This study compares the effects of two resistance training programs in peripheral and respiratory musculature on muscle mass and strength and physical performance and identifies the appropriate muscle mass parameter for assessing the intervention effects. Thirty-seven institutionalized older Spanish adults with sarcopenia were analyzed: control group (n = 17), respiratory muscle training group (n = 9), and peripheral muscle training group (n = 11). Measured outcomes were appendicular skeletal muscle mass (ASM/height2, ASM/weight, and ASM/BMI), isometric knee extension, arm flexion and handgrip strength, maximal inspiratory and expiratory pressures, and gait speed pre- and postintervention. Trained groups participated in a 12-week program and improved in maximum static inspiratory pressure, maximum static expiratory pressure, knee extension, and arm flexion (p < .05), whereas nonsignificant changes were found in gait speed and ASM indexes pre- and postintervention in the three groups. In conclusion, resistance training improved skeletal muscle strength in the studied population, and any ASM index was found to be appropriate for detecting changes after physical interventions.