Using the force-time curve to detect maximal grip strength effort

Analysis of the force–time curve and median frequency of surface electromyographic signals during isometric hand grip test for estimation of a temporal pattern for muscle strengthening

Purpose

This work presents methods developed for the analysis of dynamometric and electromyographic signals acquired during sustained maximal isometric hand grip tasks. In these analyses, we try to find a temporal pattern that could indicate the beginning of the decrease in hand grip strength. This information is essential for choosing the best isometric activity time for hand rehabilitation.

Methods

The technique applied to the dynamometric signal was to find the time interval that precedes the drop of the isometric force RMS (root mean square) curve to values lower than the effective value. The technique applied to the surface electromyography (sEMG) signals was the identification of the instant when the lowest value of the median frequency of the signal occurs. The dynamometry data collection was carried out bilaterally in 19 men and 21 women. The electromyography data collection was carried out bilaterally in only 19 women.

Results

The statistical results (5% significance level) for the dynamometry data indicated that the time from the beginning of the test to the beginning of the decay of strength was approximately 7.6 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} ± 3.2 s, while the results for the sEMG data indicated that the time from the beginning of the test to the appearance of the lowest value of the median frequency was approximately 10.1 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} ± 2.9 s.

Conclusions

The method of using the RMS values of the Force, presented by this work, found results of approximately 7 s, while the method most currently used (Median Frequency) found values of approximately 10 s. These results may help the rehabilitation professional to decide with more security the isometric time of exercises.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42600-023-00262-2.

Comparing Statistics and Machine Learning to Detect Insincere Grip Force Testing Using Manugraphy

Background Currently, there are no tests that have been proven to be capable of rating an individual's grip force measurement as sincere or insincere. However, different parameters have been found to vary in grip force testing for maximal versus submaximal effort. A novel data analysis and processing approach might be key to improving these measurements. This study explores the use of a machine learning (ML) algorithm as a means to more accurately determine the sincerity or insincerity of grip force testing. The ML algorithm compares the hand's load distribution pattern with the information generated using conventional statistical methods. Methodology This study uses manugraphy data collected as part of a previous investigation that analyzed load distribution patterns of the right and left hands of 54 healthy subjects. The subjects underwent grip force testing using maximal or submaximal effort, and the percentage contributions of each of the seven defined anatomical areas of the hand were calculated with respect to the total load applied. The predictions based on the load distribution and its use for rating individual grip force measurements as sincere or insincere were compared with the results of conventional statistical methods (thresholds for a bi-manual area-to-area comparison) and an ML algorithm. Results Based on an area-to-area comparison, our method achieved a sensitivity of 54% and a specificity of 78% to detect insincere effort. A predictive ML model developed using these data was capable of recognizing submaximal effort based on the hand's load distribution pattern, determining a sensitivity of 94% and a specificity of 99%. Conclusions Compared to conventional methods, the use of an ML algorithm considerably improved the validity of manugraphy results in discerning the sincerity or insincerity of grip effort.

Differentiating maximal and submaximal voluntary strength measures for the purposes of medico-legal assessments and para sport classification: A systematic review

Measurement of maximum voluntary muscle contractions are effort-dependent - valid measurement requires maximal voluntary effort (MVE) from participants. Submaximal efforts (SMEs) yield invalid and potentially misleading results. This is particularly problematic in medico-legal and Para sport assessments where low strength scores may confer a personal advantage. Therefore, objective methods for accurately differentiating MVE and SME are required. This systematic review aimed to identify, appraise and synthesise evidence from scientific studies evaluating the validity of objective methods for differentiating MVE from SME during maximal voluntary contractions. Four electronic databases were searched for original research articles published in English and secondary references appraised for relevance yielding 25 studies for review. Methods were categorised based on eight distinct underlying theories. For isokinetic strength assessment, methods based on two theories - Strength-measure Ratios and Inter-Trial Strength Consistency - correctly classified 100% MVE and > 92% SME. Consequently, research evaluating the relative suitability of these methods for translation into practice is warranted. During isometric strength assessments, methods based on Deceptive Visual Feedback and Force-length properties warrant further investigation. Both methods yielded statistically significant differences between MVE and SME, with minimal overlap in values, but their sensitivity and specificity have not been evaluated.

