Muscle Thickness, Echo-Intensity, Peak Force, Time Under Tension, Total Load Lifted, and Perception of Effort Comparisons Between Two Abdominal Crunch Resistance Training Protocols in Recreationally-Trained Participants.

The primary purpose of this study was to evaluate acute dose response of different intensities with total volume equalized during the abdominal crunch exercise on muscle thickness, echo-intensity, peak force, time under tension, total load lifted, and perception of effort in recreationally-trained participants. Fifteen resistance-trained participants (23 ± 3 years) performed the abdominal crunch exercise in one of two different resistance training (RT) protocols in a randomized order: RT (4 sets of 10RM / 1-min rest) or RT (1 set of 40RM). Muscle thickness (MT), echo-intensity (EI), peak force (PF), time under tension (TUT), total load lifted (TLL), and session rating of perceived exertion (sRPE) were measured pre-test and post-test (0-min and 15-min). Two-way repeated-measures ANOVAs (2 × 3) were used to test differences between RT protocols (RT and RT) and time (pre-test, post-0, and post-15) for MT, EI, and PF. Paired t-test was used to compare RT protocols for sRPE, TLL, and TUT. For MT, there were significant differences for RT between pre-x post-0 ( = 0.011), pre-x post-15 ( < 0.001), and post-0 × post-15 ( = 0.02); and for RT between pre-x post-0 ( < 0.001) and pre-x post-15 ( = 0.003). For EI, there was a significant difference for RT between pre-x post-0 ( = 0.002). For sRPE, there was no significant difference between RT protocols. For TLL and TUT, there were significant differences between RT protocols ( < 0.05). In conclusion, both RT protocols (RT and RT) induced similar increases in MT but not for EI. TLL and TUT were higher for RT. PF and sRPE were similar between RT protocols.