Variability of grip strength during isometric contraction

Economic hardship over twenty-two consecutive years of adult life and markers of early ageing: physical capability, cognitive function and inflammation

This study assesses the associations between annual measures of economic hardship (EH) across 22 years of adulthood and objective measures of early ageing in a Danish late-middle-aged population (N = 5575). EH (years < 60% of the National median equivalized household disposable income) was experienced by 18% during 1987-2008. Four or more years in EH (reference = null years in EH) was related to poorer physical capability (chair rise: - 1.49 counts/30 s [95% confidence interval (CI) - 2.36, - 0.61], hand grip strength: - 1.22 kg [95% CI - 2.38, - 0.07], jump height: - 1.67 cm [95% CI - 2.44, - 0.91] and balance: 18% [95% CI 9, 28]), poorer cognitive function (Intelligenz-Struktur-Test: - 1.50 points [95% CI - 2.89, - 0.12]) and higher inflammatory levels (C-reactive protein: 22% [95% CI 4, 44], and Interleukin-6: 23% [95% CI 10, 39]). Comparing four EH trajectories, people with a high versus low probability of EH over time had poorer physical capability (chair rise: - 1.70 counts/30 s [95% CI - 3.38, - 0.01], grip: - 4.33 kg [95% CI - 6.50, - 2.16], jump: - 1.68 cm [95% CI - 3.12, - 0.25] and balance: 31% [95% CI 12, 52]). No associations were observed with tumour necrosis factor-α. Results were adjusted for sex, age, long-term parental unemployment/financial problems, education, baseline income and cohort. This study suggested EH for four or more years to be associated with poorer physical capability, cognitive function and increased inflammatory levels in midlife. High probability of EH across adulthood was similarly related to poorer physical capability and CRP, but not cognitive function and the remaining inflammatory markers. In conclusion, preventive initiatives focusing on reducing the burden of sustained economic hardship may lead to increased healthy ageing.

CORP: Measurement of upper and lower limb muscle strength and voluntary activation

Muscle strength, the maximal force-generating capacity of a muscle or group of muscles, is regularly assessed in physiological experiments and clinical trials. An understanding of the expected variation in strength and the factors that contribute to this variation is important when designing experiments, describing methodologies, interpreting results, and attempting to replicate methods of others and reproduce their findings. In this review (Cores of Reproducibility in Physiology), we report on the intra- and inter-rater reliability of tests of upper and lower limb muscle strength and voluntary activation in humans. Isometric, isokinetic, and isoinertial strength exhibit good intra-rater reliability in most samples (correlation coefficients ≥0.90). However, some tests of isoinertial strength exhibit systematic bias that is not resolved by familiarization. With the exception of grip strength, few attempts have been made to examine inter-rater reliability of tests of muscle strength. The acute factors most likely to affect muscle strength and serve as a source of its variation from trial-to-trial or day-to-day include attentional focus, breathing technique, remote muscle contractions, rest periods, temperature (core, muscle), time of day, visual feedback, body and limb posture, body stabilization, acute caffeine consumption, dehydration, pain, fatigue from preceding exercise, and static stretching >60 s. Voluntary activation, the nervous system’s ability to drive a muscle to create its maximal force, exhibits good intra-rater reliability when examined with twitch interpolation (correlation coefficients >0.80). However, inter-rater reliability has not been formally examined. The methodological factors most likely to influence voluntary activation are myograph compliance and sensitivity; stimulation location, intensity, and inadvertent stimulation of antagonists; joint angle (muscle length); and the resting twitch.

Measuring Functional and Patient-Reported Outcomes After Treatment of Mutilating Hand Injuries: A Global Health Approach

Understanding the global burden of trauma, particularly upper extremity trauma, is necessary in addressing the need for surgical services. Critical to that mission is to understand, and accurately measure, disability and related disability-adjusted life-years from massive upper extremity trauma. The impact of these injuries is magnified when considering that they frequently occur to young people in prime working years. This article discusses these social and medical system issues and reviews components of a comprehensive approach to measuring outcomes after these injuries. Patient-reported outcomes are highlighted. Methods of optimizing outcomes measurements and studies, disability assessments, and associated research are also discussed.

