I know being late, but hope not too late, as I have an alternate proposal:

pencher⇒ vtr (incliner dans une direction) tilt⇒, incline⇒ vi
(more effort) stretch out⇒ vtr
(head (indicating effort)) crane⇒ vtr
https://www.wordreference.com/fren/pencher

"bend forward" Approximately 1,010,000 results (0.40 seconds)
"bend forwards" Approximately 37,800 results (0.39 seconds)
"bend the head forwards" About 6,350 results (0.44 seconds)
"tilt forward" About 979,000 results (0.60 seconds)
"tilt forwards" Approximately 14,400 results (0.34 seconds)
"tilt the head forwards" Approximately 3,300 results (0.37 seconds)

Il lui est demandé de se pencher en avant.
He is asked to bend forward.
Le médecin m'a dit de me pencher en avant.
The doctor told me to bend over.
Garder les jambes droites, se pencher en avant pour atteindre vers votre cheville avec le poids.
Keeping the legs straight, bend forward reaching toward your ankle with the weight.
Se pencher en avant, s'étirer, détendre le corps et ouvrir l'esprit.
Bend forward, lean back, open body and mind.
https://context.reverso.net/übersetzung/franzosisch-englisch...

Back pain when bending forwards is quite common if you experience bouts of back pain from time to time. It can also be a trigger for many people if done incorrectly, since there is a more correct form you should be adopting to bend forwards.
https://themayfairclinic.com/what-causes-back-pain-when-bend...

You can practise the following:
Feel for your hip bones on each side at the top of your thighs. Practice bending forwards slowly, from the level of these bones, whilst keeping your low back straight (it may feel like you are sticking your bottom out). You only need to bend forward about 45 degrees, then return upright and repeat.
https://osteoandphysio.co.uk/how-to-bend-forward-and-not-hur...

Aching pain in the forehead above the root of the nose which compels him to bend forward the head, (The relief caused here and in 19 by stooping forwards stands with the other symptoms, 20, 21, 58, where stooping forward aggravates, in the position of alternating action …
https://homeopathybooks.in/materia-medica-pura-samuel-hahnem...

Testing the posture via the platform equilibrium Pagani platform, we realized that subjects initially submitted a relevant antero -posterior change of posture, with a tendency to bend forward the head, which is responsible for the emergence of kyphosis, much improved in the final testing.
http://www.jskm.ro/images/pdfs/26/DANCE-INFLUENCE-ON-MEDICAL...

Suffocation and beatings in the chest when attempting to cough. Beating pain in the head and nape of the neck, with inability to bend the head forwards for the purpose of writing.
https://www.materiamedica.info/de/materia-medica/benoit-mure...

9. Throat.-Dryness and redness of upper part of pharynx.-Increased redness and soreness of upper part of pharynx, < at night, causing difficulty of deglutition, obliging her to bend the head forwards on swallowing, so as to favour it, otherwise a pain runs up to ears.
https://www.materiamedica.info/de/materia-medica/john-henry-...

• Sit in a chair and hold the bottom of the chair with your right hand
• Turn your head and neck towards the left shoulder
• Bend the head forwards so that the chin points towards the tip of the left shoulder
https://pretoriaeastchiropractor.com/wp-content/uploads/2020...

Under either circumstance it is better to bend the head forwards so that any blood coming into the mouth can be spat out and not run down into the stomach or airway where it will cause irritation.
http://www.telangiectasia.co.uk/fact3.html

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Note added at 22 hrs (2023-01-20 10:23:34 GMT)
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Same with the -ing form:

"bending forward" Approximately 2,710,000 results (0.44 seconds)
"bending forwards" About 537,000 results (0.47 seconds)
"bending the head forwards" About 3,470 results (0.58 seconds)

I will spare you the numerous examples for the nominative form.