American Parkour

I often ask people around me for a nice run. The joys of running are two fold when you have a running partner and it is an easy way to help serious runners push themselves. However, up until recently, I've never been able to convince anyone to run with me. This problem eluded me until the 'joys' of winter forced me to run inside on the gym track or risk turning out like the Ice Man. Running inside is a detriment for me, however it did let me see exactly why I was having this problem. Negating two or three people, everyone had horrible running form. Everyday it was a new clunker which enlightened me as to why no one likes to run: no one knows how!
   
Now it is exceedingly difficult to teach someone how to run properly with just text, but I hope that this paper will be a push in the right direction for some. Running is one of the most basic of instincts and for many is a necessity for basic human development. Running was our source of safety from the dangers of prehistoric times.
   
Running was designed to be done barefoot. It was our own brain growth and the development of our frontal lobe that first gave someone the idea of wrapping the feet with leather to keep them warm, and later padding to help keep them safe. Over these last thousand years, shoes have now become extensions of our feet that have the ability to amplify their characteristics.
   
Modernism has a downfall however. Shoes from early childhood are the reason why most people have lost the ability to run. Shoes provide for a margin of error which negate the immediate bad effects from improper stride. Thus, proper form is not self developed during our childhood and through adolescence many of us lose stride. Improper stride is inefficient and directly relates to the general consensus of running being dull, a headache, and most of all, hard!
   
Our society as a whole is starting to understand the issue that obesity is an epidemic and it's great to see so many new people taking to running once again. However, most of these new runners would be better off not running and finding alternate forms of exercise. Improper stride is not anatomically correct and so when it is maintained over several years, problems start to develop. The occurrence of shin splints, periostitis, vast majorities of knee and foot problems as well as back related injuries come into play.
   
So we understand the consequences of improper stride. How can we understand proper form? Proper form is based around efficiency of movement. You may not realize it, but every step you take follows a specific pattern that took thousands of years to develop. We evolved to better adapt to our surroundings and through this process, we evolved a method for efficiency.
   
I could just start diving into running mechanics, however how can we understand the mechanics of running without first understanding the mechanics of walking and why they are different? Due to the mechanics that happen while running, it is most efficient to strike in the mid-section of the foot. But why then do we not strike with the mid-section while walking? Walking is most efficiently performed when the foot follows the toe to heel path. During the initial phase of walking, the center of gravity is moved forward slightly to allow for inertia, but once a stride is achieved, the heel strikes the ground and acts as a counter-balance to keep us upright. When walking, foot strikes happen in front of the body which explains the efficiency of toe to heel movement. This action allows us to maintain steady momentum while keeping our neutral center of gravity. These mechanics explain why we can maintain a continual pace over much longer periods than we can while running. However, it also explains why we cannot walk fast.
   
Fast walking becomes clearly inefficient when following the rules just mentioned. Each stride is going to require a certain force to accelerate and propel the body forward to maintain momentum but due to the mechanics of walking, each push off is going to require a heel strike counter balance which will only expel and waste energy. This is why we run.
   
So how does running differ? Running mechanics can be broken down into steps. For the sake of simplicity, we can look at a full stride consisting of a loading and firing phase along with a foot-strike, transition, and push off phase. Other issues we'll look at will include posture, breathing, arms, and personal mindset.
   
A stride begins from rest first with a shift of weight forward in the desired direction. Because we want to continually move forward, this shift in the center of gravity will not change unless we desire to change direction or increase speed. This center of gravity shift places weight on the midsection of the foot which brings up the first phase of a stride: the push off.
   
The push off phase is one which a vast majority of people confuse and causes the first mental obstacle in regards to running. Many people destroy the efficacy of the run by first thinking that a run is something that attempts to counter-act the forces of gravity. This causes undeveloped runners to have an “up/down” mentality approach towards running. This mindset causes your body to expel unnecessary energy to propel the body up against the forces of gravity and then more unneeded energy to be expelled to slow the body's descent upon foot-strike. Push offs happen beneath the center of gravity and the body follows the path of a projectile being fired at very steep degrees. This form of running is the main reason why many people associate running with pain and work.
   