Background, design and conceptual model of the cluster randomized multiple-component workplace study: FRamed Intervention to Decrease Occupational Muscle pain - "FRIDOM"

Background

Several RCT studies have aimed to reduce either musculoskeletal disorders, sickness presenteeism, sickness absenteeism or a combination of these among females with high physical work demands. These studies have provided evidence that workplace health promotion (WHP) interventions are effective, but long-term effects are still uncertain. These studies either lack to succeed in maintaining intervention effects or lack to document if effects are maintained past a one-year period. This paper describes the background, design and conceptual model of the FRIDOM (FRamed Intervention to Decrease Occupational Muscle pain) WHP program among health care workers. A job group characterized by having high physical work demands, musculoskeletal disorders, high sickness presenteeism - and absenteeism.

Methods

FRIDOM aimed to reduce neck and shoulder pain. Secondary aims were to decrease sickness presenteeism, sickness absenteeism and lifestyle-diseases such as other musculoskeletal disorders as well as metabolic-, and cardiovascular disorders – and to maintain participation to regular physical exercise training, after a one year intervention period. The entire concept was tailored to a population of female health care workers. This was done through a multi-component intervention including 1) intelligent physical exercise training (IPET), dietary advice and weight loss (DAW) and cognitive behavioural training (CBT).

Discussion

The FRIDOM program has the potential to provide evidence-based knowledge of the pain reducing effect of a multi component WHP among a female group of employees with a high prevalence of musculoskeletal disorders and in a long term perspective evaluate the effects on sickness presenteeism and absenteeism as well as risk of life-style diseases.

Trial registration

NCT02843269, 06.27.2016 - retrospectively registered.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-016-3758-6) contains supplementary material, which is available to authorized users.

Non-sedation versus sedation with a daily wake-up trial in critically ill patients receiving mechanical ventilation--effects on physical function: study protocol for a randomized controlled trial: a substudy of the NONSEDA trial

Background

Critically ill patients rapidly loose much of their muscle mass and strength. This can be attributed to prolonged admission, prolonged mechanical ventilation and increased mortality, and it can have a negative impact on the degree of independence and quality of life. In the NONSEDA trial we randomize critically ill patients to non-sedation or sedation with a daily wake-up trial during mechanical ventilation in the intensive care unit. It has never been assessed whether non-sedation affects physical function. The aim of this study is to assess the effects of non-sedation versus sedation with a daily wake-up trial on physical function after discharge from intensive care unit.

Methods/Design

Investigator-initiated, randomized, clinical, parallel-group, superiority trial, including 700 patients in total, with a substudy concerning 200 of these patients. Inclusion criteria will be intubated, mechanically ventilated patients with expected duration of mechanical ventilation >24 h. Exclusion criteria will be patients with severe head trauma, coma at admission or status epilepticus, patients treated with therapeutic hypothermia, patients with PaO₂/FiO₂<9 where sedation might be necessary to ensure sufficient oxygenation or placing the patient in a prone position. The experimental intervention will be non-sedation supplemented with pain management during mechanical ventilation. The control intervention will be sedation with a daily wake-up trial. The co-primary outcome will be quality of life regarding physical function (SF-36, physical component) and degree of independence in activities of daily living (Barthel Index), and this will be assessed for all 700 patients participating in the NONSEDA trial. The secondary outcomes, which will be assessed for the subpopulation of 200 NONSEDA patients in the trial site, Kolding, will be 6-min walking distance, handgrip strength, muscle size (ultrasonographic measurement of the rectus femoris muscle cross-sectional area) and biomechanical data on lower extremity function (maximal voluntary contraction, rate of force development and endurance).

Discussion

This study is the first to investigate the effect of no sedation during critical illness on physical function. If an effect is found, it will add important information on how to prevent muscle weakness following critical illness.

Trial registration

The study has been approved by the relevant scientific ethics committee and is registered at ClinicalTrials.gov (ID: NCT02034942, 9 January 2014).

Reliability of isometric subtalar pronator and supinator strength testing

BACKGROUND

Due to the specific anatomy of the subtalar joint with its oblique axis, isometric pronator and supinator strength is not well documented. The purpose of this study was to determine intra- and between-session reliability of pronator and supinator strength and lower leg muscle activity measurements during maximum voluntary isometric contractions (MVIC).

METHODS

Pronator and supinator peak torques (PT), with and without supplementary visual muscle strength biofeedback (FB), and muscular activities of peroneus longus (PL) and tibialis anterior (TA) were assessed twice 3 days apart by the same examiner in 21 healthy young male adults (mean age: 27.6 years; SD = 3.9). Limits of agreement (LoA) and minimum detectable change (MDC) were evaluated.

