Assessment of Isokinetic Trunk Muscle Strength and Fatigue Rate in Individuals after Bariatric Surgery.

Background and Objectives: Lean body mass loss after bariatric surgery (BS) is remarkable, despite an effective long-term mass reduction and significant declines in comorbidities. A person's functional capacity is adversely affected when their skeletal muscle strength declines by up to 30%. This study aimed to assess the isokinetic trunk muscle strength and fatigue rate in individuals after BS. Materials and Methods: This study included fifty-eight patients, both male and female, ranging in age from 19 to 45. Twenty-seven individuals had BS and twenty-seven healthy people served as the control group. The primary outcomes were the measurement of the concentric and eccentric isokinetic muscle strength of the trunk flexor and extensor muscles. An isokinetic dynamometer (Biodex Rehabilitation and Testing System 3) was used for the assessment of the isokinetic muscle strength. Noraxon EMG was used to determine a secondary outcome, which was the median frequency slop (MF/time) and root mean square slop (RMS/time) of the lumbar erector spinea muscle at 50% of the Maximum Voluntary Isometric Contraction (MVIC). Outcome measures were assessed for both groups. Results: Compared to the control group, the bariatric group showed a lower mean value of both concentric and eccentric isokinetic muscle strength for the flexor and extensor trunk muscles (p < 0.05). In terms of the EMG fatigue rate, the RMS slope increased significantly more than that of the control group, while the MF slope decreased (p > 0.05). Conclusions: The current study found that, in comparison to the healthy subjects, the BS group showed reduced levels of fatigue and isokinetic strength in the trunk muscles. Based on these results, it is recommended that individuals who underwent BS take part in tailored rehabilitation programs to avoid potential musculoskeletal issues in the future.

How many motor units is enough? An assessment of the influence of the number of motor units on firing rate calculations.

The number of motor units included in calculations of mean firing rates varies widely in the literature. It is unknown how the number of decomposed motor units included in the calculation of firing rate per participant compares to the total number of active motor units in the muscle, and if this is different for males and females. Bootstrapped distributions and confidence intervals (CI) of mean motor unit firing rates decomposed from the tibialis anterior were used to represent the total number of active motor units for individual participants in trials from 20 to 100 % of maximal voluntary contraction. Bootstrapped distributions of mean firing rates were constructed using different numbers of motor units, from one to the maximum number for each participant, and compared to the CIs. A probability measure for each number of motor units involved in firing rate was calculated and then averaged across all individuals. Motor unit numbers required for similar levels of probability increased as contraction intensity increased (p < 0.001). Increased levels of probability also required higher numbers of motor units (p < 0.001). There was no effect of sex (p ≥ 0.97) for any comparison. This methodology should be repeated in other muscles, and aged populations.

Assessment of Self-report, Palpation, and Surface Electromyography Dataset During Isometric Muscle Contraction.

Measuring muscle fatigue involves assessing various components within the motor system. While subjective and sensor-based measures have been proposed, a comprehensive comparison of these assessment measures is currently lacking. This study aims to bridge this gap by utilizing three commonly used measures: participant self-reported perceived muscle fatigue scores, a sports physiotherapist's manual palpation-based muscle tightness scores, and surface electromyography sensors. Compensatory muscle fatigue occurs when one muscle group becomes fatigued, leading to the involvement and subsequent fatigue of other muscles as they compensate for the workload. The evaluation of compensatory muscle fatigue focuses on nine different upper body muscles selected by the sports physiotherapist. With a cohort of 30 male subjects, this study provides a valuable dataset for researchers and healthcare practitioners in sports science, rehabilitation, and human performance. It enables the exploration and comparison of diverse methods for evaluating different muscles in isometric contraction.

Reliability, Concurrent Validity, and Minimal Detectable Change of the Hand-Held Dynamometry for the Assessment of Knee Muscle Strength in Patients With Revision Total Knee Arthroplasty.

