Grip Norms And Reliability Of The Hand Grip Forcemap System

Abstract

Strength testing of the injured hand and forearm is of considerable interest to patients, treating physicians, therapists, and insurance companies. While, over the past many years, traditional parallel-bar dynamometers have made a significant and positive contribution to medical grip strength evaluation, these devices are now less than optimal for the comprehensive analysis of overall grip and finger function. The ForceMap grip force mapping system utilizes tactile array technology to assess the complex grip capability/capacity of a human hand. PURPOSE: This study‘s aim was to evaluate the reliability of the hand grip ForceMap system and to establish max grip force (MGF) and force distribution norms (D1-thumb; D2-index; D3-middle; D4-ring; D5-little finger; N/cm2) for healthy adults. METHODS: Adults (Female n=28; 38.9 ±11.0 yrs; 165.3± 6.7 cm; 69.8± 13.0 kg; Male n=28; 34.2 ±13.0 yrs; 181.3± 8.0 cm; 86.4± 15.1 kg) completed trials of maximal grip on the ForceMap system with the elbow at 90 degrees flexion. The ForceMap system is comprised of a high resolution tactile array sensor mounted to a 5 × 15 cm solid Delrin cylinder (grip map transducer) that is interfaced to an amplifier/processor and laptop computer. The ForceMap system provides visual and numerical assessment of grip force including the palm and individual digits both statically and dynamically (100 hz). The reliability of the ForceMap was determined using a Pearson Correlation Coefficient (r), Intra-class Correlation Coefficient (ICC) and a Bland-Altman Plot (BAP) of repeated trials of the male dominant hand MGF. RESULTS: Female norms dominant hand: MGF= 471.2±119.6 (N); D1=29.0 ±9.4; D2=23.6 ±8.3; D3= 25.0±5.6; D4= 20.8±6.3; D5=14.9 ±6.6 (N/cm2). Male norms dominant hand: MGF= 820.9± 210.5 (N); D1= 34.5± 9.1; D2= 29.5 ± 8.3; D3= 34.3 ± 8.8; D4= 26.9 ± 9.0; D5= 23.2 ± 9.2 (N/cm2). Male dominant hand MGF: r=0.92 and ICC=0.92. The BAP plot revealed that 100% of the differences between trails were within ±2 standard deviations of the mean difference. CONCLUSION: Given the ability of the ForceMap system to reliably assess grip force along with the establishment of grip force and force distribution norms, it appears the ForceMap system is a viable means for detailed grip assessment.