Evaluation of grip strength with a sustained maximal isometric contraction for 6 and 10 seconds

Effect of teeth clenching on handgrip force in adult men: role of periodontal mechanoreceptors

PURPOSE

Voluntary teeth clenching is shown to increase the strength of muscle reflexes contributing to the improvement of postural stability. However, the interaction between the handgrip strength and teeth clenching is not yet understood. In this study, we aimed to evaluate the change in handgrip force in response to voluntary teeth clenching, and its relation to the peripheral receptors that play a central role in the control of mastication.

METHODS

Thirty-six healthy men were divided into two groups: aged 50-59 years, no dental prosthesis, and 53-62 years with total dental prosthesis. Each individual was given handgrip and teeth clenching instructions for five experiments: only handgrip, teeth clenching followed by handgrip without teeth clenching, teeth clenching followed by handgrip with teeth clenching, and the repetition of the last two instructions while wearing mouth guards.

RESULTS

Our findings showed that maximum handgrip force decreased and the resistance to fatigue increased in complete edentulous individuals using appropriate prostheses. Also, the significantly lower maximum handgrip force and higher resistance to fatigue values of the participants with dental prosthesis using a mouth guard while teeth clenching, revealed the central roles of periodontal mechanoreceptors.

CONCLUSION

Decreases in masticatory sensory information processes influence handgrip force values which is the most important indicator of motor function. The lack of periodontal mechanoreceptors associated with dental prosthesis usage may lead to a loss in muscle strength.

Is Handgrip Strength Associated With Parkinson's Disease? Longitudinal Study of 71 702 Older Adults

BACKGROUND

To date, no study has longitudinally assessed the dose-response association between handgrip strength and incidence of Parkinson's Disease (PD).

OBJECTIVES

to investigate the longitudinal association between handgrip strength and the development of PD within a representative European population of older adults.

METHODS

Individuals aged 50 years and older from 27 European countries and Israel participated. We retrieved data from the Survey of Health, Ageing and Retirement in Europe waves 1, 2, 4, 5, 6, 7, and 8. Handgrip strength was measured using a hand dynamometer and participants reported whether they had a medical PD diagnosis. Time-varying exposure and covariates were modeled using both Cox regression and restricted cubic splines.

RESULTS

A total of 71 702 participants (mean age 65.2 years) were followed over a median period of 5.0 years. Among them, 314 participants developed PD. In the fully adjusted model, we observed a higher risk (hazard ratio [HR]: 2.50; 95% CI:1.92-3.32) of PD for participants with lower handgrip strength (third 1) and a lower risk of PD for participants in the second third (HR: 1.41; 95% CI: 1.06-1.87). In dose-response analyses, men showed lower risk of PD from 27 kg (HR:0.94; 95% CI: 0.91-0.97) to 59 kg (HR:0.10; 95% CI: 0.04-0.22), whereas women showed significant reductions from 24 kg (HR:0.68; 95% CI: 0.46-0.99) to 38 kg (HR:0.44; 95% CI: 0.22-0.88).

CONCLUSIONS

Handgrip strength ought to be incorporated as one of the measures in the prognostic toolbox for the screening of older adults who are possibly at risk of developing PD.

The effect on handgrip strength of low-frequency percutaneous electric stimulation applied to the median and cubital nerves: A randomized, double-blind controlled trial

Percutaneous electrical nerve stimulation (PENS) consists of applying an electric current of <1,000 Hz to different neuromuscular structures through acupuncture needles. Currently, there is controversy surrounding the effect of PENS on muscle strength in the scientific literature. The main objective was to assess the effect of PENS applied to the median and cubital nerves on the maximum handgrip strength (MHS) compared to sham stimulation, as well as to determine the safety of the intervention. A parallel, randomized, double-blind controlled trial in a sample of 20 healthy subjects. Participants were randomly allocated in the experimental (n = 10) and control (n = 10) groups. A blinded researcher measured MHS. Measurements of MHS of the dominant hand were taken at four time points: preintervention, immediately postintervention, 24 hr after the intervention, and at a 10-day follow-up. A 10-Hz percutaneous electrical current stimulation was employed. The control group also received the same puncture method but with no electric stimulation. Compared to baseline, the MHS decreased 10.4% (SEM = 3.2, p = .02) in the PENS group at 24 hr postintervention, with no differences observed between baseline and at 10 days postintervention. No changes in grip strength were observed at any time point in the sham group. To sum up, PENS decreased MHS at 24 hr postintervention, which does not persist 10 days after the stimulation. PENS can be considered a safe technique. Trials with larger sample sizes are required to corroborate the findings of this study. Clinical Trials Registration: NCT, NCT04662229, filed on March 12th of 2020.