Influence of Maximal or Submaximal Effort on the Load Distribution of the Hand Analyzed by Manugraphy

PURPOSE

This study aims to investigate if the hands' load-distribution pattern differs during maximal and submaximal grip.

METHODS

Fifty-four healthy subjects used the 200-mm Manugraphy cylinder to assess the load-distribution pattern of both hands. On 2 testing days, the subjects performed grip-force testing: 1 hand with maximal effort and the other with submaximal effort. Sides changed for the second testing day. The whole contact area of the hand was sectioned into 7 anatomical areas, and the percent contribution of each area, in relation to the total load applied, was calculated. Maximal and submaximal efforts were compared across the 7 areas in terms of load contributions.

RESULTS

Comparing maximum effort of the left and right hand, the load distribution was very similar without statistically significant differences between the corresponding areas. Comparing the maximal and the submaximal effort for each hand, 4 (left) and 5 (right) of the 7 corresponding areas showed statistically significant differences. Comparing the right hand, performing with maximal effort, with the left hand, performing with submaximal effort, 5 areas varied significantly. With the right hand performing submaximal effort, all 7 anatomical areas were significantly different.

CONCLUSIONS

The load distribution of a healthy hand is different when performing with submaximal effort compared with maximal effort. To analyze a hand's load-distribution pattern, the opposite hand can be used as a reference.

CLINICAL RELEVANCE

The hand's load-distribution pattern may be a useful indication of submaximal effort during grip-force testing.

Grip strength feigning is hard to detect: an exploratory study

Detecting submaximal effort when testing grip strength is difficult. Research so far has focused on the discrimination between sincere and feigning healthy participants, whereas the clinically relevant distinction is between injured patients and feigning participants. The aim of our study was to compare rapid exchange grip and isometric grip strength testing in 41 participants feigning weakness with 39 patients with decreased hand function. Various parameters that describe grip strength were recorded and tested for differences between the groups. Only the maximum grip strength during rapid exchange grip was found to be significantly higher in feigning participants compared with patients, but this cannot be used for decision-making on an individual basis. We found no parameters that are useful for the detection of feigned weakness in an individual case.

LEVEL OF EVIDENCE

III.

Determining Sincerity of Effort Based on Grip Strength Test in Three Wrist Positions

Background

Several grip strength tests are commonly used for detecting sincerity of effort. However, there is still no widely accepted standardized sincerity of effort test. Therefore, this study aimed to examine whether grip strength test in three wrist positions could distinguish between maximal and submaximal efforts.

Methods

Twenty healthy individuals (10 men and 10 women) with a mean age of 26.7 ± 3.92 years participated in this study. All participants completed two test conditions (maximal and submaximal efforts) in three wrist positions (neutral, flexion, and extension) using both hands. Each participant exerted 100% effort in the maximal effort condition and 50% effort in the submaximal effort condition. The participants performed three repetitions of the grip strength test for each session.

Results

The results showed that there is a significant main effect of the type of effort (p < 0.001), wrist position (p < 0.001), and hand (p = 0.028). There were also significant types of effort and wrist position interactions (p < 0.001) and effort and hand interactions (p < 0.028). The results also showed that grip strength was highest at the wrist in neutral position in both the maximal and the submaximal effort condition. Grip strength values of the three wrist positions in the maximal effort condition were noticeably greater than those in the submaximal effort condition.

Conclusion

The findings of this study suggest that grip strength test in three wrist positions can differentiate a maximal effort from a submaximal effort. Thus, this test could potentially be used to detect sincerity of effort in clinical setting.

