IPA: /ɜːrˈɡɒmətər/
KK: /ɜrˈɡɒmətər/
A device used to measure the amount of work done by muscles during exercise, often used in fitness and rehabilitation settings.
The athlete used an ergometer to track her performance during training.
Ergometer is formed from "ergon" (meaning work) and "metron" (meaning measure). The word describes a device that measures work or energy output during physical activity.
Think of 'work' ('ergon') being 'measured' ('metron') — that's what an ergometer does.