## 2 Materials and Methods
### Gloved Conditions  
There were four gloved conditions: bare hand and wearing one of the three types of work gloves prepared. Three types of work gloves were purchased from a local hardware store (see Figure 2). Glove 1, or simply cotton glove, is a knitted cotton polyester yarn glove. Glove 2 (SS-100, 3M, Seoul, Korea), or simply glove with NBR coating, is a knitted glove with nylon and is coated nitrile rubber (NBR) in the palmar region. Glove 3, or simply cut resistance glove, is a safety glove protecting against cuts and stabs (CP-500, 3M, Seoul, Korea). This glove is knitted with nylon, spandex, and glass fiber, and is also coated with NBR on the palmar region. The thickness of the gloves was measured in the palmar region of these gloves using a caliper (SV-03-150, E-BASE, Yunlin, Taiwan).  
The coefficient of friction (COF) between the surface of the palmar region of each type of glove on a steel plate was measured using a Horizontal Pull Slipmeter (HPS) (C.S.C. Force Measurement, Inc., Agawam, MA, USA; ASTM, F609-13) [39]. When measuring the COF, three circular (\(\O\) 1 cm) glove samples were cut from one of each type of glove and were attached to the bottom of the weight unit of the HPS (see Figure 3a). The operator pushed the drag unit downward to fix it and then turned on the power of this unit. The drag unit pulled the weight unit until the latter started to move. The COF reading was shown on the meter.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Variables** & **Female** & **Male** \\ \hline Age (years) & 30.2 (\(\pm\)10.6) & 42.8 (\(\pm\)10.0) \\ Body weight (kg) & 55.5 (\(\pm\)7.7) & 80.7 (\(\pm\)15.1) \\ Body height (cm) & 157.6 (\(\pm\)6.0) & 169.1 (\(\pm\)7.5) \\ Shoulder height (cm) & 128.2 (\(\pm\)5.0) & 138.2 (\(\pm\)7.3) \\ Elbow height (cm) & 98.2 (\(\pm\)4.1) & 104.3 (\(\pm\)6.2) \\ Knuckle height (cm) & 69.2 (\(\pm\)4.4) & 72.0 (\(\pm\)5.5) \\ Knee height (cm) & 42.9 (\(\pm\)2.4) & 47.1 (\(\pm\)2.8) \\ Hand length, Dominant (cm) & 16.7 (\(\pm\)1.4) & 19.0 (\(\pm\)1.0) \\ Hand length, Non-Dominant (cm) & 17.0 (\(\pm\)0.9) & 19.0 (\(\pm\)0.9) \\ Hand width, Dominant (cm) & 7.5 (\(\pm\)0.3) & 8.8 (\(\pm\)0.6) \\ Hand width, Non-Dominant (cm) & 7.4 (\(\pm\)0.5) & 8.7 (\(\pm\)0.6) \\ Circumference of upper arm, dominant (cm) & 26.7 (\(\pm\)3.1) & 31.9 (\(\pm\)5.6) \\ Circumference of upper arm, non-dominant (cm) & 26.2 (\(\pm\)3.4) & 31.8 (\(\pm\)5.2) \\ Circumference of lower arm, dominant (cm) & 23.2 (\(\pm\)1.8) & 27.9 (\(\pm\)1.8) \\ Circumference of lower arm, non-dominant (cm) & 22.6 (\(\pm\)1.6) & 27.2 (\(\pm\)2.0) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Mean and standard deviations of the basic data of the participants.  
Figure 1: Carrying and lifting strength measurement apparatus.  
A simple test was performed to measure the stiffness of these gloves. In this test, a tested glove was placed on the edge of a workbench with the middle finger sleeve extended outside the bench and drooped. The angle between this sleeve and the vertical, or stiffness angle, was measured to indicate the stiffness of the glove (see Figure 2(b)). A large angle indicates high stiffness of the sleeve.  
Three different sizes were prepared for each of gloves 2 and 3 so that each participant could choose the one that fit his or her hands best. Glove 1 is relatively cheap and has only one size. The glove information is summarized in Table 2.