Effects of gravitational versus iso-inertial resistance training on leg muscle force and metabolic cost of walking in healthy older adults

BACKGROUND: The purpose was to compare the effects of 8-week resistance training programs (flywheel iso-inertial [FW] versus traditional gravity-dependent resistance training [GD]) performed twice a week at the same rate of perceived exertion (RPE), on muscle force and power capacities and physical performance in healthy older participants. METHODS: Twenty-four participants were randomly assigned to either FW (male/female ratio: 7/5, age: 67.1±3.8 years) or GD (male/female ratio: 6/6, age 68.3±3.0 years) group. Knee extension maximal isometric voluntary contractions (MVC), lower limb maximal explosive power (MEP), Six-Minute Walking Test (6MWT), Timed Up-and-Go Test (TUG), metabolic cost of walking (CW) and agonist-antagonist co-contraction time (CCT) during walking were evaluated before and after training. RESULTS: absolute MEP and MEP normalized for body mass increased only in FW than GD group (+10.8% vs. +0.31%, P=0.056, respectively; +14.8% vs. +13.9%, P<0.001, respectively). Both training modalities improved MVC to a similar extent (+11.1% in FW vs. +13.4% in GD, P<0.001). Analogously, 6MWT distance increased in FW and GD (+5.2 and +5.5%, P<0.041, respectively). No effects of time and training modality were observed on the other parameters. CONCLUSIONS: The results of this study suggest that when FW and GD are administered at the same RPE with FW performed at higher movement speed in the concentric phase, both the trainings generate similar improvements in muscle strength but only the former can promote greater muscle power enhancements than GDin healthy older adults.