Assessing the repeatability of a Magnetic Resonance compatible ergometer for ankle dorsiflexion
Author
Battistella, Francesco
Term
4. semester
Education
Publication year
2018
Abstract
This study evaluated the repeatability of a self-built, magnetic resonance compatible ergometer for ankle dorsiflexion. The device was constructed from non-magnetic materials and integrated an S-shaped force transducer and a rotary potentiometer; both were calibrated to confirm linear responses and enable conversion from voltage to force and angle. Five adult participants completed two sessions two days apart, performing 30-second dorsiflexion trials against elastic-band resistance (1–4 bands; three trials per level; day two recorded two-band resistance). Signals were amplified, digitized, and recorded, then analyzed using percentage coefficient of variation (CV) for peak force and angle (within-subject, within-trial/across-subjects, and across sessions), a one-way ANOVA between days, and intraclass correlation (ICC) for inter-subject agreement. CVs were consistently below 5%, indicating good consistency, with mean within-subject CVs around 1.76% (force) and 1.64% (angle), and within-trial/across-subject CVs around 2.23% (force) and 1.92% (angle). The ICC suggested sensitivity to differences in individual execution, likely due to the absence of an imposed pace. Overall, the ergometer provided repeatable force and angle measurements during controlled ankle dorsiflexion and appears suitable for future MR applications.
Dette studie evaluerede gentagelsesnøjagtigheden af et egenbygget, MR-kompatibelt ergometer til ankel-dorsalfleksion. Ergometeret blev konstrueret af ikke-magnetiske materialer og integrerede en S-formet krafttransducer og et roterende potentiometer; begge blev kalibreret for lineær respons og konvertering fra spænding til henholdsvis kraft og vinkel. Fem voksne deltagere gennemførte to sessioner med to dages mellemrum og udførte 30-sekunders dorsalfleksioner mod elastikmodstand (1–4 bånd; tre forsøg pr. niveau; dag to kun to bånd). Signalerne blev forstærket, digitaliseret og registreret, og analyseret med procentvis variationskoefficient (CV) for topkraft og vinkel (intra-subjekt, intra-forsøg/inter-subjekt og på tværs af sessioner), envejs ANOVA mellem dage samt intraklasse-korrelation (ICC) for interpersonlig overensstemmelse. CV-værdierne lå konsekvent under 5% og indikerede god konsistens, med gennemsnitlige intra-subjekt CV på cirka 1,76% (kraft) og 1,64% (vinkel) samt intra-forsøg/inter-subjekt CV på cirka 2,23% (kraft) og 1,92% (vinkel). ICC’en tydede på følsomhed over for forskelle i deltagernes udførelse, sandsynligvis fordi der ikke blev pålagt et fast tempo. Samlet set leverede ergometeret gentagelige kraft- og vinkelmålinger under kontrolleret ankel-dorsalfleksion og er lovende for fremtidig anvendelse i MR-sammenhænge.
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