Mountain Biking Trails >
Websites like Outdooractive and VTTour describe this term as challenging sections of trails that require pushing or extra effort to overcome. For example, a trail in Ramatuelle is described as having //"quelques poussages"// (some pushing sections) along the coastal path >
https://www.outdooractive.com/mobile/en/mountain-biking-trai...

Hiking Trails >
Similarly, hiking trails may include //"poussages"// that require hikers to push through dense vegetation or navigate steep slopes. For instance, a trail in Ax-les-Thermes is described as having //"quelques poussages"// along the way > https://mxhsgirlq.wrozkagabriela.pl/

Technical Terrain >
It can also refer to technical sections of a trail that require riders or hikers to dismount and push their bikes or themselves through difficult terrain. This is evident in descriptions of trails with //"poussages"// and //"descentes techniques"// (technical descents) > https://www.ladrometourisme.com/fiches/16-pierre-chauve/

Local Guidance >
Local tourism websites and guides often mention //"poussages"// as a way to warn visitors about challenging sections of trails. For example, La Drôme Tourisme advises hikers to be prepared for //"quelques poussages"// along a particular trail > https://www.ladrometourisme.com/fiches/16-pierre-chauve/

I believe it's when you have to push down on the pedals with your full weight, i.e. stand up rather than pedal in the saddle. I've also seen 'poussage et portage' where you actually have to carry the bike.

--------------------------------------------------
Note added at 21 mins (2024-06-24 11:17:00 GMT)
--------------------------------------------------

It might even just be pushing the bike, as per Sakshi's answer!


--------------------------------------------------
Note added at 49 mins (2024-06-24 11:44:42 GMT)
--------------------------------------------------

Yes, I'd say it's definitely just pushing the bike. I also overthought it :-)

As in: "a few parts/sections where you have to get off and push).

Agree with the others about pushing the bike.
But offering this alternative which might work if you're looking for a more 'chatty' tone (with the 'you' form).

Given that the path is described as "descendant" I don't think you can use a translation that implies working hard on the pedals or similar. Something more general is required.

A quick right turn on to a gravel track we descended at speed, which is such a great way to start a morning ride, especially on this day where we have to tackle the longest and steepest climb up to Radicofani. We will also have to tackle the first section of trail that has a walking section. [ … ] I dismount and walk up the 100 or so steps dragging my bike with me and then remount when I reach the first passable street.
https://blog.3t.bike/2021/06/17612/the-tuscany-trail-2021-pa...

We grossly under estimated just how much effort was required on the trail, (and therefore our increased need for food) and I remember one day when we only managed 4km! This was a seriously difficult walking section, and we had to carry our bikes and gear separately, so you would walk 200m with the bike (and we removed the pedals to stop bashing our shins!), leave it and go back for the panniers, carry the bike.....you get the picture!
https://www.crazyguyonabike.com/doc/page/?page_id=177832

Leaving from the slipway at the Portavadie ferry,before taking to the forestry road and then onto the off road trail. I’d noted this down as a walking section,however on some sections the bike can be used,especially from the eastern side of Loch Ascog out to the B8000 rural road.
https://www.walkhighlands.co.uk/Forum/viewtopic.php?f=25&t=5...




--------------------------------------------------
Note added at 6 hrs (2024-06-24 17:47:00 GMT)
--------------------------------------------------

Nga Herenga The New Zealand Cycle Trail describe their Grade 4 as "Steep climbs, with unavoidable obstacles on a narrow trail, and there will be poor traction in places. Possibly some walking sections. Gradient: 0-7 degrees for at least 90% of trail; between 7 and 9 degrees for no more than 100 metres at a time, and maximum 12 degrees for up to 10 m at a time. If the track is designed and promoted to be ridden predominantly in one direction, then the downhills can be steeper (up to 15 degrees). Sealed trails can be steeper (same as the equivalent Grade of on-road trail; see Table 13).
https://www.mbie.govt.nz/assets/new-zealand-cycle-trail-desi...

NB confidence level. Bourth's quotes make the case for his answer being sufficient, and in use, certainly where the context makes the fact of a cycle being involved.

In fact in your question there is no stipulation, as far as I can see, that cycles are involved. So arguably you might want to dot the Ts and cross the Is like this. Or contrariwise.

As mentioned in a comment, I'm not so sure we talk much about "pushing" a bike in English ...