Up/down running is the cause of many running related injuries. Because the body is moving in an up and down manner, the hip and knee joints do not flex but rather stay straight. Because of this, there is no loading process and when the foot-strike happens, the legs must first absorb and then push off which will require greater amounts of energy. Time spent earth-bound is increased as greater forces are applied and in many cases, these forces are put on the skeletal system which leads to significant damage to skeletal structures. Looking at this from Newton's point of view, we are accelerating an object, and stopping an object, accelerating an object, and stopping an object once again. Sounds tiring.
   
Running is designed to be a movement along a horizontal plane. It should be looked at with horizontal motion in mind, which is to say you are not working against gravity you are moving perpendicular to it. A proper stride starts with a light push off in a forward direction well behind the runners center of gravity. The body itself does not make drastic changes along the vertical plane but rather should stay low to the ground. Time spent on the ground is decreased and minimal. By looking back at Newton's perspective, the object is in a constant state of motion. The power needed during each foot-strike to maintain this constant motion is relative to the speed at which you are moving.
   
While a push off is being made, the opposite leg is flexed to allow for more efficiency while moving along it's horizontal plane, as physics tells us a shorter object will circumvent space faster than a longer one. This flexion also makes for an easy transition into the loading (cocked gun) phase. By loading the leg and preparing it while in the air, we can minimize the time needed to spend on the ground which helps us decrease the amount of velocity we will lose. A load leads to a fire and the legs extend towards to ground. Because of this process, a foot-strike should always be done in the midsection of our feet and under the center of gravity. This keeps our center of gravity forward which allows for better management between momentum and inertia. This mechanic also allows us to disperse our weight amongst three major joints in our body (the ankle, knee and hip) keeping the force centered around our musculoskeletal system and off of our skeletal and joint structures.
   
Posture is just as important a factor as proper stride is. A common mistake in novice runners is the tendency to lean forward at the hip, emulating the postures of elite runners they may have seen on television. What actually occurs is an illusion that makes us think they're torsos are leaning forward. However, when looking at certain snapshots, you can see that in fact their entire body is aligned properly in a straight line leading from the firing leg, through the back and up through the head. The back is straight and the chest is out. This allows for an opening of the lungs to allow for more efficient breathing. By leaning over at the hip, you place excess amounts of stress on the lumbar vertebrae which  is the main cause for most running related back injuries. You also close your chest cavity forcing your diaphram to more forcefully contract and expand with each breath. This expels energy and causes you to fatigue faster.
   
Arms are an extension of the torso. They serve to counter act the forces generated by leg swings to maintain proper balance. However, unless you are in a dead sprint, your arms serve no other purpose. Tensing the muscles in the arms will only cause blocky, robotic like technique which once again causes your body more unneeded stress. Arms should be loosely flexed around 90 degrees and should feel utterly relaxed. Your arm motion is not an active movement, which is to say they are not moving themselves. Arm motion is brought about by the legs and not vice versa. A good technique I follow is the two finger method, which places my thumb in between my four fingers. This supposedly helps keep the forearm relaxed.
   
Breathing is potentially the least accounted for mechanic that causes most novice runners discomfort. In 1971, Bowerman and Brown suggested that breathing should be synchronized and rhythmic. Twelve years later,  Bramble and Carrier found that as performance levels of runners increased, so too did their reliance on rhythm and synchronization. The rhythm is important as it brings harmony between the energy demands of the stride and the process which provides it's energy. This is a technique that requires experimentation as everyone will be slightly different. As an asthmatic, this technique alone is what spurred on my enjoyment of running. It suppressed the desire for wheezing when in conjunction with proper posture. Rhythmic breathing allowed me to optimize the oxygen I was taking in, serving as a buffer for the thirty percent scar tissue I have caused by severe asthma. As an example, during a light to moderate pace run, I inhale over the course of four strides and exhale over three. Breathing itself should feel just as relaxed as everything else regarding a run. A tense runner is an unhappy runner.
   
When your status as a runner increases and you become more accustomed to faster paces, a technique suggested by Thomas S. Miller, Ph.D, called belly breathing becomes increasingly useful. Belly breathing is best exemplified by pursing your lips during an exhale. The action causes your stomach muscles to tighten to push out the air. At first this technique sounds rather inefficient, however when looking closer, the push from the stomach muscles actually forces out all the carbon dioxide held with in the lungs. As your muscles relax, a vacuum is created which easily draws air into the lungs and efficiency is maintained.
   
