Bilateral back squat strength is increased during a 3-week undulating resistance training program with and without variable resistance in DIII collegiate football players

Background Optimizing training adaptations is of the utmost importance for the strength and conditioning professional. The pre-season of any sport is particularly important to ensure preparedness of the athletes. In DIII Collegiate Football pre-season consists of approximately 3 weeks. The abbreviated time of the pre-season increases the importance of optimizing training using safe methods, including alternative loading strategies. The purpose of the current study was to determine if a 3-week variable resistance training VRT during an undulating (UL) resistance training program elicited a greater increase in back squat strength compared to traditional loading methods. Methods and Materials Forty DIII Football players (age range: 18–25 years) participated in a 3-week UL bilateral back squat (BBS) program. Both groups performed the BBS 3 times per week with a minimum of 24 hours between exercise sessions. The control group (C) (n = 20) (height = 182.3 + 5.1 cm, body mass: pre = 102.8 ± 17.7 kg, post = 104.1 ± 17.8 kg) used traditional loading methods (i.e., Olympic weights only) and the experimental group (E) (n = 20) (height = 180.7 ± 8.0 cm, body mass: pre = 100.3 ± 27.1 kg, post = 101.0 ± 27.7 kg) used traditional loading methods and variable resistance (i.e., resistance bands). The variable resistance accounted for approximately 20% of the total resistance while 80% of the resistance was supplied by traditional loading methods. Results When all data was pooled, subjects had a significant increase (p < 0.05) in 1-RM BBS from pre (154.2 + 26.1 kg) to post (166.8 + 26.2 kg), with a percent increase of 8.13% at the completion of the 3-week training program. There was no significant difference (p > 0.05) between the C and E groups for muscular strength, muscular power, or vertical jump. Volume-loads were not significantly (p > 0.05) different between groups for any of the weeks (C: Week 1 = 858.1 + 101.3, Week 2 = 588.6 + 69.2, Week 3 = 332.5 + 38.9, Total = 1179.2 + 209.4 vs. E: Week 1 = 835.2 + 179.7, Week 2 = 572.2 + 123.4, Week 3 = 323.5 + 68.8, Total = 1730.9 + 371.8) or for the pre-season as a whole. Conclusion A traditional UL resistance training program and training program with variable resistance are both effective methods at increasing back squat strength during 3 weeks of training. Resistance band variable resistance (VR) does not enhance training effects within a 3-week mesocycle greater than traditional resistance.

A New Approach to the Modeling of Magnetorheological Dampers and Application to Resonance Control

A predetermined flow pattern in a magnetorheological damper providing continuously variable resistance to flow is required for efficient damping of a given load. The required predetermined flow pattern rests on the a priori determination of the constitutive properties of the magnetorheological (MR) fluid determined to generate variable resistance to flow. The inverse problem of constructing the predetermined response of the damper with a specific displacement pattern of the piston in the damper for efficient damping of a given load is solved. The magnetorheological (MR) fluid in the damper is modeled as a Bingham phase change material with time dependent yield stress offering continuously variable resistance to the flow in the piston to achieve the required specific displacement pattern. The governing equations are solved for any time history of the dimensionless yield stress of the fluid which in turn is determined from the imposed response of the damper. Analytical tools developed can be used in optimizing damper performance. The application of the method to resonance mitigation is illustrated.