10x may be utilised by almost anyone, regardless of fitness level or age (Vishen's father began at the age of 70). However, in order to get the best results and follow along comfortably, we recommend that you have a decent degree of health and fitness for your age.
This implies you should be able to perform basic resistance exercises without difficulty and be free of any debilitating injuries or illnesses that would prevent you from exercising on a regular basis.