Are HIIT Workouts That Use Sprint Intervals Safe?

 You’ve most likely heard about some of the incredible health benefits of high-intensity interval training. HIIT involves short bursts of intense exercise followed by periods of recovery. This strategy helps boost your metabolism, lower blood pressure, and reduce blood sugar.

Following this exercise strategy forces you to work much harder in short bursts than any other exercise regimen. Since it doesn’t require hours of exercise, it appeals to many people. While it might be popular, some are concerned about the negative impact HIIT workouts with sprints can have on your body.

Let’s break these exercises down and explain how to stay safe when doing HIIT.

Don’t do HIIT Sprints Daily

The US government guidelines say you need two and a half hours of physical activity per week and two days of muscle-strengthening per week. That means that you should not be doing high-intensity workouts every day. Any exercise can become harmful if you overdo it; the same goes for HIIT.

HIIT is an effective form of exercise for those who are consistent and stick to a workout plan. You need to have everything figured out ahead of time, so you don’t overwork yourself. Make sure you keep your current level of fitness in mind as well. If you have never done these types of exercises before, don’t expect to jump right in. Take it at your own pace.

Mix Up Your HIIT Workouts

Doing high-intensity interval training sprints daily results in shin splints, ankle problems, and joint pain. If you want to do this type of training four or five days a week you’ll need to mix it up or else it could become harmful to your body. You might not notice the negative effects right away, but eventually, you’ll experience a decrease in performance, plateaus, and frequent injuries.

Working harder is not always the right choice when it comes to physical training. You want to work smarter. Alternate between treadmill sprints and outdoor sprints. Incorporate cycling into your workout plan as well.

Why HIIT Workouts with Sprints Could be Unsafe

We’ve covered some ways to prevent injury when doing HIIT but what if you already suffered an injury before and you’re nervous about trying high-intensity interval training again. Maybe it worked great for you, and you want to get back into it, but you’re unsure. Here are some of the reasons why HIIT could be unsafe.

Lack of warm-up

The number one reason anyone suffers a sports or training injury is that they didn’t stretch out well enough before. If you work in an office like most people, you sit at a desk all day with limited activity. You’re all stiff, and then you take off like a lightning bolt expecting to adjust in a matter of seconds. The body doesn’t work that way.

You need to understand that warming up and stretching is an integral part of training and fitness. Skipping this step will only come back to bite you later on.

Bad instruction

Unfortunately, you might not have had the right trainer or coach showing you what to do. Everyone has a different way of training, and some are not afraid to skip steps like stretching; they may not even show you the proper way to warm up before HIIT. You always want to make sure you have a licensed coach who understands how to train in HIIT properly. You also want to ensure you get plenty of rest in between intervals, especially if you are starting out.

Due to shows like “The Biggest Loser” and some of these other training and weight loss shows, we think it’s okay for coaches to push you to the absolute limit. There is some truth to that, but you need to know your limits. If your coach is pushing you too far, you need to be open with them. If they don’t understand and they don’t respect your honesty, find another coach.

Improper form

If you got injured from HIIT, you might not know the correct way to do the exercise you were doing. If you use high-intensity sprints for your training you might need to tweak your form and technique. The most important part of any workout is having the correct method. Ask any expert who considers themselves knowledgeable in their style of training, and they will tell you that technique trumps strength and skill any day of the week.

The downside to HIIT is that the focus is on numbers and speed, which takes away from the fact that you need to learn how to train properly first. You need to make sure you’re conducting your exercises correctly, so you not only get the most out of them but so you also prevent injury.

Lack of recovery time

As we said at the beginning of this article. You need to put a lot of emphasis on rest and recovery when you’re doing HIIT because you are pushing your body to the absolute limit. You must take plenty of rest periods between your levels of high-intensity, so you give your body a chance to heal.

At the same time, you don’t want to exercise every day because overtraining your body is a serious thing. You shouldn’t work out more than four times a week, and you need to swap out HIIT for other things. In between workout days you should try things like yoga and other flexibility work like gymnastics.

Doing these things along with your HIIT, will not take away from your exercise, it will only compliment it.