OBJECTIVE: To determine the concurrent validity, reliability, and minimal detectable change (MDC) of the hand-held dynamometry (HHD) for knee strength measurement in patients with revision total knee arthroplasty (r-TKA). DESIGN: A reliability and validity analysis. SETTING: Orthopedic and physical therapy services of university hospital. PARTICIPANTS: The study included 42 patients with r-TKA (N=42). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Knee muscle strength assessments were performed by 2 physiotherapists in 3 different sessions by using HHD. Participants were instructed to exert a maximal force for lasting 5 seconds against HHD. The first examiner performed the strength testing, and after 30-minutes rest, the second examiner performed the same procedure for inter-examiner reliability. One hour after the initial testing, the first examiner reperformed the strength testing for intra-examiner reliability. The correlations of the knee extensors and knee flexors strength with 50-foot walking test and 30-second chair stand test were assessed for concurrent validity. RESULTS: The inter-examiner reliabilities of knee extensors and flexors strength measurements were 0.97 and 0.95, respectively. The SEM and the minimal detectable changes at 95% confidence level (MDC95) for knee extensors were 10.39 and 28.65 Newton-meters (Nm), and SEM and MDC95 for knee flexors were 8.70 and 23.99 Nm, respectively. The intra-examiner reliabilities of knee extensors and flexors strength measurements were 0.96. SEM and MDC95 for knee extensors were 12.00 and 33.09 Nm, and SEM and MDC95 for knee flexors were 7.78 and 21.45 Nm, respectively. The knee muscle strength showed strong significant correlations with physical performance tests (all, P<.05). CONCLUSIONS: The HHD is a reliable and valid method for assessment of static knee strength after r-TKA. The HHD can be used to quantify changes in knee strength and also assists the clinicians to determine the effect of rehabilitation programs on muscle strength following r-TKA surgery.

Comparison of strategies for assessment of rate of torque development in older and younger adults.

There is increasing appreciation of the role of rate of torque development (RTD) in physical function of older adults (OAs). This study compared various RTD strategies and electromyography (EMG) in the knee extensors and focused on discriminating groups with potential limitations in voluntary activation (VA) and associations of different RTD indices with functional tests that may be affected by VA in OAs. Neuromuscular function was assessed in 20 younger adults (YAs, 22.0 ± 1.7 years) and 50 OAs (74.4 ± 7.0 years). Isometric ballistic and peak torque during maximal voluntary contractions (pkTMVC), doublet stimulation and surface EMG were assessed and used to calculate VA during pkTMVC and RTD and rate of EMG rise during ballistic contractions. Select mobility tests (e.g., gait speed, 5× chair rise) were also assessed in the OAs. Voluntary RTD and RTD normalized to pkTMVC, doublet torque, and peak doublet RTD were compared. Rate of EMG rise and voluntary RTD normalized to pkTMVC did not differ between OAs and YAs, nor were they associated with functional test scores. Voluntary RTD indices normalized to stimulated torque parameters were significantly associated with VA (r = 0.319-0.459), and both indices were significantly lower in OAs vs YAs (all p < 0.020). These RTD indices showed significant association with the majority of mobility tests, but there was no clear advantage among them. Thus, voluntary RTD normalized to pkTMVC was ill-suited for use in OAs, while results suggests that voluntary RTD normalized to stimulated torque parameters may be useful for identifying central mechanisms of RTD impairment in OAs.Clinical trial registration number NCT02505529; date of registration 07/22/2015.

Within- and between-day reliability and repeatability of neuromuscular function assessment in females and males.

