Add spaces: Sitontheball,backstraight.

Answer: Sit on the ball, back straight.

Add spaces: MassagebeltasaccessoryforallDr.Kernmassageequipment.

Answer: Massage belt as accessory for all Dr. Kern massage equipment.

Add spaces: In1731JonespublishedDiscoursesoftheNaturalPhilosophyoftheElements.

Answer:
In 1731 Jones published Discourses of the Natural Philosophy of the Elements.