A static dynamometer measuring simultaneous torques exerted at the upper limb

The state of pelvic floor muscle dynamometry: A scoping review

AIMS

To discuss the advantages and limitation of the different pelvic floor muscle (PFM) dynamometers available, both in research and industry, and to present the extent of variation between them in terms of structure, functioning, psychometric properties, and assessment procedures.

METHODS

We identified relevant studies from four databases (MEDLINE, Compendex, Web of Science, and Derwent Innovations Index) up to December 2020 using terms related to dynamometry and PFM. In addition, we conducted a hand search of the bibliographies of all relevant reports. Peer-reviewed papers, conference proceedings, patents and user's manuals for commercial dynamometers were included and assessed by two independent reviewers.

RESULTS

One hundred and one records were included and 23 PFM dynamometers from 15 research groups were identified. From these, 20 were considered as clinical dynamometers (meant for research settings) and three as personal dynamometers (developed by the industry). Overall, significant heterogeneity was found in their structure and functioning, which limits development of normative data for PFM force in women. Further research is needed to assess the psychometric properties of PFM dynamometers and to standardize assessment procedures.

CONCLUSION

This review points up to the heterogeneity of existing dynamometers and methods of assessing PFM function. It highlights the need to better document their design and assessment protocol methods. Additionally, this review recommends standards for new dynamometers to allow the establishment of normalized data.

Portable Dynamometer-Based Measurement of Pelvic Floor Muscle Force

OBJECTIVE

In attempts to improve the quality of life of women, continuous projects are sought between rehabilitation intervention and engineering. Using the knowledge of the pelvic floor muscle (PFM) physiology, assessment and training methods are developed to reduce lower urinary tract symptoms such as urinary incontinence. Therefore, this paper covers the design and implementation of a portable vaginal dynamometer.

METHODS

A PFM probe is designed, 3D printed, assembled, and tested in ten women to assess its acceptability and usability. The feedback from the usability study is used to optimize the PFM probe design. A vaginal dynamometer is developed based on the designed PFM probe, then tested for linearity, repeatability, hysteresis, noise and heat effect, and power consumption. The variability between the different produced PFM probe prototypes is evaluated.

RESULTS

Force measurements are made using a load cell. Wireless communication is performed through a Bluetooth low energy transceiver v5.0, with a corresponding interface on both computer and smartphone. The device operates at a 3.3V supply and achieves a power consumption of 49.5 mW in operating mode. Two PFM probe sizes are designed to accommodate different vaginal hiatus sizes, based on usability study feedback. The proposed system allows the physiotherapist to wirelessly monitor variation in pelvic floor muscle force during assessment and/or training.

DISCUSSION/CONCLUSION

The testing results showed that the newly designed system has the potential to measure the PFM function in functional conditions such as the standing position.

Comparison of strength measurements under single-joint and multi-joint conditions in hemiparetic individuals

Objective: It has been suggested that the measurement of strength is inappropriate in patients with stroke, in large part because of the presence of abnormal synergy patterns. The aim of the present study was to characterize force production during multi-joint maximal exertion involving different combinations of activation between shoulder and elbow flexors and extensors.

Design: Cross-sectional study.

Setting: Rehabilitation centre.

Subjects: A convenience sample of 16 chronic hemiparetic stroke subjects.

Main outcome measures: Maximal torques in flexion and extension at the shoulder and the elbow were measured using static dynamometers (single-joint condition). In addition, the maximal forces produced at the wrist were measured in four directions in the sagittal plane requiring different torque combinations between shoulder and elbow flexors and extensors (multi-joint condition).

Results: No difference was found across directions for the ratios of maximal forces (paretic/nonparetic) in the multi-joint condition (p = 0.227; mean ratios (9±SD) for each direction ranging from 0.599±0.23 to 0.689±0.27), suggesting that the ability to produce force did not change as a function of the required torque combination. In addition, relative torques (% of the maximal torque in the single-joint condition) exerted during the multi-joint exertions were similar on the paretic and the nonparetic side.

Conclusions: These results do not support the assumption that force production is limited by abnormal synergy patterns between flexors and extensors at the shoulder and the elbow in hemiparetic patients.

Reliability of maximal static strength measurements of the arms in subjects with hemiparesis

OBJECTIVE

To evaluate the reliability of maximal static strength measurements of five arm muscle groups and of strength ratios (paretic/non-paretic) in subjects with poststroke hemiparesis.

DESIGN

The generalizability theory was used to estimate the reliability coefficients and standard errors of measurement of maximal strength for various combinations of trials and sessions and of the strength ratios for one and two sessions. Grip maximal voluntary force and/or maximal voluntary torques exerted by flexor and extensor muscles at both the elbow and shoulder joints were measured in 17 subjects with poststroke hemiparesis. Multiple trials were performed by subjects during two sessions.

SETTING

Rehabilitation centre.

SUBJECTS

A convenience sample of 17 subjects with poststroke hemiparesis.