The study evaluated the reliability and repeatability of the force and surface electromyography activity (EMG) outcomes obtained through voluntary and electrically evoked contractions of knee extensors in females (n = 18) and males (n = 20) and compared these data between sexes. Maximal isometric voluntary contractions (iMVCs) of knee extensors associated with electrical stimulation of the femoral nerve were performed over 4 days (48-h interval), with the first day involving familiarization procedures, the second involving three trials (1-h interval), and the third and fourth involving just one trial. The intraclass correlation coefficient (ICC), coefficient of variation (CV), and repeatability of outcomes from within- and between-day trials were determined for each sex. Females presented lower maximal voluntary force during iMVC (iMVCForce) and associated vastus lateralis EMG activity (root mean square, RMSVL), force evoked by potentiated doublet high-frequency (Db100Force) and single stimuli (Qtw), and M-wave amplitude than males (P ≤ 0.01, partial eta squared ≥0.94). Voluntary activation (VA) and RMSVL/M-wave amplitude did not differ between sexes. iMVCForce, VA, Db100Force, Qtw, and M-wave amplitude were the most reliable outcomes in within-day trials, with similar results between sexes (ICC > 0.62; CV < 6.4%; repeatability: 12.2%-22.6%). When investigating between-day trials, the iMVCForce, VA, Db100Force, and Qtw were the most reliable (ICC > 0.66; CV < 7.5%; repeatability: 13.2%-33.45%) with similar results between sexes. In conclusion, females presented lower iMVCForce and evoked response than males. Although reliability and repeatability statistics vary between trials, data (e.g., from EMG or force signal), and sexes, most of the outcomes obtained through this technique are reliable in females and males.NEW & NOTEWORTHY Although reliability and repeatability of knee extensors vary according to the type of neuromuscular function outcome (e.g., from force or EMG responses), the trial intervals (i.e., hours or days), and the sex of the participant, most force and EMG outcomes obtained through these neuromuscular assessment protocols present ICC > 0.75, very good CV (<10%), and repeatability <25% in within- and between-day trials in both sexes.

Muscle fatigue, bioenergetic responses and metabolic economy during load- and velocity-based maximal dynamic contractions in young and older adults.

We evaluated whether task-dependent, age-related differences in muscle fatigue (contraction-induced decline in normalized power) develop from differences in bioenergetics or metabolic economy (ME; mass-normalized work/mM ATP). We used magnetic resonance spectroscopy to quantify intracellular metabolites in vastus lateralis muscle of 10 young and 10 older adults during two maximal-effort, 4-min isotonic (20% maximal torque) and isokinetic (120°s-1 ) contraction protocols. Fatigue, inorganic phosphate (Pi), and pH (p ≥ 0.213) differed by age during isotonic contractions. However, older had less fatigue (p ≤ 0.011) and metabolic perturbation (lower [Pi], greater pH; p ≤ 0.031) than young during isokinetic contractions. ME was lower in older than young during isotonic contractions (p ≤ 0.003), but not associated with fatigue in either protocol or group. Rather, fatigue during both tasks was linearly related to changes in [H+ ], in both groups. The slope of fatigue versus [H+ ] was 50% lower in older than young during isokinetic contractions (p ≤ 0.023), consistent with less fatigue in older during this protocol. Overall, regardless of age or task type, acidosis, but not ME, was the primary mechanism for fatigue in vivo. The source of the age-related differences in contraction-induced acidosis in vivo remains to be determined, as does the apparent task-dependent difference in the sensitivity of muscle to [H+ ].

Development of a Low-Cost Portable EMG for Measuring the Muscular Activity of Workers in the Field.

This study explores the development and validation of a low-cost electromyography (EMG) device for monitoring muscle activity and muscle fatigue by monitoring the key features in EMG time and frequency domains. The device consists of a Raspberry Pico microcontroller interfacing a Myoware EMG module. The experiment involved 34 volunteers (14 women, 20 men) who performed isometric and isotonic contractions using a hand dynamometer. The low-cost EMG device was compared to a research-grade EMG device, recording EMG signals simultaneously. Key features including root mean square (RMS), median power frequency (MDF), and mean power frequency (MNF) were extracted to evaluate muscle fatigue. During isometric contraction, a strong congruence between the two devices, with similar readings and behavior of the extracted features, was observed, and the Wilcoxon signed rank test confirmed no significant difference in the ability to detect muscle fatigue between the devices. For isotonic contractions, the low-cost device demonstrated behavior similar to the professional EMG device in 70.58% of cases, despite some susceptibility to noise and movement. This suggests the potential viability of the low-cost EMG device as a portable tool for assessing muscle fatigue, enabling accessible and cost-effective management of muscle health in various work scenarios.