Measures of Maximal Tactile Pressures during a Sustained Grasp Task Using a TactArray Device Have Satisfactory Reliability and Concurrent Validity in People with Stroke

Sensor-based devices can record pressure or force over time during grasping and therefore offer a more comprehensive approach to quantifying grip strength during sustained contractions. The objectives of this study were to investigate the reliability and concurrent validity of measures of maximal tactile pressures and forces during a sustained grasp task using a TactArray device in people with stroke. Participants with stroke (n = 11) performed three trials of sustained maximal grasp over 8 s. Both hands were tested in within- and between-day sessions, with and without vision. Measures of maximal tactile pressures and forces were measured for the complete (8 s) grasp duration and plateau phase (5 s). Tactile measures are reported using the highest value among three trials, the mean of two trials, and the mean of three trials. Reliability was determined using changes in mean, coefficients of variation, and intraclass correlation coefficients (ICCs). Pearson correlation coefficients were used to evaluate concurrent validity. This study found that measures of reliability assessed by changes in means were good, coefficients of variation were good to acceptable, and ICCs were very good for maximal tactile pressures using the average pressure of the mean of three trials over 8 s in the affected hand with and without vision for within-day sessions and without vision for between-day sessions. In the less affected hand, changes in mean were very good, coefficients of variations were acceptable, and ICCs were good to very good for maximal tactile pressures using the average pressure of the mean of three trials over 8 s and 5 s, respectively, in between-day sessions with and without vision. Maximal tactile pressures had moderate correlations with grip strength. The TactArray device demonstrates satisfactory reliability and concurrent validity for measures of maximal tactile pressures in people with stroke.

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.

A novel sensor-embedded holding device for monitoring upper extremity functions

There are several causes that can lead to functional weakness in the hands or upper extremities (UE), such as stroke, trauma, or aging. Therefore, evaluation and monitoring of UE rehabilitation have become essential. However, most traditional evaluation tools (TETs) and assessments require clinicians to assist or are limited to specific clinical settings. Several novel assessments might apply to wearable devices, yet those devices will still need clinicians or caretakers to help with further tests. Thus, a novel UE assessment device that is user-friendly and requires minimal assistance would be needed. The cylindrical grasp is one of the common UE movements performed in daily life. Therefore, a cylindrical sensor-embedded holding device (SEHD) for training and monitoring was developed for a usability test within this research. The SEHD has 14 force sensors with an array designed to fit holding positions and a six-axis inertial measurement unit (IMU) to monitor grip strength, hand dexterity, acceleration, and angular velocity. Six young adults, six healthy elderly participants, and three stroke survivors had participated in this study to see if the SEHD could be used as a reference to TETs. During result analyses, where the correlation coefficient analyses were applied, forearm rotation smoothness and the Purdue Pegboard Test (PPT) showed a moderate negative correlation [r (16) = −0.724, p < 0.01], and the finger independence showed a moderate negative correlation with the PPT [r (10) = −0.615, p < 0.05]. There was also a highly positive correlation between the maximum pressing task and Jamar dynamometer in maximum grip strength [r (16) = 0.821, p < 0.01]. These outcomes suggest that the SEHD with simple movements could be applied as a reference for users to monitor their UE ability.

