Do you ever exert full physical force in internal styles?

[atip]

When you strike an enemy, do you ever exert your full physical force? It seems that internal arts focus on slow and harmonic movements rather than striking as hard as you can and screaming your magick word.

But when I read about iron palm (or any other iron training for that matters) it require you to exert full physical impact - either striking your palm as hard as you can at a bag or striking an object at parts of your body. It does not sound like internal arts to me. I know Thai kickboxers who contion their body in a similar way too. They toughen up their legs and arms to withstand blow bit hitting themselves with a bottle. They also use their special massage oil. They don't claim anything internal about it, yet it appears to be effective as well.

What does chi have anything to do with this? What do most people here think? Do you think of chi as just some philosophical way to imagine or visualize certain movements, or do you really think of it as internal energy?