RESULTS

The reliability coefficients for the strength measurements were in the range of 0.81-0.97 with standard errors of measurement accounting for 4% to 20% of the group means. For the strength ratios, the coefficients of generalizability ranged from 0.76 to 0.95 with standard errors of measurement equal to 6% to 19% of the group means.

CONCLUSIONS

The maximal strength measurements of the arms in subjects with hemiparesis are reliable. The strength ratios are also reliable and can be used to quantify strength impairment.

Dynamic shoulder dynamometry: a way to develop delay onset muscle soreness in shoulder muscles

A dynamic shoulder dynamometer has been designed to develop a vertical downward force over a measured range of motion, i.e. scapular elevation. The dynamometer is force-controlled to apply a required force within the range of motion. Calibration procedures were performed to assess the reliability of the force and displacement measurements. The system is designed to operate in isometric or eccentric conditions. For eccentric exercise the dynamometer has, for the first time, provided possibilities to elicit delay onset muscle soreness in shoulder muscles. In future, the apparatus will enable investigations of sensory-motor interactions in the shoulder region.

Continuous monitoring of upper-limb activity in a free-living environment

OBJECTIVE

To develop and evaluate a system for the objective measurement of upper-limb activity during a person's activities of daily living.

DESIGN

Construct validation study.

SETTING

Home and work environment.

PARTICIPANTS

Ten able-bodied participants and 10 stroke patients.

INTERVENTIONS

A novel activity monitor was developed for monitoring upper-limb activity. The Strathclyde Upper-Limb Activity Monitor (SULAM) gave a signal proportional to the vertical displacement of the wrist with respect to the shoulder. Participants wore the SULAM on both upper limbs for 8 hours while performing their normal daily activities.

MAIN OUTCOME MEASURES

SULAM-derived variables quantified the total upper-limb activity and the range in which movement of the upper limb occurred.

RESULTS

Data showed that the dominant arm of the able-bodied participants was 19% more active than the nondominant arm, whereas the unaffected arms of the group of stroke patients was used 3 to 6 times more than their affected arm. For all the variables, in both groups, there were significant differences between their upper limbs except for movement below midtrunk. There were also significant differences between groups for bimanual movement time ( P =.000) and composite movement time ( P =.000).

CONCLUSIONS

The results suggest that the quantification of vertical position of the wrist with respect to the shoulder might reflect upper-limb activity. By using the SULAM, it is possible to monitor upper-limb activity over the course of a person's normal day, with minimal interference. This study provides preliminary evidence of the SULAM as a useful tool for objectively evaluating interventions aimed at improving upper-limb activity and function.

Relative shoulder flexor and handgrip strength is related to upper limb function after stroke

OBJECTIVE

To compare the relative strength of different muscle groups of the paretic upper limb and assess the relationship with motor performance.

DESIGN

Descriptive study.

SETTING

Secondary care rehabilitation centre.

SUBJECTS

A convenience sample of 13 chronic hemiparetic stroke subjects.

MAIN OUTCOME MEASURES

The maximal active torques of five muscle groups were measured in both upper limbs (UL) and converted into relative strength (paretic/nonparetic). The UL function was assessed using the Box and Block Test, the Finger-to-Nose Test, the Fugl-Meyer Test and the TEMPA (Test Evaluant les Membres supérieurs des Personnes Agées).

RESULTS

The Friedman two-way analysis of variance shows a significant difference across the relative strength of the different muscle groups (p = 0.017), but subsequent multiple comparisons indicate a significant difference between handgrip and elbow extension only (relative strength of 0.52 +/- 0.27 and 0.73 +/- 0.23 respectively). However, data show the presence of large intrasubject imbalances between muscle groups. The relative forces for shoulder flexion and handgrip are the best predictors of the UL function, the higher Spearman's rho correlation coefficients for each clinical test ranging from 0.70 to 0.81.

CONCLUSIONS

These results do not confirm classical clinical teaching regarding the distribution of weakness following stroke (e.g., proximal to distal gradient; extensors more affected than flexors) but support the hypothesis that strength is related to the function of the paretic upper limb.

Evidence for strength imbalances as a significant contributor to abnormal synergies in hemiparetic subjects

Abnormal synergies in the paretic shoulder and elbow of hemiparetic subjects were quantified during maximal voluntary contractions (MVCs) in 27 subjects with a history of stroke and 8 age-matched control subjects. A six-axis load cell allowed simultaneous measurement of the primary torque the subject was attempting to maximize and the secondary torques at other joint actions. For example, during MVC of shoulder flexion, shoulder flexion is the primary torque and the secondary torques are internal/external rotation, abduction/adduction, and elbow flexion/extension. In general, the stroke subjects had increased secondary torques compared to controls, resulting in abnormal joint torque coupling within the set consisting of elbow flexion, internal rotation, adduction, shoulder flexion. Unlike previous studies, abnormal secondary torques in several cases were due to strength imbalances, which occur when the strength deficit for a particular joint action is greater than the strength deficit in the opposite joint action. This hypothesis was supported by electromyographic recordings and by the finding that subjects with larger strength imbalances tended to produce larger secondary torques. Possible mechanisms and consequences for rehabilitative treatments are discussed.

