Electromyographic evaluation of different handle shapes of masons' trowels.

The effects of five different handle shapes of masons' trowels on muscle activity of the arm and forearm muscles (through electromyographic [EMG] measurements of the biceps brachii [BB], flexor digitorum superficialis [FDS], pronator teres [PT] and extensor carpi ulnaris [ECU]) were evaluated in a simulated masonry task. The results showed a significant effect of handle shape on the muscle activity of the BB, PT and ECU. The muscle activity of the extensor (ECU) and flexor (FDS) were generally larger than those of the supinator (BB) and pronator (PT). Some improvements were found in terms of muscular exertions with the prototype designs C, D and E, which had either handles with variable diameter (designs C and E) or slightly bended handle (design D). These findings have practical implications for the design of single-handle hand tools but may need further validation for specific contexts of use.