Effects Of Autoregulatory Progressive Resistance Exercise On Upper-body Rate Of Force Development And Cross-sectional Area

Rate of force development (RFD) is used to measure explosive strength during a rapid contraction of a muscle action and is also important for athletes who prioritize explosiveness and quickness. Reports indicate autoregulatory progressive resistance exercise (APRE) yields greater physical performance adaptations than traditional linear periodization models. PURPOSE: The purpose of this study was to compare isometric bench press RFD and skeletal muscle cross-sectional area (CSA) of the triceps longhead following 4-weeks of an APRE training program. METHODS:Eight resistance trained males (age: 21.5 ± 2.3 yrs; height: 176.5 ± 6.8 cm; weight: 70.3 ± 17.8 kg) participated in a 4-week APRE training program that consisted of a split regimen for upper and lower body exercises taken to volitional fatigue for 2 sets at approximately 85% of 1RM. Additionally, accessory exercises were incorporated with variable parameters to promote hypertrophy. An isometric bench press was used to measure the RFD during the initial stages of the force production (0-50 ms, 50-100 ms, and 100-150 ms), and peak force at baseline and following the training intervention. Ultrasonography was also used to compare changes in CSA in the long head of the triceps. A mixed factorial analysis of variance was used to compare RFD in 50 ms epochs during the early phase of the bench press (time [pre v post] x RFD [0-50 ms v 50-100 ms v 100-150 ms]) and paired samples t-test were used to compare the pre and post measurements for CSA and peak force. RESULTS:There was not a significant difference in CSA (p = 0.37; 13.15 ± 0.99 to 12.61 ± 1.18; mean ± SE), or peak force (p = 0.84; 774.37 ± 93.86 to 788.12 ± 81.58; mean ± SE) from pre to post. Furthermore, there were no significant time x RFD interactions (p = 0.241) or main effects in time (p = 0.134) or RFD (p = 0.274) between the early phase 50 ms epochs. CONCLUSIONS: The results indicate there were no significant adaptations in muscle CSA or force production, which might reflect the training style of APRE programs. Resistance training populations typically experience notable hypertrophic development after 8-12 weeks of training. Furthermore, extending the APRE protocol beyond 4 weeks is recommended to accurately assess the effect of APRE on muscle morphology and force production measures.