Ionic: ion-nav-bar declared "globally" does not work?

I've got this strange behaviour.

In my index.html I declared:

<body>  
    <ion-nav-view></ion-nav-view>
</body>

Then in my page.html I used the followin markup:

<ion-view title="Purchases" hide-back-button="true">
    <ion-nav-buttons side="left">
        <button menu-toggle="left" class="button button-icon icon ion-navicon"></button>
    </ion-nav-buttons>
    <ion-content> ... </ion-content>
</ion-view>

The view correctly set a button to toggle side menu, but also, automatically, create a header:

<ion-nav-bar class="bar-stable nav-title-slide-ios7 bar bar-header nav-bar disable-user-behavior">

How can I change its styles? For instance: I would like to set it as a "bar-energized".

I also tried to insert, in index.html above , the following markup (amany examples show), but it does not seem to work (nav bar header remains grey):

<ion-nav-bar class="bar-energized nav-title-slide-ios7"></ion-nav-bar>

The only way it seems working is by declaring and buttons inside each and every

Just realized it was really a newbie question! I was starting from a Ionic sidemenu template, and the misterious "bar-stable" was declared inside "ion-pane ion-side-menu-content" in my menu.html file. Hope it may helps someone other!