How to Properly do HIIT Sprints

If you find all of this a little overwhelming, you should check out the Sprinterval app which helps you tackle all of these HIIT issues. It’s like having a workout buddy there to cheer you on, make sure you’re staying on track, and to ensure you don’t overwork yourself!

Can HIIT Workouts Build Muscle?

 If you’re looking for a fat burning and muscle building workout, you might have stumbled upon high-intensity interval training or HIIT. Over time, athletes and fitness enthusiasts have utilized this form of intense training to develop lean muscle mass and maintain an incredibly cut physique.

There are a lot of misconceptions about HIIT and every other workout strategy alike. The bottom line is, if you’re looking for an intense workout that will guarantee you serious fat loss and lean muscle building, then you want to check out high-intensity interval training for yourself.

Understanding the Science Behind HIIT

The whole basis of high-intensity interval training is that everything is short and explosive. People who practice this kind of training believe that short, intense bursts of exercise have a lasting impact on your body composition. Take this for example,

Many people believe that endurance running is the ultimate way to build lean body mass, but practitioners of HIIT say that pushing yourself to the absolute limit for a short period is the way to go. Instead of running at a moderate pace for a half hour, you would break that up into a bunch of segments. You might run at your absolute limit for one minute and then cool down for two. You would repeat this process for the length of your workout.

The American Council on Exercise describes this training like this:

Most endurance workouts, such as walking, running, or stair-climbing —are performed at a moderate intensity, or an exertion level of 5-6 on a scale of 0-10.

High-intensity intervals, on the other hand, are done at an exertion level of 7 or higher, and are typically sustained for 30 seconds to 3 minutes, although they can be as short as 8-10 seconds or as long as 5 minutes; the higher the intensity, the shorter the speed interval. Recovery intervals are equal to or longer than the speed intervals.

So, as you can see, the difference lies in the intensity of each workout. You need to take yourself to your absolute max consistently and during those periods is when the most fat burning and muscle building takes place.

How HIIT Shreds Body Fat

First, let’s take a look at how HIIT impacts body fat. HIIT has shown across many studies to be one of the most powerful workouts for burning stubborn body fat.

We looked at a study of participants who agreed to three days a week of high-intensity exercise, and we compared them to another group of people who did five days a week of low intensity. The results were, people who committed to HIIT lost more fat in less time than the people who did the low-intensity workout.

If you’re having a hard time losing weight with some of your other exercises, this might be the easy way out. While the workouts are strenuous and you need to train yourself to push your body to the absolute limit, in the long run, it’s worth it. You’ll end up working out less and achieving better results for your efforts.

HIIT for Muscle Building?

The big question of the day is whether or not you can use high-intensity interval training for building muscle. The short answer here is yes you can. If you are looking to build lean muscle mass, this is the way to do it.

Short burst sprints followed by slow jogs is the essential way to utilize HIIT for muscle building. During those slow jogs is your opportunity to work on your endurance and build muscle faster. One of the easiest ways to promote muscle growth is to shorten your breaks and lengthen your bursts.

If you’re starting with ten-second bursts, for example, you might want to increase those to a full one minute burst. If your break is a lengthy five minutes, you might want to swap that out for a 30-second one. Flip-flopping your burst with your break is a great way to develop muscle faster during your down times.

Another great way to build muscle using HIIT is to pair it with something else. During your break times, instead of jogging or walking, you could do something else. You could jump rope, do push-ups, sit-ups, or even lift weights if you are at home.

One of the best benefits of HIIT is that it helps increase the size of fast-twitch muscle fibers instead of slow-twitch. These muscles are the main factors that determine your strength and speed, so it’s important to train them as you age continuously. Once you stop training fast twitch fibers, you lose them, and they’re gone forever. The best way to train them is with short bursts of HIIT.

Lastly, HIIT is a well-rounded exercise strategy for a variety of reasons. Not all of these directly play into muscle growth, but they all have a significant impact on overall health and wellness, which helps with muscle building.

HIIT is faster than traditional cardio which leaves more room for muscle building exercises, HIIT is effective in boosting V02 max which helps with endurance, and most people who practice this style of exercise say they enjoy it more because it’s more manageable over time.


