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.
