High knees can definitely help you move more but many people wonder if they are cardio, resistance training, or even intense enough to be considered a workout.
In theory, whether high knees are cardio or resistance training depends on your personal fitness capabilities. That being said, high knees are cardio for most people.
As long as you can do 30 to 50 high knees per leg without fatiguing your muscles, high knees are not really considered resistance training.
On the other hand, as long as you do high knees at an intensity where your heart is beating at 70% of its maximum speed or higher, they are considered intense enough to be a cardiovascular workout
High knees do engage muscles like your hip flexors and calves to some extent. However, for most people not enough to be considered a resistance training workout.
Cardiovascular vs resistance training
Most people wonder whether high knees are either cardio(vascular) training or resistance training. These are the two main categories of workouts.
Cardio workouts focus on training your cardiovascular system, your heart and lungs. Resistance training is done with the goal of growing and strengthening skeletal muscles.
These two workout categories are not completely separate. A cardiovascular-focused exercise like running could help individuals who don’t do resistance training build or preserve a small amount of muscle.
Doing a few deadlifts with 260 pounds (118 kg) will definitely get your heart beating faster.
However, to really get the benefits of cardiovascular workouts, you typically want to choose something that gets your heart rate up for longer sessions at a time.
The exact difference between these two workout categories is not the most precise but a rough guideline is that if you can do more than 50 repetitions/steps of an exercise without your muscles fatiguing, you are likely doing cardio.
You can even argue this is already the case at 25-30 repetitions/steps.
That means your personal muscle strength influences whether high knees are cardio or not for you personally.
Are high knees intense enough to be cardio?
Most people who have done a session of high knees won’t question this but you could ask yourself whether high knees are even intense enough to be considered cardio.
Again the guidelines are not the most precise but most people agree that any activity where your heart rate is above 70% of its maximum can be considered a cardiovascular exercise.
You can get a rough estimation of your maximum heart rate by subtracting your age from 220. For example, if you are 50 years old, the estimation would be that your maximum heart rate is around 170 beats per minute.
The actual number is highly dependent on your activity levels and other factors.
So if you do high knees at an intensity where your heart rate is more than 70% of your maximum, most people would consider this a cardiovascular exercise.
After that, whether knees are aerobic or anaerobic depends on how far you take it. Most people consider anaerobic exercise to be where your heart rate is between 80% and 90% of your maximum.
Are high knees cardio for you?
In short, if you can do about 50+ high knee repetitions with each leg without your muscles fatiguing, you are likely doing a cardio workout.
Even if you can only do about 30 repetitions you could already consider high knees cardio. How many high knees you should do after that depends on things like your training goals, time, speed, etc.
Something else to keep in mind is that you want to do your high knees at a pace that is intense enough to get your heart beating at 70% of your maximum heart rate or faster.
This should be easy to achieve since one of the benefits of high knees is that you can easily switch up the pace for your fitness levels and goals. You can even make it a high-intensity workout relatively easily.
These things mean that for most people, high knees will be cardio.
At the same time, there are a few exceptions where individuals have weak hip flexors, calves, and other leg muscles. In these cases, the muscles used in high knees could get muscle endurance training.