Getting started with HIIT but not sure where to start? Check out Sprinterval.

Cheat Sheet: HIIT & When To Eat

 Are you planning to start doing high-intensity interval training (HIIT) and you're curious about how to handle the nutrition and eating aspect? Or maybe you already have a HIIT routine and you think your diet might be hindering your results?

Either way, you're probably wondering how you can boost your nutrition to maximize the benefits you get from your training. Knowing when to eat and what nutrition to focus on can make a huge difference.

Here are the tips to maximize your health benefits during HIIT.

Know Your Goals

A HIIT routine can help you keep your heart rate high and burn fat more quickly than longer steady-state workouts. A HIIT routine can boost your metabolism for up to 48 hours after you stop working out.

The reason this style of exercise is so popular is that many people are very pressed for time. HIIT can allow you to get great results in a very short amount of time.

Like many workouts, though, you have to eat right in order get results. The goals of HIIT involve cardio workouts and fat-burning, so you’ll need to eat in a way that supports those aims. Your pre- and post-workout food will be middle to high in carbohydrates and will also include some protein.

Here’s how to set up a successful HIIT eating plan.

Pre-Workout Nutrition

Unless you love being sick, you should not eat directly before a HIIT workout. Your body won’t have time to absorb the food and nutrition before you exercise, and you won’t get the benefit you’re looking for.

Whether you do your HIIT routine in the morning or later in the day, you’ll need to plan your pre-workout eating plan. The best idea is to eat a carb and protein meal or snack an hour or so before your workout.

Ideas for this pre-workout nutrition include:

• Peanut butter and crackers or toast
• Cottage cheese and fruit
• Yogurt with granola
• Nuts and raisins

If you feel light-headed or lethargic during your HIIT workout, your body is telling you that you don’t have enough carbs and energy for it to draw on. Continue to work on your eating schedule until you feel strong and are able to work out intensely the whole time.

Post-Workout Meals

After you do a HIIT routine, your body needs to replenish. Your body used a lot of glycogen to keep you going during that intense workout, and now it’s time to recover.

You need to recover in both your muscles and your energy, so once again you should mix carbs with protein. Many people like to eat a small protein snack within 20 minutes of finishing the workout, and then eat a full meal with complex carbohydrates a few hours later.

You can enjoy a protein shake, eggs, meat, or other high-protein food shortly after the HIIT routine. Don’t let the day’s busyness cause you to forget to eat your full meal, though!

Some complex carbs and protein you can use include:

• Chicken and rice
• Multigrain bread with lean meat and fresh fruit
• Cereal with soy milk and fruit
• Whole-wheat crackers with fruit and cheese

Having a full meal a few hours after your workout will help you keep your metabolism high and keep your energy up as you move through your day. If you skip your post-workout food, you’ll experience fatigue, soreness, and low blood sugar.

Support HIIT With Overall Nutrition

You probably realize that you need to support your workout routine with overall good health. Taking care of your body in ways that reduce fat, maintain energy, build muscle, and more is a 24/7 endeavor.

The best way to eat is with a well-rounded diet that takes advantage of all the recommended food groups. You can focus on lean protein, complex carbohydrates, and plenty of fruits and vegetables.

It’s important not to eliminate any food groups or follow eating fads if you want to practice HIIT in a healthy way. Your body needs all kinds of nutrient, including carbs and protein, in order to function in a high-intensity workout.

If you don’t have enough fuel in your body, you will unfortunately end up burning muscle instead. That will undo all the hard work you’re putting in to reach your goals. Be sure that all of your meals and snacks help support your goals and provide your body with enough energy to support your health.

Stay Hydrated!

Another mistake a lot of people make when they are pursuing a HIIT routine is that they don’t drink enough water. During your workout, be sure you take drink between your sets. You don’t want to drink so much you feel ill, but you need water to keep going.

If you don’t drink enough water, you’ll feel fatigue, muscle cramping, and you can also be contributing to muscle breakdown. Considering you’re trying to get stronger, that’s very counterproductive.

