EMS machines for loosening tight back muscles?

After sitting for a duration of time i get tight muscles mainly in the upper back close to the neck. I want to loosen these up. Ive started doing yoga and stretching etc. During the meditation section i am particularly aware of the tightness in the upper back which becomes more uncomfortable as time progresses even though my posture is good (whilst in a seated kneeling position). Ive been looking into EMS machines but im confused by the terminology eg EMG, ETS, NMS etc. Would one of these machines used regularly help to loosen up these muscles and if so what machine from the link below would be most effective:

Products - Verity Medical Ltd.

NeuroTrac® Sports XL - Verity Medical Ltd.

hi dear
yoga really help u to eradicate this problem.the best devices for this problem are laser and ultrasound and then TNS or IFC.
all the best

Thats something to think about. The lazer devices appear to be too expensive to buy for home use. Ill stick to the yoga and perhaps experiment with an ultrasound device for the tighter spots in the upper back. Thanks for your suggestions.

- - - Updated - - -

Just wondering, would it be beneficial to wear a TENS or IFC device continuously during periods of sitting to slow down the rate at which the muscles of the upper back become become tighter/uncomfortable?