Abstract
The primary purpose of this study was to evaluate the acute effects of different durations of the isometric forearm plank exercise (IFPE) on peak force, echo intensity, muscle thickness, and perception of effort in recreationally-trained participants. Fifteen resistance-trained participants (23±3years, 76.4±6.5kg, 173.3±6.5cm) performed the IFPE with bodyweight in one of three durations in a randomized order: a). 1-min, b). 2-min, and c). 3-min. Muscle thickness (MT), echo intensity (EI), peak force (PF), and rating of perceived exertion (RPE) were measured pre-test and post-test. Two-way repeated-measures ANOVAs (2×3) were used to test differences between tests (pre-test and post-test) and treatment (1-min, 2-min, and 3-min) for PF, MT, and EI. One-way ANOVA was used to compare RPE between treatments (1-min, 2-min, and 3- min). There was a significant increase between pre- and post-test only for 3-min IFPE (p=0.008). For EI, there was a significant increase between pre- and post-test only for 3-min IFPE (p<0.001). For PF, there were observed significant reductions on post-test between 1-min vs. 3-min (p<0.001) and 2-min vs. 3-min IFPE (p<0.001). For RPE, there were statistical differences between 1-min vs. 2-min (p<0.001), 1-min and 3-min (p<0.001), 2-min and 3-min (p=0.001). In conclusion, only 3-min IFPE induced an increase in MT and EI and a reduction in PF when compared to 1-min and 2-min (during the post-test). RPE increased with the increase in the duration of the IFPE.