RESULTS

By applying FB, reliability of both pronator and supinator PT was improved: LoA were reduced from 32% to 26% and from 20% to 18% and MDC from 20% to 15% and from 16% to 12% in supinator and pronator PT, respectively. Learning effects in pronator and supinator PT (p < 0.05), which were present without FB, were eliminated using FB. Except for TA during pronation, muscle activities showed low reliability indicated by LoA of 51% to 79%.

CONCLUSIONS

Using supplementary biofeedback, isometric subtalar pronator and supinator strength testing is reliable in healthy subjects. LoA of 18% and 26% have to be exceeded for pronator and supinator PT, respectively, to detect relevant effects in repeated measures.

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.

Weight loss among female health care workers--a 1-year workplace based randomized controlled trial in the FINALE-health study

BACKGROUND

Weight management constitutes a substantial problem particularly among groups of low socio-economic status. Interventions at work places may be a solution, but high quality worksite interventions documenting prolonged weight loss are lacking. This paper presents results of an intervention aimed to achieve a 12 months weight loss among overweight health care workers.

METHODS

Ninety-eight overweight female health care workers were randomized into an intervention or a reference group. The intervention consisted of diet, physical exercise and cognitive behavioral training during working hours 1 hour/week. The reference group was offered monthly oral presentations. Several anthropometric measures, blood pressure, cardiorespiratory fitness, maximal muscle strength, and musculoskeletal pain were measured before and after the 12-months intervention period. Data were analyzed by intention-to-treat analysis.

RESULTS

The intervention group significantly reduced body weight by 6 kg (p < 0.001), BMI by 2.2 (p < 0.001) and body fat percentage by 2.8 (p < 0.001). There were no statistical reductions in the control group, resulting in significant differences between the two groups over time.

CONCLUSIONS

The intervention generated substantial reductions in body weight, BMI and body fat percentage among overweight female health care workers over 12 months. The positive results support the workplace as an efficient arena for weight loss among overweight females.

TRIAL REGISTRATION

NCT01015716.

Lifetime occupational physical activity and musculoskeletal aging in middle-aged men and women in denmark: retrospective cohort study protocol and methods

Background

Physical function is essential for performing most aspects of daily life and musculoskeletal aging leads to a decline in physical function. The onset and rate of this process vary and are influenced by environmental, genetic, and hormonal factors. Although everyone eventually experiences musculoskeletal aging, it is beneficial to study the factors that influence the aging process in order to prevent disability. The role of occupational physical activity in the musculoskeletal aging process is unclear. In the past, hard physical work was thought to strengthen the worker, but current studies in this field fail to find a training effect in jobs with a high level of occupational physical activity.

Objective

The aim of this study is to examine the influence of lifetime occupational physical activity on physical function in midlife. The study follows the “occupational life-course perspective,” emphasizing the importance of occupational exposures accumulated throughout life on the musculoskeletal aging process taking socioeconomic and lifestyle factors into consideration.

Methods

This study is a retrospective cohort study including a cross-sectional measurement of physical function in 5000 middle-aged Danes. Data was obtained from the Copenhagen Aging and Midlife Biobank (CAMB) which is based on three existing Danish cohorts. Using questionnaire information about the five longest-held occupations, the job history was coded from the Danish version of the International Standard Classification of Occupations (D-ISCO 88) and a job exposure matrix containing information about occupational physical activity in Danish jobs was applied to the dataset. The primary outcomes are three tests of physical function: handgrip strength, balance, and chair rise. In the analyses, we will compare physical function in midlife according to accumulated exposure to high levels of occupational physical activity.

Conclusions

We have a unique opportunity to study the influence of work on early musculoskeletal aging taking other factors into account. In this study, the “healthy worker effect” is reduced due to inclusion of people from the working population and people who are already retired or have been excluded from the labor market. However, low participation in the physical tests can lead to selection bias.

Diet, physical exercise and cognitive behavioral training as a combined workplace based intervention to reduce body weight and increase physical capacity in health care workers - a randomized controlled trial

BACKGROUND

Health care workers comprise a high-risk workgroup with respect to deterioration and early retirement. There is high prevalence of obesity and many of the workers are overweight. Together, these factors play a significant role in the health-related problems within this sector. The present study evaluates the effects of the first 3-months of a cluster randomized controlled lifestyle intervention among health care workers. The intervention addresses body weight, general health variables, physical capacity and musculoskeletal pain.

