Contrast
This exercise is for noticing how a muscle lets go after a short tension. It is not a warm-up and not something to do during an attempt.
It fits an athlete whose hands and shoulders lock up before a start, and a rest pause after a strength exercise. The point is to recognise relaxation from your own sensation, not from someone else's description.
Skip it if squeezing the fist hurts. Do not strain the eyes or the abdomen.
Сядьте поудобнее. Сожмите правую руку в кулак. Сжимайте крепче, почти с максимальным усилием! Через 10–12 секунд свободно бросьте руку на бедро, закройте глаза и прислушайтесь к ощущениям в кисти и правом предплечье.
Translation: the instruction above is quoted in Russian, as printed.
A cue marks the start of the squeeze and the moment you drop the hand. Then you name what you felt, in your own words.
An exercise. It is not an assessment and it does not replace a session with a specialist.