Potential role of blood constituents in pain-relief associated with fibromyalgia treatment with extremely low magnetic field: Spectroscopic investigation

•Blood autofluorescence indicates that extremely-low frequency magnetic field enhances the energetic pathways and accordingly the cellular activities.•UV–visible spectra reveals that treatment with ELF-magnetic field is associated with increased hemoglobin-oxygen affinity.•FTIR measurements provide evidence that ELF-magnetic field treatment was associated with the domination of α-helix structure in hemoglobin molecule.•Osmotic fragility measurements show that the RBCs membrane elasticity and fluidity are increased due to ELF-magnetic field treatments.