29.8 Nm in trunk flexion and 39.1-68.5 Nm in trunk extension.

CONCLUSIONS

The Biodex 3 system can be used reliably to assess maximum isometric trunk muscle strength with the aforementioned protocols in healthy persons and persons with CNSLBP. All muscle strength outcomes showed comparable agreement (%SEM < 10%).

Validity and Reliability of a Novel Integrative Motor Performance Testing Course for Seniors: The "Agility Challenge for the Elderly (ACE)"

Background: Assessing traditional neuromuscular fall risk factors (i.e., balance, gait, strength) in the elderly has so far mainly been done independently. Functional and integrative testing approaches are scarce. The present study proposes an agility course for an integrative assessment of neuromuscular and also cardiocirculatory capacity in seniors – and tests its criterion validity and reliability.

Methods: Thirty-six seniors (age: 69.0 ± 2.8 years; BMI: 25.4 ± 3.5 kg/m²; sex: 19 males/17 females; weekly physical activity: 9.4 ± 5.5 h) participated. They completed four trials of the Agility Challenge for the Elderly (ACE)-course in two sessions separated by 1 week. The course consists of three segments focusing on different agility aspects. Cardiovascular capacity was assessed by 6-min walk test (6MWT), neuromuscular capacity by static, dynamic and perturbed standing balance tasks, habitual gait speed assessment, and rate of torque development testing. Parameters’ predictive strength for the ACE performance was assessed by regression analysis. Reliability was calculated with intraclass correlation coefficients and coefficients of variation.

Results: Men completed the course in 43.0 ± 5.7 s and women in 51.9 ± 4.0 s. Overall and split times were explained by 6MWT time (ηp2 = 0.38–0.44), gait speed (ηp2 = 0.29–0.43), and to a lesser extent trunk rotation explosive strength (ηp2 = 0.05–0.12). Static and dynamic balance as well as plantar flexion strength explained the performance in some segments to a very small extent (ηp2 = 0.06–0.08). Good between- and within-day reliability were observed for total course and split times: The ICC for the between-day comparison was 0.93 (0.88–0.96) and ranged between 0.84 and 0.94 for split times. The within-day ICC was 0.94 (0.91–0.97) for overall time and 0.92–0.97 for split times. Coefficients of variation were smaller than 5.7% for within and between day analyses.

Conclusion: The ACE course reflects cardiocirculatory and neuromuscular capacity, with the three ACE segments potentially reflecting slightly different domains of neuromuscular (static and dynamic balance, ankle, and trunk strength) performance, whereas cardiocirculatory fitness and gait speed contribute to all segments. Our test can detect changes in overall performance greater than 5.7% and can thus be useful for documenting changes due to interventions in seniors.

Paraspinal Muscle DTI Metrics Predict Muscle Strength

Background

The paraspinal muscles play an important role in the onset and progression of lower back pain. It would be of clinical interest to identify imaging biomarkers of the paraspinal musculature that are related to muscle function and strength. Diffusion tensor imaging (DTI) enables the microstructural examination of muscle tissue and its pathological changes.

Purpose

To investigate associations of DTI parameters of the lumbar paraspinal muscles with isometric strength measurements in healthy volunteers.

Study Type

Prospective.

Subjects

Twenty‐one healthy subjects (12 male, 9 female; age = 30.1 ± 5.6 years; body mass index [BMI] = 27.5 ± 2.6 kg/m²) were recruited.

Field Strength/Sequence

3 T/single‐shot echo planar imaging (ss‐EPI) DTI in 24 directions; six‐echo 3D spoiled gradient echo sequence for chemical shift encoding‐based water–fat separation.

Assessment

Paraspinal muscles at the lumbar spine were examined. Erector spinae muscles were segmented bilaterally; cross‐sectional area (CSA), proton density fat fraction (PDFF), and DTI parameters were calculated. Muscle flexion and extension maximum isometric torque values [Nm] at the back were measured with an isokinetic dynamometer and the ratio of extension to flexion strength (E/F) calculated.