Effects of the resting time associated with the number of trials on the total and individual finger forces in a maximum grasping task

The repetitive and excessive workload accompanying grip strength- or hand-intensive tasks are often considered to be common causes of work-related upper limb musculoskeletal disorders. For this reason, numerous experimental studies have been performed on maximum grip strength. However, due to an absence of standard guidelines, researchers have adopted different resting times and number of trials suited for their particular research purposes. The effects of resting time and the number of trials on the maximum total grip strength and individual finger forces of 24 participants over 20 trials were investigated. Results showed that the total grip strength and individual finger strengths differed significantly according to the resting time and the number of trials (p<0.05). Overall, grip strength tended to increase with a reduction in resting time (% reduction: 7.8%, 9.1%, 11.1%, and 13.0% for 3 min, 2 min, 1 min, and 30s resting time, respectively) as well as with an increase in the number of trials (% reduction: 8%, 10%, 13%, and 16% for 5th, 10th, 15th, and 20th trials). The effects of resting time and the number of trials also showed statistically significant effects on individual finger forces. Regression equations of total grip strength and finger forces with resting time and number of trials were established. These equations were then applied to formulate guidelines for appropriate resting times in experiments based on the number of trials and acceptable reductions in grip strength. Data from this and future studies regarding decreasing grip strength and the contribution of each finger are expected to form the groundwork for ergonomic hand tool design and development.

Differential Item Functioning in a Computerized Adaptive Test of Functional Status for People with Shoulder Impairments is Negligible across Pain Intensity, Gender, and Age Groups

People with shoulder impairments ( N = 3,767) reported upper extremity function using a 37-item shoulder-specific computerized adaptive test (shoulder CAT). The authors determined whether items of the shoulder CAT have differential item functioning (DIF) by pain intensity (low and high), gender (men and women), and age groups (young-adult, middle-aged and old-adult). They assessed whether items have uniform and/or non-uniform DIF using an ordinal logistic regression and item response theory approaches and applied large and small DIF criteria to assess the magnitude of DIF. The analyses revealed that uniform DIF was absent in all 37 items. Only six items exhibited non-uniform DIF using the large DIF criterion. Adjusting the person-ability measures for DIF had minimal practical impact on the overall measure of shoulder function estimated using the shoulder CAT. The shoulder CAT provided a precise measurement of function without discriminating for pain intensity, gender, and age among patients referred to rehabilitation with shoulder impairment.

Using the "visual target grip test" to identify sincerity of effort during grip strength testing

We devised a sincerity of effort assessment based on "tricking" a person into exerting maximal effort by providing incorrect visual feedback. The assessment involves deriving a target line from nonvisual peak gripping force, instructing participants to reach it with each grip repetition, and then secretly changing its position, which requires doubling the force necessary to reach it. Accordingly, participants are tricked into exerting more force than intended to reach the deceptive target line. We examined the validity of this test by comparing force values between "trick" and "non-trick" trials in 30 healthy participants. The study design used was a prospective cohort. Providing incorrect visual feedback caused significantly greater increases in force during submaximal effort (69%) than during maximal effort (28%). This test effectively detected submaximal effort (sensitivity=0.83 and specificity=0.93). Although this test is not safe for patients during initial therapy, it may be appropriate for patients who can safely exert maximal grip force.

LEVEL OF EVIDENCE

Not applicable.

Identifying sincerity of effort based on the combined predictive ability of multiple grip strength tests

STUDY DESIGN

Retrospective Cohort.

INTRODUCTION

Detecting sincerity of effort (SOE) of grip strength remains a frustrating and elusive task for hand therapists because there are no valid, reliable, or widely accepted assessments for identifying feigned effort. Some therapists use various combinations of different SOE tests in an attempt to identify feigned effort, but there is lack of evidence to support this practice.

PURPOSE

The present study examined the ability of a combination of three grip strength tests commonly used in the clinic to detect SOE: the five rung grip test, rapid exchange grip test, and coefficient of variation. A secondary purpose was to compare the predictive ability between the logistic and linear regression models.

METHODS

Healthy participants (n=146) performed the three SOE tests exerting both maximal and submaximal efforts. We compared the ability of two regression models, the logistic and linear models, to predict sincere versus insincere efforts.

RESULTS

Combining the three tests predicted SOE better than each test alone. Yet, the full logistic model, which was the best predictor of SOE, explained only 42% of variance and correctly classified only 58% of the efforts.

CONCLUSIONS

Our findings do not support the clinical practice of combining these three tests to detect SOE.

