Mapping the interplay between fitness parameters, physiological indicators, and non-invasive monitoring systems: a schematic literature review

There are numerous fitness monitoring devices widely available to the public and athletes. However, surprisingly, there is no adequate existing international standard for these devices. Despite this, researchers have significantly developed noninvasive fitness monitoring methods, which are now incorporated into commercially available devices. This review focuses on observing research findings from the past decade that relate to athlete fitness parameters, physiological indicators, and non-invasive monitoring techniques, specifically near-infrared spectroscopy (NIRS). Conducted using a schematic literature review methodology, this review aims to provide end-users with an understanding of the complexity and reliability of noninvasive fitness monitoring devices.