Let's say that there's a group of humans walking across a plain.
Incredibly strong winds blow across this plain at predictable intervals on an hourly basis.
For one hour, the wind magically blows in from behind the travelers, pushing in the direction they're traveling - so much, in fact, that they need to wear weighted packs on their backs in order to pull themselves backwards and stop themselves from tipping over.
The next hour, the wind dies to absolutely nothing. Zero. Nada. Zilch.
The next hour, the wind magically blows in from in front of the travelers, pushing away from the direction they're traveling. Again, they need to wear weighted packs in order to stop themselves from tipping over; however, in this case, they have to be on their front, in order to lean them forwards into a wind that's trying to push them backwards.
The next hour, the wind dies again, and the cycle repeats from the beginning.
Hunkering down during the windy hours and moving during the clear ones is not doable for a couple of reasons that are irrelevant within the scope of this question, as is splitting the group up. This means that they have to carry the packs constantly, rather than ditching them.
Assume that they magically have infinite endurance (not strength, endurance; they can't carry infinite weight, but they can carry some weight forever), don't need to sleep, etc.
Question: how heavy of a backpack can the average human wear on their front or back while still maintaining a walking pace and not tripping/falling over/etc?
Let's say that they're wearing a high-quality hiking backpack that transfers most weight to their hips.