One of the biggest risks for running injury is increasing mileage too quickly. The old logic of more is better seems to happen rather quickly with new runners. Hey—it’s exciting when you find your running groove. You start to feel the runner’s high and thus the addiction begins… 
While there are no firm “rules” on increasing weekly mileage, it has been suggested that you not increase your weekly mileage more than 10% each week. Obviously you don’t have to follow this rule of thumb to the tenth of a mile, however it is a good way of preventing yourself from getting overzealous!
One of the main reasons for not increasing you mileage too quickly is that it simply takes your body and all of its bones, muscles, and tendons time to adapt to your newfound activity level. Rather than shocking them, you are allowing them to gradually adapt to your higher activity level.
There are situations when you can make an exception to the rule and maybe bump up by 20%, but it isn’t really recommended to jump more than that. In the end, it’s not really worth the risk of injury.
I think it’s also a great idea to incorporate down weeks into your training. For example you may build up mileage over 3 weeks, and then take a down week on the 4th week. It’s nice to give your body a little more time during that week to relax and get ready for the next increase.
As always, everyone is different. Some people seem to be able to handle larger weekly mileage increases. I am certainly not one of them! The older I get, the more I realize the prudence in this training suggestion!
How much do you generally increase your weekly mileage in a training cycle?
in a completely serious way this is an UP SIDE to my non-running addiction.
I have zero temptation for speed work and mileage increasing when I dont have to!!
I increase by no more than 10% a week, make sure my long run is no more than 50% of my weekly mileage, and build in cut back weeks. For the cutback weeks I tend to need more than most people recommend, so I end up building my own training plans around what I know my body can handle. This training session (working towards a half in Nov.) I am upping mileage for 3 weeks and then cutback week. Next time I will change that to a cutback every 2 weeks. A lot of cutbacks, yes, but I’m a newbie who seems to be injury prone.
I feel like I am so injury prone lately, so I am on the conservative side like you! 🙂
Clear, concise and to the point – this is great! Thank you.