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What if the epic training montage from Rocky IV (YouTube it if you haven't seen it) were real life? While we can't all have a song like Hearts on Fire as our personal soundtrack or own an American Flag robe like Apollo Creed's, we can still take some lessons from Rocky's training.

Let's pretend for a minute that this montage is actually a single exercise session. In the aforementioned film clip, Rocky and Ivan Drago are shown performing interval training involving resistance exercise intermixed with bouts of high intensity cardio. This type of high intensity interval training (HIIT) is extremely popular at the moment.

It involves furious bouts of intense exercise followed by bouts of rest or lower intensity exercise for a short 20-30 min workout. It advertises more "bang" for the proverbial "buck." Programs like T25, P90x, Crossfit, Insanity, the Grit Series, etc. promise less time and more results.


There are some distinct advantages to this type of workout. Here are a few of the commonly cited benefits to HIIT:

•It strengthens your heart

•It builds muscle and burns fat

•It improves metabolism

•It can be done without much equipment

•It can be done almost anywhere

•It is relatively time efficient

•It can be done alone or in a group setting

Perhaps most important of all, HIIT can also be a fun and social way to exercise (say goodbye to the lonely and mind-numbingly boring 60 minutes on that hamster wheel you call a treadmill). The fun and fast-paced qualities cannot be ignored. Whatever gets people unplugged from their devices and plugged into getting moving, getting healthier, and getting fit must surely be a good thing, right?



Just like with most things, there are some caveats. The training paradigm used in some of these workouts values completion of the workout above all else. Mix that with some healthy competition and add a dash of peer pressure from the instructor or your friends cheering you on and you've got an atmosphere where it is "go hard or go home." Minus the actual fighting, it's sort of like a real life version of Fight Club in your local gym or living room. Imagine being peer pressured to see if you can best your previous workout record while ignoring your body's physical limitations. It's exciting and it will push you, but is it safe? In this push to work past physical boundaries and ignore fatigue, improper form and poor movement execution can occur. This is sometimes necessary on the athletic field or in other unique situations (ex: being chased by a pack of feral dogs). Unfortunately, it also opens the door to significant musculoskeletal injury, such as sprains, strains, overuse injuries, or traumatic injuries such as tears, ruptures, or fractures.

HIIT can also cause some other serious problems. For example, cardiovascular issues, overtraining, stress incontinence, and rhabdomyolysis (among others) have also been shown to occur with improperly supervised or performed HIIT. Rhabdo is particularly alarming – it can result in dead muscle cells flooding the bloodstream and overwhelming kidney function causing a massive shutdown and even death. While the above injuries are not common, I do see a constant stream of injuries from these types of HIIT programs at my clinic – HIIT aficionados are quickly becoming even more ubiquitous than runners in my clinic. While I like the job security, I don't like people getting hurt. Fortunately, other than some wrist fractures and some shoulder dislocations, I have yet to work with a significant number of people who were seriously injured doing these HIIT routines beyond the normal overuse injuries.

One of my PT mentors often advises me to think simpler when confronted with patient exercise progression. His advice is sound and essentially boils down to the following statement; master the basics. Then, and only then, is it safe and appropriate to move on to the next step. Due to its high level of multi-joint, three dimensional, and plyometric movements that can be coupled with heavy force production, HIIT can involve significant complexity. It should safely be progressed into as part of a general fitness routine once exercise-appropriate basic skills are mastered.


Correctly utilized HIIT can function well within a workout routine. It can help provide variety and safely challenge our cardiovascular and neuromuscular systems. A properly instructed and supervised HIIT program that respects individual fitness levels can work well in conjunction with traditional resistance and cardiovascular exercise.

It can greatly improve many of the things listed above when it is coupled with an understanding of proper form, proper workout variety, and proper amounts of rest and recovery. Just like with any exercise program, consultation with a doctor, physical therapist, or qualified health professional is always advised before starting any HIIT.

Talking with a Physical Therapist can also help you before you begin. Most of the patients I see that are injured from HIIT have a condition I like to call "Overdoit-itis." They overdo it with HIIT or with a similar exercise activity that in small amounts would otherwise be appropriately challenging. In an everyday or even multiple days per week frequency, it simply becomes too much for their body to handle. Sure enough, like drops of water in a bucket, eventually the bucket overflows and suddenly they are hurt. I hear it all the time: "I've been doing this for 3 months with no problem – why am I hurt now?"

Stress and microtrauma are cumulative in the body, compound that with poor exercise form and complex high intensity exercise and you have a recipe for disaster. Subsequently, complete HIIT workouts are not an everyday thing or even a multiple days per week thing and should be employed sparingly; the body will break down without adequate rest and recovery (sleep, hydration, food, active rest, deep tissue mobilization, stretching, etc.). Damaged muscles and tissues rebuild and renew on rest and recovery days; don't skip them!


A good Physical Therapist will not only address your injury, but also the cause of the injury. Far from providing a Shakespeare-style verbal scolding ("I bite my thumb at you!"), a Physical Therapist will address this issue by educating you. This education might include what exercises are contributory to current or potential injuries, how they can be modified and performed safely, appropriate levels of participation for your current fitness level, safe recovery or rest activities, and how to safely incorporate HIIT into your existing exercise or fitness routine. If you want, you can even rock out to Hearts on Fire or Eye of the Tiger while you are doing it. Properly performed HIIT can be a great way to get fit, stay fit, and keep you moving while adding some engaging variety to your routine. Just don't overdo it.


Bergeron, M.F. (2011). Consortium for Health and Military Performance and American College of Sports Medicine Consensus Paper on Extreme Conditioning Programs in Military Personnel. TheAmerican College of Sports Medicine, 10(6), 383-389. doi: 1537-890X/1006/383Y389

Danny Singles, PT, DPT, MA

Danny is a sports physical therapist who specializes in manual therapy. His clinical interests include injury prevention, working with sports and orthopedic injuries, pre and post surgical rehab, and working with the pediatric patient population. He attended the University of Delaware for his Doctorate in Physical Therapy. Currently, he works full time as an outpatient sports therapist and provides educational outreach through lectures at local schools and fitness centers. He can be reached at Elite PT in Hockessin, DE at: (302-234-1030) or emailed directly at: This email address is being protected from spambots. You need JavaScript enabled to view it.. He can also be followed on Twitter (@MoveEqualsLife) for current updates about health and wellness.

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