Runners, what causes injury, speed or distance?

Both can. Increasing distance too quickly can cause the most damage.

Trying to go too fast or pushing yourself into long distances too quickly can cause repetitive stress injury. Its very important to build speed and distance gradually. And not at the same time, Ie one day do speed work, and another do your long runs at a slow pace.

You also do not want to overexert yourself or you are setting yourself up for failure. I would limit your running to about 3x a week at first and incorporating intervals into the run (rather than one short fast run or one long slow run). This will limit your risks of injury and prevent discouragement. If you are a particularly drivey person, alternate running with walking (Mon-run, Tues-walk, Wed-run, etc) or alternate it with another activity such as swimming or yoga (low impact).

There are countless ways to injure ourselves running (I know as I've done most of them). I'd work on your distance first, the speed will come naturally as you build your endurance.

I'm a fan or listen to your body vs. rules of thumb. I'm not sure who exactly is best served by the 10% deal.

If you are running 3 miles, you can bump up to 3.3 but not 3.5? If you are running 7 miles, you can bump up to 7.7 but not 8.25? Doesn't make sense to me.

If you are struggling as you increase, them I'll buy into the 10%ish, but if you are feeling great, then I say just go with it.

Trying to go too fast or pushing yourself into long distances too quickly can cause repetitive stress injury. Its very important to build speed and distance gradually. And not at the same time, Ie one day do speed work, and another do your long runs at a slow pace.

Ok so for example i can work on my speed for 3 miles one day doing intervals, then the next do a slow steady run for 4 miles or so at 6mph? Is that safe?

If you're a new runner I would suggest skipping the speed work for now and continue just building a base. The speed will increase naturally with time. After you have a sufficient base then you can proceed safely with speed work with a reduced chance of injury.

Run a lot, mostly easy sometimes hard.

wise advice from the panda

as for pace, don't worry about the number, just keep it "conversational"

you want to be running at a pace where you can easy carry on a conversation with very little huffing or puffing

I agree with most of the advice you've gotten so far and will lean toward "listening to your body". I would like to add something that most runners either don't know or avoid admitting because it's a little more effort. I'll keep it short and simple. When you run for extended periods without sufficient pre-exercise carbs or protein, you force your body into a position where it has to find energy somewhere else, which it ends up taking from your bones (calcium). Almost all the runners I know have had some or other problem at some stage due to this issue, especially if the marathion runners! Luckily on the other hand the opposite is also true. Should you do resistance training, whilst taking in enough protein and carbs pre-exercise, your bone density will increase. What to do: my suggestion would be to add some or other resistance based exercise to your current regime ( and remember, running alone will not tone up your muscles). So for that reason, if your also aiming to tone up, consider some resistance training. Alternatively, just make sure you take in 30gr of carbs and 10 gr of protein prerun and take a calcium supplement each night. Good Luck!

For me it was just doing too much. It wasn't tied to when I'd increase distance, speed or time. It would be when I wouldn't do anything else but running, and trying to run every single day. I always ended up injured after a few weeks. Since I started alternating running with other cardio and strength nights I haven't had a running related injury in months (which is a long time for me). And I've been building my distance on my long runs by a half mile each week and my speed is just naturally improving as I go, without trying to make it happen.

this is a bit of a loaded question as technically both can cause injury. I believe running with bad form causes more running related injuries than increasing intensity too fast does. After that I would go with running too far, and running too fast way down on the scale.

I also think "speed" is a very relative term. If you are newer to running, just by running more will increase your speed as you build a base. Doing "speed work" is really not neccessary for most recreational runners, until they reach a certain level, have a solid base, and want to work on true speed. I also feel that when doing real speed work, warming up properly is paramount to avoiding injury and that is why people get hurt, rather than from the actual speed workouts themselves.

Lastly I think a person has to be realistic & understand what thier bodies are capable of. Some can go far beyond the 10% rule, other's may need to increase even slower.