There are even inverted positions to counter-balance gravity. In the Sanskrit language of ancient India tha means moon and ha means sun. The spine is integral for physical balance. Self-awareness is integral for emotional balance. The attitude one brings to hatha practices is as important as the practice itself.
Exercise is physical effort, but in yoga the effort is primarily mental.
On a treadmill the mind can be a million miles away while the person achieves a physical benefit but in yoga the mind must be present, attentive in the moment, noticing what is happening and aware of how it feels. It is often said that awareness is the first step in change. If we have things we want to change physically, mentally, emotionally and even in the amount of available daily energy and stamina-our willingness to see and accept them as they are may be a key to enabling change, movement and growth. Hatha yoga practice gives us time to look at ourselves, and that time spent will be fruitful to the extent that we are genuinely willing to explore and discover our limits. As you stretch and breathe be aware of any competitive thoughts or judgments.