METHODS

98 female, overweight health care workers were cluster-randomized to an intervention group or a reference group. The intervention consisted of an individually dietary plan with an energy deficit of 1200 kcal/day (15 min/hour), strengthening exercises (15 min/hour) and cognitive behavioral training (30 min/hour) during working hours 1 hour/week. Leisure time aerobic fitness was planned for 2 hour/week. The reference group was offered monthly oral presentations. Body weight, BMI, body fat percentage (bioimpedance), waist circumference, blood pressure, musculoskeletal pain, maximal oxygen uptake (maximal bicycle test), and isometric maximal muscle strength of 3 body regions were measured before and after the intervention period.

RESULTS

In an intention-to-treat analysis from pre to post tests, the intervention group significantly reduced body weight with 3.6 kg (p < 0.001), BMI from 30.5 to 29.2 (p < 0.001), body fat percentage from 40.9 to 39.3 (p < 0.001), waist circumference from 99.7 to 95.5 cm (p < 0.001) and blood pressure from 134/85 to 127/80 mmHg (p < 0.001), with significant difference between the intervention and control group (p < 0.001) on all measures. No effect of intervention was found in musculoskeletal pain, maximal oxygen uptake and muscle strength, but on aerobic fitness.

CONCLUSION

The significantly reduced body weight, body fat, waist circumference and blood pressure as well as increased aerobic fitness in the intervention group show the great potential of workplace health promotion among this high-risk workgroup. Long-term effects of the intervention remain to be investigated.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01015716.

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.

Changes in physical performance among construction workers during extended workweeks with 12-hour workdays

PURPOSE

To investigate changes of physical performance during long working hours and extended workweeks among construction workers with temporary accommodation in camps.

METHODS

Nineteen construction workers with 12-h workdays and extended workweeks participated. Physical performance in the morning and evening of the second and eleventh workdays was tested by endurance, ability to react to a sudden load, flexibility of the back, handgrip strength and sub-maximal HR during a bicycle test. HR was registered throughout two separate workdays.

RESULTS

HR during each of the two separate workdays corresponded to a relative workload of 25%. Sub-maximal HR was lower, reaction time faster and handgrip strength higher in the end of each test day. In the end of the work period, sub-maximal HR was lower, reaction time faster and sitting balance was better.

CONCLUSION

No trends of decreased physical performance were found after a workday or a work period.

Evaluation of the torque-velocity test of the BTE-Primus as a measure of sincerity of effort of grip strength

An inverse linear relationship exists between torque and velocity in the mid-ranges of an isotonic maximal contraction in a single joint movement (such as the elbow and knee). We hypothesized that submaximal effort does not produce a linear torque-velocity relationship because replicating a submaximal isotonic contraction requires an enormous amount of proprioceptive feedback and the nervous system may not be able to accurately replicate both force and speed of contraction. If this hypothesis is true, the torque-velocity test of the BTE-Primus would be an effective method for assessing sincerity of effort. The purpose of this study was to examine if differences exist in the linear torque-velocity relationship between maximal and submaximal grip strength effort. Due to the fact that a test is not valid unless it is reliable, an additional purpose was to calculate the test-retest reliability of velocity during isotonic contraction using the torque-velocity test of the BTE-Primus' grip tool. Participants included 32 healthy, right-hand dominant (16 male, 16 female) persons, aged 20-50 years (mean age 25+/-8.0), with no history of upper-extremity injury. The subjects participated in two days of grip-strength testing (approximately two weeks apart) and were instructed to exert maximal effort with both hands on one day, and to feign injury with one hand on the other day. Each day included two sessions of testing, which consisted of performing the "torque-velocity test" on the BTE-Primus grip attachment (#162). We randomly assigned the feigning hand (dominant vs. nondominant) and the effort (maximal vs. submaximal). The test administrator was blinded to the level of effort. On each day, four isotonic grip-strength tests were performed at loads of 20%, 30%, 40%, and 50% of isometric test scores. Three repeated isotonic grip strength trials were performed at each load and the average was plotted. One plot was generated for the maximal effort and another for the submaximal efforts. Average torque was plotted against the average velocity at each of the four loads and for each level of effort (maximal vs. submaximal). The linear relationship of the torque-velocity curve was examined by performing regression analysis, calculating the intercept, slope, correlation coefficient (r), and the coefficient of determination (r(2)) for each curve. Paired t-tests were used to compare the intercept, slope, and r(2) between maximal and submaximal efforts. Bonferroni correction set the alpha level at 0.0167. Sensitivity and specificity values were calculated for linearity (r(2)) and a Receiver Operator Characteristic (ROC) curve was constructed to obtain the optimal sensitivity and specificity combination. In addition, test-retest reliability was determined for velocity of maximal isotonic effort using Intraclass Correlation Coefficient. Significant differences between maximal and submaximal efforts were found for the intercept (t=5.069; p<0.001) and for linearity as expressed by r(2) (t=5.414; p<0.001). Mean r(2) was 0.89 for maximal effort and 0.53 for submaximal effort. The slopes of maximal and submaximal efforts were not significantly different (t=0.14; p=0.888). The ROC curve revealed the optimal combination of sensitivity (0.69) and specificity (0.72) values. Test-retest reliability of maximal isotonic grip effort for velocity was r=0.843. The differences in intercepts suggested that velocity was greater during maximal effort. Greater r(2) values indicated greater linearity for maximal efforts than submaximal efforts. These findings suggest that the torque-velocity test of the BTE-Primus can distinguish between maximal and submaximal efforts during grip-strength testing. However, the test misclassified 31% of submaximal effort and 28% of maximal error, for a total error of 59%. Therefore, this test does not possess adequate sensitivity and specificity values to justify its use in the clinic.

