Study on the influence of contact pressure on diffuse spectroscopy measurement of in vivo tissue

•This work study on the mechanism of contact pressure on in vivo diffuse spectrum measurement.•The simulation demonstrated the changes of optical properties in the in vivo tissue related to pressure change, while, the experimental results revealed increase in transmittance and decrease in reflectance.•The optimal contact pressure has been determined from the experiments.•The simulation and experiment results would be helpful for setup practical guidelines of clinical applications.