Heavy lifting, twisting and bending can do damage to the discs in the back by reducing the flow of nutrients to the disc cells, a study says.
Disturbing the balance of nutrients in the discs can then lead to the onset of degenerative disease.
Writing in PLoS Computational Biology, Spanish experts say a normal level of physical activity helps cell nutrition.
Lower back pain, which is linked to degenerative spinal discs, could be caused by this lack of nutrients.
Previous research has shown that 80% of the active population suffers from low back pain at some point in their lives.
But little was known about the chain of events which changes normal, healthy ageing discs into degenerative discs.
Using computer models of the human disc in their study, a team of scientists from Barcelona's Institute for Bioengineering looked at the nutritional and mechanical effects of stress on the discs of the lower back.
By using the models, the researchers were able to see what happened when they changed disc height, cell density and made degenerative changes to the disc.
It would not have been possible to carry out this quality of research in a living person.
The results showed that external loads on the disc influenced the solute concentration - the amount of glucose and lactate present in the disc.
The cells need glucose but do not want too much lactate, an acid which hinders the nutrition process and can kick-start the degenerative process.
Dr Jerome Noailly, study author and expert in the biomechanics and mechanobiology group at the Institute, said the study showed that nutrients could be the key factor.
"If we know that lack of nutrition is involved in accelerating the degenerative process and the properties of a degenerative disc hinder nutrition, then this will increase cell death and the disc tissue will start to degenerate more and more.
"In order to bring back the function of the degenerated disc, we must address the nutrition problem.
"This means restoring the water content of the disc and the volume of the disc. A degenerated disc is like a collapsed sponge which needs to be restored to its normal size."
The research team says the findings could open up new areas of research in the field of disc regenerative medicine.
Dr Brian Hammond, chair of the charity BackCare, said: "We are what we eat and the spine is no exception. A balanced diet, adequate fluid intake and regular exercise are essential for a healthy back and neck.
"There is little doubt that poor diet, being immobile for long periods and bad habits like smoking contribute to spinal degeneration and the high incidence of back and neck pain in the UK."