Psychometric properties of a standardized protocol of muscle strength assessment by hand-held dynamometry in healthy adults: a reliability study.

BACKGROUND: Maximal isometric muscle strength (MIMS) assessment is a key component of physiotherapists' work. Hand-held dynamometry (HHD) is a simple and quick method to obtain quantified MIMS values that have been shown to be valid, reliable, and more responsive than manual muscle testing. However, the lack of MIMS reference values for several muscle groups in healthy adults with well-known psychometric properties limits the use and the interpretation of these measures obtained with HHD in clinic. OBJECTIVE: To determine the intra- and inter-rater reliability, standard error of measurement (SEM) and minimal detectable change (MDC) of MIMS torque values obtained with HHD. METHODS: Intra and Inter-rater Reliability Study. The MIMS torque of 17 muscle groups was assessed by two independent raters at three different times in 30 healthy adults using a standardized HHD protocol using the MEDup™ (Atlas Medic, Québec, Canada). Participants were excluded if they presented any of the following criteria: 1) participation in sport at a competitive level; 2) degenerative or neuromusculoskeletal disease that could affect torque measurements; 3) traumatic experience or disease in the previous years that could affect their muscle function; and 4) use of medication that could impact muscle strength (e.g., muscle relaxants, analgesics, opioids) at the time of the evaluation. Intra- and inter-rater reliability were determined using two-way mixed (intra) and random effects (inter) absolute agreement intraclass correlation coefficients (ICC: 95% confidence interval) models. SEM and MDC were calculated from these data. RESULTS: Intra- and inter-rater reliability were excellent with ICC (95% confidence interval) varying from 0.90 to 0.99 (0.85-0.99) and 0.89 to 0.99 (0.55-0.995), respectively. Absolute SEM and MDC for intra-rater reliability ranged from 0.14 to 3.20 Nm and 0.38 to 8.87 Nm, respectively, and from 0.17 to 5.80 Nm and 0.47 to 16.06 Nm for inter-rater reliability, respectively. CONCLUSIONS: The excellent reliability obtained in this study suggest that the use of such a standardized HHD protocol is a method of choice for MIMS torque measurements in both clinical and research settings. And the identification of the now known metrological qualities of such a protocol should encourage and promote the optimal use of manual dynamometry.

Assessment of motor unit firing by high-density surface electromyography detects motor neuronal hyperexcitable state in amyotrophic lateral sclerosis.

INTRODUCTION/AIMS: In amyotrophic lateral sclerosis (ALS), the impact of motor neuron dysfunction on the motor unit (MU) firing pattern remains to be elucidated. The aim of this study was to clarify the characteristics of the MU firing rate and its association with clinical factors in ALS patients using high-density surface electromyography (HDSEMG) and MU decomposition analysis. METHODS: Nineteen ALS patients and 20 controls prospectively underwent HDSEMG recording of the vastus lateralis muscle during ramp-up (30% of maximum voluntary contraction) and sustained (10% of maximal voluntary contraction for 60 seconds) contractions on performing isometric knee extension. After decomposition analysis, instantaneous firing rates (IFRs) of individually identified MUs were calculated. Comparison of IFRs and clinical variables between ALS patients and controls and analysis of the correlation between individual mean IFR and clinical variables in ALS patients were performed. RESULTS: The number of identified MUs was lower in ALS patients than in controls (P = .017). Mean IFRs of MUs (i.e., mean MU firing rates) were higher in ALS patients than in controls at some force levels on ramp-up contraction (P < .05) and at 50 to 60 seconds during sustained contraction (9.1 [ALS] vs 8.3 [controls] pulses per second; P = .036). There was no correlation between the clinical parameters and mean IFR of each patient. DISCUSSION: ALS patients had a higher MU firing rate during muscle contraction at a low force level. Noninvasive assessment of the MU firing rate by HDSEMG can detect a motor neuronal hyperexcitable state in ALS patients.

