Blender 3D modeling tool supports all kinds of 3D formats, including .c3d 3D biomechanics data standard and such can process and save the data in its default .blend file type. Likely the only way how to produce .blend files from .c3d sources.
Convert 3D biomechanics data standard to Blender 3D data file.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert c3d to blend on Windows
A very popular free program used for work with 3D graphics
Convert from c3d file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.