Exercise & meditation

Namaste Prabhuji!
In your previous answers,you have suggested physical activity,intellectual activity and God meditation to channelize the excess energy conserved through Brahmacharya,otherwise it gets converted into tamasic energy.
I am experiencing the same thing,Tamasic enegy(feeling lazy,inerita,etc..)
So,my question is that
1.Can Surya Namaskar replace sports for physical activity?I don't find enough time to play sports and have no one to play with,...so can I practice Surya Namaskar instead of cricket badminton,etc...
2.If one sits in Padmasana,concentrating on his breath and repeating some mantra mentally, what actually is it?would it be right to call it meditation or is it japa?I do not have enough time to do mediation and japa both...so i will have to sacrifice either of these,which one should i give up?Meditation or japa?
Thank You prabhuji!