The purpose of this study was to explore utility of handgrip strength measured by the hand-grip dynamometer for assessment of nutritional status in protein-calorie malnutrition. The first study included six subjects (all right-handed), who had grip strength measured daily for five days, then weekly for three weeks. Intra-individual variability was approximately 10%. No learning or training effect was observed. Change in leg position from feet on the floor to elevation of feet made no significant difference in grip-strength measurement. In Phase Two, 43 healthy adult subjects (three left-handed) prior to elective surgery, height was significantly related to handgrip strength (r = 0.82, p < 0.001). Males were stronger than females. After surgery, the non-dominant hand lost significant strength (2.68 kilograms) and recovered more quickly than the dominant hand. Multiple regression analyses provided predictive equations for pre-surgery left hand-grip strength using age, sex, and height (R² = 0.77); from age, sex, hand measured, and grip strength two days after surgery or three days after surgery (R² = 0.89 for each). Ten sequential grip-strength measurements analyzed by repeated measures analysis of variance with orthogonal comparisons showed a difference in measurements between hands as well as before and after surgery. The slope of the measurement line was more linear before and three days after surgery, but more quadratic in shape two days after surgery. The effects seen by type of surgery were inversion of the slope of right hand sequential measurements two days after knee surgery and before-surgery drop and increase from trial five to trial seven in left hand sequential measurements of knee and vaginal hysterectomy subjects. In a six-month-long case study, grip-strength measurements were followed in a seriously-ill 68-year-old patient hospitalized for surgical repair of hiatal hernia and mucous fistula who underwent several periods of nutritional depletion. Grip strength varied throughout the period (although not differently from healthy subjects), but did not directly parallel changes in serum albumin or prealbumin. The conclusion was that hand strength measured by the handgrip dynamometer did not change enough with fasting and surgery from normal day-to-day variability to be useful for nutritional assessment.

The control of object manipulation tasks involves the close interplay of predictive and reactive control mechanisms. For example, when lifting an object, people typically predict the weight based on object size and material as well as sensorimotor memory obtained from previous lifts of the object. When lifting objects with a precision grip, people increase vertical load force to a target level that slightly exceeds the predicted weight. When the object is heavier than expected, the mismatch between expected and actual tactile signals associated with lift-off triggers a corrective action within ~100 ms, that involves probing increases in load force that continue until the object is lifted. Here we investigated whether this correction action can be adaptively influenced by experience. Participants repeatedly lifted an object that was instrumented with force sensors to measure the forces applied by the fingertips, with weight that could be varied without the knowledge of the participant. In 80% of trials, the weight was set to 2 N and, in different blocks of 110 trials, the remaining 20 % of trials (2 trials randomly selected from each successive 10 trials) was set to either 4 or 6 N. We found that the rate of change of the reflexively triggered increase in load force that occurred in the 4 or 6 N trials, scaled with the additional weight. That is, following the initial increase in load force to ~2 N, the subsequent increase in load force was more rapid for the 6 N object than the 4 N object. In contrast, the onset time of the reactive increase in load force was independent of the additional weight. Finally, this adaptation of reactive load force control took place quickly and was evident after only a few lifts of the heavier weight. These results indicate that the reactive increases in load force that occur when a lifted object is heavier than expected can be adapted and tuned, to refine behavior. This further suggests that multiple predictions can be generated about object weight when lifting. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2013-02-02 13:34:20.533

