I am not sure of the stiffness values of human body in vertical or longitudinal direction, but some Vibration standards give different weightage for exposure to vibrations on human body in different axis. For example according to ISO 2631 std for whole body vibrations, the limits for human body are different in different direction (vertical and longitudinal) and varies according to exposure time as a function of frequency. Vertical vibrations are considered more severe as compared to longitudinal. Also as per ADS-27A-SP standard, the vertical vibrations are normailsed as 50% weightage as compared to longitudinal. Hence vertical are considered double in terms of severity for human body.

Your question is very interesting. I think you are looking for the stiffness values to use them in a model representing a human body in the laying down position. Although the limits for vertical and horizontal positions are given in current standards (as mentioned by the colleague above), I am not aware of these stiffness values nor a corresponding model published in the literature. I saw a paper that gives some values for a seated person that may be useful in your research. You can find the article here:

Article Evaluation of Human Body Response for Different Vehicle Seat...

I hope this would help.

Best regards,

JPA

I would say you cannot.The vertical stiffness will mainly depend on the stiffness of the skeleton and articulations while the horizontal stiffness (lying down) will be more likely determined by the flesh properties.

Dear Lucas,

I agree with answers above. You can track back your information from the different weightage proposed in standards.

Once a given average stiffness value is defined (e.g., from literature) you could estimate the related stiffness for other postures on the basis of severity of weightage. Anyway, values of stiffness related to human body (and related to singular "elements" such as head, shoulder, thorax, ...) can largely vary, but you can have an indication of the variability of our estimation, at least.

Best regards

Alessandro

Your question is likely to be related to how a human body is likely to lie down. In case the persons are lying down over time it will be on something comfortable like a bed or a sofa. Then probaly the dynamics of the body mass, or body parts, and the sofa or bed cushion material is the esential information needed. The resonances governing body mass and its cushioning underlay and not the body parts alone per se.