Remember that your muscles are 75% water, and water also helps cushion vital organs in your body. You can’t afford to wait until you’re thirsty. Drink water before, during, and after your workout.

Make Nutrition Part of Your HIIT Commitment

The whole purpose of HIIT or any other workout program is to make your body healthier. You simply can’t do that if you don’t have the right eating schedule and nutrition to go with it.

If you think that not eating will boost your HIIT burn, you’re going to be sorely disappointed. What you’ll experience instead is fatigue, muscle loss, and a foggy mind. Low blood sugar can cause dizziness and disorientation.

When you eat properly surrounding your HIIT workout, you'll avoid unnecessary injuries as well. Unfortunately, those who don't rebuild their muscles properly with nutrition find that they have more pulls and strains.


Your body works really hard for you. Be sure that you take good care of it. Eat regularly, and be sure your meals include plenty of protein, complex carbohydrates, and fruits and vegetables. Drink a lot of water, both during your workout and throughout the day.

Your HIIT workouts can make a big difference in your life if you combine them with great eating habits.

If you're getting started with HIIT, be sure to check out Sprinterval.

 

Everything You Need to Know about HIIT Workouts During Pregnancy

When you’re pregnant, it’s normal to make dramatic changes in your health and life in general. You might sleep more (or try to at least), eat healthier, reduce your caffeine, and try to stay fit during your pregnancy.

If you’re used to HIIT (high-intensity interval training), you might think that you have to change your entire workout plan because of your pregnancy. This is not entirely true, and HIIT can actually be an excellent way for you to maintain your health and fitness while you’re pregnant.

The key thing to remember is that you might have to modify your workouts, but you don’t have to eliminate them. Of course, it’s always important to seek counsel from your doctor before engaging in any HIIT.

Benefits of HIIT Workouts During Pregnancy

It’s no secret that HIIT is a great way to maintain a healthy weight and build lean muscle mass. This stands true during your pregnancy, as well. With the right modifications, HIIT is great for you and your baby.

1. Strengthen your back to reduce pain and aches: Carrying a baby bump all the time does a number on your back and pelvis, which can lead to severe aches and pains. Building muscle in your lower body and back is a great way to reduce the amount of pain you feel throughout your pregnancy.

2. Helps reduce constipation: One common issue that many women face during pregnancy is severe constipation. Getting moving and staying active right from the beginning will help increase your metabolism and help your digestive system flow smoothly.

3. Reduce fatigue: It’s no secret that regular exercise, paired with a proper diet helps you feel more energetic. It can be easy to give yourself a pass because of your pregnancy, but you are in complete control. HIIT on a regular basis will help you stay active and maintain a high level of energy throughout the day.

4. Promotes healthy weight gain: It’s normal to gain weight during your pregnancy but utilizing a regular exercise regimen is a great way to ensure that you bounce right back to your normal self after giving birth. HIIT creates an “after-burn.” This means you burn calories for 48 hours after your workout is over. This will help you to maintain a healthy pregnancy weight without any extra pounds.

5. Reduce anxiety and depression symptoms: It’s normal to feel emotional or even depressed during your pregnancy. It’s important to have distractions and anything that can take your mind off things for a while. Getting the blood pumping and the heart going is a great way to get the endorphins flying, which will help you feel happier and more relaxed.

6. Prepares your body for labor: People who exercise regularly generally have better breathing habits which will help with labor.

Modify Your HIIT Workouts Based on Your Trimester

As we said, you don’t have to stop your HIIT workouts completely, and now you understand a lot of the great benefits working out can have on your body. It’s important to listen to your body and let it tell you what you can do. Regardless of how your pregnancy goes, at some point, you will have to modify your workouts to accommodate your baby. Here are some tips based on which trimester you’re in.

First Trimester

During the first trimester, most women will not have to modify their workouts at all as long as they are already used to HIIT. Now would not be the time to start up a new HIIT if this is something you’ve never done before.

Either way, you still want to listen to your body and let it tell you what to do. During this stage of pregnancy, a lot of women might feel lethargic and nauseous so HIIT might not be the best workout for everyone.

