Effect of sit-to-stand-based training on muscle quality in sedentary adults: a randomized controlled trial Lizama Pérez, Rodrigo Alberto Chirosa Ríos, Luis Javier Guido, Contreras Díaz Jerez Mayorga, Daniel Alejandro Muscle power Sarcopenia Chair stand Muscle architecture The aim of this study was to compare the effects of sit-to-stand (STS) training programs with 5 vs. 10 repetitions on muscle architecture and muscle function in sedentary adults. Sixty participants were randomly assigned into three groups: five-repetition STS (5STS), 10-repetition STS (10STS), or a control group (CG). Participants performed three sets of five or 10 repetitions of the STS exercise three times per week for 8 weeks. Before and after 8 weeks, all groups performed ultrasound measures to evaluate muscle thickness (MT), pennation angle (PA), and fascicle length (FL), and the five-repetition STS test to estimate the relative STS power and muscle quality index (MQI). After 8 weeks, both experimental groups improved MQI (40–45%), relative STS power (29–38%), and MT (8–9%) (all p < 0.001; no differences between the 5STS vs. 10STS groups). These improvements in both groups resulted in differences regarding the CG, which did not present any change. In addition, only the 5STS group improved PA (15%; p = 0.008) without differences to the 10STS and CG.This suggests that STS training is time-effective and low-cost for improving muscle function and generating adaptations in muscle architecture 2023-10-05T09:39:45Z 2023-10-05T09:39:45Z 2023-07-12 journal article Lizama-Pérez R, Chirosa-Ríos LJ, Contreras-Díaz G, Jerez-Mayorga D, Jiménez-Lupión D, Chirosa-Ríos IJ. 2023. Effect of sit-to-stand-based training on muscle quality in sedentary adults: a randomized controlled trial. PeerJ 11:e15665 [https://doi.org/10.7717/peerj.15665] https://hdl.handle.net/10481/84850 10.7717/peerj.15665 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional PeerJ team