The Precision of the Human Hand: Variability in Pinch Strength and Manual Dexterity

Changes in hand morphology throughout human evolution have facilitated the use of forceful pad-to-pad precision grips, contributing to the development of fine motor movement and dexterous manipulation typical of modern humans. Today, variation in human hand function may be affected by demographic and/or lifestyle factors, but these remain largely unexplored. We measured pinch grip strength and dexterity in a heterogeneous cross-sectional sample of human participants (n = 556) to test for the potential effects of sex, age, hand asymmetries, hand morphology, and frequently practiced manual activities across the lifespan. We found a significant effect of sex on pinch strength, dexterity, and different directional asymmetries, with the practice of manual musical instruments, significantly increasing female dexterity for both hands. Males and females with wider hands were also stronger, but not more precise, than those with longer hands, while the thumb-index ratio had no effect. Hand dominance asymmetry further had a significant effect on dexterity but not on pinch strength. These results indicate that different patterns of hand asymmetries and hand function are influenced in part by life experiences, improving our understanding of the link between hand form and function and offering a referential context for interpreting the evolution of human dexterity.

Biomechanical Exposure to Upper Extremity Musculoskeletal Disorder Risk Factors in Hospital Laboratories

Exposure to ergonomic risk factors has been reported for laboratory workers over decades. However, these exposures are not well characterized with respect to the type of laboratory or work organization. This study compared biomechanical exposure to upper extremity (UE) postures and hand activity levels (HALs) in general hospital laboratories by job, work, and laboratory type. The study used observational data gathered using a revised version of the Posture, Activity, Tools, and Handling (PATH) method, generating frequencies of categorized exposures. Eighteen workers were observed in 11 job titles (seven laboratories) in a single hospital by two investigators over a 7 month period. A taxonomy was constructed to categorize the extent to which the laboratory operations were automated. Overall, there were markedly high exposures to postural strain for the distal UE, especially wrist/forearm deviation (73% of observations), gross grasp (71%), and pinch grip (49%). For the HAL categories, 61% of the observations were in the moderate range (3.3–<6.7). Shoulders and elbows tended to remain in the neutral postural range. Posture frequencies were similar among the job categories studied and laboratory types. HAL was higher when the hand was in a pinch grip. Manual operations represented a higher proportion of work time than semi-automated or automated operations. Biomechanical exposure can be documented more extensively and diversely when using the revised PATH approach along with the taxonomy, with respect to exposure variables, such as the type of job, work, or organization in the industry including the hospital laboratories.

Influence of Pulsed Magnetic Field Therapy on Hand Function Post Flexor Tendon Repair: A Randomized Controlled Trial

IntroductionPurpose: The study was conducted to investigate the influence of pulsed magnetic field therapy on hand function, grip and pinch grip strength in post flexor tendon repair patients.Material and methodsMethods: Fifty male patients with flexor tendon repair took part in this research, with ages ranging from 25 to 50 years. They were assigned randomly into two groups: Group A (experimental) received pulsed magnetic therapy together with exercise, whereas Group B (control) received only exercise. Evaluation of hand grip strength with Jamar hydraulic hand dynamometer, pinch strength with Baseline pinch gauge and hand function with Michigan Hand Outcomes Questionnaire, all measurements were made before and after the treatment. They were received 16 sessions for 8 weeks (2 sessions/week).ResultsResults: 2 x2 mixed design MANOVA revealed that no significant difference between both groups pre- treatment and post treatment in MHOQ total, function, aesthetic (p>0.05) and in hand grip strength while there was a significant difference across groups after treatment in the strength of pinch grip, MHOQ ADL, pain and satisfaction p <0.05), there was also a significant difference between pre- and post-treatment within groups in all outcome measures. (p <0.05).ConclusionsConclusion: PMF increases the efficiency of physical therapy treatment and it also increases the strength of both hand grip and pinches grip in patients after flexor tendon repair in zone II.

