Solution
okay all the biological stuff are true as far as i know but i am here to give solutions that relate directly to the way you are playing, your techniques involved and your practice procedures. here are a few solutions that you might want to follow to solve this problem because i myself have faced that problem and these few things have helped me greatly.
1)Adrenaline- this happens to most drummers. i am sure there have been times where you try to reach a certain speed with your single strokes on your double pedals and when you practice it at home it is difficult. on the other hand, when you go jam at the studio or perform on stage, somehow or another you can reach a certain speed which is beyond the limit that you could possibly go practicing at home. this is due to our body's adrenaline which causes us to go at that speed for a period of time. the problem is if you continue pushing yourself at the speed you are at when you are having that "Adrenaline rush" you will get cramps. i have been in that situation and what i do to overcome that is to ensure that i keep within the limit of the fastest speed that i can go at and nothing more. Another problem that this brings about in the long run would be that you will naturally start rushing while playing a song and this would defeat the purpose of even being a drummer because your timing would be affected.
2)Relaxation- The reason why your muscles tense up at the first place when you are playing at fast speeds is because you might not be relaxing when you are playing. i have seen many drummers who start tensing up while they are playing and this is is firstly not helping them in their technique and secondly they would naturally slow down or even stop halfway through the song. The rule of thumb is the faster you want to go and sustain it at the tempo, the more you have to relax. this means that if you are practicing a certain speed exercise, you should basically troubleshoot your techniques at a slower tempo and once the tempo is set to go faster, you have to put your full concentration on relaxing. this is one thing which solved my whole muscle tension problem
3)Head Room-If you ever noticed, a lot of the greatest drummers in the world can play very fast and they make it seem very effortless on their faces. many drummers i have seen can play fast but with so much agony on their faces and they can really sweat it out and they rarely last because of muscle tension. the difference would be the concept of practicing with headroom. if you want to play your blast beats and be able to switch to and from other grooves or subdivisions without tensing up your muscles, you need to practice your speed beyond your goal. one idea that i put across to my students would be to play it four "steps" higher than the tempo you are aiming for. i like to use the word "steps" which means each step would be an increase in 4 bpm. what i would do is to practice exercises four steps higher than my goal. for example, if i want to play single strokes on the double pedal at 240bpm comfortably, i practice the exercise at 240,244,248,252, and 256 bpm. most of of the time when you reach the highest "step", your muscles start tensing up. when this happens, stop immediately and rest for a 30 seconds or so and start again. i usually practice my starting tempo 8 "steps" below my goal. the most important thing to remember would be to start slow and build your exercise up to speed. the slower tempos warm your muscles up to be able to handle the faster tempos. use this practice procedure and you will be able to blast without cramps in no time.
4)Pedal tension-This is an excerpt from one of the previous posts that i put up regarding pedal adjustment.Pedal tension is completely subjective and personal to every drummer. so to get the right setting for this you need to do trial and error. from what i see, if you play metal and your pedal tension is maxed out, it could be one of the major reasons why you are getting tensed up. if your spring is too tight, you are going to put in a lot of effort for each stroke. if your spring tension is too loose, you are not going to get any rebounds after each stroke. for double pedals try to even out the tension between both pedals. two things you can do would be firstly to grab both pedals, pull them back the same distance and release them simultaneously and see if they spring back and forth simultaneously. secondly, the bolts maintaining the tension on both springs should be of an equal height from the floor. in your case you might want to experiment with lesser tension on the springs so that you put in lesser effort for each stroke.
I hope i have answered your question regarding your muscle tension
