Joseph was born in Mönchengladbach, Germany on 9 December 1883. As a child he suffered from rickets, asthma and acute rheumatic fever, and consequently devoted his whole life to improving his physical resistance. As a youth, he practiced physical education, wrestling and gymnastics (which he later also taught). By the age of 14, he was muscular enough to pose for anatomical charts.

In 1912 Joseph moved to England, where he became a boxer and circus performer and taught self-defence. When the First World War broke out in 1914, he was treated as a “foreign enemy” and interned with other Germans in camps near Lancaster and on the Isle of Man. It was during this time that he developed the foundations of the Pilates method, using the mattress springs of the camp beds to add resistance and support to his exercises. He would later explain that his years of internment were invaluable as they gave him time to develop his method.

He became a nurse in the camps, which allowed him to work on the rehabilitation of the sick and wounded. He also taught the other prisoners the physical exercises he had developed. He would later proudly claim that thanks to his daily physical training, none of the internees under his supervision succumbed to the 1918 flu epidemic that killed thousands across England.