LEVEL OF EVIDENCE

Not applicable.

Influence of pain associated with musculoskeletal disorders on grip force timing

STUDY DESIGN

Retrospective repeated-measures design.

INTRODUCTION

Pain is a common symptom associated with musculoskeletal conditions.

PURPOSE

This study examined if pain resulting from a unilateral upper extremity musculoskeletal injury compromises the person's ability to rapidly initiate and release handgrip.

METHODS

Delays in initiating and releasing a handgrip were determined for 28 individuals with "low pain" and 12 individuals with "high pain" in the injured upper extremity. All participants had no pain in the uninjured upper extremity.

RESULTS

The high-pain group was 10% slower in initiating and releasing a grip than the low-pain group, in both injured and uninjured upper extremities, for both maximal and submaximal grips. In addition, delay in grip initiation was, on average, 8% longer for the injured than for the uninjured upper extremity.

CONCLUSIONS

Unilateral musculoskeletal pain appears to delay grip initiation and relaxation bilaterally, perhaps due to a centrally mediated mechanism.

LEVEL OF EVIDENCE

n/a.

A test case: does the availability of visual feedback impact grip strength scores when using a digital dynamometer?

A cross-sectional, quantitative study of clinical measurement utility. New technological advances can challenge the efficacy of even the most widely accepted and respected tests. For example, grip strength instruments offer digital or computerized displays, precision scoring, and varied interfaces that differ from traditional Jamar™ dynamometers (Lafayette, IN). This test case explores how the opportunity to view grip strength scores during testing can influence outcomes. One hundred forty-six healthy subjects, aged 18-24 years, were tested for grip strength under visual feedback and no visual feedback conditions, using the JTech Grip Dynamometer (Salt Lake City, UT). Participants achieved a small, yet statistically significant, 1.74 lb stronger grip score with visual feedback (p<0.002). The order of grip testing conditions yielded no statistically significant differences (p=0.559). These findings suggest the need to consider how new features, unavailable with the analog Jamar™ dynamometer and unaccounted for in existing clinical guidelines could potentially influence grip scores.

LEVEL OF EVIDENCE

Not applicable.

Using the force-time curve to determine sincerity of effort in people with upper extremity injuries

This was a prospective cohort study. In a previous study, the slopes of the force-time (F-T) curve were shown to differentiate between maximal and submaximal grip effort in healthy participants. The objective of the study was to examine if the slopes of the F-T curve can determine the sincerity of effort in people with upper extremity injuries. Forty participants with unilateral upper extremity injury performed maximal and submaximal grip efforts. The F-T curve was recorded, and the slopes of the force-generation and force-decay phases were calculated. Repeated-measures analysis of variance revealed significantly steeper slopes for maximal than those for submaximal efforts. However, receiver operating characteristic curves showed that, at best, the slope of the force-generation phase yielded overall error rates of 55% for women and 60% for men. Therefore, sensitivity and specificity values were insufficient to effectively differentiate maximal from submaximal efforts. The slopes of the F-T curve did not validly measure the sincerity of effort in participants with upper extremity injury, perhaps, because they were protective of their injured hand and, thus, exerted only submaximal effort even at their best grip attempt.

LEVEL OF EVIDENCE

Not applicable.

Validity and Critical Driving Errors of On-Road Assessment for Older Drivers

OBJECTIVES. We examined the validity of our on-road driving assessment to quantify its outcomes.

METHOD. Older drivers (N = 127) completed a driving assessment on a standardized road course. Measurements included demographics, driving errors, and driving test outcomes; a categorical global rating score (pass–fail); and the sum of maneuvers (SMS) score (0–273).

RESULTS. There were significant differences in the SMS (F = 29.9, df = 1 p ≤ .001) between drivers who passed the driving test and those who failed. The SMS cutoff value of 230 points was established as the criterion because it yielded the most optimal combination of sensitivity (0.91) and specificity (0.87). The strongest predictors of failure were adjustment to stimuli and lane maintenance errors.

CONCLUSION. The SMS differentiated between passing and failing drivers and can be used to inform clinical decision making.