I'm new here, but I'm an old rider.

The answer has to be: ride more. Simply, you become a stronger rider the more you ride.

My wife and I used to do long tandem road rides and we would have to stand for certain situations. My wife would always want to sit down earlier than I would, and sometimes sat without warning.

The body tells us when it is tired.

Of course you have to find the right gear to stand and pedal in first.

My favorite form of riding is single speed mountain biking. This requires sometimes extended periods of standing and mostly in a gear ratio that is not ideal.

Bike fit is crucial. What passes for a good fit is a never ending discussion. Single speeding over the years has revealed a lot to me about standing, climbing trails.

We went back on the tandem after a couple years of not using it. The narrow bar width and the grip over the hoods wasn't ideal for standing. I did it, but had to compensate.