Manual muscle testing, load cell coupled with a signal conditioner, and handheld dynamometry are three widely used techniques for measuring isometric muscle strength. In this study, we examined both the criterion validity, inter-day reliability and intra-day reliability of a microcontroller-based load cell amplifier for quantifying muscle strength and we compared its results the other means of strength evaluation. Before we start, let’s get acquainted with these devices! This is the HX711 load cell amplifier, it is used to get measurable data out from a load cell and strain gauge.