Assessment of exercise-induced hypoalgesia in chronic low back pain and potential associations with psychological factors and central sensitization symptoms: A case-control study.

INTRODUCTION: Exercise is the most recommended treatment for chronic low back pain (CLBP) and is effective in reducing pain, but the mechanisms underlying its effects remain poorly understood. Exercise-induced hypoalgesia (EIH) may play a role and is thought to be driven by central pain modulation mechanisms. However, EIH appears to be disrupted in many chronic pain conditions and its presence in people with CLBP remains unclear. As people suffering from chronic pain often exhibit psychological factors and central sensitization symptoms influencing pain perception, EIH might be associated with these factors. OBJECTIVE: The aim of this study is to compare the level of EIH between participants with and without CLBP following back and wrist exercises and to assess the associations between EIH, psychological factors, and symptoms of central sensitization (using the central sensitization inventory - CSI) in CLBP. METHOD: Twenty-eight participants with CLBP and 23 without pain were recruited. Pressure pain thresholds (PPT) were measured at 4 sites (2 bony sites = capitate, S1|2 muscle sites = wrist flexors, lumbar erector spinae) before and after each of two exercises (wrist flexion and lumbar extension). Exercise-induced hypoalgesia was defined as percent change in PPT from pre- to post-exercise. Participants with CLBP also completed questionnaires to measure psychological factors (e.g., kinesiophobia, catastrophizing, anxiety, and self-efficacy) and symptoms of central sensitization (CSI), and correlations with EIH were calculated. RESULTS: After wrist exercise, EIH measured at the muscle sites was lower in the CLBP group compared with the pain-free group (p = 0.047) but no differences were found at bony sites (p = 0.49). No significant differences for EIH were observed following back exercise at muscle sites (p = 0.14) or at bony sites (p = 0.65). Exercise-induced hypoalgesia was not correlated with any psychological factors or with the CSI score. CONCLUSION: The lower EIH following wrist exercises may represent an alteration in pain modulation control in CLBP. However, psychological factors and central sensitization symptoms may not explain the differences observed.

Design Validation of a Low-Cost EMG Sensor Compared to a Commercial-Based System for Measuring Muscle Activity and Fatigue.

Electromyography (EMG) sensors have been used for measuring muscle signals and for diagnosing neuromuscular disease. Available commercial EMG sensor are expensive and not easily available for individuals. The aim of the study is to validate our designed low-cost sensor against a well-known commercial system for measuring muscle activity and fatigue assessment. The evaluation of the designed system was done through a series of dynamic exercises performed by volunteers. Our low-cost EMG sensor and the commercially available system were placed on the vastus lateralis muscle to concurrently record the signal in a maximum voluntary contraction (MVC). The signal analysis was done using two validation indicators: Spearman's correlation, and intra-class cross correlation on SPSS 26.0 version. For the muscle fatigue assessment, the root mean square (RMS), mean absolute value (MAV) and mean frequency (MNF) indicators were used. The results at the peak and mean level muscle contraction intensity were computed. The relative agreement for the two systems was excellent at peak level muscle contraction range (ICC 0.74-0.92), average 0.83 and mean level muscle contraction intensity range (ICC 0.65-0.85) with an average of 0.74. The Spearman's correlation average was 0.76 with the range of (0.71-0.85) at peak level contraction, whiles the mean level contraction average was 0.71 at a range of (0.62-0.81). In determining muscle fatigue, the RMS and MAV showed increasing values in the time domain, while the MEF decreased in the frequency domain. Overall, the results indicated a good to excellent agreement of the two systems and confirmed the reliability of our design. The low-cost sensor also proved to be suitable for muscle fatigue assessment. Our designed system can therefore be implemented for rehabilitation, sports science, and ergonomics.

The rate of force development scaling factor: a review of underlying factors, assessment methods and potential for practical applications.

