The speech reflected his own personality and life experience. Roosevelt was sickly and asthmatic as a youngster, and had to sleep propped up in bed or slouching in a chair during much of his early childhood. He was in poor physical condition as a result. Roosevelt's father compelled the young Roosevelt to take up exercise, including boxing lessons in order to ward off bullies.
The influence stuck. Upon graduating from Harvard University, Roosevelt underwent a physical examination and his doctor advised him that due to serious heart problems, he should find a desk job and avoid strenuous activity. Roosevelt disregarded the advice. As an adult, he exercised regularly and took up boxing, tennis, hiking, rowing, polo, and horseback riding. As governor of New York, he boxed with sparring partners several times a week, a practice he regularly continued as President until one blow detached his left retina, leaving him blind in that eye (a fact not made public until many years later). Thereafter, he practiced jujutsu and continued his habit of skinny-dipping in the Potomac River during winter.
As a result, the phrase "the strenuous life" has become highly connected to Roosevelt's life. Nathan Miller's biography of Roosevelt, Theodore Roosevelt: A Life, begins by saying that "the strenuous life" is one of "the things that immediately come to mind when Theodore Roosevelt's name is mentioned."
The speech also reflected the American spirit at the turn of the 20th century. The increasing industrialization and urbanization of America led many to become fearful of growing weak. College sports were on the rise, as were recreational athletics such as bicycling. American culture embraced masculinity, patriotism, and nationalism. Issues of masculinity were especially predominant during this time, given the various women's movements of the age. Critics and scholars, including author Henry James, worried about a femininization of America. The time was ripe for Roosevelt to extol the masculine virtues of the strenuous life. Roosevelt used the speech to justify American imperialism as well.