By making these changes to stride and posture, one will feel much more relaxed during a run. The run becomes more fluid and efficient which brings with it more levels of enjoyment. A run is exhilarating and dynamic; It becomes something that makes you feel energized, rather than something that brings thoughts of pain and toil. Running should be looked at as a pleasure; something soothing, fluid and relaxing. With this mindset comes enjoyment!
   
To better understand these elements of running, hopefully some visual examples can better solidify their interpretation.

(http://img356.imageshack.us/img356/1381/footstrikesidemodifiedxc7.jpg)

Here you can see the period just before contact is made for the foot-strike phase. As you can see, the leg is already extending towards the ground to fire and make for a quick transition. The opposite leg is flexed to allow for more efficient movement along the same axis while also being prepared for the firing foot-strike and transition phase. The left foot is on a gradual decline and is everted slightly to ensure contact in the midsection of the foot.

(http://img337.imageshack.us/img337/7185/posturesidemodifieduc8.jpg)

Here demonstrates posture. The back is up and the chest is out. Despite this I could probably even modify this slightly and straighten out the line that is being made from the firing leg through my torso by leaning forward just slightly more. Elbows are flexed but relaxed, being guided by the motion generated by my lower body. My head is up and looking forward, not haunched over or sagging.

(http://img505.imageshack.us/img505/3180/siderunningqj2.jpg)

When looking at the previous photo compared to this one you can see the horizontal element coming into play. The static horizontal made by the fence serves as a reference to show how my vertical position changes from push off to mid stride. The change is insignificant and only a couple of inches. This demonstrates a more “rock skipping” type stride rather than an “up/down” technique which is inefficient and causes excessive fatigue.

These are not demonstrations of perfect technique though. Perfection takes years of dedication and hard work to achieve and serves as a demonstration of utter beauty. The best possible example I could ever give is Hicham El Guerrouj's world record setting mile run in 1999. Watch closely their technique. These are elite runners and they make it look so effortless! They do not huff and puff and they never haunch over. They appear to be in complete harmony as they fluidly fly across the track. There is no better demonstration of proper form.

http://www.youtube.com/v/XvCsj7eJKKA&rel=0&hl=en

The technique required for proper form revolves around proper condition of the ankle stabilizers. I'm a big advocate for barefoot running, however until strength is gained, no serious or extended running should be performed without shoes. Light barefoot jogging I found beneficial to serve as a guideline similar in concept to rolling on concrete when learning how to roll. Learning should always be done on soft surfaces with an occasional concrete roll to gauge performance. So too should you practice with shoes and slowly work your way towards workouts involving some form of barefoot jogging.
   
Regardless whether you do or do not wear shoes, strength of the ankle stabilizers will help you maintain proper stride and help you avoid such injuries mentioned previously in this paper. There are some very simple ways to condition your ankle stabilizers to safely and effectively handle such loads of stress if you are a beginning runner. Lose the shoes and socks and do some of these walking drills that take no more than 5 minutes everyday:

-Walking on the edges of the feet
(http://img245.imageshack.us/img245/6313/lateralwalkinghd2.jpg)

-Walking on the inside of the feet (Note: this involves a very slight lift of the outer toes)
(http://img232.imageshack.us/img232/7509/medialwalkingso8.jpg)

-Walking with toes facing in
(http://img387.imageshack.us/img387/8927/invertedwalking2ip7.jpg)

-Walking with toes facing out
(http://img232.imageshack.us/img232/7758/duckwalking2wi3.jpg)

-Walking on the heel of the foot (Note: if there is no soft surface around, put your shoes back on)
(http://img232.imageshack.us/img232/1005/heelwalking2mr1.jpg)

In conclusion, running is a learned skill that sadly has lost priority in our modern age. Many people misjudge it's role in effectively maintaining a healthy state of being throughout our lives. Because running is no longer pushed at young ages, and because more and more kids end up with shoes on their feet at younger and younger toddler years, we never acquire the condition needed to provide as a base for proper running technique throughout our lives.
   
As stride efficiency increases, so too does our enjoyment of it's performance. It is a tool we can use to center our thoughts and for some is a method of personal meditation. This form of running is one that leaves you invigorated and refreshed looking forward to the day or the tasks that lie ahead. Running is not something to be loathed but embraced and all it takes is a little knowledge, some motivation, and dedication. Soon you'll be finding yourself running faster and for longer with out ever noticing it!