When humans perform isometric ballistic contractions of different intensities, a strong linear relationship is observed between peak force and peak rate of force development. The slope of this relationship, termed the rate of force development scaling factor (RFD-SF), has been proposed as a measure of neuromuscular quickness of submaximal contractions. The RFD-SF is largely dependent on motor unit firing rate and its modulation with contraction intensity, and possibly by agonist-antagonist coordination. The purpose of this review was to critically evaluate the available literature on RFD-SF, including the underlying physiological mechanisms, assessment protocols and methodological considerations, practical application to clinical and sports practice and additional factors such as sex, muscle group, task and fatigue. The main findings of the review are: (a) RFD-SF is very sensitive to impairments associated with aging and neurological diseases, (b) the literature lacks studies on the importance of RFD-SF for athletes, with some evidence that RFD-SF may affect the accuracy of submaximal movements, (c) RFD-SF is not largely influenced by fatigue and sex, (d) the RFD-SF values have been very consistent across muscle groups, with an exception of ankle muscles, (e) the methodology for RFD-SF assessment appears to be well established and standardized. Future research is needed to determine if RFD-SF provides any independent information that cannot be captured with peak force/torque and RFD.

Muscle volume vs. anatomical cross-sectional area: Different muscle assessment does not affect the muscle size-strength relationship.

Muscle volume (MV) and anatomical cross-sectional area (CSA) are used as measures of muscle-size, but determining these from magnetic resonance imaging (MRI) is a very time-consuming process. Additionally, it is unclear if the use of different muscle size assessments (all vs. reduced number of slices images) would impact the muscle size-strength relationship. Thus, this study aimed to investigate if muscle size calculation by using a reduced or all slices images from pectoralis major (PM) would maintain a similar muscle size-strength relationship with bilateral maximal dynamic and isometric contractions on a bench press exercise. Twenty-four healthy males underwent an MRI examination to measure PM muscle size, and maximal isometric and dynamic contractions (by one repetition maximum, 1RM) were performed. Correlations between maximal isometric voluntary force (MVF) and dynamic strength (1RM) with muscle size variables [three images from the largest part of PM (CSA3MAX), three images accounting for the shape -first image, middle image, final image- of the PM (CSA3), and MV] were performed. The correlation between 1RM with MV, CSA3, and CSA3MAX were 0.84, 0.832, and 0.727 (p < 0.001), respectively. The correlation between MVF with MV, CSA3, and CSA3MAX were 0.738, 0.733, and 0.604 (p < 0.001), respectively. Overall, PM MV and CSA3 exhibit a stronger and similar muscle size-strength relationship during maximal dynamic and isometric tests than CSA3MAX. Therefore, a reduced number of slices (CSA3) could be used as an alternative to considerably reduce the time of analysis without compromise muscle size-strength relationship.

Assessment of shoulder rotation strength, muscle co-activation and shoulder pain in tetraplegic wheelchair athletes - A methodological study.

Objective: To develop a feasible protocol for testing maximum shoulder rotation strength in tetraplegic wheelchair athletes, and investigate concurrent validity of maximum isometric handheld dynamometer (HHD) towards maximum isokinetic dynamometer (ID) strength measurements; secondly, to study shoulder muscle activation during maximum shoulder rotation measurements, and the association between shoulder strength and shoulder pain.Design: Descriptive methodological.Setting: Danish Wheelchair Rugby (WCR) association for WCR tetraplegic athletes from local WCR-clubs.Participants: Twelve adult tetraplegics.Interventions: N/A.Outcome measures: Wheelchair User's Shoulder Pain Index (WUSPI) and Visual Analog Scale (VAS) measured shoulder pain, isometric HHD and ID (60°/s) measured maximum internal (IR) and external (ER) shoulder rotation strength. Surface Electromyography normalized to maximum EMG measured muscle activity (mm Infraspinatus and Latissimus Dorsi) during maximum shoulder rotation strength.Results: Concurrent validity of isometric HHD towards ID showed Concordance Correlation Coefficients of left and right arms 0.90 and 0.86 (IR), and 0.89 and 0.91 (ER), with no difference in muscle activity between isometric HHD and ID, but larger co-activation during ER. There was no association between shoulder strength and pain, except for significantly weak negative associations between ID and pain during ER for left and right arms (P = 0.03; P = 0.04).Conclusion: Standardized feasible protocol for tetraplegic wheelchair athletes for measuring maximum shoulder rotation strength was established. Isometric HHD is comparable with ID on normalized peak torques and muscle activity, but with larger co-activation. Strength was not clearly associated with shoulder pain.

