From this study, Low-and High-Volume of Intensive Endurance Training Significantly Improves Maximal Oxygen Uptake after Ten Weeks of Training in Healthy Men comes this quote:
“Our study demonstrated that slightly overweight and healthy individuals only required brief, duration bouts of exercise with good effort three times a week, to produce large increases in VO2max and work economy and reduce blood pressure and fasting glucose levels.”
“The present study demonstrates that a relatively intense stimulus administered only once and for a relatively short duration can substantially improve VO2max and work economy. A single bout of 4-minute interval training three times per week will not solve all lifestyle-related problems for people already obese or overweight, and it is not the only solution for inactive persons with a BMI below 25.”
In the study one group of men performing just one high intensity session three times a week (walking, jogging, or running on a treadmill) for 10 weeks saw a VO2max increase of 10%, and the other group that did four sprints three times a week experienced a boost of 13%.
This protocol of four bursts is called the 4x4 12-minute workout. Other protocols are the Tabata protocol (20 seconds of intense work, followed by 10 seconds of rest for eight cycles), the Timmons protocol (20 seconds of cycling at total effort followed by 2 minutes of gentle cycling), and the Gibala protocol (60 seconds of work at 95% VO2max with 75 seconds of rest repeated for 8 to 12 cycles).
There are an infinite number of possible high intensity interval training (HIIT) workouts that can be performed. They cannot be both long and intense. Done right they will be brief and intense. You will have to build up to this. AtAustin Personal Training and at New Orleans Fitness Trainers we can help you gradually build up to a high intensity regime that is safe, effective, and efficient for your age and condition. You need not spend hours in the gym to feel better, look better, and perform better.