Previous methodologies have lacked some clinical relevance by using a small range of frequencies and non-physiological load magnitudes. We we will be employing physiological loads and frequencies spanning a wider range of 0.1-15Hzcite{PanjabiMMAnderssonGBJorneusLHultEMattsson1986InJBJS}cite{Pope1991IntervertebralVibration}.The IVD exhibits viscoelastic properties under deformation, such as time-dependent strain and recovery when loaded and unloaded, showing that it possesses both fluid and solid properties. These properties can be modeled using a combination of springs and dashpots. Although the origins of degeneration of the disc are mostly unknown, the nutrient supply to the disc is shown to be cause/effect of degeneration as shown by T Grunhagen et al.cite{GRUNHAGENTHIJSMSCWILDEGEOFFREYBSCSOUKANEDAHBIAMOKHBIBSCSHIRAZI-ADLSAEEDA.PHDURBAN2006NUTRIENTJBJS}. As the largest avascular structure in the body, with less than 1$\%$ of its volume being cells,  the nutrient transport pathways are essential to the maintenance and repair of the disc.  WC Hutton et al.cite{HuttonWilliamC.DScElmerWilliamA.PhDBodenScottD.MDHyonSteveBSToribatakeYasumitsuMDTomitaKatsuroMDHair1999TheSpine} conclude that ‘Hydrostatic pressure directly affects the synthesis of collagen and proteoglycan by the intervertebral disc cells’.Whereas M.B Giers et al.cite{Giers2017BiomechanicalDisc} compare conflicting results of many papers, each providing theories of increasing or decreasing nutrient transport when mechanical loads are applied. An increased knowledge of the pressure profile of the disc may help with further research into these conflicting theories. Current solutions for lower back pain are that when conservative treatments are inadequate, surgery may be carried out, which also has its complications. Spinal fusion, the leading surgical treatment, has poor long term pain relief and artificial disc replacements have frequent complications and mixed long term outcomes. More in-depth research is needed for more successful long term treatmentscite{Giers2017BiomechanicalDisc}.subsubsection{label{sec:aims}Aims}Through compression of the disc and end-plates, with varying magnitude, frequency and amplitude of loading, we will achieve greater insight in to their mechanical properties.Identifying the variations of pressure in different positions of the disc in response to the frequency of loading will show how the viscoelastic properties of the disc behave at particular frequencies and loads.This information would lead to identification of which frequencies will be hazardous to the disc, by the display of abnormal properties of disc mechanics, which will be able to tell us which occupational exposures could lead to accelerated degeneration of the disc.Having a complete knowledge of the reaction of the IVD to various stimuli could allow us to identify synthetic materials of the same properties for possible disc replacement implants. Once the pressure profile and frequency response are known, the diffusion and convection rates can be investigated by electrochemical techniquescite{GRUNHAGENTHIJSMSCWILDEGEOFFREYBSCSOUKANEDAHBIAMOKHBIBSCSHIRAZI-ADLSAEEDA.PHDURBAN2006NUTRIENTJBJS}. This area of research could lead to regenerative techniques such as injecting cells for the repair and maintenance of the disc. subsection{label{sec:level2}Anatomy}We are interested in the IVD between adjacent vertebrae found in the lumbar portion of the spineFIG 2.The mechanical properties of the IVD within the spine, have to be able to sustain weight without collapsing, yet deformable to accommodate rocking while keeping strength and preventing injurycite{Bogduk2005ClinicalSacrum}.%egin{figure}h%centering%includegraphicswidth=0.2 extwidth{spineinbody.png}%caption{label{fig:Loads} %Spinal column showing intevertebral discs separating adjacent vertebrae. The vertebral bodies of the lumbar spine are the largest because they bear the majority of the body’s weightcite{spineinbody}{}}%end{figure}There are 3 major components to the IVD: The annulus fibrosus (comprised of concentric rings of collagen fibers interspersed in a viscoelastic fluid) encapsulating a soft gelatinous nucleus pulposus and two cartilaginous end-plates separating the disc from the adjacent vertebral bodiesFIG 3.The constituents of the IVD are mostly water, proteoglycans (large and small), collagen fibers and elastin fibers but their relative concentrations vary for each component of the disc, giving each component specialized mechanical properties for the mechanics of spine movement.A major ($\%15$ and $\%5$ of wet weight for the nucleus and annulus respectively) component of the extracellular matrix of the disc are proteogylcans, which maintain tissue hydration by the absorption and expelling of water due to the osmotic properties from their highly negatively charged polymer chains interspersed in a viscoelastic gel.Osmotic pressure of the system acts so that increasing the compressive load leads to fluid displacement causing the internal swelling pressure to increase. %***mention elastin and colagen to explain recoil of the disc!%egin{figure}h%centering%includegraphicswidth=0.4 extwidth{JPUrbandisc.jpg}%caption{label{fig:Loads} Cross section showing the components of the IVD. The Vertebral Body,VB, Cartilaginous End-plate,CEP, Spinal Cord,SC, Annulus Fibrosus,AF, Nucleus pulposus,NP, Apophyseal Joint (Facet Joint),AJ and the Nerve Root,NR cite{urban2003degeneration}}%end{figure}subsubsection{Nucleus Pulposus}Found in the center of the IVD the nucleus pulposus is constrained radially by the annulus and vertically by the end-plates.Type II collagen fibers and radially arranged elastin fibers make the nucleus well adapted to pressure. Consisting of $sim70-90\%$ watercite{Bogduk2005ClinicalSacrum}, when compressed the nucleus behaves as an incompressible fluid structure, exerting pressure radially outwards on to the annulus fibrosis.The  radial pressure exerted by the nucleus will be equal to the tension developed in the annulus for each equilibrium when load is applied. A natural swelling pressure is found in the nucleus simply by being constrained by the annulus.This intrinsic swelling pressure is what we will measure our relative pressure readings from, as it depends upon the constituents of each disc individually. The nucleus is clearly distinguishable and resembled a clear fluid when in a young and healthy disc, but becomes more solid and merges with the annulus when degenerated.