Recovery and Fatigue Behavior of Forearm Muscles during a Repetitive Power Grip Gesture in Racing Motorcycle Riders

Despite a reduction in the maximal voluntary isometric contraction (MVC_isom) observed systematically in intermittent fatigue protocols (IFP), decrements of the median frequency, assessed by surface electromyography (sEMG), has not been consistently verified. This study aimed to determine whether recovery periods of 60 s were too long to induce a reduction in the normalized median frequency (MF_EMG) of the flexor digitorum superficialis and carpi radialis muscles. Twenty-one road racing motorcycle riders performed an IFP that simulated the posture and braking gesture on a motorcycle. The MVC_isom was reduced by 53% (p < 0.001). A positive and significant relationship (p < 0.005) was found between MF_EMG and duration of the fatiguing task when 5 s contractions at 30% MVC_isom were interspersed by 5 s recovery in both muscles. In contrast, no relationship was found (p > 0.133) when 10 s contractions at 50% MVC were interspersed by 1 min recovery. Comparative analysis of variance (ANOVA) confirmed a decrement of MF_EMG in the IFP at 30% MVC_isom including short recovery periods with a duty cycle of 100% (5 s/5 s = 1), whereas no differences were observed in the IFP at 50% MVC_isom and longer recovery periods, with a duty cycle of 16%. These findings show that recovery periods during IFP are more relevant than the intensity of MVC_isom. Thus, we recommend the use of short recovery periods between 5 and 10 s after submaximal muscle contractions for specific forearm muscle training and testing purposes in motorcycle riders.

A Systematic Review of Handgrip Strength Measurement in Clinical and Epidemiological Studies of Kidney Disease: Toward a Standardized Approach

In chronic kidney disease (CKD), handgrip strength (HGS) is recommended as a surrogate measure of protein-energy status and functional status. However, it is not routinely used because of inconsistencies such as the optimal timing of the HGS measurement and unclear guidance regarding technique. We aimed to determine the extent of variation in the protocols and methods of HGS assessment. We aimed to identify clinical and epidemiological studies conducted on CKD that reported on the use of HGS as an outcome. A systematic literature search identified n = 129 studies with a total participant population of n = 35,192. We identified large variations in all aspects of the methodology including body and arm position, repetitions, rest time, timing, familiarization, and how scores were calculated. The heterogeneous methodologies used reinforce the need to standardize HGS measurement. After reviewing previously employed methodology in the literature, we propose a comprehensive HGS assessment protocol for use in CKD.

Clinical malnutrition predictive model among gynecologic cancer patients prior to elective operation: A cross-sectional study

BACKGROUND

Malnutrition is common among cancer patients regardless of stage of cancer. Given the strong association between malnutrition with prolonged hospitalization, delayed recovery and even higher post-operative complications among gynaecologic cancer (GC) patients, it is important to understand its predictive factors. The current study aimed to determine malnutrition predictors among GC patients before elective operation.

METHOD

A cross-sectional study was conducted among surgical GC patients who were admitted for elective surgery. Data on socio-demographic characteristics, clinical status (diagnosis, the staging of cancer, comorbidities and family history on cancer), anthropometric measures [ Body Mass Index (BMI), weight changes, the percentage of weight loss past one month, muscle mass, fat mass, fat-free mass and mid-upper arm circumference (MUAC)], biochemical profiles [C-reactive protein, albumin and C-reactive protein (CRP) to albumin ratio (CAR)], handgrip strength, total daily energy and protein intake, and malnutrition status [scored Patient Generated-Subjective Global Assessment (PG-SGA)] were assessed during admission.

RESULTS

Study recruited 124 participants and 57.2% (n = 71) were malnourished. Mean for age, weight changes past one month, handgrip strength, total daily energy and protein intake, PG-SGA score and CAR of participants were 49.9 ± 12.5 years, -4.9 ± 7.2%, 15.6 ± 6.2 kg, 25±7 kcal/kg/day, 1.0 ± 0.3 g/kg/day, 6.5 ± 5.4 and 0.7 ± 1.9, respectively. Multiple linear regression test revealed that the percentage of weight loss past one month, haemoglobin, CRP and handgrip strength were the significant predictors of malnutrition.

CONCLUSION

Malnutrition is common among GC patient even before elective operation. The early malnutrition screening following with proper nutritional intervention is crucial to optimize nutritional status among GC patients before elective operation.

Investigating the functional grip strength of elderly fallers in Singapore

Background:

Static grip strength has been a reliable method for assessing the functional capacity of the individual and can be a useful marker for identifying elderly people at risk of functional deterioration leading to a fall. However, static grip strength alone may not represent the true maximum strength that an individual could exert in his/her daily life, especially if the task requires simultaneous forces from gripping and a forearm twisting action, which is termed as functional isometric grip strength. Hence, the objectives of this study were to determine the differences in the fallers’ grip strengths at static-neutral grip position and during isometric forearm pronation/supination, as well as the differences between the maximum and sustained isometric grip strengths.