IMPACT OF LEAP MOTION CONTROLLER ON PINCH GRIP IN SUB-ACUTE AND CHRONIC STROKE PATIENTS

Stroke patients have limited everyday tasks. For that videogame-based training (VBT) with the effect of virtual reality helps to improve the role of upper limb and motor function of hand rehabilitation (finger pinch grip). The Leap motion controller can track the both extremities (hand and fingers) fine movements. The study will demonstrate the impact of the leap motion controller on pinch grip in patient with sub-acute and chronic stroke. The total of 40 participants will be taken for study as per inclusion and exclusion criteria. The duration of the study will be six months with intervention. Leap motion -based, augmented reality training will be provided to patients for half hour, Every single day, 5days of the week a month. Formant’s sign and system usability scale will be taken. Those two will be the patient’s measure outcomes. Impact of the leap motion controller device will be evaluated by using the system usability scale and Formant’s sign. The result from the study will significantly provide evidence on the use of Leap motion controller on pinch grip in subacute and chronic stroke patient.

Association of Age with Hand Grip Strength, Pinch Strength and Reaction Time in Gynaecologists and Obstetricians

According to scientific literature, evidence of relationship exists between dexterity and age. With increasing age, the performances get slower, less smooth, less coordinated and less controlled. Lesser the reaction time, better is the achievement seen sports, music, driving, academics and also in day-to-day activities. We can always predict reacting abilities of an individual based on his reaction time. In case of surgeons, this helps us to identify the surgeons with prolonged reaction time and identify the cause. Some studies suggest that there is direct relationship that exists between muscle strength and increased age. Aim: This study aimed in assessing the association of age with hand grip strength, pinch strength and reaction time in Gynaecologists and Obstetricians. Methods: This study involved 30 Gynaecologists and Obstetricians. Hand grip strength, Pinch Grip Strength and Reaction time were assessed on both dominant and non- dominant hand. Results: The result showed positive correlation of age with hand grip strength and pinch strength and negative correlation of age with reaction in Gynaecologists and Obstetricians. Conclusion: There is low association of age with hand grip strength and pinch strength, there is reduction in reaction time as age increases in Gynaecologists and Obstetricians. Key words: Age, Hand grip strength, Pinch Grip Strength, Reaction time, Gynecologists.

Comparison of subjective peripheral sensation, F-waves, and somatosensory evoked potentials in response to a unilateral pinch task measured on the contractile and non-contractile sides

Depression of sensory input during voluntary muscle contractions has been demonstrated using electrophysiological methods in both animals and humans. However, the association between electrophysiological responses of the sensory system and subjective peripheral sensation (SPS) during a voluntary muscle contraction remains unclear. Our aim in this study was to describe the changes in SPS, spinal α-motoneuron excitability (F-wave to M-wave amplitude), and somatosensory evoked potentials (SEPs) during a unilateral pinch-grip task. Outcome variables were measured on the side ipsilateral and contralateral to the muscle contraction, and at rest (control). Participants were 8 healthy men, 20.9±0.8 years of age. The isometric pinch-grip task was performed at 30% of the maximum voluntary isometric force measured for the right and left hand separately. The appearance rate of the F-wave during the task was significantly higher for the ipsilateral (right) hand than for the contralateral (left) hand and control condition. Although there was no difference in F-wave latency between hands and the control condition, the amplitude of the F-wave was significantly higher for the ipsilateral (right) hand than for the contralateral (left) hand and the control condition. There was no difference in the amplitude of the SEP at N20. However, the amplitude at P25 was significantly lower for the ipsilateral (right) hand than for the contralateral (left) hand and the control condition. The accuracy rate of detecting tactile stimulation, evaluated for 20 repetitions using a Semmes–Weinstein monofilament at the sensory threshold for each participant, was significantly lower during the pinch-grip task for both the ipsilateral (right) and contralateral (left) hand compared to the control condition. Overall, our findings show that SPS and neurophysiological parameters were not modulated in parallel during the task, with changes in subjective sensation preceding changes in electrophysiological indices during the motor task. Our findings provide basic information on sensory-motor coordination.