During transport of hand-held objects, the grip force is modulated in parallel with the load force changes. The control scheme underlying this grip-load force coupling involves subtle interplay between feedforward and feedback mechanisms. Based on internal models of the motor system and object properties, the load force can be predicted and the GF motor command can be specified in a feedforward manner. Moreover, during the course of arm movement, the CNS is informed by sensory feedback about mechanical events such as the lift-off of the object, slippage or excessive grip force. This information is used to correct the motor commands and to update the internal model of the motor apparatus and object. In this thesis, three experiments were conducted to examine the relative contributions of sensory-driven and anticipatory control of GF adjustments during cyclic vertical movement with a hand-held load. The main point was to assess whether internal models underlying the grip-load force coupling are robust when the environmental context was changed or when the sensory feedback was suppressed. Two experiments in parabolic flight were conducted to study the effects of a change in gravity on the dynamics of prehension. The main perturbation was that the novice subjects applied unnecessarily high safety margins during their first trial at 0 and 1.8 g in order to secure the grasp insofar as the gravitational component of the load force was unpredictable. By contrast, the temporal coupling between GF and LF was maintained regardless of the gravity conditions because the inertial component of the load could be still predicted from the arm motor command (efference copy). In the second study performed during parabolic flight, we have observed that the subjects were able to exert the same grip force for equivalent load generated either by a change of mass, gravity or acceleration despite the fact that it requires different arm motor commands. These two experiments brought further evidence that the predictive mechanisms largely contribute to the GF adjustment. Static forces such gravity are taken into account in the motor plan allowing adequate motor command and precise prediction of the incoming load force change. The GF output would depend on the precision of this prediction that can be evaluatedonly after the movement onset through sensory information about the actual state of the system. The third experiment performed in this thesis studied the role of cutaneous afferents in object manipulation by anesthetizing the thumb and index finger. In addition to their phasic slip-detection function, the cutaneous afferents are required for setting the background level of the grip force. Actually, in absence of tactile feedback, the temporal coupling between the grip and load forces is maintained but the mean magnitude of GF progressively decreases leading to object slipping. It is hypothesized that accumulating error occurred in the LF prediction leading to inadequate level of GF. Cutaneous afferents are thus required to correct and maintain the internal model of the arm-hand object system.

During transport of hand-held objects, the grip force is modulated in parallel with the load force changes. The control scheme underlying this grip-load force coupling involves subtle interplay between feedforward and feedback mechanisms. Based on internal models of the motor system and object properties, the load force can be predicted and the GF motor command can be specified in a feedforward manner. Moreover, during the course of arm movement, the CNS is informed by sensory feedback about mechanical events such as the lift-off of the object, slippage or excessive grip force. This information is used to correct the motor commands and to update the internal model of the motor apparatus and object. In this thesis, three experiments were conducted to examine the relative contributions of sensory-driven and anticipatory control of GF adjustments during cyclic vertical movement with a hand-held load. The main point was to assess whether internal models underlying the grip-load force coupling are robust when the environmental context was changed or when the sensory feedback was suppressed. Two experiments in parabolic flight were conducted to study the effects of a change in gravity on the dynamics of prehension. The main perturbation was that the novice subjects applied unnecessarily high safety margins during their first trial at 0 and 1.8 g in order to secure the grasp insofar as the gravitational component of the load force was unpredictable. By contrast, the temporal coupling between GF and LF was maintained regardless of the gravity conditions because the inertial component of the load could be still predicted from the arm motor command (efference copy). In the second study performed during parabolic flight, we have observed that the subjects were able to exert the same grip force for equivalent load generated either by a change of mass, gravity or acceleration despite the fact that it requires different arm motor commands. These two experiments brought further evidence that the predictive mechanisms largely contribute to the GF adjustment. Static forces such gravity are taken into account in the motor plan allowing adequate motor command and precise prediction of the incoming load force change. The GF output would depend on the precision of this prediction that can be evaluatedonly after the movement onset through sensory information about the actual state of the system. The third experiment performed in this thesis studied the role of cutaneous afferents in object manipulation by anesthetizing the thumb and index finger. In addition to their phasic slip-detection function, the cutaneous afferents are required for setting the background level of the grip force. Actually, in absence of tactile feedback, the temporal coupling between the grip and load forces is maintained but the mean magnitude of GF progressively decreases leading to object slipping. It is hypothesized that accumulating error occurred in the LF prediction leading to inadequate level of GF. Cutaneous afferents are thus required to correct and maintain the internal model of the arm-hand object system.