Methods:

Data were analysed from 31 elderly people (11 males and 20 females) aged 70 and over. Using a custom-made hand strength measurement device, three measurements were taken: (1) grip strength in neutral forearm position; (2) grip strength during isometric forearm pronation; and (3) grip strength during isometric forearm supination.

Results:

Elderly fallers could only achieve approximately 60%–80% of the maximum normative strength. Additionally, it was found that their functional isometric grip strengths were generally weaker than their static maximal grip strength, especially during isometric supination as either maximum or sustained isometric supination grip strengths (Dominant hand: 10.6 kg and 8.5 kg, respectively (males); 6.0 kg and 4.4 kg, respectively (females)).

Conclusion:

Elderly fallers are weaker when their grip is subjected to additional torque, endurance or both. Hence, these findings have potential implications for designing better screening tools for the geriatric population.

Clusters of cardiovascular risk factors and its association with muscle strength in adults

BACKGROUND

Cardiovascular diseases are the leading cause of death globally. The aim of the study was to investigate the relationship between muscle strength (MS) and clusters of metabolic syndrome (MetS) components in adults.

METHODS

Population-based cross-sectional study comprising 533 adults (45.3±11.1 years) from Florianópolis, Brazil. MS - calculated as the ratio between absolute strength (kgf) and body mass (kg) - was measured by handgrip dynamometry. Data on blood pressure, waist circumference, lipids and blood glucose were used to identify MetS components that were analyzed as individual variables and clusters. Multiple linear regression adjusted was used.

RESULTS

Individually, MS was inversely associated with all MetS components (1, 2, 3 and 4 factors, β of at least -0.08 kgf/kg). In addition, MS was negatively associated with number of positive MetS components (1, 2, 3 and 4 factors; β of at least -0.05 kgf/kg). Individually or combined in clusters of two, three and four risk factors (β of at least -0.20 kgf/kg), abdominal obesity was directly associated with lower MS values. All combinations of 3 and 4 MetS components (β of at least -0.13 kgf/kg) were inversely associated with MS.

CONCLUSIONS

Greater number of individual MetS components were related to lower MS values.

Intertrial Rest for Maximum Grip and Key Pinch Strength in Japanese Young Adults

OBJECTIVE

This study investigated the most appropriate intertrial rest period for maximum grip and key pinch strength measurements involving three trials.

METHOD

The study included 40 male and 40 female participants. Using a repeated-measures design, six intertrial rest periods-15 s, 30 s, 60 s, 90 s, 120 s, and 150 s-were investigated, one per day on 6 different days.

RESULTS

A repeated-measures analysis of variance or Friedman test found significant decreases in grip and key pinch strength over the three trials in all test conditions. However, for both hands, only small differences were observed in test conditions (≥90 s, male grip; ≥60 s, female grip; male and female key pinch; effect sizes of <0.5).

CONCLUSION

If a rest of ≥150 s is not possible, 90 s of rest between trials for grip strength and 60 s of rest between trials for key pinch strength can be considered.

An instrumented object for hand exercise and assessment using a pneumatic pressure sensor

Measurement of grip force is important for both exercise training and assessment of the hand during physical rehabilitation. The standard method uses a grip dynamometer which measures the force between the fingers and opposing thumb. The primary limitation of the grip dynamometer is the restriction of measurement to cylindrical grasps. Any deformation of the hand due to muscular or skeletal disease makes the grip dynamometer difficult or impossible to use. An alternative to the grip dynamometer is a sealed pneumatic object that can be gripped by the hand. Measurement of the internal pressure in the object can be related to the grip force. In this paper, we analyze such a pneumatic pressure sensing object for hand grip assessment and also describe an easy fabrication of the grip sensor. The instrumented object presented in this paper is designed to assess both the maximal voluntary grip forces and continuous grip force to monitor control of hand function during exercise under instruction from a therapist. Potential uses of such a pneumatic pressure sensing object for hand grip are in physical rehabilitation of patients following paralysing illnesses like stroke and spinal cord injury.

