Trunk flexion strength is an essential component of core muscle performance, playing a critical role in spinal stability, injury prevention, and athletic function. While isokinetic dynamometers remain gold standard for trunk strength assessment, their high cost and limited accessibility restrict their use in most clinical and field settings in Pakistan. There is a need for reliable, affordable alternative that can be used by physiotherapists and sports practitioners without access to specialized laboratory equipment. Therefore, this study aims to evaluate the reliability of a custom-made standing platform for measuring trunk flexion isometric strength in healthy young adults. Establishing the reliability of this device will enable clinicians and researchers to confidently use it as a practical and cost effective tool for trunk strength assessment in both clinical and sports settings.