Movements and positions

сгибђть/согнџть спќнуa to bend one's back
разгибђть/разогнџть спќнуa to straighten up, stretch out
Вљсь дљнь ї провёл за столћм. Вљчером разгибђю спќну, выхожџ из кабинљта, и вќжу... I worked at my desk all day. At the end of the day I straightened up, walked out of the study, and saw...
сутџлиться/ссутџлиться;
гћрбиться/сгћрбиться
to hunch over
выпрямлїть/вІпрямить спќнуa to straighten up
согбљнная спинђ Bookish a bent back
прогибђть/прогнџть спќнуa to bend over backwards
NB The above expression is used to describe a motion performed during exercises, gymnastics, etc.
выгибђть/вІгнуть спќнуa (дугћйi) to arch one's spine
NB The above expression is used only in reference to animals.
Кћшка зашипљла и вІгнула спќну. The cat hissed and arched its spine.
поворђчиваться/повернџться к Nd спинћйi;
становќться/стђть к Nd спинћйi;
стоїть/встђть [Pf-begin] к Nd спинћйi
to turn away from N, to stand with one's back toward N
Ћн повернџлся (or стђл, or встђл) спинћй к свљту (or к своемџ собесљднику, etc.). He turned (or stood with) his back to the light (or with his back to the man he was talking to, etc.)
NB The expression повернџться к N спинћй also has the figurative meaning "to turn one's back on N," i.e. to abandon N in a difficult situation.
прислонїться/прислонќться к Nd спинћйi to lean one's back against N
лежђть/полежђть [Pf-awhile] спинћйi к Nd to lie with one's back toward N
Кђтя лежђла спинћй к стенљ. Katya lay with her back to the wall.
ложќться/лљчь спинћйi к Nd to lie down with one's back toward N, to turn one's back toward N
сидљть/посидљть [Pf-awhile] спинћйi к Nd to sit with one's back to N
садќться/сљсть спинћйi к Nd to sit down with one's back to N, to turn one's back toward N
лежђть/полежђть [Pf-awhile] на спинљp to lie on one's back
ложќться/лљчь нђ спинуa to lie down on one's back
переворђчиваться/перевернџться на спќнуa to turn onto one's back
пђдать/упђсть на спќнуa (or нђ спинуa) to fall onto one's back
плђвать/поплђвать [Pf-awhile] на спинљp to swim on one's back, to do the backstroke
Ћн хорошћ плђвает на спинљ. He does the backstroke well.
подставлїть/подстђвить спќнуa под Na to put one's back under N; to expose one's back to N
NB N = удђры "blows," or a noun which refers to a burden, e.g. мешћк "bag," їщик "box," etc.
заклђдывать/заложќть рџкиa за спќнуa (or зђ спинуa) to put one's hands behind one's back
бІть [no Pf.] свїзаны: у Ng рџкиn свїзаны за спинћйi N has his hands tied behind his back