Detecting submaximal effort in power grip by observation of the strength distribution pattern

This study examined patterns of grip strength when maximal and submaximal effort are applied. Using a sensor glove, 50 healthy subjects performed two different power grips. Both maximal and submaximal gripping showed characteristic patterns of strength distribution that were independent of the degree of power applied. Significant differences were also noted in the strength distribution patterns, depending on whether the grip was performed at maximal, or submaximal, strength. The small finger plays a decisive role in this. In maximal strength gripping, the total measured strength is distributed relatively evenly over all four fingers, with each finger contributing between 23% and 27% of the total strength. In submaximal strength gripping, the little finger is involved very little and only contributes between 14% and 15% of the total strength, with the remainder of the gripping distributed relatively evenly between the index, middle and ring fingers, each of which contributes between 26% and 32% of the total.

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

Currently, there are no universally accepted assessment methods for detecting insincere effort during grip strength testing. We examined the validity of the slopes of the force-time curve (during force-generation and force-decay phases) as indicative of sincerity of effort. Thirty healthy subjects performed both maximal and submaximal grip strength trials. The test administrator was blinded as to the nature of the effort. A force-time curve was generated for each individual trial. The slopes of the force-generation phase and the force-decay phase were calculated. Both slopes were significantly steeper for the maximal than the submaximal efforts (p</=0.0001). Sensitivity and specificity analyses revealed that the slope of the force-generation phase was a more effective assessment of sincerity of effort for women, whereas the slope of the force-decay phase was a more effective assessment for men. The most notable finding was that for the force-decay phase, for slope cutoff values of -0.75 and -1.0, none of the men who exerted maximal effort were mistakenly identified as exerting a submaximal effort, whereas only 7% of the men who exerted submaximal effort were incorrectly identified as exerting a maximal effort. Thus, the slopes of the force-time curve are valid and effective in detecting sincerity of effort in healthy subjects. This study represents the first step in establishing the feasibility and validity of a new sincerity of effort assessment using the slopes of the force-time curve. Future research is needed to establish the validity and effectiveness of this sincerity of effort assessment in people with hand injury.

Reliability and validity of the DynEx dynamometer

Abstract The purpose of the study was to examine the reliability and validity of the digital DynEx dynamometer. Grip strength testing was conducted on 100 healthy subjects (aged 20-40 years) using both the Jamar and DynEx dynamometers in the second handle position. The data were analyzed for test-retest reliability and concurrent validity using the intraclass correlation coefficient. A repeated-measures analysis of covariance was conducted to reveal differences in grip strength between instruments. In addition, measurement error was calculated with known weights. The DynEx dynamometer was found to have high test-retest reliability both with human subjects ( r = 0.9864) and with known weights suspended from the dynamometer's handle ( r = 0.9999). The DynEx dynamometers had a smaller measurement error (1.63%) than the Jamar dynamometers (7.74%). Although significant differences were found between grip scores obtained on the Jamar and the DynEx (F = 6.222; p = 0.014), the concurrent validity between the two instruments was excellent ( r > 0.98). The results of this study indicate that clinicians can use the DynEx dynamometer at the second handle position knowing that it is reliable, valid, and comparable to the second handle position of the Jamar dynamometer.

