Paragraph B states that the modern version of HIT "traces back to Arthur Jones... in the 1970s." The words "traces back" and the mention of the 1970s indicate a historical origin.

Section D describes how the body manufactures more "mitochondria, the microscopic powerhouses within cells that generate energy," explaining how energy production is enhanced at the cellular level.

The "High Intensity Training" text is a frequently recurring passage in the IELTS Academic Reading subtest. It explores the physiological science, historical background, and health benefits of High-Intensity Interval Training (HIIT) compared to traditional, steady-state cardio.