Effect of force-feedback treatments in patients with chronic motor deficits after a stroke

OBJECTIVE

To assess the effects a motor reeducation approach based on static dynamometers used to provide feedback on the force produced.

DESIGN

The study design was a single-blind, randomized, controlled trial. Chronic stroke subjects participated in a 6-wk, thrice-weekly, force-feedback program of either the upper paretic limb (n = 13) or the lower paretic limb (n = 12). Baseline and postintervention assessments of the performance of both the upper and the lower limb were measured for each subject, the untreated paretic limb of each group serving as a control for the other group.

RESULTS

With the exception of the handgrip force, strength measurements of the treated limb increased after completion of the treatment. The outcome measurements of the upper limb of the subjects included in the upper paretic limb were not significantly different after treatment from those measured in the lower paretic limb. In contrast, gait velocity and the distance walked in 2 min increased after treatment in the lower paretic limb as compared with the upper paretic limb, whereas the scores in the Fugl-Meyer test for the lower limb and the timed up-and-go test did not increase for either group after treatment.

CONCLUSION

The results indicate that treatment of the lower limb based on force feedback produces an improvement of gait velocity.

A transducer to measure isometric elbow moments

OBJECTIVE

The purpose of this study was to design and implement a transducer to measure accurately the isometric elbow moments produced by individuals with tetraplegia.

DESIGN

The device needed to be insensitive to off-axis moments and proximal joint motions and be capable of being used over a wide range of elbow and shoulder positions in an outpatient clinic setting.

BACKGROUND

Measurement of the smaller isometric moments produced by individuals with tetraplegia is especially sensitive to the errors that can be introduced by inaccurate lever arm determination, off-axis loads, and proximal joint motions. Devices traditionally utilized for quantifying isometric strength are difficult to implement for the spinal cord injured population.

METHODS

The elbow moment transducer consists of two four-bar parallelogram linkages joined by a lockable pivot. Strain gauges mounted on one beam of the parallelogram produce an output proportional to the elbow moment.

RESULTS

Calibration of the device indicates that it accurately quantifies isometric elbow moments over a range that is appropriate for evaluating elbow extension strength in individuals with tetraplegia.

CONCLUSIONS

A device was developed and implemented that accurately quantifies isometric elbow moments over a range that is appropriate for evaluating elbow extension strength in individuals with tetraplegia.

RELEVANCE

The ability to quantitatively evaluate elbow strength in persons with tetraplegia is useful for understanding and improving the clinical outcomes of rehabilitative interventions that involve the elbow.

Effects of upper and lower limb static exertions on global synkineses in hemiparetic subjects

OBJECTIVES

Global synkineses are nonpurposive pathological involuntary muscle activities or movements elicited at several or all of the joints of the affected limb or limbs during voluntary forceful resisted contractions. The purpose of this study was to assess the effect of upper and lower limb exertions on manifestations of upper limb global synkineses in hemiparetic subjects.

DESIGN

Involuntary muscle activities on the affected upper limb of 11 hemiparetic subjects and on the left or right upper limb of 10 control subjects were recorded using surface electromyography during successive bilateral maximal ankle exertions and during contralateral grips.

RESULTS

Significant differences in the level of involuntary electromyography (EMG) activities were observed between experimental conditions (ANOVAs, p < 0.05). EMG levels in hemiparetic subjects were significantly higher during contralateral grip tasks than during the ankle exertions.

CONCLUSION

These results suggest that upper limb global synkinases are more prevalent in specific tasks and that this task specificity may reflect the neurophysiological mechanisms involved in the generation of global synkinases.

A static dynamometer measuring simultaneous torques exerted at the upper limb

The majority of available dynamometers are designed to measure force or torque in one specific direction, one joint at a time. For the quantification of motor incoordination in neurological patient populations, these dynamometers provide limited information about the global behavior of the limb under investigation. This report describes the potential use and function of a static dynamometer measuring torques exerted simultaneously at the shoulder (flexion-extension, abduction-adduction, internal-external rotation), elbow (flexion-extension), and forearm (pronation-supination). Orthogonal forces were measured at the arm and wrist using strain gauge transducers interfaced with a laboratory computer. The lever arms were specified to a software program and the joint torques were calculated in real time according to static equilibrium equations. The use of the dynamometer is illustrated by characterizing for one hemiparetic subject, the joints torques recorded at the shoulder, elbow, and forearm during isolated submaximal grip exertions at different force levels on both sides. The torques generated at the shoulder, elbow and forearm during the hand grip tasks on the affected side were significantly higher than those obtained on the nonaffected side and increased with the grip force level. These differences probably reflect the loss of movement selectivity observed following a lesion in the central nervous system. Further studies are currently being undertaken in neurological patient populations to characterize and quantify motor deficits using this dynamometer. As a long term goal, we hope that the method and technologies described here will contribute to the evaluation and rehabilitation of these populations.