| Summary: | Purpose: This research design compares mean peak integrated electromyography (I-EMG) and mean peak ground reaction forces (GRFs) between a standard steel Olympic barbell (SB) and flexible barbell (FB) during the squat (SQ) exercise for human subjects, as well as GRFs for a similar machine-driven lift. Methods: A lifting machine set atop a force plate and lifted either a SB or FB with a total loaded weight of 47.6 kg at a rate of 52 repetitions per minute for a minimum of 12 repetitions. Next, ten NCAA Division I football players familiarized with both bars were randomly assigned the SB and FB loaded at 30% one repetition maximum (1RM) and performed 7-10 repetitions at the same rate as the machine. I-EMG data was collected from surface electrodes placed on the legs and trunk according to the SENIAM protocol where appropriate. Results: Paired t-tests between the SB and FB revealed significant increases (p<0.05) in GRFs for the FB during the machine-driven lift and the SQ exercise. I-EMG was significantly higher for the FB when compared to the SB for the vastus lateralis (VL), rectus abdominis (RA), rectus femoris (RF) and external oblique (EO). Results show increases in some leg and trunk muscle activity and increases in GRFs when using a FB loaded at 30% 1RM for the SQ exercise when compared to a SB. Conclusions: A FB, when used under certain conditions, may illicit increased muscle activity for the SQ exercise for some leg and trunk muscle groups compared to a SB.
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