Det här examensarbetet gjordes för Cranab i Vindeln. Cranab tillverkar gripare för det mekaniserade skogsbruket, som används för att samla upp och förflytta avverkat timmer. En gripare består av två huvuddelar, gripklorna samt en vagga. Vaggan är uppbyggd av flertalet olika delar, varav två sidoplåtar, en höger samt en vänsterplåt. Sidoplåtarna skärs ut i en laserskärprocess och bockas i en pressmaskin, för att sedan svetsas samman. I dagsläget sker inmätningen av sidoplåtarna i pressmaskinen manuellt, vilket tar lång tid samt att det finns en risk att resultaten inte blir konsekvent.Arbetet gick ut på att ta fram ett konstruktionsförslag av en pressfixtur till Cranab. Genom att skapa en fixtur kan pressmomentet genomföras snabbare och med högre kvalité på slutprodukten. Detta bidrar till att göra Cranabs tillverkning effektivare och mer flexibel. Fixturen ska anpassas till den befintliga pressmaskinen och kunna hantera båda sidoplåtarna.Vid konstruktion av en fixtur är det många parametrar att tänka på, konstruktionen måste anpassas till den befintliga maskinutrustningen och uppfylla uppsatta krav på både kvalitet och arbetsmiljö. Samråd genomfördes med produktionspersonalen för att ta tillvara deras praktiska erfarenheter och åsikter. Det färdiga konstruktionsförslaget är en tydlig förbättring jämfört med nuvarande hantering och uppfyller de uppsatta kraven och önskemålen. / This bachelor thesis was made for Cranab in Vindeln. Cranab manufactures grapples for the mechanized forestry, which are used to collect and move harvested timber. A grapple consists of two main parts, the gripping claws and a cradle. The cradle is made up by several different parts, whereof two side plates, a right and a left side plate. The side plates are cut in a laser cutting process and are then bent in a press machine, before they are welded together. In the present situation the side plates are feed in to the press machine manually, which takes a long time and the risk is that result is not consistent.This work was to develop a design proposal of a press fixture to Cranab. By creating a fixture the pressing step can be performed more quickly and with higher quality to the final product. This contributes to making Cranabs production more efficient and flexible. The fixture has to be adapted to the existing press machine and must be able to handle both side plates.When designing a fixture there are many parameters to consider, the design must be adapted to the existing machinery and meet the set requirements for both quality and work environment. Consultation with the production staff were carried out to take advantage of their practical experiences and opinions. The final design proposal is a clear improvement over the current handling and meets the stated requirements and demands.

Job rotation is recommended to prevent musculoskeletal disorders (MSD). The premise is by involving different tissues a “working rest” for other tissues is created. The possible health benefits from this relief have not been investigated with regards to different grips in hand intensive jobs. The purpose of this study is to investigate hand intensive tasks and determine whether rotating between the power grip and lateral pinch grip can provide a benefit. A psychophysical load adjustment protocol was used. To investigate the effect of rotation, three different trials were collected. These included: power grip only, lateral pinch only, and alternating the two grips. Each trial was 60 minutes in duration, with a 12second cycle time, and 25% duty cycle. Fourteen subjects were recruited and pre-screened for any upper extremity disorders. Subjects were instructed to “work as hard as you can without straining your hand, wrist or forearm”; by adjusting their resistance settings to achieve a maximum acceptable force (MAF). Grip forces were exerted on an adjustable system using a hand grip dynamometer. Ratings of perceived discomfort were reported every 10minutes. Electromyography (EMG) was collected on eight forearm muscles during the combination trial. The demand for both lateral pinch and power grip tasks were at self selected levels and no fatigue was reported within MAF, EMG recordings, and discomfort reports. The rotation between lateral pinch and power grip had no apparent effect on MAF. However, EMG data hinted that there was a rotation of activation between first dorsal interossei and the forearm flexors (not statistically significant). Less discomfort was reported within the combination trial than the single grip (not significant). The study found no measurable difference in MAF when rotating between the power grip and lateral pinch. Considering there was no increase in demand, there is potential benefit to rotation, with trends to rotating activation between muscles, less discomfort being reported, and a general preference for the rotation. Given the high rates of MSD, and rotation being an effective tool to lower exposure, further investigations are required to understand relationships between similar muscles groups within hand intensive work environments.

