High-Intensity Aerobic Training (HIIT)
Roger Bannister broke the four-minute mile in 1952, running about two miles during each training session. He used high-intensity interval training methods developed by Eastern European, Australian, and British coaches.
Short bouts of maximal-intensity exercise build high levels of fitness quickly. Canadian researchers found that six sessions of high-intensity interval training on a stationary bike increased muscle oxidative capacity (citrate synthase) by almost 50 percent, muscle glycogen (stored carbohydrate) by 20 percent, and cycle endurance capacity by 100 percent. The subjects made these amazing improvements exercising a mere 15 minutes in two weeks.
A follow-up study in moderately-active women using the same training method showed that interval training increased whole-body and skeletal muscle capacity for fat use during exercise. A third study compared traditional endurance training (training on a stationary bike for 60-90 minutes per workout) versus interval training (6 sets, 30 seconds at maximum intensity, with four minutes rest between sprints). Improvements in fitness and biochemical factors were nearly identical. The key element in all three studies was training at 100 percent of maximum effort. These studies showed the importance of high-intensity training for building aerobic capacity and endurance.
The body uses different biochemical pathways to help it adapt to endurance or strength training. Guys training to look buff try to develop large, symmetrical muscles and minimize fat. Unfortunately, these processes often work against each other— low-calorie diets and aerobic exercise can compromise muscle growth. Muscle hypertrophy requires muscle tension, anabolic hormones, amino acids, calories, and adequate recovery. This environment activates signaling mechanisms inside the cells that turns on protein synthesis and builds muscle.
Athletes cut fat through a combination of low-calorie diets and endurance exercise, both of which can compromise protein synthesis and muscle growth. Usually, training simultaneously for muscle growth and endurance compromises muscle hypertrophy. Strength and endurance training initiate different signaling pathways within the muscle cells. Endurance training activates AMPK— an important energy-sensing enzyme that monitors cellular energy status. AMPK inhibits mTOR, a cell-signaling chemical that promotes muscle protein synthesis and muscle hypertrophy.
Short-duration, intense muscular exercise is typically associated with resistance training that turns on cell biochemical pathways in muscle that stimulate growth. Canadian scientists found that high-intensity interval exercise training (HIIT) caused rapid cellular and cardiovascular changes that resemble traditional endurance training. HIIT did not, however, turn off signaling pathways that stimulate muscle protein synthesis and growth.
Practice the high-intensity interval training workout three days per week. You can do the kettlebell and HIIT workouts on the same day, but the workout is challenging. For HIIT, the elliptical or stationary bike is best, but you could also use a Stairmaster or stair climber machine.
HIIT for Elliptical Trainers
Elliptical trainers are great for interval training because you can train intensely without beating up your knees, hips, and back. Interval training on this machine varies the striding speed, resistance, and ramp height. For beginners, a basic program is to alternate between fast and slow striding rates. For example, set the ramp and resistance at low levels (1-5) and “run” for two minutes at 70 strides per minute (spm). Alternate between one minute at 110 spm and one minute at 70 spm. Begin with 5 intervals and increase them as you become more fit.
When you can do 10 one-minute intervals at 80 percent effort, you are ready for the HIIT program on the elliptical trainer: 6 to 8 sets of 30 seconds at top stride speed, maximum ramp height (high knees), at the heaviest load you can maintain, at least 100-150 spm with four minutes rest between intervals. You must work at maximum intensity to get the full benefit!
HIIT for Stairclimbing Machines
HIIT routines for the stairclimber are similar to those of the elliptical trainer— you vary the resistance and stepping rate. An example of a beginning routine is to set the resistance at a low level and work at a step rate of 50-60 steps per minute (spm) for two minutes. Alternate between one minute at 80-90 spm and one minute at 50-60 spm. When you can do 10 intervals at 80 percent effort, you are ready for the HIIT workout on the stairclimber: 6 to 8 sets of 30-second intervals at 100 percent effort, with four minutes rest between intervals.
HIIT for Stationary Bikes
If you are a beginner, ride at an intense pace for 10 to 15 sets of two minutes, with one to two minutes rest between sets. When you can complete 15 sets, you are ready for the stationary bike HIIT workout: On the stationary or supine bike, sprint as fast as you can for 30 seconds, rest for four minutes, and then repeat six to eight times. High-intensity interval training builds aerobic capacity quickly, and the key is to exercise at maximum intensity.