Second Trimester

During the second trimester, you’ll start to experience some discomfort performing exercises you normally would have no problem with. At this stage, you don’t want to spend any time laying horizontal, and you don’t want to jump around at all. Now is when you should start modifying your HIIT to meet your needs. Here are some examples:

Instead of regular burpees, perform them at an incline to put less pressure on your back
Since you’re already carrying extra weight, use lighter weights during lunges and curls
Don’t jump when doing box jumps, step up one foot at a time, and use your baby bump as your resistance.

Third Trimester

Now is when it’s time to listen to your body and do what it tells you. At this stage of the pregnancy, your belly is its largest, and you are likely struggling to stay balanced. At this stage you also release a hormone called Relaxin, this loosens up ligaments in the pelvis to help with the birth.

This factor will make it easier for you to pull a muscle if you exercise too hard. You want to consider the modifications we suggested and go at a pace that you feel most comfortable with.

Possible Risks and HIIT Workouts to Avoid During Pregnancy

We’ve touched on it a little, but there are precise movements you want to avoid with HIIT during pregnancy. You should not jump, shake, twist, or quickly change direction. These movements will increase the strain on your joints and possibly cause injury.

If you want to continue working with an instructor or class, make sure you make the trainers and your other group members aware of your pregnancy. Take water breaks whenever you feel you need them, don’t wait for a break.

Make sure you focus on your breathing during all of your exercises. Your baby needs plenty of oxygen, so you want to emphasize that.

Lastly, listen to your body! If something doesn’t feel right, even once, don’t do it again. It’s great that you want to keep up a high level of fitness and health during your pregnancy, but it’s also essential that you keep yourself and that precious baby safe. 

Thinking of getting into HIIT, but not sure where to start? Sprinterval is an introductory HIIT program using sprints that works like Couch-2-5k.
 

The Truth About HIIT Workouts vs Running

Have you been looking for a way to accelerate your weight loss and improve muscle tone? Then this may be the most important article you read all year.

You see, one of the most beneficial workouts that people neglect to do is HIIT (high-intensity interval training). But it turns out that HIIT workouts not only burn more fat faster. They also increase your speed, improve your health, and define your muscles.

And they do all of this better than long distance running or jogging.
Curious about how HIIT works? Read on to find out more about the benefits…

HIIT workouts help you lose more weight

According to a report by the Centers for Disease Control and Prevention, only about 22.9 percent of adults in the US get enough exercise. CDC guidelines suggest that adults between the ages of 18 and 64 get 75 minutes of “vigorous-intensity aerobic physical activity” per week or 150 minutes of “moderate-intensity aerobic physical activity.”

The truth is a little different though. The type of activity you do actually matters more than the number of minutes you clock.

Fitness experts say that you only need 15 to 30 minutes per week of HIIT to accelerate fat loss. When you do HIIT, you perform aerobic exercise at close to your maximum intensity level for just a few minutes, and then you slow down to a moderate walking speed for a break. You then do another interval of all-out effort. Each high-intensity interval is called a sprint.

These short intervals of high-intensity exercise send signals to your cells to burn fat in order to have enough energy for the intensity level. Long bouts of running, on the other hand, signal to your body to hang on to fat deposits in order to not run out of energy for the long exertion ahead.

Of course, that doesn’t mean the CDC has it all wrong. Humans need lots of physical activity. And when you're not sprinting, moderate-intensity walking (or similar activities like casual swimming, cycling, or dancing) should be a daily occurrence.

How do you know if you’re working hard enough for your exercise to be considered HIIT? Your heart rate should reach 80 to 90 percent of your max. But if you don’t want to mess with measurements, you should make sure that you aren’t able to carry on a conversation during the workout. This is not a brisk walk while you chat.

Sprinting also causes you to work anaerobically, meaning your muscles are not getting fully fueled by oxygen. That leads to the afterburn effect, also called excess post-exercise oxygen consumption. That sounds complicated, but what it means for your weight loss is that you continue burning calories even after you have stopped working out. The afterburn effect occurs because your body is still recovering from the high-intensity exercise.