Analysis of the statistical methods used to detect submaximal effort with the five-rung grip strength test

Controversy exists in the literature concerning the ability of the five-rung grip test to identify submaximal effort. The purpose of this study was to analyze four methods commonly used to evaluate the shape of the curve generated by maximal versus submaximal efforts. Thirty hand therapy patients performed the five-rung grip test maximally and submaximally with both their injured and uninjured hands. Grip strength scores were recorded at each of the five-rung positions. Next, four methods were used to analyze the data 1) visual analysis, 2) analysis of variance, 3) normalization, and 4) calculation of the standard deviation across the five strength scores. Analysis by all methods demonstrated that there were no differences between the injured hand exerting maximal effort and the uninjured hand exerting submaximal effort. In all four methods, the five-rung grip strength test was unable to distinguish between the injured hand exerting maximal effort and the uninjured hand exerting submaximal effort. The results suggest that the five-rung grip strength test should not be used to determine sincerity of effort in people with hand injuries, and that the shape of the curve generated by the five-rung grip strength test may not be related to level of effort but rather to the amount of force generated by the gripping hand.

Time course of stretch-induced isometric strength deficits

Stretching in the warm-up has been shown to decrease several muscular performance variables, but the dose-response of this effect is unknown. This study documented the change in isometric grip strength over ten trials in a convenience sample of young adults randomly assigned to control (n=22) or repeated bouts of 10-s static stretches of the wrist flexors (n=35). There was a significant (P<0.05) difference in the change in mean normalized grip strength between the control and stretching groups that was not significantly different across gender. Grip strengths in the control group were consistent with a linear trend, while the grip strengths in the stretching group declined in a logarithmic fashion to 88.8% with 100 s of stretching. Statistically significant (P<0.05) differences in normalized grip strength between the two groups appeared after 40 s of stretching. Meaningful decreases in isometric grip strength following static stretching are likely to appear in young adults following 20-40 s of static stretching.

Critical issues in the use of muscle testing for the determination of sincerity of effort

Over the past 20 years, there have been numerous attempts to identify methodologies that are capable of the determination of sincerity of effort during muscle testing. The ensuing paper reviewed this literature and drew several conclusions. Injured patients and healthy volunteers do produce less force and more variable force while performing submaximal contractions than maximal contractions. However, submaximal efforts during strength testing can be reproduced and the use of force variability is not adequate to distinguish sincerity of effort. Visual examination of the shape of force output curves is also not adequate for distinguishing sincerity of effort. Furthermore, much of the research using strength ratios, difference scores, and an assortment of different parameters derived during strength testing has not established reliable and clinically useful methods of differentiating effort levels. Methods examining motion variability, radial/ulnar force output ratios, difference scores of eccentric-concentric ratios, and electromyography offer some promise, but numerous critical issues need to addressed. The use of the coefficient of variation, for example, is statistically untenable given the number of trials appropriate for clinical samples. Several studies have inadequate sample size to number of variable ratios. Many studies have questionable or at least unknown generalizability to patient samples and actual functional capacity. It is critical that other explanatory variables such as fear of injury, pain, medications, work satisfaction, and other motivational factors be considered. It is our opinion that there is not sufficient empirical evidence to support the clinical application of muscle testing to determine sincerity of effort.

Effectiveness of the Five–Handle Position Grip Strength Test in Detecting Sincerity of Effort in Men and Women

OBJECTIVE

The five-handle position (five-rung) test is used to determine sincerity of effort of grip strength. However, there is a controversy in the literature concerning its validity and effectiveness. The purpose of the study was to investigate whether test results are affected by the amount of strength exerted by the gripping hand and to determine the test's effectiveness.

DESIGN

A total of 30 hand therapy patients performed the five-rung grip test both maximally and submaximally with both the injured and uninjured hands. The standard deviation across the five strength trials was used to measure the shape of the curve. Sensitivity and specificity values were calculated for each sex.

RESULTS

The repeated measures analyses of variance revealed that average strength and the standard deviation were greater for men than for women, for maximal effort than for submaximal effort, and for the injured hand in comparison with the healthy hand. The most optimal standard deviation cutoff value was 8.5 (sensitivity, 0.70; specificity, 0.83), and the proportional area under the receiver operator characteristic curve was greater for the men (89%) than for women (80%).

