Objective: To evaluate the effectiveness of iso-inertial resistance training on eccentric power compared to gravitational training in physically active middle-older adults. Methods: Parallel-group, randomised controlled trial at Espai Esport Wellness Center (Granollers, Spain). Forty-four physically active adults (>57 years of age) were randomised to iso-inertial (n=21) or gravitational (n=23) training groups (R software; 1:1 ratio). Participants had to complete a 6-week training program (2 sessions/week) consisting of three exercises (forward lunge, side lunge, forward lunge with row). Primary outcome: power in the eccentric phase of each exercise evaluated with both iso-inertial and gravitational devices. Secondary outcomes: concentric power, physical performance, risk of falls. Only outcome evaluators were blinded. We used multivariate linear regression models to analyse the effect of interventions. Results: Iso-inertial training showed better eccentric power gains than gravitational training for iso-inertial system evaluation, although the difference was only statistically significant for the side lunge. Forward lunge: between-group difference 3.99 W (95% CI: -3.99 to 11.33, p: 0.28); side lunge: difference 8.50 W (95% CI: 2.13 to 14.87; p: 0.01); forward lunge with row: difference 14.07 W (95% CI: -2.07 -to 30.20, p: 0.09). We observed no differences for the gravitational system evaluation nor for concentric power, physical performance, and risk of falls. The two groups improved remarkably from baseline for all outcomes. Conclusions: Iso-inertial resistance training might lead to better eccentric power gains than gravitational training. Both approaches seem equally effective in improving concentric power and physical performance, and reducing the risk of falls. Trial registration: ClinicalTrials.gov (NCT06160089).

The authors have declared no competing interest.

NCT06160089

This study did not receive any funding.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Drug Research Ethics Committee of the Universitat Internacional de Catalunya (Code: FIS-2023-03) gave ethical approval for this work.

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I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

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Data were stored and encoded in three Excel files to protect confidentiality before, during, and after the study. The first of these files contains the personal data of the participants (name and surnames, age, and sex), is accessible only to the administrative staff of the center, and served only to manage the recruitment of the participants. The second and third files are managed entirely by the research team and contain the registry of all the study outcomes. In these files, participants were identified by a code. Only the research team can relate the data collected in the study to the identity of the participants, which will not be available to anyone except in the event of a medical emergency or legal requirement. These two files have been shared in a public repository.

https://zenodo.org/records/11125189