Moderate intensity exercise, like a casual jog, does not cause the afterburn effect, so you don’t burn more calories after the workout is over.

Sprint intervals increase running speed

When we talk about running and fitness, we often think about marathons and endurance. But long-distance running doesn't necessarily make you faster. Even if you are training for a marathon, incorporating HIIT workouts can help you increase your speed.

Part of the reason that HIIT increases speed is that it builds muscle faster than long-distance running. When you sprint, you engage the large muscle groups in your lower body in order to create that burst of speed. The more those muscles are trained, the bigger burst of speed and energy they can release.

Because sprinting increases mitochondrial function, it actually improves performance for long distance runners and cyclists, as well as sprinters. Of course you’ll need to continue training at long distances, but sprints will improve your overall athletic ability for running and cycling. It makes you more powerful and makes your energy expenditure more efficient.

So if you’re planning to train for a marathon, incorporating shorter sprinting sessions into your training can improve your overall performance.

HIIT is better for your health and body

A study in the November 2018 issue of American Journal of Physiology-Regulatory, Integrative and Comparative Physiology revealed that 20 minutes of sprint intervals (in which only 2 minutes were spent sprinting for 30 seconds at a time, and the remaining 18 minutes were 4.5 minute recovery periods) improved mitochondrial function just as well as 30 minutes of moderate exercise with no breaks.

They basically showed that you can get the same results with 2 minutes of full effort as you could spending an entire 30 minutes jogging.

If you’re wondering how HIIT could be better for your heart than long bouts of aerobic exercise, remember that your heart is a muscle. How do you build muscle? You increase the intensity of the exercise by adding more weight or using bursts of energy, as in plyometric exercises. The heart-health equivalent is to add more intensity through speed.

In addition to improving mitochondrial function and heart health, HIIT workouts help you better regulate blood sugar levels by lowering insulin resistance. Better insulin resistance reduces your chance of developing diabetes.

Another health benefit is improved oxygen efficiency. And that’s not just a benefit to your muscles and lungs. Your brain also benefits from receiving more oxygen. In fact, HIIT has been shown to improve learning, memory, and mood regulation.

And sprinting increases muscle mass, something that long-distance running does not help with much. In fact, the bursts of energy used to sprint build up muscle similar to the way plyometric exercises do. So if you are looking for an exercise that improves your physical appearance by creating muscle definition, HIIT can do that, too.

If you're ready to benefit from high-intensity interval training, it's easy to add to your routine. You can use any kind of aerobic activity to do HIIT. So start with whatever exercises you already like to do.

The most basic form of sprinting is to run in short bursts. But you can also do HIIT by cycling, swimming, jumping rope, dancing, doing push-ups or squats, or doing burpees. You can pick whatever activity you like as long as it gets your heart rate up.

How HIIT Keeps You Young

Let’s get real - everyone wants to stave off the aging process as long as possible and tap into the fountain of youth. But before you reach for the botox and start guzzling green juice, consider taking up HIIT.

HIIT or high-intensity interval training has been proven to help turn back the clock and boasts a whole range of other health benefits, too. Whether you are looking to slow down the aging process mentally or physically, HIIT workouts are fast becoming a favorite among the 50+ set to keep themselves looking and feeling young.

Read on as we take a look at the rise in popularity of this new workout craze, explain what it is and how it can help you turn back the clock.

What is HIIT?

High-Intensity Interval Training is no new thing, but the booming health and fitness industry has seen this form of exercise explode in popularity. Another factor contributing to HIIT’s success is the rise of fitness chains promoting HIIT based workouts, think Barry’s Bootcamp, Orangetheory, F45, and SoulCycle.

Far from being limited to one workout, HIIT is essentially any form of exercise that combines bouts of intense physical activity with rest periods - essentially pushing the body to the limit, resting and repeating. HIIT workouts can take many forms, including weight and endurance training, cycling, running or any combination of the above.

How does it work?

Many of the benefits of HIIT come from pushing the body to its limit and significantly elevating the heart rate in the process. Let’s take a look at the many ways HIIT can help you turn back the clock.