Temporally stable beta sensorimotor oscillations and cortico-muscular coupling underlie force steadiness

As humans, we seamlessly hold objects in our hands, and may even lose consciousness of these objects. This phenomenon raises the unsettled question of the involvement of the cerebral cortex, the core area for voluntary motor control, in dynamically maintaining steady muscle force. To address this issue, we measured magnetoencephalographic brain activity from healthy adults who maintained a steady pinch grip. Using a novel analysis approach, we uncovered fine-grained temporal modulations in the ~20-Hz sensorimotor brain rhythm and its coupling with muscle activity, with respect to several aspects of muscle force (rate of increase/decrease or plateauing high/low). These modulations preceded changes in force features by ~40 ms and possessed behavioral relevance, as less salient or absent modulation predicted a more stable force output. These findings have consequences for the existing theories regarding the functional role of cortico-muscular coupling, and suggest that steady muscle contractions are characterized by a stable rather than fluttering involvement of the sensorimotor cortex.

Prospective Evaluation of Low-Dose External Beam Radiotherapy (LD-EBRT) for Painful Trapeziometacarpal Osteoarthritis (Rhizarthrosis) on Pain, Function, and Quality of Life to Calculate the Required Number of Patients for a Prospective Randomized Study

Background: Retrospective studies have described the effectiveness of low-dose radiotherapy (LD-EBRT) in painful arthrosis of small finger joints, but two recent prospective studies have yielded ambiguous results. To generate accurate data for the planning of a trial, we conducted a prospective, monocentric, observational study to describe the effects of LD-EBRT as precisely as possible. Methods: Twenty-five consecutive patients with symptomatic trapeziometacarpal (TMC) arthrosis were irradiated with 6 × 0.5 Gy. Before, 3, and 12 months after LD-EBRT, we assessed subjective endpoints (modified “von-Pannewitz score”, 10-point visual analogue scale (VAS), “patient-rated wrist evaluation” (PRWE)), and objective measurements (“active range of motion” (AROM), Kapandji index, grip strength, pinch grip). Results: At 3/12 months, 80%/57% reported partial and 4%/18% complete remission according to the “von-Pannewitz” score. VAS “overall pain” significantly decreased from a median of seven (IQR 4) at baseline to three (IQR 6; p = 0.046) and to two (IQR 2; p = 0.013). Similar results were obtained for VAS “pain during exercise”, VAS “pain during daytime”, and VAS “function”. “PRWE overall score” was reduced from 0.5 at baseline (SD 0.19) to 0.36 (SD 0.24, p = 0.05) and to 0.27 (SD 0.18, p = 0.0009). We found no improvements of the objective endpoints (AROM, Kapandji, grip strength) except for flexion, which increased from 64° (SD 12°) at baseline to 73° (SD 9.7°, p = 0.046) at 12 months. Conclusions: We recommend the PRWE score as a useful endpoint for further studies for this indication. To prove a 15% superiority over sham irradiation, we calculated that 750 patients need to be prospectively randomized.

Pinch grip strength and fine manual control in children with diplegic cerebral palsy: a cross-sectional study

Background In children with spastic diplegia, efficient use of the upper extremity especially the hands play an important role in participation in daily living. Hands can perform heavy activities and also enable to perform extremely gentle, skillful, and precise activities. Inadequate hand strength and fine motor skills may lead to functional limitations. This study was planned to investigate the pinch grip strength and fine manual control in children with spastic diplegic cerebral palsy and to determine if there is a relation between them. Thirty children with diplegic cerebral palsy and 30 normal developed children from both sexes between 5 and 10 years old were included in this study as diplegic and control groups. For all children, pinch grip strength measured by Baseline Mechanical Pinch Gauge and Bruininks-Oseretsky Test of Motor Proficiency, Second Edition used to evaluate fine manual control. Results Children with diplegic cerebral palsy have significant impairment in the pinch grip strength (tip, tripod, and key) and the fine manual control (fine motor precision and integration) compared to their healthy peers of the same age. There was large positive significant correlation (r > 0.5, p < 0.05) between tip and tripod pinch strength, and fine motor precision and medium positive significant correlation (r = 0.47, p < 0.05) between key pinch and fine motor precision in children with spastic diplegia. Also, there was large positive significant correlation between tip pinch and fine motor integration (r = 0.54, p < 0.05). The correlations are small and medium positive between tripod and key pinch strength, and fine motor integration respectively but they are not statistically significant. Conclusions Pinch grip strength and fine manual skills are affected in children with spastic diplegia. Also, there is a significant correlation between the pinch strength and activities require precise control of the hand.