Novel Assessment of Isometric Hip Extensor Function: Reliability, Joint Angle Sensitivity, and Concurrent Validity.

ABSTRACT: Goodwin, JE and Bull, AMJ. Novel assessment of isometric hip extensor function: reliability, joint angle sensitivity, and concurrent validity. J Strength Cond Res 36(10): 2762-2770, 2022-Closed-chain hip extension function has not been well examined. The aim of this study was to examine the reliability, joint angle sensitivity, muscle recruitment, and concurrent validity of a force plate-based isometric hip extensor test (isometric hip thrust). All subjects were active men aged 19-29 years. In part 1, bilateral and unilateral hip extensor testing was completed on 4 occasions by 14 subjects to evaluate repeatability of force and torque measures. In part 2, joint angle sensitivity of force, torque, and surface electromyography was assessed by 10 subjects completing testing at 4 hip joint angles in a single test session. In part 3, concurrent validity of joint torque was assessed relative to standing and supine test positions on an isokinetic dynamometer, by 10 subjects in a single test session. The repeatability study found small changes in the mean from sessions 1-2 (mean standardized change d = 0.31) and close to no change in later sessions (mean d = 0.12). Typical error was predominantly low to moderate (mean 0.42), and intraclass correlation coefficient (ICC) was typically high (mean ICC = 0.87). The joint angle sensitivity study showed that increasing the hip flexion resulted in increases in peak extension force ( p = 0.001) and gluteus maximus activation ( p = 0.003) and a reduction in biceps femoris activation ( p < 0.001). There was no change in torque ( p = 0.585) and vastus lateralis activation ( p = 0.482). The concurrent validity study found that torque was correlated with supine dynamometry ( R2 = 0.555) but not with standing dynamometry ( R2 = 0.193). In summary, the isometric hip thrust is repeatable, but benefits from familiarization. Force output and muscle recruitment are sensitive to joint position, providing an opportunity to assess different functional output.

Getting the best GRIP on blood pressure control: Investigating a cost-effective isometric handgrip alternative.

OBJECTIVES: The World Health Organization emphasises the need for cost-effective alternative methods to lower blood pressure (BP). Endorsed nationally in HTN guidelines, isometric handgrip (IHG) training is an alternative method of BP control. The purpose of this study was to compare the BP, heart rate (HR) and rates of perceived exertion (RPE) responses between a bout of IHG training performed using the traditional computerized device and a more affordable, inflatable stress ball. METHODS: Twenty healthy adults performed one bout (4, 2-min isometric contractions, with 1-min rests between each contraction at 30% maximal voluntary contraction) of IHG training using the traditional computerized device, and one bout with the inflatable stress ball. BP, HR, and RPE were recorded. RESULTS: No statistically significant differences between devices were observed with HR, BP, and RPE (p < 0.05). However, average RPE for both devices ranged between 5 and 6 indicating that participants were rating 30% of their MVC, consistent with previous work. DISCUSSION: The similar cardiovascular and psychophysical responses provide support for the potential use of this low individual- and provider-burden, cost-efficient IHG device, and lay the foundation for a future training study to test the hypothesis of benefit.

Reliability of Quadriceps Femoris Muscle Strength Assessment Using a Portable Dynamometer and Protocol Tolerance in Patients With Chronic Obstructive Pulmonary Disease.