A Brief Review of Handgrip Strength and Sport Performance

Cronin, J, Lawton, T, Harris, N, Kilding, A, and McMaster, DT. A brief review of handgrip strength and sport performance. J Strength Cond Res 31(11): 3187-3217, 2017-Tests of handgrip strength (HGS) and handgrip force (HGF) are commonly used across a number of sporting populations. Measures of HGS and HGF have also been used by practitioners and researchers to evaluate links with sports performance. This article first evaluates the validity and reliability of various handgrip dynamometers (HGD) and HGF sensors, providing recommendations for procedures to ensure that precise and reliable data are collected as part of an athlete's testing battery. Second, the differences in HGS between elite and subelite athletes and the relationships between HGS, HGF, and sports performance are discussed.

A comparison of electronic and manual dynamometry and goniometry in patients with fracture of the distal radius and healthy participants

The purpose of this study was to assess the intra-rater and inter-rater reliability of electronic and manual dynamometry and goniometry in healthy volunteers, and the inter-instrument reliability in the assessment of healthy volunteers and patients recovering after a fracture of the distal radius. Grip strength, grip fatigue, pinch strength and range of motion were assessed in all participants with both the manual and electronic instruments by two physiotherapists and orthopaedic specialist trainee. The measures of dynamometry demonstrated excellent reliability (intra-class correlation coefficient >0.90), with the instruments found to be interchangeable with the exception of the grip fatigue. Variable intra-rater and inter-rater reliability was demonstrated with all planes of movement for the goniometry measures regardless of the instrument used. The results of this study support the continued use of dynamometry in the clinical setting, but raise questions regarding the use of goniometry measurements.

LEVEL OF EVIDENCE

Diagnostic level III.

Prophylactic Effects of Sauna on Delayed-Onset Muscle Soreness of the Wrist Extensors

BACKGROUND

High-intensity of exercise or unaccustomed eccentric exercise can cause the phenomenon of Exercise-Induced Muscle Damage (EIMD) which usually results in cramps, muscle strain, impaired muscle function and delayed-onset muscle soreness.

OBJECTIVES

This study investigated the prophylactic effects of sauna towards the symptoms associated with muscle damage from eccentric exercises of wrist extensor muscle group.

PATIENTS AND METHODS

A total of twenty-eight subjects (mean age 20.9 years old, SD = 1.6) were randomly divided into the sauna group (n = 14) and the control group (n = 14). In the sauna group, subjects received sauna before eccentric exercise of the wrist extensor. The eccentric exercises were conducted on the non-dominant arm by using an isokinetic dynamometer. Pain Intensity (PI), Pressure Pain Threshold (PPT) and passive range of motion of wrist flexion (PF-ROM) and extension (PE-ROM) were measured as pain variables. Grip Strength (GS) and Wrist Extension Strength (WES) were measured as variables of wrist extensor muscle function. All the measurements were performed at baseline, immediately after and from 1st to 8th days after the exercise-induced muscle damage.

RESULTS

The sauna group significantly demonstrated a lower deficit in ROM (passive flexion and passive extension), GS and WES following exercise than that of the control group (P < 0.05).

CONCLUSIONS

Sauna application prior to the exercise-induced muscle damage demonstrated effectiveness in reduction of sensory impairment (PF-ROM and PE-ROM) and improvement of muscle functions (GS, and WES) in wrist extensor muscle group.

The Relationship Between Sleep Disturbance and Functional Status in Mild Stroke Patients

Objective

To investigate the sleep state of mild stroke patients and relationship between sleep disturbance and functional status.

Methods

A total of 80 acute stroke patients were enrolled in this study. The criteria for inclusion in the study was as following: 1) first stroke, 2) cognitive function preserved enough to perform the test (Mini Mental State Examination ≥24), 3) good functional levels (Modified Rankin Scale ≤3), 4) upper extremity motor function preserved enough to perform occupational tests (hand strength test, Purdue pegboard test, 9-hole peg test, and Medical Research Council score ≥3), and 5) less than 2 weeks between the stroke and the assessment. Quality of sleep was assessed by using Pittsburg Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), Insomnia Severity Index (ISI), and Stanford Sleepiness Scale (SSS). Activities of daily living was assessed by using the Modified Barthel Index (MBI) and depressed mood was assessed by using the Beck Depression Inventory (BDI). Gross and fine motor function of the upper extremity was assessed by using hand strength test (Jamar dynamometer), Purdue pegboard test, and the 9-hole peg test.

