Training Load

Some people can run daily, while others only 2-3 times a week. Training load is very individual and depends on many factors. Some can be changed with strengthening and better technique, while others like individual bio-mechanics are more difficult.
Often understanding pain or discomfort and managing training load is the key to stay injury free. 
Going longer and/or faster than you ever have before involves getting out of your comfort zone. Learning to deal with discomfort in training and racing is necessary for improvement in running. If you are experiencing mild to moderate muscle soreness that lingers for 12-48 hours after a tough workout or race, this is relative normal. 
As you increase your running volume and different training intensities, your body will need to adapt to the new stresses that are being placed upon it. Soreness is your body’s way of telling you that it’s repairing and rebuilding itself to come back stronger over the coming days, weeks and months.
One of the most important skills you develop as a runner is learning to discern discomfort from pain. While learning to deal with temporary discomfort is necessary for taking your running to the next level, letting a dull, persistent pain linger for a long time can lead to injury.

SOME USEFUL TIPS
1. BE CAREFUL NOT TO DO TOO MUCH TO SOON. AS A RULE, YOU SHOULD INCREASE A RUN BY NO MORE THAN 10%.
2. REST AND RECOVERY DAYS ARE IMPORTANT. This where you absorb all the hard work that you are putting in. More on this in a later TIP. 
3. Running easy on a set of sore muscles is fine, but save the long runs and faster workouts for when the soreness has subsided. Cross training is a great way to allow recovery and maintain fitness. Allow a recovery or a rest day before and after a hard training session.
4. Sharp, sudden pain that seemingly comes on out of nowhere should not be ignored. Don’t try to run through it. Stop running, evaluate the situation and seek advice if necessary. Be especially careful with joints and tendon pain. Start by taking a few days off from running and only attempt to run again once you’re able to go about your daily activities without pain.
5. If a pain is present but you are still able to train without effect, then maintain that level. If pain is worse the next day then decrease the load until symptoms settle.

COMING BACK FROM AN INJURY
Have an injury which is recovering? It’s often hard to know how much pain you can run with. 
Bone pain from stress fractures should be minimal, while tendon pain can still be felt for long periods even after the tendon has repaired and is strong again. A guide here is no more than 3/10 pain the next day. 
Tendons need to be loaded to repair. Complete rest weakens them and pain can be worse. Gradual strengthening and weight bearing is needed to increase load tolerance of tissues and allows you to get back to running and increase distance and speed safely.