OBJECTIVE: This study aimed to evaluate the intrarater and interrater reliability of isometric quadriceps strength (IQS) using a portable dynamometer in individuals with chronic obstructive pulmonary disease (COPD) and to verify their tolerance to the protocol. METHODS: A cross-sectional reliability study was conducted with 50 individuals with stable COPD (34 men and 16 women; mean age = 70 years [SD = 8]). The main outcome measure was obtained using a portable dynamometer (Microfet 2) to assess IQS. Two masked raters performed 2 assessments in the dominant lower limb on 2 nonconsecutive days. The intraclass correlation coefficient (ICC) was used to verify the intrarater and interrater reliability and was considered excellent when >0.90, with a 5% significance level. RESULTS: Rater 1 and 2 intrarater reliability was as follows: ICC = 0.96 (95% CI = 0.94 to 0.98) and ICC = 0.97 (95% CI = 0.95 to 0.98), respectively. The interrater reliability was as follows: ICC = 0.96 (95% CI = 0.93 to 0.98). The minimum detectable difference was 4 to 5 peak isometric strength, in mean, for intrarater and interrater reliability. Not all patients presented relevant changes in physiological responses, dyspnea, and lower limb fatigue. CONCLUSION: There was an excellent intrarater and interrater reliability for IQS, and the participants tolerated the protocol. IMPACT: This tool can be used to assess quadriceps strength in clinical practice in patients with COPD.

Concurrent Validity and Reliability of a Low-Cost Dynamometer to Assess Maximal Isometric Strength in Neck Movements.

OBJECTIVE: This study aimed to evaluate the concurrent validity and reliability of a low-cost digital dynamometer to assess maximal isometric strength in neck movements. METHODS: Twelve recreationally active participants (6 women, 6 men; age: 24.1 ± 3.4 years; height: 1.71 ± 0.06 m; weight: 64.6 ± 11.7 kg) performed neck flexion, extension, and lateral flexion, and maximal isometric strength was simultaneously measured using an isokinetic dynamometer (gold standard) and a digital dynamometer to evaluate the concurrent validity of the latter. One week later, all the participants repeated 3 trials of each neck movement (3 minutes apart) registered only with the digital dynamometer. The first and second trial were guided by tester 1 and the third trial was guided by tester 2. RESULTS: The concurrent validity of the digital dynamometer showed a nearly perfect correlation between both devices (r > 0.986, P < .001), with Bland-Altman plots showing absolute agreement. Intertester and intratester reliability were nearly perfect for all neck movements (intraclass correlation coefficient > 0.86). CONCLUSION: The low-cost digital dynamometer showed valid and reliable measurements of maximal isometric strength in neck movements.

Reliability and agreement of a dynamic quadriceps incremental test for the assessment of neuromuscular function.

The quadriceps-intermittent-fatigue (QIF) test assesses knee extensors strength, endurance and performance fatigability in isometric condition. We aimed to assess reliability and agreement for this test in dynamic conditions and with the use of transcranial magnetic stimulation. On two separate sessions, 20 young adults (25 ± 4 yr, 10 women) performed stages of 100 knee extensors concentric contractions at 120°/s (60° range-of-motion) with 10% increments of the initial maximal concentric torque until exhaustion. Performance fatigability across the test was quantified as maximal isometric and concentric torque loss, and its mechanisms were investigated through the responses to transcranial magnetic and electrical stimulations. Reliability and agreement were assessed using ANOVAs, coefficients of variation (CVs) and intra-class correlation coefficients (ICCs) with 95% CI. Good inter-session reliability and high agreement were found for number of contractions [489 ± 75 vs. 503 ± 95; P = 0.20; ICC = 0.85 (0.66; 0.94); CV = 5% (3; 7)] and total work [11,285 ± 4,932 vs. 11,792 ± 5838 Nm.s; P = 0.20; ICC = 0.95 (0.87; 0.98); CV = 8% (5; 11)]. Poor reliability but high agreement were observed for isometric [-33 ± 6 vs. -31 ± 7%; P = 0.13; ICC = 0.47 (0.05; 0.75); CV = 6% (4;8)] and concentric [-20 ± 11% vs. -19 ± 9%; P = 0.82; ICC = 0.26 (-0.22; 0.63); CV = 9% (6; 12)] torque loss. The dynamic QIF test represents a promising tool for neuromuscular evaluation in isokinetic mode.