Results

The results of the occupational assessment were fine in the good sleepers. The PSQI, ESS, and ISI were correlated with some of the assessment tools (BDI, MBI, Purdue pegboard, 9-hole peg, and hand strength).

Conclusion

In conclusion, this study emphasizes that sleep disturbance can affect the functional status in mild acute stroke patients. Therefore, clinicians must consider sleep status in stroke patients and need to work to control it.

Reliability of fitness tests using methods and time periods common in sport and occupational management

CONTEXT

Fitness testing is used frequently in many areas of physical activity, but the reliability of these measurements under real-world, practical conditions is unknown.

OBJECTIVE

To evaluate the reliability of specific fitness tests using the methods and time periods used in the context of real-world sport and occupational management.

DESIGN

Cohort study.

SETTING

Eighteen different Cirque du Soleil shows.

PATIENTS OR OTHER PARTICIPANTS

Cirque du Soleil physical performers who completed 4 consecutive tests (6-month intervals) and were free of injury or illness at each session (n = 238 of 701 physical performers).

INTERVENTION(S)

Performers completed 6 fitness tests on each assessment date: dynamic balance, Harvard step test, handgrip, vertical jump, pull-ups, and 60-second jump test.

MAIN OUTCOME MEASURE(S)

We calculated the intraclass coefficient (ICC) and limits of agreement between baseline and each time point and the ICC over all 4 time points combined.

RESULTS

Reliability was acceptable (ICC > 0.6) over an 18-month time period for all pairwise comparisons and all time points together for the handgrip, vertical jump, and pull-up assessments. The Harvard step test and 60-second jump test had poor reliability (ICC < 0.6) between baseline and other time points. When we excluded the baseline data and calculated the ICC for 6-month, 12-month, and 18-month time points, both the Harvard step test and 60-second jump test demonstrated acceptable reliability. Dynamic balance was unreliable in all contexts. Limit-of-agreement analysis demonstrated considerable intraindividual variability for some tests and a learning effect by administrators on others.

CONCLUSIONS

Five of the 6 tests in this battery had acceptable reliability over an 18-month time frame, but the values for certain individuals may vary considerably from time to time for some tests. Specific tests may require a learning period for administrators.

Comparison of an intermittent and continuous forearm muscles fatigue protocol with motorcycle riders and control group

Motorcycle races' long duration justify the study of forearm muscles fatigue, especially knowing the frequently associated forearm discomfort pathology. Moreover, while continuous fatigue protocols yield unequivocal results, EMG outcomes from an intermittent protocol are quite controversial. This study examined the forearm muscle fatigue patterns produced during these two protocols, comparing riders with a control group, and relating maximal voluntary contraction with EMG parameters (amplitude - NRMS and median frequency - NMF) of both protocols to the forearm discomfort among motorcycle riders. Twenty riders and 39 controls performed in separate days both protocols simulating the braking gesture and posture of a rider. EMG of flexor digitorum superficialis (FS) and carpi radialis (CR) were monitored. CR revealed more differences among protocols and groups compared to FS. The greater CR activation in riders could be interpreted as a neuromotor strategy to improve braking precision. When FS fatigue increased, the control group progressively shift toward a bigger CR activation, adopting an intermuscular activation pattern closer to riders. Despite the absence of NMF decrement throughout the intermittent protocol, which suggest that we should have shorten the recovery times from the actual 1 min, the superior number of rounds performed by the riders proved that this protocol discriminates better riders against controls and is more related to forearm discomfort.

Monitoring hand flexor fatigue in a 24-h motorcycle endurance race

Motorcycle riders must endure high levels of muscle tension for long periods of time, especially in their arms and forearms, when steering and using handlebar controls. Because the right hand operates the gas handle and front brakes, the present research focuses on fatigue in the right hand flexors. Ten adult riders, aged 32.5±5.5years, volunteered to participate in this study. During the 24h race each rider, on completion of a relay stage, visited the assessment box to do the following handgrip test sequence: (1) 10s of EMG recording at rest, (2) one 3-s maximal voluntary contraction (MVC), (3) 1min rest interval and (4) 50% MVC maintained during 10s. EMG amplitude (MP: μV) and median and mean frequency (MF and MPF: Hz) over the superficial finger flexors were recorded during the whole handgrip test sequence with adhesive surface electrodes. MVC values were maintained during the first two relays (50-60min duration in total) and dropped gradually thereafter (p<0.01). During the monitoring of the 50% MVC, mean amplitude increased (p=0.024) while median and mean frequency tended to decrease. These results suggest fatigue is produced in motorcycle riders in a 24h race. However, the expected reduction of EMG frequency was not confirmed given to a potentially large variability.

