Older women participated in a 12-week high-speed resistance training program under two supervisor-to-subject ratio methods (i.e., high versus low supervision) to assess its effects on muscle strength, power, functional performance, and quality of life assessed before (T1) and after (T2) intervention. Women were divided into either the control group (CG, n = 15), high supervision group (HSG, n = 30), or low supervision group (LSG, n = 28). The training program included exercises requiring high-speed concentric muscle actions. No differences were observed among groups at T1. Between T1 and T2, the HSG showed a higher (p<.05) improvement in muscle strength (ES = 0.36-1.26), power (ES = 0.5-0.88), functional performance (ES = 0.52-0.78), and quality of life (ES = 0.44-0.82) compared with LSG and CG. High-speed resistance training under closer supervision is more effective for improving muscle strength, power, functional performance, and quality of life in older women.