It increases oxygen capacity in cells

In studies undertaken on individuals embarking on HIIT and other exercise regimes, those who had been performing the HIIT workouts presented considerable increases in mitochondrial capacity - the process by which the body’s cells take in oxygen to produce energy.

As we age, our cells’ mitochondrial capacity typically begins the decline. By helping increase
mitochondrial capacity, HIIT workouts help cells take in oxygen and transport it around the body to provide energy and maintain normal cellular function.

It burns fat

As in any anaerobic workout, HIIT training not only burns fat while you’re exercising by turning it into fuel, the intensity of the workout means your body continues to burn fat after the fact as it works to repair muscle and return to its natural resting state. Talk about the workout that keeps on giving!

It prevents cell death

OK, this one sounds a little shocking we know, but stay with us. Ever heard of telomeres? Well, you can think of these guys as little caps that sit on the end of your chromosomes, protecting them from all sorts of damage. Environmental and lifestyle factors like poor diet or smoking can work to shorten these telomeres effectively leading to a shortened lifespan of the cell and, eventually, the human.

The good news is, high-intensity exercises like HIIT have been proven to prevent the shortening of telomeres and prolong the lifespan of cells.

It improves heart health

Another benefit of HIIT is the impact on stroke volume. By ramping up your cardiovascular system, interval training literally gets your blood pumping, increasing the amount pumped from the left ventricle of the heart per beat.

It increases muscle growth

Muscle growth can seriously slow as we get older. Interval training has been proven to stimulate several bodily functions that lead to muscle growth. By putting a large amount go stress over major muscle groups, HIIT stimulates the release of human growth hormone, testosterone and a hormone similar to insulin that works to repair muscles and encourage new growth.

In addition to promoting new muscle growth, HIIT training can help prevent the deterioration of existing muscle. Interval training has a proven ability to boost the activity of ribosomes, a cellular particle that plays a large role in stopping muscular deterioration.

It helps your body recover 

The intensive nature of HIIT produces a lot of metabolic waste which are removed by the body during rest periods. The repetitive nature of interval training encourages the body to adapt to quick turnaround time and repair itself quicker to be ready for the next bout of exercise. In a real-world context, this primes the body and ensures it is better able to recover from falls and other incidents that can affect older people.

Is that all? 

But wait, there’s more. One of the most appealing things about HIIT is that you don’t need to do it every day to see results. In fact, some studies have shown that in order to get the best results it’s most beneficial to perform HIIT workouts a maximum of three days per week with rest days in between.

Is HIIT just for older people?

Absolutely not! While studies have shown the age-defying benefits are more pronounced in older adults, interval training brings big benefits to those of all ages. In fact, younger adults with no preexisting health issues may be able to get more out of their workout by pushing themselves further. Mentally, the benefits of establishing good habits while young are huge. Physically, in addition to promoting fat loss and cardiovascular health, muscle growth tends to be easier for younger adults and is easier to maintain over time than grow in old age.

Are there any risks?

As with any exercise, HIIT workouts can post some risk to those with pre-existing medical conditions or limited heart function. Especially for older individuals, it’s a good idea to consult your doctor before beginning any new type of workout.

If you are concerned about overexerting yourself, try wearing a heart monitor to measure your heart rate and start slow, building up to more and more challenging workouts, taking regular breaks as required.

How HIIT Affects Your Bones

High-intensity Interval Training (HIIT) has quickly emerged as one of the most popular training techniques of the last decade, and rightfully so.

By leveraging intermittent, abrupt bursts of exercise followed by rest periods, millions of people around the world are enjoying enormous health benefits, including significantly better cardiovascular fitness, lower mortality rates, better cognition & alertness, and more. Coupled with breakthroughs on the health benefits of weight training, structured resistance-based HIIT is the single most effective training system on the market.

What, then, is the catch?

For years the concern around HIIT (and really, cardiovascular exercise in general), has been the toll it puts on your bones. One camp of adherents religiously decries it for the negative impact so much consistent force places on your joints and cartilage. The other insists the cartilage effects are overstated, and that HIIT is a godsend for bone density and strength.