Job rotation is recommended to prevent musculoskeletal disorders (MSD). The premise is by involving different tissues a “working rest” for other tissues is created. The possible health benefits from this relief have not been investigated with regards to different grips in hand intensive jobs. The purpose of this study is to investigate hand intensive tasks and determine whether rotating between the power grip and lateral pinch grip can provide a benefit. A psychophysical load adjustment protocol was used. To investigate the effect of rotation, three different trials were collected. These included: power grip only, lateral pinch only, and alternating the two grips. Each trial was 60 minutes in duration, with a 12second cycle time, and 25% duty cycle. Fourteen subjects were recruited and pre-screened for any upper extremity disorders. Subjects were instructed to “work as hard as you can without straining your hand, wrist or forearm”; by adjusting their resistance settings to achieve a maximum acceptable force (MAF). Grip forces were exerted on an adjustable system using a hand grip dynamometer. Ratings of perceived discomfort were reported every 10minutes. Electromyography (EMG) was collected on eight forearm muscles during the combination trial. The demand for both lateral pinch and power grip tasks were at self selected levels and no fatigue was reported within MAF, EMG recordings, and discomfort reports. The rotation between lateral pinch and power grip had no apparent effect on MAF. However, EMG data hinted that there was a rotation of activation between first dorsal interossei and the forearm flexors (not statistically significant). Less discomfort was reported within the combination trial than the single grip (not significant). The study found no measurable difference in MAF when rotating between the power grip and lateral pinch. Considering there was no increase in demand, there is potential benefit to rotation, with trends to rotating activation between muscles, less discomfort being reported, and a general preference for the rotation. Given the high rates of MSD, and rotation being an effective tool to lower exposure, further investigations are required to understand relationships between similar muscles groups within hand intensive work environments.

Thesis (M. Med. Sc.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 68-69).

Thesis (M.S.)--Rutgers University, 2009. / "Graduate Program in Biomedical Engineering." Includes bibliographical references (p. 52-54).

Grip kinetics are emerging as an important measure in clinical assessments of handwriting pathologies and fine motor rehabilitation as well as in biometric and forensic applications. The signature verification literature in particular has extensively examined the spatiotemporal, kinematic, and axial pressure characteristics of handwriting, but has minimally considered grip kinetics. Therefore, the focus of this thesis was to investigate the variability of grip kinetics in adults during signature writing. To address this goal, a database of authentic and well-practiced bogus signatures were collected with an instrumented pen that recorded the forces applied to its barrel. Four different analytical studies were conceived. The first study investigated the intra- and inter-participant variability of grip kinetic topography on the pen barrel based on authentic signatures written over 10 days. The main findings were that participants possessed unique grip force topographies even when the same grasp pattern was employed and that participants could be discriminated from each other with an average error rate of 1.2% on the basis of their grip force topographies. The second study examined the stability of different grip kinetic features over an extended period of a few months. The analyses revealed that intra-participant variation was generally much smaller than inter-participant variations even in the long term. In the third study, grip kinetics associated with authentic and well-practiced bogus signatures were compared. Differences in grip kinetic features between authentic and bogus signatures were only observed in a few participants. The kinetics of bogus signatures were not necessarily more variable. The variation of grip kinetic profiles between participants writing the same bogus signature was evaluated in the fourth study and an average error rate of 5.8% was achieved when verifying signatures with kinetic profile-based features. Collectively, the findings of this thesis serve to inform future applications of grip kinetic measures in biometric, clinical and industrial applications.