The increasing demand for enhanced performance in cutting-edge technology has fueled extensive research in engineering materials. Thanks to their unique mechanical properties, engineered materials have been used to manipulate the propagation of acoustic and elastic waves. The literature review primarily focuses on state-of-the-art Locally Resonant Mechanical Metamaterials (LRMMs), designed for vibration isolation by utilizing the principles of local resonances. It explores their working principles and performance in terms of bandgap tunability, aiming to get a better understanding of the available designs and identify their limitations, with the goal of enhancing the performance and applicability of this concept. Locally resonant mechanical metamaterials in this work are classified as passive or active materials based on their ability to alter the range of band gaps during operation. Passive LRMMs can effectively isolate constant vibrations in specific regions where the band gap remains fixed. However, they are unable to attenuate frequencies that lie outside the fixed bandgap range. Active LRMMs, on the other hand, can dynamically alter the band gaps during operation through external stimuli or integrated actuation. The applicability and tunability of band gaps in large lattices are the main limitations of the LRMMs reported in the literature. Moreover, the designs aimed at achieving low-frequency band gaps are often complex and challenging to realize. Additionally, the actuation principles used to maintain design functionality significantly contribute to these limitations, as nearly all reported active LRMM designs rely on either complex or impractical actuation mechanisms. This research work proposes a tunable vibration isolation system based on locally resonant mechanical metamaterials. The system consists of four unit cells capable of altering the bandgap across a wide range of frequencies by adjusting the stiffness of the resonators. It operates by applying global pres training to the lattice, which in turn compresses the resonators through the other masses in each unit cell, reducing their effective stiffness. The FEM resonator stiffness measurements revealed a reduction in the stiffness, which remains positive up to an applied strain of 0.72%. Specifically, the resonator stiffness decreased from 287.3 N/m at the initial state to 188.8 N/m at a strain of 0.36%, and further decreased to 74.1 N/m at 0.72%. At a higher applied strain of 1.09%, the stiffness became negative, reaching approximately -213.8 N/m and continuing to decrease with greater strain values. The transmissibility simulations demonstrated a wide tunability range for the formulated bandgap, confirming the effectiveness of the proposed design in altering the bandgap. The design was realized using Fused Deposition Modeling (FDM). Experimental results supported the modeling findings, with the bandgap shifting from an initial range of 77.14 Hz to 99.11 Hz to a wider range of 69.71 Hz to 97.47 Hz under a pre-applied strain of 0.54% on a lattice of four unit cells. These findings highlight the capability of the proposed lattice design to shift the bandgap to a lower frequency range.