Damien O'Meara

Static friction properties between human palmar skin and five grabrail materials.

The purpose of this study was to investigate the static friction properties between human palmar skin and five grabrail materials (chrome, stainless steel, power-coated steel, textured aluminium and knurled steel) for dry, wet and soapy hands. Thirty subjects (15 female, 15 male) participated in this study, their ages ranging from 19 to 45 years with a mean age of 28 years. The normal force, friction force, and coefficient of static friction were determined by measuring three-dimensional forces while slipping the palm of the hand over the surface of a grabrail. A repeated measures ANOVA indicated that gender, age, hand size and trial effect had no significant influence (p >0.05) on these results. The coefficient of friction (p <0.001) and friction force (p <0.001) were significantly lower when the hand was soapy than when it was dry or wet. The normal force applied when the hand was soapy was significantly greater (p <0.001) than when it was dry or wet. No significant difference was found between dry and wet hands. The two textured materials displayed superior friction properties when the hand was soapy, while the smooth materials performed best when the hand was dry.

Biomechanical analysis of dragon boat paddling: A comparison of elite and sub-elite paddlers

Abstract In this study, video and force analysis techniques were used to distinguish between dragon boat paddlers of different ability. Six elite paddlers (three males, three females) and six sub-elite paddlers (two males, four females) were compared during high-intensity paddling (80–90 strokes · min−1). Video filming was conducted for two-dimensional kinematic analysis and an instrumented paddle was used to collect force data. Paddling efficiency, paddle force characteristics, and paddler kinematic variables were measured. Elite paddlers achieved higher paddling efficiency than sub-elite paddlers (elite: 76 ± 4%; sub-elite: 67 ± 10%; P = 0.080). Elite paddlers also showed higher peak force (elite: 16.3 ± 4.8 N · kg−2/3; sub-elite: 11.4 ± 2.6 N · kg−2/3; P = 0.052), average force (elite: 7.9 ± 2.8 N · kg−2/3; sub-elite: 5.5 ± 1.4 N · kg−2/3; P = 0.084), and impulse (elite: 3.0 ± 0.9 (N · s) · kg−2/3; sub-elite: 1.9 ± 0.4 (N · s) · kg−2/3; P = 0.026) than sub-elite paddlers, but these three results should be viewed with caution due to the small sample size and the unequal number of males and females in the two groups. Superior technique and greater strength enable the elite paddlers to achieve higher paddling efficiency. Paddlers use different joint movement patterns to develop propulsion, which are reflected in variations in the force–time curve.

Functional handgrip test to determine the coefficient of static friction at the hand/handle interface

The aim was to devise a method of measuring friction at the hand/handle interface during a functional handgrip task. No descriptions of methods of this kind was found in the literature. An indirect technique of measuring normal grip force was employed to determine friction at the hand/handle interface while performing a functional handgrip action with a grabrail. The coefficient of static friction was calculated between palmar skin (dry, wet, and soapy hands) and five grabrail materials (stainless steel, powder-coated steel, chrome, textured aluminium and knurled steel). Thirty subjects participated (15 female, 15 male), who were aged from 17 to 45 years with a mean age of 30 years. Knurled steel produced a significantly larger mean coefficient of static friction than chrome, powder-coated steel and stainless steel, and textured aluminium had a significantly larger coefficient of static friction than stainless steel. Soapy hands produced the lowest mean coefficients (0.46 ± 0.04), significantly less then dry (1.72 An anatomical/functional argument for the existence of both, 0.16, p <0.001) and wet hands (1.42 ± 0.16, p <0.001). This study has demonstrated the influence of grabrail material and palmar skin treatments on static friction at the hand/handle interface. The use of a functional test that incorporates an indirect determination of normal handgrip force has provided a quantitative method of observing stability at the hand/handle interface.

Determining optimal trial size using sequential analysis

Abstract When characterising typical human movement profiles, the optimal number of trials analysed for each participant should ensure a stable mean. Sequential analysis is one method able to establish the number of trials to stability by assessing a moving point mean against a set bandwidth. As the total trial number determining this bandwidth is selected arbitrarily, the effect of applying different total trial numbers on the results of sequential analysis was investigated. Twenty participants performed 30 trials of overarm throwing, and sequential analyses were applied to three dimensional (3-D) kinematic data over 10, 20 and 30 trial numbers. We found a total of 20 to be the preferred trial number for sequential analyses. Erroneous results were produced consistently by 10 trial number groups, while moving point means were statistically unchanged after the 10th trial. Subsequently, sequential analyses were applied to 20 trials to establish trials to stability in discrete and time series elements of the 3-D kinematic data. The results suggest that a trial size between 13 and 17 provides stable means for overarm throwing kinematics.

OBTAINING FOOT ANTHROPOMETRICS WITH A 3 CAMERA FOOT IMAGE SYSTEM (FIS)

Foot anthropometrics and morphology has become increasingly more important from a scientific, clinical and commercial perspective. Especially as children’s feet develop very quickly and have distinct characteristics that are important for shoe comfort and foot development. The use of digitised 2D images to determine foot morphology is common in research and commercial use. This approach offers a cheaper method than laser scanning, radiography and is a convenient and time efficient method of collecting data [Luximon, 2005]. The purpose of the current study is to investigate the reliability of several foot measurements obtained from a digital photograph and from calliper measurements.