Summary -

-Running is movement along a horizontal plane, not up and down!
-Center of gravity should always be forward
-Strides should make very light “fwap, fwap, fwap” sounds NEVER loud CLUNKS!
-Foot-strikes, transitions and push off should happen very quickly, try to spend as less time as you can on the ground
-You should always land on the mid-section of the foot. This allows utilization of all three lower body joints
-Back should be straight and your chest should be out
-Arms should be loosely held at 90 degrees and should be very relaxed
-Look forward! Not at the ground. There's a lot to look forward to ahead
-Breathing should be in rhythm and synchronized with your strides. It too should feel relaxed and easy no matter what obstacles you may have (asthma or equivalent)
-Run outside! There's a lot to enjoy!
-Don't listen to music while running. Get in tune with your body and focus on breathing and strides. Let it sink in
-A running partner is always a great way to have fun while pushing yourself
-Last but not least, it's never a bad idea to SMILE!!

Sources -

Bakoulis, Gordon. Getting Real About Running. New York. Ballantine Publishing Group, 2002.

Broer, Marion R. Ph.D. Efficiency of Human Movement. Philadelphia. W. B. Saunders Company, 1960.

Miller, Thomas S, PhD. Programed to Run. Champaign, IL: Human Kinetics, 2002.

Morris, Rick. "Running Form for Distance Runners." Running Planet. March 15, 2008 <http://www.runningplanet.com/training/running-form.html>.

That was a very nice write up.  +1 karma for you. I loved the mile World Record video, elite milers run so smooth most people don't realize that these runners are running at a pace faster than most people can sprint (avg 14 sec per 100 meters, 56 seconds per 400 meters).

That's hands down the best example for perfect form. If you notice, once you get over the shock, he doesn't drop down on the ground completely spent, gasping for breath. He starts running more! Now possibly that's the adrenaline kicking in...but that's runners high if I've ever seen it!

Excellent, excellent write-up! I enjoyed this immensely.

Thanks for the feedback. If anyone sees anything they don't see in this write up or would like something answered please speak up and I'll do my best to add/keep this updated as much as possible.

+1, beautiful! I read the whole thing! It is amazing how something so EXTREMELY basic can be overlooked. Great job.

I do that thumb and finger technique! My dad got me doing it when I was little. Another thing about arms though, since the goal is to have efficient motion, wouldn't straight forward and back movement be the most beneficial? I know a lot of runners that swing their arms across their bodies.

Wow. Probably the most informative piece of literature I've ever read. Thanks a ton, I'm going to reform my technique now. . .

This is what I was getting at for pointers. Totally forgot to mention fallacies with arm swing. Granted most people who do cross their mid-section are doing so because they are not allowing their legs to generate the motion of the arm swing. I'll update once I'm out of class

I read the article, and im still confused... you've probably seen the army TV adds right? you've seen how they run, would you say that is good form? If it is then im ok...

That's definitely not good form.  Chugging along in combat boots is probably the epitome of heel-toe running, though it'd probably be hard to run properly while wearing said combat boots.



In addition to Chad's post, here's something I wrote a while ago about the problems with heel-toe running:
http://patrickhdonnelly.blogspot.com/2008/01/heel-toe-running.html

Running ftw. What can I say. Running is like videogames alive. I started running last summer and can't stop.

Your endurance is amazing!  I can't run 10 minutes straight, and here you've been running for months!  :-Sarcasm ;)




Seriously, though, this article was amazing.  I've been tweaking with my running form for the last few months.  I still don't feel like I've gotten it, but this article has given me lots of clarity and insight.  I look forward to incorporating what I've just learned!

not the one where their running in combat boots, its the one where the reservists are running in a group all wearing the army t-shirt. Oh well, iv been tweeking my running form since i last posted and i havent noticed any change so far... ill keep at it though

Most people don't think about it, but you do actually have to learn how to run.  This article was pretty good about that.  I ran cross country and track back in high school, and even though I haven't run much afterwards [maybe 3 dozen times in 4 years], I could still go out and run 5+ miles without dying.   Sure, it wouldn't be fast, but it'd be possible.

most people who arent grossly obesse should be able to run at least 5 miles, slowly yes, but they should be able to do it... unfortunatly most americans wont even try if their obesse.

not to say your obesse or anything..

