A major fitness-related goal is to improve the function and capacity of your energy systems.
People often utilize cardio workouts in an effort to achieve these adaptations. However, "cardio" is an incredibly broad term.
Some prefer steady state cardio (which is highly aerobic in nature) while others prefer high-intensity interval training (which requires more of a contribution from the anaerobic system).
Steady state cardio is simply aerobic exercise performed at a steady pace for an extended period. It's an intensity where your body's oxygen demand meets its oxygen consumption. Maintaining a stable heart rate throughout the session is a hallmark of steady state exercise. In a sport like running, steady state is also often referred to as long, slow distance training, or LSD.
According to the textbook Essentials of Strength and Conditioning, long, slow distance training is typically recommended to be performed at intensities equivalent to "70% of VO2 max (or about 80% of maximum heart rate)".
High Intensity Interval Training, or HIIT, involves repeated bouts of high-intensity exercise in between periods of rest or active recovery. The exact work-to-rest ratio utilized will impact which energy systems are being relied upon, but generally speaking, HIIT will recruit more anaerobic mechanisms than steady state cardio, which is essentially exclusively aerobic by nature.
This training is characterized by significant increases and decreases in heart rate throughout the workout, and the total duration of these workouts is generally much shorter than those of steady state workouts. HIIT also burns more calories per minute and more calories post-exercise.
Essentials of Strength and Conditioning cites research from Buchheit and Laursen that an optimal stimulus from HIIT requires athletes to "spend several minutes within the HIIT session above 90% of the VO2 max."
Both can yield great cardiovascular results, so neither is a bad choice. Certainly, either one is far better for you than just sitting on the couch.
But if you're simply a person interested in achieving greater fitness, which one is right for you?
I find a blend of both to be a better option in many cases than simply opting for exclusively one or the other. Instead of performing only slower, steady state cardio or more intense HIIT, I recommend utilizing both. The program you choose should reflect a balance of getting good at what you're not good at, and even better at what you are good at.
You can measure intensity in a variety of ways: number of reps, distance covered in a specific amount of time, or the time it takes to complete a specific number or reps or distance.
Traditionally, intensity has been monitored by tracking heart rate, but this isn't always reasonable for everyone. Tracking your Rate of Perceived Exertion, or RPE, can also be a useful tool for dialing in intensity.
If you're just starting out or it's the first time you've worked out in a while, use heart rate to help track intensity if possible, but also keep track of how you feel performing different forms of exercise at different intensities. This way, you'll be able to incorporate a wider variety of movements into your workout while still having a valid method to quantify intensity.
For those looking to get in better shape, I recommend starting by improving your overall aerobic threshold. Some great exercises for steady state are:
- Outdoors: brisk walking, biking, rowing, jogging
- Indoors: stationary bike, treadmill climbing/walking, elliptical training
It's always good to get outdoors if you can, as exercising in nature seems to have a larger overall positive effect on our well-being than solely training in a drab gym.
Using the aerobic zone, or the intensity at which your body is using its aerobic metabolism system to produce energy, will improve your cardiovascular system and prepare your muscles for moving at greater speeds.
Once you feel you've got your aerobic fitness moving in the right direction, try integrating HIIT sessions. I like to recommend riding, running, rowing, climbing, etc., as hard as possible for between 10-30 consecutive seconds and then allowing yourself full recovery. This can be full-on recovery where you completely stop exercising or "active" recovery where you simply continue to do the activity but at a much less strenuous pace. A way to tell if you're achieving full recovery from one bout to the next is if you're burning about the same number of calories or covering about the same distance in each subsequent high-intensity bout.
Some of the best activities for HIIT are:
- Sprinting (flat or uphill)
- Shuttle runs (5 yards and back, 10 yards and back, 15 yards and back)
- Stationary bike intervals
- Treadmill sprints
- Rowing intervals
A balanced training program should use different combinations of these exercises and different intensity levels to create varied and personalized workouts. You can spend more time in the aerobic zone initially and progress to performing intervals, where you will spend more time in higher-intensity zones to improve your overall endurance, strength, and power.
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