Reliability of muscle function and sensory perception measurements of the wrist extensors

This study determined the reliability of muscle function and sensory perception measures of the wrist extensors. The test-retest reliability of the measurements was determined by an intraclass correlation coefficient (ICC), coefficient of variation (CV), standard error of measurements (SEMs), and one-way repeated measures ANOVA using the values collected from 25 young (20.6 +/- 1.3 years) healthy male volunteers on two occasions separated by 1 day. The measures consisted of grip strength, wrist extension strength (WES), range of motion in active and passive wrist flexion and extension, choice reaction time (CRT), vibration sense (VIB), joint position error sense (JPE), cold pain (CP) and heat pain threshold, and pressure pain threshold. An acceptable reliability was determined as the ICC values greater than 0.85, CV less than 15%, and SEMs less than 5%. ICC of all measures except for JPE were greater than 0.85, only CV of JPE, CP, and VIB exceeded 15%, SEMs were higher than 5% only for JPE and CP, and the ANOVA showed a significant time effect for CRT and WES. It is concluded that most of the measurements except JPE are reliable and can be used to investigate effects of a physiotherapy intervention on the wrist extensors.

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.

Test-retest reliability of grip-strength measures obtained over a 12-week interval from community-dwelling elders

This study examined the test-retest reliability of hand-grip strength measured over a 12-week period. Twenty-one apparently healthy elders (age=75.0+/-5.9 yr) participated. Single strength measurements obtained bilaterally using a Jamar dynamometer were compared across time. Test and retest measurements did not differ significantly over time on either side. Intraclass correlation coefficients were 0.954 and 0.912 for the left and right hands, respectively. Technical errors of measurement were 15.8 and 21.3N for the left and right hands, respectively. Measurements of hand-grip strength obtained from elders over a 12-week period are reliable.

Force tracking system for the assessment of grip force control in patients with neuromuscular diseases

BACKGROUND

The majority of hand functionality assessment methods consist of the maximal voluntary grip force measurement. Additional knowledge on sensory-motor control can be obtained by capturing functional grip force in a time frame. Tracking methods have been successfully used for the assessment of grip force control in stroke patients and patients with Parkinson's disease.

METHODS

A novel tracking system for the evaluation of grip force control is presented. The system consists of a grip-measuring device with the end-objects of different shapes which was used as input to a tracking task where the patient applied the grip force according to the visual feedback. The grip force control was assessed in 20 patients with neuromuscular diseases and 9 healthy subjects. The performance of two tracking tasks was analysed in five grips. The ramp-tracking task was designed to assess the grip strength and muscle fatigue. The sinus-tracking task was used to evaluate grip force control during periodic muscle activation.

FINDINGS

The results suggest that in some patients the disease did not affect their grip force control despite evident muscular weakness. Most patients produced larger tracking errors in precision grip while the healthy subjects showed less significant differences in performance among the grips tested.

INTERPRETATION

The current study investigated force control in patients with neuromuscular diseases where detection of small changes in motor performance is important when following the progress of disease. The presented evaluation method can provide additional information on muscle activation and fatigue as compared to traditional grip strength testing.

Average versus maximum grip strength: which is more consistent?

The average of three consecutive measurements is the most frequently used method for grip strength assessment. The purpose of this study was to compare the consistency of the maximum value with that of the average value of three consecutive measurements of grip strength. One hundred healthy volunteers participated in this study. Three measurements of grip strength were taken on two occasions separated by 2 weeks. For each hand, two average values and two maximum values were obtained. Ninety-five per cent limits of agreement for the average method were - 8.3 (-23%) to +7.2 (+20%)kg and for the maximum method were - 8.8 (-23%) to + 8 (+21%)kg. Both methods of grip strength assessment were found to be highly consistent with no statistically significant difference.