Assessment of the reproducibility of strength and endurance handgrip parameters using a digital analyser

Abstract

A group of 40 healthy individuals (27 women and 13 men) participated in a handgrip test and were retested 1-2 months later. A strain-gauge sensor with a digitised signal and computerized printout was used. A 5-s maximal squeeze test was first made three times, followed by one endurance test with 45%-55% power of the maximal value. The best maximal value was most often (42%) achieved in the third (initial test) or second (retest) attempt. The reproducibility of maximal value was very good; the Pearson correlation coefficient between initial test and retest (r = 0.98) was even slightly higher than in studies with older analogue instruments. The difference of maximal values [361 (SD 109) N, initial test and 368 (SD 110) N, retest] was insignificant. A moderate 12% long-term change in maximal value was statistically significant. Reproducibility of the power factor (integrated area of power with time) was also very good in this short test, correlating closely (r = 0.98-0.99) with the maximal value. Other indexes (grip rate, fatigue percentage and relaxation rate) were not stable enough to be practical. Endurance results were somewhat variable (r = 0.73), which implied in the main variable motivation. Only marked changes of over 50% in endurance were statistically significant. Endurance power increased significantly in the retest, which, in spite of an r-value of 0.82, would make its use in a follow-up study difficult. We found the computer-based handgrip test both precise and practical in assessing maximal voluntary strength; endurance was more difficult to reproduce.

Force-time parameters during explosive isometric grip correlate with muscle power

“…Until now, many researchers [5,7,14,15,20] have suggested that the rising force phase of the force-time curve in explosive isometric contraction can evaluate different muscle functions from maximal strength, explosive strength (power) or muscle contraction speed.…”

“…Analysis of the rising force phase (the initial phase until reaching the peak force) in force-time curves during explosive isometric contraction has revealed the existence of individual differences and gender differences [6][7][8][9][10][11][12][13][14]. Walamies and Turjanmaa evaluated the integrated area until the peak strength (impulse) during explosive isometric grip as a 'power factor' with a similar concept to muscle power [14].…”

“…Walamies and Turjanmaa evaluated the integrated area until the peak strength (impulse) during explosive isometric grip as a 'power factor' with a similar concept to muscle power [14]. Moreover, Demura et al reported that the relationship between maximal isometric strength and peak increase in force during the rising force phase was low (r = 0.100-0.273) [15].…”

Age and Sex Differences of Controlled Force Exertion Measured by a Computer-generated Sinusoidal Target-pursuit System

“…The size of the grip was set so that the subject easily controlled the grip. The test of controlled force exertion was similar to a commonly used test of grip strength (Walamies and Turjanmaa, 1993;Skelton et al, 1994), except for the exertion of prolonged submaximal grip. The subject stood upright with the wrist in the neutral position between flexion and extension and the elbow extended and close to the body and then exerted the grip.…”

Influence of grip types and intensities on force-decreasing curves and physiological responses during sustained muscle contractions

“…Static muscle endurance has, generally, been evaluated by sustained isometric or intermittent repeated muscle contraction using relative intensity based on each individual's maximal strength [3][4][5][6][7]. In the case of sustained isometric contractions above 50% MVC, the force output decreases markedly in the initial phase and reaches an almost steady state at 15-20% MVC within 150-180 s [4,[6][7][8][9] With intermittent repeated muscle contractions, the force output is largely influenced by an exertion interval as well as sustained time [10] because of repeated muscle contraction and relaxation.…”