Influence of resistance training on muscle architecture in older adults: A systematic review and meta-analysis of randomized controlled trials

•Resistance training (RT) promotes changes in muscle architecture in older adults.•The thickness of the medial gastrocnemius increased after intervention with RT.•RT showed no effect on the fasciculus and pennation angle and vastus lateralis.•Training variables interfere with morphological adaptations in the elderly. Resistance training (RT) consists of planned exercise programs to increase muscle strength capacity through neural and structural adaptations, such as changes in the geometric arrangement of muscle fibers. This study aimed to analyze the influence of RT on muscle architecture in older people. This PROSPERO-registered systematic review and meta-analysis (identification number CRD42022340477) followed the PRISMA guidelines. Four electronic databases were searched for eligible randomized controlled trials (RCTs) that observed older individuals submitted to RT programs that reported muscle architecture outcomes. Seventeen RCTs met the eligibility criteria with a total of 488 participants. The main results of the meta-analysis showed that RT interventions had a significant effect on the thickness of the medial gastrocnemius (SMD = 0.12; 95% CI: − 0.07 to 0.17; p < 0.00001; I2 = 0%). Based on available evidence, studies included in this review showed improvement in maximum isometric force, pennation angle, fascicle length, thickness, and muscle activation after RT interventions. In turn, the meta-analysis suggested a potential for improving the thickness of the medial gastrocnemius after the intervention. However, any clinical implications drawn from the analyses should be interpreted with caution, as these findings are substantially limited due to a low number of included studies and a potential heterogeneity between studies.