Statistical Tests

Pearson correlation coefficients; multivariate regression models.

Results

Significant positive correlations were found between the ratio of extension to flexion (E/F) strength and mean diffusivity (MD) (P = 0.019), RD (P = 0.02) and the eigenvalues (λ1: P = 0.026, λ2: P = 0.033, λ3: P = 0.014). In multivariate regression models λ3 of the erector spinae muscle λ3 and gender remained statistically significant predictors of E/F (R²_adj = 0.42, P = 0.003).

Data Conclusion

DTI allowed the identification of muscle microstructure differences related to back muscle function that were not reflected by CSA and PDFF. DTI may potentially track subtle changes of back muscle tissue composition.

Level of Evidence: 3

Technical Efficacy: Stage 2

J. Magn. Reson. Imaging 2019;50:816–823.

Effects of Isokinetic Training on Trunk Muscle Fitness and Body Composition in World-Class Canoe Sprinters

In canoe sprint, the trunk muscles play an important role in stabilizing the body in an unstable environment (boat) and in generating forces that are transmitted through the shoulders and arms to the paddle for propulsion of the boat. Isokinetic training is well suited for sports in which propulsion is generated through water resistance due to similarities in the resistive mode. Thus, the purpose of this study was to determine the effects of isokinetic training in addition to regular sport-specific training on trunk muscular fitness and body composition in world-class canoeists and to evaluate associations between trunk muscular fitness and canoe-specific performance. Nine world-class canoeists (age: 25.6 ± 3.3 years; three females; four world champions; three Olympic gold medalists) participated in an 8-week progressive isokinetic training with a 6-week block "muscle hypertrophy" and a 2-week block "muscle power." Pre- and post-tests included the assessment of peak isokinetic torque at different velocities in concentric (30 and 140°s-1) and eccentric (30 and 90°s-1) mode, trunk muscle endurance, and body composition (e.g., body fat, segmental lean mass). Additionally, peak paddle force was assessed in the flume at a water current of 3.4 m/s. Significant pre-to-post increases were found for peak torque of the trunk rotators at 30°s-1 (p = 0.047; d = 0.4) and 140°s-1 (p = 0.014; d = 0.7) in concentric mode. No significant pre-to-post changes were detected for eccentric trunk rotator torque, trunk muscle endurance, and body composition (p > 0.148). Significant medium-to-large correlations were observed between concentric trunk rotator torque but not trunk muscle endurance and peak paddle force, irrespective of the isokinetic movement velocity (all r ≥ 0.886; p ≤ 0.008). Isokinetic trunk rotator training is effective in improving concentric trunk rotator strength in world-class canoe sprinters. It is recommended to progressively increase angular velocity from 30°s-1 to 140°s-1 over the course of the training period.

Association of paraspinal muscle water-fat MRI-based measurements with isometric strength measurements

OBJECTIVES

Chemical shift encoding-based water-fat MRI derived proton density fat fraction (PDFF) of the paraspinal muscles has been emerging as a surrogate marker in subjects with sarcopenia, lower back pain, injuries and neuromuscular disorders. The present study investigates the performance of paraspinal muscle PDFF and cross-sectional area (CSA) in predicting isometric muscle strength.

METHODS

Twenty-six healthy subjects (57.7% women; age: 30 ± 6 years) underwent 3T axial MRI of the lumbar spine using a six-echo 3D spoiled gradient echo sequence for chemical shift encoding-based water-fat separation. Erector spinae and psoas muscles were segmented bilaterally from L2 level to L5 level to determine CSA and PDFF. Muscle flexion and extension maximum isometric torque values [Nm] at the back were measured with an isokinetic dynamometer.

RESULTS

Significant correlations between CSA and muscle strength measurements were observed for erector spinae muscle CSA (r = 0.40; p = 0.044) and psoas muscle CSA (r = 0.61; p = 0.001) with relative flexion strength. Erector spinae muscle PDFF correlated significantly with relative muscle strength (extension: r = -0.51; p = 0.008; flexion: r = -0.54; p = 0.005). Erector spinae muscle PDFF, but not CSA, remained a statistically significant (p < 0.05) predictor of relative extensor strength in multivariate regression models (R²_adj = 0.34; p = 0.002).

