ABSTRACT
Twenty black African males with a mean age of 22.7 years yrs (±2.8) voluntarily participated in a study that evaluated strength expression in common movements associated with manual work. To date there has been an absence and/or paucity of research and/or data on black Africans that describe upper limb strength expression in applied work tasks. Given the growing industrialization taking place in Africa it is necessary to provide a more informed understanding of the relevant performance attributes of persons who are likely to be exposed to associated manual tasks. Anthropometric measures of the participants indicated a mean stature of 1.73 m (±0.08) and mass of 73.1 kg (±10.35), along with a mean wrist and humerus width, respectively of 5.33 cm (±0.5) and 7.90 cm (±1.04). Strength expression means included a bench press of 61.1 kg (±18.2). A Lafayette dynamometer measured hand grip (right and left respectively) of 483.16 N (±57.4) and 462.5 N (±46.5). Isokinetic strength was measured using a Biodex System 3 PRO dynamometer, where maximal voluntary muscle contractions were recorded at testing speeds of 30, 60 and 90o/sec, peak torque (Nm). Mean values included wrist extension 7.15 Nm (±3.2), wrist flexion 5.4 Nm (±1.4), forearm supination of 11.2 Nm (±3.4), forearm pronation of 8.3 Nm ±2.4). The following work simulation strength tests revealed the following means: valve (36 cm diameter) clockwise turn (close) of 90.2 Nm
grasp valve parallel grip utilizing pronation/supination forces resulted in means of rotate away (supination) 8.45 Nm (±2.1), rotate toward (pronation) 8.31 Nm (±2.6). Simulated screwdriver means included screw away (supination) 8.89Nm (±1.3), screw toward (pronation) 9.5 Nm (±2.7). An isokinetic test using a large wrench (horizontal) resulted in the following mean outputs isokinetic wrench forced away 325.39 Nm (±74.90), isokinetic wrench forced toward 290.4 Nm (±44.3). Isometric (static) fatigue tests using the wrench (mean maximal force per 30 second static load, with 10 second rest) produced the following outputs for episode 1: 337.6.2 Nm (±59), episode 2: 327.1 Nm (±70.8), and episode 3: 309 Nm (±74.5). Correlations were conducted on the variables, and it was interesting to note that bench press a standard measure of gross upper body strength was poorly correlated with pronation, supination,, extension and twisting actions associated with manual tasks using tools, and was significantly correlated only with isokinetic wrist flexion (0.64) and isokinetic wrench turning movements ( 0.55). These findings provide an indication of the strength expression in a cohort of young African males and should assist engineering design, as well as providing the foundation for a normative data base for assessing the readiness of individuals for work in physically demanding industrial situations.
