Vol.:(0123456789) 1 3 Journal of Science in Sport and Exercise (2021) 3:125–137 https://doi.org/10.1007/s42978-020-00077-y ORIGINAL ARTICLE Inter‑Individual Rapid Force Improvements after Mixed Session and Traditional Periodization in Aging Adults: A Randomized Trial Bruno Monteiro Moura 1  · Ewertton de Souza Bezerra 1,2  · Lucas B. R. Orssatto 1,3  · Antonio Renato Pereira Moro 1  · Fernando Diefenthaeler 1 Received: 17 October 2019 / Accepted: 8 August 2020 / Published online: 10 September 2020 © Beijing Sport University 2020 Abstract Background Diferent periodization models have been widely used to improve maximum and rapid force in aging adults. However, it is unclear if some specifc model can infuence the remarkable heterogeneity of responsiveness to rapid torque improvements following resistance training. Aims Compare the efects of mixed session periodization (MSP) and traditional (TP) models on neuromuscular performance and individual responsiveness in aging adults. Methods Twenty-two aging men and women (64.6 ± 5.2 years old; 1.68 ± 0.1 m; 77.8 ± 16.0 kg) completed the intervention period. They were assigned into MSP (n = 11) or TP (n = 11) resistance training for lower limbs. The outcome measures normalized dynamic leg press (5-RM: BM ), absolute and normalized knee isometric peak torque (PT and PT: BM ) and rate of torque development, and impulse were assessed at baseline and after three blocks of a 9-wk resistance training (3 sessions per week). Thigh leg lean mass was assessed by dual-energy x-ray absorptiometry at baseline and after the intervention. Results Similar increases were observed for 5-RM: BM (MSP: 28.8% ± 13.5% and TP: 26.4% ± 7.6%, P < 0.001), PT (MSP: 223.7 ± 50.7 N·m and TP: 189.9 ± 58.6 N·m, P < 0.001), but it was not observed for PT: BM (MSP: 16.4% ± 16.5% and TP: 4.7% ± 9.2%, P > 0.05). Absolute and normalized RTD remained unchanged throughout intervention (P > 0.05), but both groups improved impulse (MSP: 22.1% ± 25.7% and TP: 12.6% ± 45.2%, P < 0.001). Only MSP responders (n = 5) presented signifcant time efect for absolute RTD (P < 0.05) and impulse (P < 0.05). Conclusion Although both periodization protocols increased 5-RM: BM and PT, it was not interchangeable through improve- ments in RTD even adopting power training session. Furthermore, these results suggest a great inter-individual variability following diferent periodization models for aging people. Keywords Rate of torque development · Impulse · Strength training · Muscular strength · Hypertrophy · Periodization Introduction During aging, the neuromuscular system structure and function are impaired, resulting into a natural decline in the ability to produce high levels of maximal and rapid force (i.e., explosive force) [7, 30]. Rapid force capacity refects how fast an individual produces force in a short time interval (~ 250 ms) and it is usually measured by the rate of force/torque development (RTD) or impulse at earlier (~ 0–75 ms) and later phases (~ 150–250 ms) [27]. Low levels of maximal and rapid force negatively infuence ability of daily living activities (i.e., functional capacity among aging adults) [28, 31, 32] and play a role in their postural sway and static and dynamic balance [17]. Therefore, low levels of maximal and rapid force increase Electronic supplementary material The online version of this article (https://doi.org/10.1007/s42978-020-00077-y) contains supplementary material, which is available to authorized users. * Fernando Diefenthaeler fernando.diefenthaeler@ufsc.br 1 Universidade Federal de Santa Catarina, Centro de Desportos, Laboratório de Biomecânica, Florianópolis, CEP  88040-900, Brazil 2 Universidade Federal do Amazonas, Faculdade de Educação Física e Fisioterapia, Laboratório de Estudo do Desempenho Humano, Manaus, CEP  38400-678, Brazil 3 School of Exercise and Nutrition Sciences, Queensland University of Technology, Brisbane 4059, Australia