CONCLUSIONS

PDFF measurements improved the prediction of paraspinal muscle strength beyond CSA. Therefore, chemical shift encoding-based water-fat MRI may be used to detect subtle changes in the paraspinal muscle composition.

KEY POINTS

• We investigated the association of paraspinal muscle fat fraction based on chemical shift encoding-based water-fat MRI with isometric strength measurements in healthy subjects. • Erector spinae muscle PDFF correlated significantly with relative muscle strength. • PDFF measurements improved prediction of paraspinal muscle strength beyond CSA.

Specific Physical Training in Elite Male Team Handball

Wagner, H, Gierlinger, M, Adzamija, N, Ajayi, S, Bacharach, DW, and von Duvillard, SP. Specific physical training in elite male team handball. J Strength Cond Res 31(11): 3083-3093, 2017-Specific physical training in elite team handball is essential for optimal player's performance; however, scientific knowledge is generally based on temporary training studies with subelite athletes. Therefore, the aim of the study was to analyze the effects of specific physical training in an elite male handball team over the entire season. Twelve players of a male handball team from the First Austrian Handball League conducted a 1-year specific physical training program in addition to their normal (team handball techniques and tactics) weekly training. Performance was measured with 5 general and 4 specific tests as well as game statistics during competition. Repeated measures analysis of variances and paired sample t-test were used to analyze differences in performance during training. We found a significant increase in oxygen uptake, offense time, defense time, fast break time, and jump height in the specific tests. Game performance statistics revealed a lower throwing percentage in the hosting team (59%) compared with the rival teams (63%). Our results indicated that specific endurance and agility are an acceptable modality in elite male team handball. However, performance in competition is strongly influenced by specific techniques and tactics. We recommend to strength and conditioning professionals that they tailor strength and power training, coordination and endurance as specific as possible, using free weights, agility exercises that include change in direction and jumps as well as short (10-15 seconds) high-intensity intervals.

Reliability and validity of an agility-like incremental exercise test with multidirectional change-of-direction movements in response to a visual stimulus

The aim of the study was to evaluate the reliability and validity of cardiorespiratory and metabolic variables, that is, peak oxygen uptake (V'O_2peak) and heart rate (HR_peak), obtained from an agility-like incremental exercise test for team sport athletes. To investigate the test-retest reliability, 25 team sport athletes (age: 22 ± 3 years, body mass: 75 ± 7 kg, height: 182 ± 6 cm) performed an agility-like incremental exercise test on the SpeedCourt (SC) system incorporating multidirectional change-of-direction (COD) movements twice. For each step of the incremental SC test, the athletes covered a 40-m distance interspersed with a 10-sec rest period. Each 40 m distance was split into short sprints (2.25-6.36 m) separated by multidirectional COD movements (0°-180°), which were performed in response to an external visual stimulus. All performance and physiological data were validated with variables obtained from a ramp-like treadmill and Yo-Yo intermittent recovery level 2 test (Yo-Yo IR2). The incremental SC test revealed high test-retest reliability for the time to exhaustion (ICC = 0.85, typical error [TE] = 0.44, and CV% = 3.88), V'O_2peak, HR_peak, ventilation, and breathing frequency (ICC = 0.84, 0.72, 0.89, 0.77, respectively). The time to exhaustion (r = 0.50, 0.74) of the incremental SC test as well as the peak values for V'O₂ (r = 0.59, 0.52), HR (r = 0.75, 0.78), ventilation (r = 0.57, 0.57), and breathing frequency (r = 0.68, 0.68) were significantly correlated (P ≤ 0.01) with the ramp-like treadmill test and the Yo-Yo IR2, respectively. The incremental SC test represents a reliable and valid method to assess peak values for V'O₂ and HR with respect to the specific demand of team sport match play by incorporating multidirectional COD movements, decision making, and cognitive components.