Is Static Stretching Dangerous?

No.

There is lots of scaremongering around static stretching.  Articles written like this, use language to confuse people. “static stretches may even do harm….stretching “cold” muscles damages them…… hold each stretch for 20 to 30 seconds”.

Stretching

Let me clear this up for you. Static stretching held for more than 4 sets of 30s holds with a 15s rest period (alternatively, in other research static stretching for upwards of 5 minutes) does reduce maximal strength endurance, maximal power and strength efforts.

Static stretching is not harmful, but it may reduce your performance in the short term. But don't stop reading here. 

Now, if you are a powerlifter, sprinter, Olympic weightlifter, etc. and attempting a new personal best, you might consider not doing static stretching before your competition.

HOWEVER, the effects of increased flexibility only last from 6-25 minutes.

After this time, your flexibility returns to your prestretch position. It could be argued that the negative effects static stretching has on performance, will have subsided by this time too.

So, if you are stiff, tight, inflexible and need to increase your flexibility, then static stretching is advantageous ONLY if you hold for a minimum of 5 minutes to get a significant effect.

I wouldn't suggest stretching before big competitions or events, it is too late and it can be built into your training program, not pre competition. If you insist then make sure it's 30-60 minutes before you start and follow it with a dynamic stretch as the effects of decreased strength and power will have worn off. 

Here is your stretching protocol for any muscle:

Hold 20s - Relax 10s X 15 times = 5 minutes

OR

Hold 30s – Relax 15s X 4 times = 2 minutes

My information has come from the following research papers.