CONCLUSIONS

The shape of the curve generated by the five-rung test was strength dependent; thus, the test may yield biased results when assessing sincerity of effort in people with weakened hands. The five-rung test was less effective for women than for men. Thus, we recommend that the five-rung test not be used to detect sincerity of effort.

Simultaneous bilateral testing: validation of a new protocol to detect insincere effort during grip and pinch strength testing

The detection of feigned weakness in hand grip strength assessment is difficult. The authors review several proposed methods and their weaknesses. A comparison of unilateral testing and simultaneous bilateral testing with the Jamar dynamometer and the Baseline pinch gauge is demonstrated as a solution. An experiment involved 100 asymptomatic subjects who were tested twice, once under instructions to give a full effort and once under instructions to feign weakness. Seven statistical criteria of noncompliance were chosen. Defining noncompliance as failing two or more of the seven criteria, 99% of the instructed noncompliant subjects were correctly classified as noncompliant. No subjects were incorrectly classified as noncompliant during instructed compliant testing. Twelve subjects failed on a single criterion. On retesting, all but one were correctly classified. One subject in the instructed noncompliant group passed all criteria. Accuracy was 99.5%, including retesting of the 12 "gray-zone" subjects.

The coefficient of variation as a measure of sincerity of effort of grip strength, Part I: the statistical principle

The coefficient of variation (CV) is a widely used measure of sincerity of effort of grip strength despite contradictory research findings and lack of empirical support in the literature. The purpose of this study was to investigate whether the CV is an appropriate measure of sincerity of effort. One hundred forty-six uninjured volunteers underwent a series of grip strength tests. The mean, standard deviation (SD), and CV of repeated strength trials were calculated, and paired comparisons were conducted between maximal and submaximal efforts. While the mean of maximal trials was significantly greater, there were no differences in SD between maximal and submaximal trials. Therefore, the increased CV associated with submaximal effort was an artifact of reduced torque rather than an indicator of a true increase in variability. Consequently, the CV is not an appropriate measure of sincerity of effort of grip strength.

The coefficient of variation as a measure of sincerity of effort of grip strength, Part II: sensitivity and specificity

The coefficient of variation (CV) is commonly used to detect sincerity of effort. The purpose of this study was to examine whether the CV possessed adequate sensitivity and specificity to effectively detect sincerity of effort of grip strength. One hundred forty-six uninjured volunteers underwent a series of grip strength tests. Sensitivity and specificity values were calculated for various CV cut-off values (between 2.5% and 22%) of the static grip test. The receiver operating characteristic (ROC) curves based on these values demonstrated the trade-offs between specificity and sensitivity. For example, the "traditional" 15% cut-off value yielded poor sensitivity (0.55), whereas the 11% cut-off value yielded poor specificity (0.74). Selecting any cut-off value along the continuum did not provide adequate sensitivity or specificity for labeling an effort sincere or insincere. Although the CV differentiated between maximal and submaximal effort, it was not sensitive or specific enough to do so effectively. Thus, the CV should not be used to assess sincerity of effort of grip strength.

Effect of muscle mass and intensity of isometric contraction on heart rate

The purpose of this study was to determine the effect of muscle mass and the level of force on the contraction-induced rise in heart rate. We conducted an experimental study in a sample of 28 healthy men between 20 and 30 yr of age (power: 95%, alpha: 5%). Smokers, obese subjects, and those who performed regular physical activity over a certain amount of energetic expenditure were excluded from the study. The participants exerted two types of isometric contractions: handgrip and turning a 40-cm-diameter wheel. Both were sustained to exhaustion at 20 and 50% of maximal force. Twenty-five subjects finished the experiment. Heart rate increased a mean of 15.1 beats/min [95% confidence interval (CI): 5.5-24.6] from 20 to 50% handgrip contractions, and 20.7 beats/min (95% CI: 11.9-29.5) from 20 to 50% wheel-turn contractions. Heart rate also increased a mean of 13.3 beats/min (95% CI: 10.4-16.1) from handgrip to wheel-turn contractions at 20% maximal force, and 18.9 beats/min (95% CI: 9. 8-28.0) from handgrip to wheel-turn contractions at 50% maximal force. We conclude that the magnitude of the heart rate increase during isometric exercise is related to the intensity of the contraction and the mass of the contracted muscle.