Well im 5'9", 140 lbs. I doubt i could run 5 full miles. most likely one. maybe 2. but i dont think 5. do i have that bad of form? or am i uber weak? i dont think im obese.

I think you completely forgot about how important the cardiovascular system is...

So true, man.  Have a heart condition slows down my progression a ton.  But, hey, what's another obstacle?  :D

Oh, i kinda forgot i did have asthma. That might not help. But i cant recall having to use an inhaler in like 8 years.

yea it sounds like your the same build as i am.. just a bit taller... just work on your form and youre breathing...it should click eventualy

Actually it's kinda interesting about aerobic development. From last summer I progressed from being unable to run sub 7:30 mile to running 11 miles at 7:30 pace without struggle in breathing. However, what interests me is that I don't see that huge of an improvement of my cardiovascular system in the real life. I still breath heavily sometimes and get out of breath when carrying something or even walking at a brisk pace. Like right now I have to consciously take huge breaths from time to time even when posting this post.

Great write up, and that was an amazing 3:43 minute mile.

I'm in the same boat with exercise induced asthma. Never stopped me and actually I found running to be a better help than drugs ever were.

proof that it teaches you to breath

I love it! It's helped sooooo much. That line about running farther and faster without even knowing it is true! Before, when we'd do the two-lap warm up, I could feel it after one. (I wasn't running heel to toe, but I didn't have the back extended and up with chest out and forward lean, and I wasn't hitting under my center of grav) I wasn't gasping for breath, but I had to take a few heavy breaths and stop for a little.
With just form alone by reading this article, I finished wayyyyy faster, and didn't even feel it. I was ready to go into our cals.

If you want, it could be useful to add in the tips of not static stretching before, that's only an after thing. Do dynamic instead. That's actually seemed to help a lot.

All this info I'm learning I'm doing my best to spread throughout my track team, so I'm eternally glad for all of this. Not just for me, but my fellow teammates.
You rock, +1 karma

Thanks for this! I had to print it out so I could read it over again. I used to hate running and only started doing it the last few years. Finally I developed a liking for it (not quite a love yet, *grins*, some days I suppose). There were quite a few things in there I didn't even realize.

this is slightly off topic, but: we had to run the mile in gym yesterday with no warmup at all. when the class finnished the teacher was like 'most of you have failed to get below the 8 minute mark, but more importantly, a few of you have even gotten over 11 minutes. this is unacceptable.' 

now correct me if im wrong, but shouldnt you warm up before attempting to get a 7 minute mile? I managed to finnish in under 7 minutes, but it felt like I was going to have a heart attack... If I can do it and almost have a heart attack, imagine what it must have been like for the overweight kids that got 11 minutes... they must actualy have died after class ended..

I really dislike phys ed teachers...

I'll also add in most cases a smplified and lighter version of the exercise that you are about to do is uaully a good warm up. In this case it would be a simple jog.

Here's our warm up for track:
First, a light two lap run
then calisthenics:
Slow jog/form run
High Knees
Butt Kickers
Carioca
High Kicks/Marching Bands
Lunges
 

And perhaps a few other things,

It's a nice warm up, helps get you going and has some dynamic stretching in it,
the problem is, after our warm up we all go into a circle and do static stretching....Which is bad for running, as far as I'm informed, since it halters the stretch-shorten reflex in your legs, which do that a lot during a run. So for about 15 minutes, you aren't running as optimally as you could be..

Yep, just do dynamic stretching.

Awesome guide, thanks! I just recently started running, and this helps a lot. I'm having trouble correcting my ankle position though. My feet seem to want to angle in when I run; not the toes pointing in, but my feet roll in such a way that when they come down, the outside edge of my foot hits the ground first, if that makes sense. I'm trying to correct it, but when I compensate for it it feels goofy and unnatural. Is this a common issue with newbie runners or do I just have goofy feet or something?

I do the exact same thing you do.
I don't know for sure whether I'm wrong or right, but I think that's fine.
Try this: Run barefoot, and land with the inside of your foot first. It hurts! For some reason, it tends to be more sensitive to impact... Try running with what you're naturally doing: having the blade of your foot hit first: It feels a lot better and more natural! With that alone, I figured it was fine and kept doing it.