The answer, as always, is somewhere in the middle, although leaning on one side more than the other. We’ve tried to do a reasonable, objective assessment of the impacts of HIIT on your skeletal system as well as a few recommendations near the bottom of the article on how to improve your response.

Read on.

Bone Density

Many studies have shown a strong causal link between HIIT and strong bone density. In facts, some studies have shown improved bone mineral density/content in as little as 6 weeks of interval training. When it comes to general bone health, the literature is clear: HIIT has a clear, obvious & nearly immediate impact on improving your bone density.

So how does it handle longer-term & chronic bone conditions?

HIIT and Osteoarthritis

Women, in particular, are affected heavily by this debate, and often avoid high-intensity exercise in an effort to stave off osteoarthritis/osteoporosis in the future. For decades there has lingered an idea that high-intensity exercise leads to poor bone health in women - unfortunately, this avoidance of exercise often ends up having the opposite effect.

A new Medicine & Science in Sports & Exercise found that doing high-impact jumping exercises three times a week for 55 minutes actually strengthens knee cartilage in women who have osteoarthritis.

"High-impact movements have been thought to harm the cartilage and accelerate the progression of osteoarthritis," says study author Jarmo Koli. "But our research supports the view that cartilage benefits from gliding with compression, since the knee glides in front of the femur bone during the kinds of exercises we studied."

The literature surrounding a possible causal link between interval training and bone damage is unclear. What is clear, however, is that when an individual already struggles with osteoarthritis/osteoporosis, HIIT can actually help improve the situation.

The flip side

What’s clear with HIIT is that it inarguably improves your bone density. What’s unclear is the net gain of HIIT on your entire mobilization system - what good are strong bones if you can’t move them? There are a lot of question marks about whether HIIT is good for your ability to move and act in the long term.

The question marks around this is primarily based on one thing: human error.

In a vacuum, if you do HIIT perfectly, and couple it with proper rest periods, you won’t have any issues. You’ll enjoy great cardiovascular health, strong bone health, the works. So what’s the issue?

Most people don’t do it correctly.

Incorrect & hurried HIIT as well as insufficient rest periods leads to inflammation and, ultimately, damage. The most common damage comes in the form of tears - tears of meniscal cartilage shock absorbers, usually in the knees. Exercises like burpees and squats put tremendous pressure on the cartilage in your knees (the equivalent of 7-8 times your bodyweight), and is largely responsible for most of the fear around “bone health” and HIIT.

So, how do you deal with this and make your interval training responsible and effective?

1. No pain, no gain is bull. Avoid the gymbro machismo and be reasonable with your training. There is no reason that training should hurt, and even if it does hurt, it shouldn’t feel like your joints are hurting - you should be able to recognize the difference between muscle pain and joint pain, and stop immediately if it’s the latter.

2. Your diet matters. One of the primary causes of chronic injuries and HIIT is inflammation. A proper diet enables you to recover quickly and keeps inflammation to a minimum, allowing you to work out at your best.

3. Adequate rest periods. First-time gym goers suffer from this the most. Quality over quantity is the name of the game - killing yourself for 3 hours a day isn’t going to improve your life. HIIT should fit in with the rest of your week, and you should have adequate rest - much more than you think you need. Take at least 2 or 3 rest days a week from HIIT.

4. Talk to your doctor. I know, this advice sucks to hear - nobody wants to go to a doctor. The fact is, if you don’t have great joint health, you need to take a much more structured approach to HIIT. Go get a check up and make sure everything’s in working order - you can still enjoy the benefits of HIIT without doing exercises that will cripple your knees.

And that's pretty much it! High intensity interval training is a fantastic way to get in amazing shape, see elevated moods, increased energy and, yes, improve your bone strength - a lot. However, you won't reap those benefits unless you do things the right way, and avoid cartilage damage.

Also, consider supplementing your HIIT with weight/resistance training. Strengthening your large muscle groups will enable you to distribute weight off of your joints during HIIT, and lead to a better mobilization of your bones. Just like with the interval training itself, your exercise routine should be balanced.

Happy training!

Sprinterval is an app for iPhones and Android that helps you get started with Sprint Interval Training.