How too much HIIT can kill your progress

Many medical and sports groups suggest intense interval training shouldn’t be completed more than three times/week to avoid these negative metabolic side effects. And from a joint health perspective, I agree that HIIT should not be used more than a few times/week, if at all. 

So if we can only gain the benefits of HIIT 2 to 3 days a week, are we just sedentary on the other days? Should we train in different ways on the days where we aren’t working out intensely? 

Another study that looked at the benefits of short, intense exercise vs. longer, more gentle workouts provides us with another interesting finding. 

The study took overweight men, divided them into groups, and had them exercise on a bike for a different amount of time and intensity. 

Group 1 performed short, all-out workouts on the bike such as 30-second sprints with minimal rest in between. This group only exercised 3 days/week. 

Group 2 exercised more moderately: 30-40 min on the bike at a moderate heart rate (60%) 5 days/week. 

Both groups were more fit by the end of the study. However, the group in the moderate-intensity group shed more body fat, saw greater improvements in their blood pressure, and were able to metabolize the extra fat better.

The study concluded that more frequent, gentle workouts were overall more favorable than less frequent, intense workouts. 

With both of these study results in mind, we know that we need to work out frequently, but probably can’t work out both frequently and intensely. 

So what’s our answer? Do we turn to HIIT? Steady-state cardio? Where does strength training come in? 

The answer is that it completely depends on who you are, and how much you’re doing. We want to strike the balance between applying enough exercise that we will see changes in our bodies, without overdoing it and backtracking. 

From my research and experience, I’ve found the most favorable outcomes are when most of your workouts are light or moderately intense, and focus on building muscle. 

Although these studies help demonstrate the short-term benefits of exercise, what they did not touch on is the adaptation of your muscular system, which takes a bit longer, anywhere from 8 to 24 weeks.

But good things come to those who wait. Increasing muscle mass has amazing benefits for your body. It improves our metabolism, bone density, cardiovascular health, and much more. 

The more muscle you can add to your frame, will help lean out easier, keep your heart healthier, and avoid many life-altering injuries as you age. 

So my recommendation is that on most of your workout days (anywhere from 4 to 5), keep your focus on strength training. What many people don’t realize is that your strength training workouts can often double as cardio, eliminating the need to add another workout to your routine. 

Your heart and lungs don’t know the difference between lifting a weight and riding a bike. They only know there is an increased demand to your tissues, so your heart and lungs need to pump faster and harder to accommodate that demand. 

So we might as well save time and effort by picking up the weights and receive the dual benefit of improving muscle mass. 

Not only can strength training double as cardio in the moment, but it can also improve your cardiovascular system in the long term. When you have more muscle, your heart and lung capacity is increased because the body has more dense tissue to serve and oxygenate. 

So if we begin to think of strength training as doubling for cardio, with the extra credit that improving or maintaining muscle mass also linearly improves our heart health, how much more cardio do we really need? 

In my opinion, it really isn’t necessary for overall health to do a bunch of dedicated, intense cardio. 

Studies show that HIIT is not the only form of exercise that improves our mitochondrial size and function. 

Moderate intensity exercise also improves mitochondrial function, and when it is stacked up over time, it has great benefits to the mitochondria’s function. So in your body’s long-term interest, both for your joint function and for your mitochondrial health, choosing the moderate-intensity routine (like lifting weights and elevating your heart rate moderately) will pay off.

Fat Loss 

Before we wrap up, I want to address another popular reason for exercise: fat loss.

Cardio is a popular exercise for those people wanting to lose weight because it aids in a caloric deficit. 

As we touched on earlier, because strength training is less repetitive and generally slower, it isn’t thought of as cardio, and therefore, often isn’t seen as a “weight loss” tool. 

However, I’ll say: If you’ve ever taken one of my lower body build classes, your heart is pumping just as much as it would if you had gone on a run. But since we are moving slow, we don’t classify it as cardio and think we need to supplement with a run to lose weight.

But, as that first study shows us, overdoing it on intense cardio can spiral you into more insulin resistance, making your body hesitant to let go of fat and inhibiting your metabolism. 

Oftentimes, what ends up happening is the people who rely on exercise to lose weight, overdo it on the intensity and/or frequency. This inhibits their body’s natural ability to recover in their mitochondria and in their muscles, which means they add less muscle mass, potentially increase their insulin resistance, and overeat because their hunger cues are distorted.

In short, if your goal is fat loss, where you should be focusing is the kitchen. 

Of course, some people do intense cardio all the time and see great results. But odds are that they have figured out their body’s right dosage. 

But cardio tends to be over-emphasized for weight loss when nutrition should be the primary tool if fat loss is your goal. Of course, we can then complement that with a routine that allows you to build muscle.

If you use exercise strategically as a way to gain muscle and improve your metabolic processes, then fuel it properly you are working with your body instead of against it. You’ll improve your metabolism and ability to stay lean sustainably without crash diets.

Bottom line: Do you need higher intensity workouts at all? Especially if it’s wearing down your joints? I think that question remains unanswered.

So I’ll leave you with a rough framework of how much cardio to add into your routine, based on where find yourself in your fitness journey:

If you’re coming from a place of feeling broken down with chronic joint pain, chronic fatigue, OR if you’re a newbie to exercise, cardio should not be your priority right now. 

We need to get your inflammation down and focus on building protective muscle by strength training in ways that stress your muscles, instead of your joints, thus improving your metabolism and fitness.

You do this by using 4-5 strength workouts/week and never working the same muscle groups on consecutive days. Your muscles need at least a day to recover, or you won’t see them strengthen and grow. Overusing them will only feed the body’s inflammation and inhibit optimal results. 

Since daily activity seems to be the best for overall health, we want to ensure you’re still moving your body on most days. So even on your non-workout days, going for a short and gentle walk, hike, or bike ride may be beneficial. Think about activities that get your heart rate up a tiny bit, but that don’t completely exhaust you as a HIIT session would. 

Some days you won’t do anything on your recovery day, and it doesn’t mean you’re losing ground! Please give yourself permission to rest.

Now, if you feel that you’re at a point where your inflammation is at bay (which can take months by the way, so be patient!), you can begin to add some brief, more intense workouts, if you want, maybe 2x/week. In my program, we do two 15 minute cardio burst classes, one of which is low-impact so it’s still gentle on your joints but gives you the higher intensity effect. 

Using my classes is obviously based on personal preference, but I am confident in my understanding of joint mechanics and how to choose exercises that don’t overstress your joints, I have lots of clients who run, and you can still incorporate running intervals, although it isn’t my preference because of the impact to your joints. 

Good Things take Time

Remember, you are not going to see results overnight. There’s some trial and error in the beginning. You may have to make adjustments to your frequency, intensity, or nutrition based on what’s best for your body. 

We are in this for the long haul, so it pays off to stay curious, not get frustrated, and give yourself space to explore, go back to the drawing board, and keep trying until you find your sweet spot. It’s completely normal to over or underdo it from time to time, but you just notice, adjust, and try again. 

If you’re ready to join a program that is structured in a way for you to see results without wearing down your joints, I’d love to have you in my Evlo classes. I teach new classes Monday through Friday, I’m always educating along the way in a refreshing and fun way, all while building up your body in healthy, sustainable ways. 

Come back next week, where we will break down the addition of steady-state cardio, and how much, if any, you really need.