I will take this from a more general perspective.
A Cessna 172 is part of the CS-23 category (in EASA land, see the equivalent Part 23 for FAA land).
In the relevant document , point CS 23.143, we find the maximum forces a pilot might be required to exert on the control columns so that the aircraft can be certified.
As the Cessna 172 is certified, we then know that it respects these requirements, so the maximum forces required to pilot a Cessna 172 (and any other CS-23 aircraft) are: \begin{array}{l|c|c|c|}\textrm{Values in Newton applied} & & & \\\textrm{to the relevant control} & \textrm{Pitch} & \textrm{Roll} & \textrm{Yaw}\\\hline\
\
\
\ \textrm{For
temporary application –} & & & \\\textrm{Stick} & 267 \textrm{ N} & 133 \textrm{ N} & \\\textrm{Wheel (two hands on rim)} & 334 \textrm{ N} & 222 \textrm{ N} & \\\textrm{Wheel (one hand on rim)} & 222 \textrm{ N} & 111 \textrm{ N} & \\\textrm{Rudder pedal} & & & 667 \textrm{ N}
\\\hline\
\
\ \ \textrm{For
prolonged application –} & 44.5\textrm{ N} & 22\textrm{ N} & 89\textrm
{ N} \\\end{array}
aviation.stackexchange.com/users/1467/Federico
It depends on what you mean by "strength".
In general, it is "not much".
I've flown a lot of sims and also flown a real Cessna 172.
It is true that most sim controllers (especially joysticks) require almost no effort to move at all.
In that perspective, then yes, flying a real airplane takes some strength, especially if you compare the force required to achieve max deflection (not recommend in flight!!!).
The flight controls of a light aircraft are still light enough that a healthy adult can manipulate them very easily.
In fact, the correct technique is to use two or three fingers on the yoke.
Most first-time students grab the yoke firmly in their hands, this is wrong because you cannot feel the airplane.
If one has the strength to drive a modern-day road car, one can certainly fly a light airplane.
I have also spent some time in a B737 training simulator (not PC simulators -
I mean the real sims used for training).
I was surprised to find the controls much heavier.
I would describe the feeling as solid and fluid.
They are still easy enough to manipulate such that my mind can focus on elsewhere instead of the physical movements of the control.
aviation.stackexchange.com/users/3386/kevin
I've never flown a 172, but I fly a Piper Warrior which is in the same ballpark.
You definitely need to apply a lot more force than with a flight sim yoke and provide positive pressure (Remember, you're fighting the airflow ultimately), but you don't need to be "strong".
I'd imagine anyone who can drive a car would have the strength to fly a plane.
Remember, most flying is one handed and most pilots will use their less-dominant hand (Left hand)
so it can't be that bad!
I do find the Warrior needs a lot of backpressure to rotate and flare.
I've struggled to find any mathematics to add to this, but I've found a few quotes which imply you need approximately 1lb of backpressure to hold the plane level for every 6kts without trim
(The whole point of trim is to avoid this and make life easier)
So, at 100kts that's 16lbs / 7kgs.
aviation.stackexchange.com/users/2160/Dan
I taught people of all sizes to fly for about 30 years.
I taught my commercial students how to take off and land without even touching the yoke.
So it is possible to control a c- 172 with no yoke force whatsoever.
Just rudder, throttle and trim.
So by the use of proper trim use, one can control the aircraft using the yoke with only ounces of force.
Don't let people discourage you.
aviation.stackexchange.com/users/33703/Anthony
I have several hundred hours in a 172, while it's a bit heavier on the controls than a 152 it isn't much.
If you have normal movement then you can likely fly a 172.
A benefit to control force in real aircraft vs Sims is the feedback you get through the controls with renders Sims largely ineffective in many cases.
OK for some stuff mostly instrument related but it will never replace actual flying.
The 172 was a lot easier to fly than the turbine modified Grumman Goose I flew, that thing was like trying to fly a dump truck with manual steering.
aviation.stackexchange.com/users/33702/Dick foster
The amount of physical exertion required while flying a 172 depends largely on what you're trying to accomplish; for example, cruising in a trimmed attitude requires almost no effort whatsoever.
However, purposely inducing an aggravated stall/spin action then recovering requires considerably more effort.
Since recovering from all situations is important while flying as a PIC, one should give it a try before pursuing training in earnest.
Personally, the most exertion required is climbing up to manually check the fuel levels in the wing tanks.
But once I got the hang of it, it became quite easy.
aviation.stackexchange.com/users/33708/Steve Woods
I fly both Cessna and piper aircraft.
The flight controls on a 172 require a lot less force.
The flight controls on a piper feel much heaver..
you feel like your flying a much bigger airplane.
So to answer your question it does not take a lot of strength to fly one.
aviation.stackexchange.com/users/33706/Robert costa
I have heard a number of folks tell me that one needs a certain amount of physical strength to be able to control the Cessna 172. Is that true? I'm flying sims now, just wanted to know.
How much physical strength is required to control a Cessna 172?
aviation.stackexchange.com
<flight-controls><cessna-172>
aviation.stackexchange.com/questions/54237
aviation.stackexchange.com/users/33647/lpydawa
Flying a 172 requires only the same amount of physical strength as driving a car. Any able-bodied adult should be able to do it.  For some people, it does not take a lot of stength to fly a Cessna 172, but only a normal amount is needed. More specifically, it needs as much stength as to drive a modern car. According to an answer, the calculated result of the strength is 16lbs / 7kgs. While more force than when using a flight simulation yoke is required, it is still not a difficult task. Finally, for some people the strength needed depends on what the pilot tries to accomplish during the flight.
Generally, it does not take a lot of stength to fly one. A normal amount of stength is needed.  It needs as much stength as to drive a modern car.  The strength needed depends on what the pilot tries to accomplish during the flight.  The calculated result of the strength is 16lbs / 7kgs.   While more force than when using a flight simulation yoke is required, it is still not a difficult task.