Q: I have a tendency to tilt forwards and arch my back when I ride. How can I learn to sit up straighter, with a straighter back?
A: Tilting forwards and arching the back can be related issues. Arching of the back can cause a rider to tilt forwards and make it easier for your horse to pull you out of the saddle, but similarly, both of these issues can and do have independent causes.
Tilting forwards on its own is often an anxiety-related issue. Whenever we are nervous, it is tempting to assume the foetal position! Becoming more confident is not an easy or quick process, but the more you ride in confidence-building situations (on safer horses and with an instructor you trust), the better and more relaxed you will feel.
In terms of immediately combatting the tilting forwards as its own issue, the best advice is to sit back on your seat bones and open up your shoulders. Opening up your shoulders opens your chest and forces you to look forwards rather than downwards. The only thing to beware of in terms of your shoulders, is forcing them back too much. Forcing your shoulders backwards can create a rigid position that affects the rest of your riding.
The arching of your back is corrected by engaging your core muscles. The feeling of pulling your belly button back to your spine helps to engage your core muscles and remove the arch in the lower back. An engaged core helps your riding enormously and will naturally reduce your tilting forwards, along with the the arching of your back. A flat back is necessary to give you the strength and stability needed for good riding.
Working on these issues will improve the problem, but nothing can replace a session with a qualified instructor, who can target the work to your particular area of need.