Rubber based resistance and the bench press exercise: force and power outputs
The application of rubber based resistance (RBR) to traditional isoinertial resistance exercises as a method of manipulating exercise kinematics and kinetics has gained popularity within the strength and conditioning fraternity. However, the tensile properties of RBR have not been thoroughly quantified and practitioners cannot prescribe loading parameters with absolute certainty given the inconsistencies in research methodologies. It was the purpose of this research to a) report the tension-deformation (T-D) characteristics for several sizes of RBR bands and b) determine whether differences exist between free weight (FW) and RBR bench press repetition, set and total set kinematics and kinetics. The T-D and fatigue characteristics of six sets of RBR bands were determined by measuring pre- and post-intervention mean vertical ground reaction forces. Force platform data was sampled at 200Hz for 5 seconds over a range of ascending and descending displacements. Subsequent to the establishment of the T-D relationship, fourteen well-trained male rugby players performed three sets of six bench press repetitions under three conditions, in a randomised crossover manner. A 50% 1RM load was equated between conditions at the apex of the concentric phase. RBR resistance contributed to either 0% (FW), 20% (RBR20) or 40% (RBR40) of the total apex resistance. A customised bench, force platform and linear position transducer were used in conjunction with a power rack fitted with sliding safety bars. A pair of RBR bands were attached to either end of a barbell and anchored by the safety bars, accounting for the anthropometrical differences between participants. The force- and displacement-time data were sampled at 200Hz by a computer based data acquisition and analysis programme. Descriptive data were presented as means ± SD, and the magnitudes of the observed differences, 90% confidence limits and clinical inferences were interpreted qualitatively. Results showed the T-D relationships exhibited curvilinear properties most appropriately fitted by second-order polynomial functions (R2 > 0.99). Analysis of repetition kinematics and kinetics revealed greater force values for both RBR conditions during the middle stages (30-70%) of the concentric phase compared to FW. Total set peak force was greater for RBR20 than for FW (110 ± 90% confidence limits, 71 N). However, mean force was greater for FW than for RBR40 (57 ± 30 N). Repetition power was greater for RBR40 than for FW and RBR20 from 10-50% and from 90-100% of the relative concentric displacement. Total set peak power was greater for RBR40 than for FW (42 ± 58 W) but mean power was greater for FW than RBR40 (34 ± 39 W). The magnitudes of these effects were considered to be likely (≥92.4%) meaningful. This investigation indicates that the application of RBR to an isoinertial bench press leads to decreased concentric force and increased power values during the middle stages and increased force values at the end stages of a repetition. Over multiple sets, RBR increased peak power outputs but decreased mean force and mean power outputs. RBR training may be most appropriate for athletes required to produce power characterised by high velocities such as shot putters compared to those required to produce power characterised by high force outputs such as rugby props. RBR training may be an appropriate periodisation tool to increase power outputs as athletes approach competition.