Normalized forces and active range of motion in unilateral radial epicondylalgia (tennis elbow)

STUDY DESIGN

Single group pretest-posttest.

BACKGROUND

There is a lack of consensus concerning the preferred assessment and treatment for radial epicondylalgia.

OBJECTIVES

Determine whether deficiencies in muscle force, joint range of motion, or painful force threshold are detected when measurements from the involved upper extremity are normalized to values from the uninvolved extremity.

METHODS AND MEASURES

Ten patients (70% men) 42 +/- 7 years in age with unilateral radial epicondylalgia participated. The visual analog pain scale and 6 measurements involving either muscle force, joint range of motion, or painful force threshold were examined.

RESULTS

When comparing the initial assessments to final assessments, a significant improvement was found for the visual analog pain scale (5 +/- 3 vs 1 +/- 3) and for the following normalized scores: grip (78 +/- 26% vs 101 +/- 20%) and isometric wrist extension forces (68 +/- 24% vs 95 +/- 35%), painful force threshold over the lateral epicondyle (49 +/- 22% vs 94 +/- 14%), and active wrist extension range of motion (83 +/- 13% vs 96 +/- 10%).

CONCLUSIONS

Normalized force and range of motion measurements following treatment for unilateral radial epicondylalgia are sensitive assessments of patient progress. In comparison with measurements of force and range of motion that are not adjusted to a baseline score, normalized measurements detect changes in patient responses when baseline scores vary.

Coefficient of variation in maximal and feigned static and dynamic grip efforts

The purpose of this study was to investigate the validity of the coefficient of variation as an identifier of feigned grip effort. Seventeen healthy female aged 20 to 25 yr participated in the study. Maximal and feigned efforts were measured isometrically and isokinetically (concentric and eccentric) using the Jamar and KinCom dynamometers, respectively. Findings indicated that, in all situations, the coefficient of variation derived from the maximal effort was significantly (P < 0.0001) lower than that derived from the feigned effort. However, the extent of overlapping between the two was sufficiently large to render the test sensitivities very low. Consequently, regardless of the measurement method, the coefficient of variation is not a valid tool for identifying feigned grip effort in healthy subjects.

Subjectivity of forces associated with manual-muscle test grades of 3+, 4-, and 4

This study examined the subjectivity of forces applied by 10 testers during simulated manual-muscle testing. Individual testers were able to modify appropriately the forces they applied for muscle test grades of 3+, 4-, and 4, that is, the forces rose concomitantly with the grades. Testers were consistent between trials in the forces they applied for each grade while testing each specific action. They varied, however, in the forces they applied for each grade during the testing of the two different muscle actions. Moreover, testers differed significantly from one another in the forces they applied for each manual muscle test grade (3+, 4-, and 4). If an individual's strength is to be monitored using manual-muscle testing, grades obtained by a single tester are recommended.

Measurement variability and sincerity of effort: clinical utility of isokinetic strength coefficient of variation scores

Although the use of measures of strength variability as a means of judging sincerity of effort is becoming common practice, the accuracy of doing so has been questioned. Coefficient of variation (CV) cut-off points, indicating the upper limit of variability for repeated maximal efforts, are routinely used to identify workers providing submaximal efforts during various strength tests. However, the stability of the CV itself has not been considered when comparing an individual's observed CV score to these cut-off points. The purpose of the present study was to examine the day-to-day variability of the CV calculated from maximal isokinetic knee extension efforts, and to describe how this measurement error affects the accuracy of the CV as a distinguishing criterion between maximal and submaximal efforts. Thirty-one healthy males (mean age 25 +/- 4.5 years) completed three maximal and three submaximal isokinetic knee extension efforts on two separate occasions. Although submaximal CVs were significantly greater than maximal CVs (15.6 versus 3.7%; p < 0.01), there was considerable overlap between submaximal and maximal CV frequency distributions. More importantly, an individual observed CV could vary +/- 3.1% as a result of day-to-day variation or measurement error. This range in possible CV scores should be considered when comparing an individual's score to proposed cut-off points. Since individual CVs vary considerably from day-to-day, and since precise cut-off values distinguishing between maximal and submaximal conditions cannot be identified, CV scores must be interpreted cautiously, and the potential errors in relying extensively on this approach to identifying insincere efforts should be recognised.