I myself have also developed over the years both with how the human body functions on a bike under load and found simple explanations for problems and developed and learnt to make more people comfortable on their bike.
First of all, if you want to perform, be comfortable, be aggressive etc.. you need to have have an good amount structural fitness in regards to flexibility, movement, strength. The better your body functions and moves off the bike the better your body will function on the bike. Most outlining issues are caused by 70% of this, rather than a seating position, too many people are try to be too aggressive to what their structural fitness can hold.
With cycling there are mainly two general causes of injury, pain and sometimes performance on the bike.
The first problem is the persons position on the bike, and bike fitters like me can address that issue, but you can say we are a temporary fix rather than a complete overhaul..

We can´t change the person, but we can relate that person to the bike they are on and how the body functions/works on that particular bike.
Take your arms for example, they are merely a relaxed prop. They should bare only a small amount of weight when pedaling under load. The amount of people i have dealt with numb hands over the years is in the hundreds.

No matter what your structural fitness is, the arms should bare the least weight of that sitting on the bike.
The more weight we add to the front of the bike by having the saddle further forward the more structural fitness comes into play, the more the body needs to adjust and compensate to hold the body in position, because the weight has to be borne somehow and then the arm, neck and upper back will take the majority of this.

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What we are aiming for is that we sit further enough back on saddle to support the sit bones and produce a stable pelvis, and bare a small amount of weight on the arms. The better structural fitness a person has can affect the saddle position on a bike. The more structurally sound a person is, typically the further forward they can sit. In this position we inlist the glutes/hamstrings and quadriceps should work in harmony, rather than overloading one of these specific muscle groups, then having to use the same muscle group to help stabilize the body under load. Walking down stairs with extremely sore quadriceps? does this ring a bell??

Aerodynamics yes we can agree that we need to be as aerodynamic as possible since 90% of the drag comes from your body on a bike…but this needs to be consistent with our proportions, structural fitness etc. To sum things up directly…set your bike position to your structural fitness.

The other most common problem i have seen, is numbness under the groin.

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The bicycle market tells us we are using the wrong saddle width, design etc..and go on to explain that at this measurement we need this size, shape, design etc.. Yes this is correct to a point but seeing how many shops directly say the person needs to change their saddle to this model, without actively seeing that person sitting on a bike astounds me.

One of the outlining causes of this,can the saddle set too far forward, which is rotating the pelvis and re positioning the body to compensate for this. What we are trying to achieve is to load the majority of the weight on the sit bones at the base of the pelvis. Numerous other factors can be a too long of a reach to the drops, hoods on the handlebars..enforcing the body to re position itself further forward, again shifting that bearing weight off the sit bones.
Before you go changing your saddle, make sure around 70% of the weight bearing load is situated on the sit bones and that you can comfortable reach both the drops and hoods with minimal movement.

All changes made to your position should be adjusted under load, because your body is naturally going to move into a position that is more efficient for that person or they are moving into another position to effectively shorten or raise the saddle height, shorten the reach to the handlebars…or compensate for the lack of structural fitness..

… Re adjust and test under pressure.

I am a big fan of not forcing a person into a position, rather helping the body become more stable under load, so we see less movement of the pelvis, create stability of the body and reduce the majority of the load off arms, neck, back etc..

90% of the people i fit are your average cyclist, being comfortable and efficient under load is the most important thing rather than being over aggressive, and forcing the body to sit in a position which the structural load is too much.