Optimum pinch grips in the handling of dies

Normative data for the Baseline® 5 position hydraulic pinch meter and the relationship between lateral pinch strength and pinch span

INTRODUCTION

The Baseline® 5 position hydraulic pinch meter allows pinch strength assessment at five different pinch spans. The present study used this newly developed meter to assess where pinch span force is the greatest as previous literature is conflicting.

PURPOSE OF THE STUDY

The primary aim of the study was development of normative data using health subjects, whereas the secondary aims were to evaluate meter inter-rater reliability and to identify in which pinch span the greatest force was produced.

STUDY DESIGN

This is a clinical measurement, cross-sectional study.

METHODS

Ten occupational therapy student raters examined inter-rater reliability by calculating an average intraclass correlation. Recruitment of normative data subjects occurred across various locations in West Michigan to include a diverse population and followed testing procedures recommended by the American Society of Hand Therapists. Data were stratified by age categories and sex to develop normative standards. Data were analyzed using a one-way repeated measures ANOVA and a three-way mixed ANOVA.

RESULTS

Normative data were calculated from a sample of 605 subjects (292 males and 313 females). One-way ANOVA demonstrated a significant difference at the five different spans, noting a small effect size. Also noted were a nonsignificant three-way interaction between age category, pinch spans, and sex using both the right and left hands, along with a significant two-way interaction between spans and sex bilaterally.

DISCUSSION

The meter showed an excellent inter-rater reliability with an intraclass correlation = .98 and indicated the pinch span that produced the greatest amount of force was not consistent with previous literature.

Shaping Rollable Display Devices: Effects of Gripping Condition, Device Thickness, and Hand Length on Bimanual Perceived Grip Comfort

OBJECTIVE

To examine the effects of the gripping condition, device thickness, and hand length on bimanual perceived grip comfort associated with unrolling hand-held rollable screens.

BACKGROUND

Rollable displays can be rolled and unrolled to change screen size. Although diverse rollable display device concepts have been suggested, little is known regarding ergonomic forms for comfortable screen unrolling.

METHOD

Thirty young individuals (10 in each hand-length group) evaluated three rollable display device prototypes in three gripping conditions (no restriction on using side bezels, minimal use of side bezels, and restriction on the gripping type). Prototypes differed in their right-side thickness (2, 6, and 10 mm). Side bezel regions grasped during screen unrolling and corresponding bimanual grip comfort ratings were obtained.

RESULTS

To improve perceived grip comfort and accommodate user-preferred gripping methods, rollable display devices should be 6 mm (preferably 10 mm) thick (vs. 2 mm) and have at least 20-mm-wide side bezels. Relative to device thickness, gripping conditions were more influential on grip comfort ratings. The "no restriction" condition improved grip comfort ratings and strengthened bimanual coupling in terms of grip comfort ratings.

CONCLUSION

Contrary to current smartphone trends toward thinner and bezel-less designs, hand-held rollable display devices should be sufficiently thick and have sufficiently wide side bezels for screen unrolling.

APPLICATION

Hand-held rollable display devices should be 6- or preferably 10-mm thick (vs. 2 mm) and have at least 20-mm-wide side bezels to ensure higher perceived grip comfort during bilateral screen unrolling.

Measuring pad–pad pinch strength in a non-human primate: Macaca fascicularis

The primary purpose of this study was to establish a methodology for determining and perhaps predicting (via regression analysis of anthropometric measures) Macaca fascicularis isometric pinch strength for a specific task. The larger purpose of this work was to properly scale a pinching task for the monkeys in order to study dose-response relationships in a non-human primate model for carpal tunnel syndrome. Three female and one male macaque (n=4) of varying size and age were trained to perform a left-handed pad-pad pinch. The task required 60 degrees of wrist flexion at a static pinching distance of 3 cm between the thumb and fingers. Subjects were trained for a period of 20-weeks. After that time, an analysis of performance gradients found that they had each reached a plateau in their force output. Pinch strength for the four animals ranged from 29.4 to 59.8 N. Regression analysis revealed that body mass (kg) and wrist circumference (cm) were both predictive of pinch strength, exhibiting adjusted R(2) values of 0.93 (p=0.024) and 0.96 (p=0.015), respectively. Thus, the results suggest that maximal pinch strength could be acceptably estimated in future subjects using either the wrist circumference or the body mass measures, as both were strong predictors of pad-pad pinch strength.