is tensing
Presente progresivo para el sujeto he/she del verbo tense.

tense

Popularity
500+ learners.
You know, your voice is tensing up.
Tú sabes, tu voz se está tensionando.
I said earlier to someone that if he regulates his speed it shows that he is tensing his muscles.
Le dije a alguien anteriormente que si regulara su velocidad se demostraría que está tensando sus músculos.
Palabra del día
la pista de patinaje