+1, if I could, I would give you plus two; One for the article itself which was brilliant, and two for the advice and how to actually run. My neighbor has a field which is about 60-70 yards long and about 100 yards wide. Before, reading the article, if I tried to run the perimeter, I would be gasping for breath by the end and would still be extremely winded for a while afterwards. Until reading this article I always wondered why I never got a 'second wind' while running, but know I know that it was because my back wasn't straight and I didn't belly breathe.

However when I went and ran the perimeter of the field again, keeping in mind everything you said in your post, I was barely winded at all, and my leg  muscles felt good, like I had used them properly for the first time in my life. It felt great because I had never been able to run that far without being winded and having to catch my brath, which in turn made me think that my cardio-vascular system was in horrible shape. But, thanks to your article, I feel great because I now know that I am in much better shape than I had previously thought. Sorry for the long post that is somewhat repetitive in parts, but I feel awesome now, and it is in thanks to your article.

That was a wonderfull article. I myself was not a very good runner so it turns out, though I still don't have much endurance. So tell me, is the best way to build running endurance to run longer distances and times, simply to run as long as you can every time as it gradually improves, or is there a better way in gaining that kind of endurance?
Also, I don't have asthma or anything, but when I run, and get tired, I am ussually very out of breath, and(and ?I'm not sure if this feeling is entirely normal, as I don't really know any runners) but my chest, specifically right in the middle begins to actually (the closest word I can think of is hurt, but it's a really dull kind of pain), is that entirely normal? Will that pain eventually go away as I grow used to running more?(maybe it has something to do with my mother and sister being a smoker and me being around it all my life)
Along with that if a weird throat feeling, feels like I'm running in winter, even when it's hot out, it gets really sore and that doesn't really help that rythemic breathing.
Of coarse this could all just be standard problems for new runners, but I figured I would get some input and advice on it.

Thanks, I guess after reading over the whole thing I had forgotten about those parts. Also, I'll try and change my breathing.

Great job :D!
I found the article to coincide with everything I've been taught.  I consider myself a "decent" runner.  I couldn't find anything in the article on swinging of the arms  :-X
It really bugs me when people swing their arms across their chest since it is such a waste of energy (esp. in girls >.>, keeping your hands in a thumbs-up position helps this)
Also, looking down can really help if you're in a natural environment where you're at risk of twisting an ankle.  Looking down to where you step can save you from tripping and falling.  But if there isn't any danger one should look ahead.
Just my two cents.

Thank you for the article, I learned a lot  :).

I have a small question though. You encourage landing on the mid-section of the foot... by this do you mean the balls of our feet?

And also, when I run, I support myself only with the balls of my feet; my ankles never touch the ground. I hear from other forums that this places a lot of stress on my ankles, but they never really feel any tiredness or overuse. What are your thoughts on this; is it safe?

If you watch this video http://www.youtube.com/watch?v=bLg4j4gMzqA starting at about :53 seconds you can slow motion mid-foot strike.  It looks like the runners are about to strike on their heals but then they actually land on the back of the balls of their feet.  They also swing their arms slightly across their chest and let their  shoulders move in a relaxed manner to counter act the torque of their legs.

Everything I've learned from college sprinting says that landing "full footed" decreases the amortization phase of running, which is to say: the amount of time your foot is on the ground.  I've never heard of it from the perspective of lowering joint stress.  Plyos are taught this way as well.  When you land on the balls of your foot there is too much time loss as your anke has to flex and extend again.  If you're looking for speed, then full-footed is the way.  If you have the musculature, especially in the hamstrings, you should be able to handle any landing stresses.

Sprinting is a different technique than running involving a "pulling" type motion. If you're looking for sprinting then yes full footed and a slight change in mechanics is needed. However, for recreational runners (the main audience this article was directed toward) mid-section landing is warranted with slight changes depending on your pace.

I say mid-section because each person is different and the possibilities for structural changes are vast. Mid-section is an area that is not the toes nor is it the heel which should give those learning how to run properly a good idea of where a foot-strike should happen. This helps them adapt to their own unique running sequence.

Thanks for the concise guide. I realize now that I've been running heel-to-toe with a hunch this whole time. I'll have to pass this info along to some of my friends.

hmmm i land my sprints on the balls of my feet...whenever I go full footed i notice significant decreases in my sprint speeds...but there are always exceptions to these rules