The process start with a 48 days of fasting. Fasting here is not only on food (where they only consume 1 moderate vegetarian meal after the evening prayers) but it is also fast to the mind, body, ego, emotions, desire and joy of worldly matters.
The state of mind and the mind and senses should be focused inwards (PRATYAHARA OR ABSTRACTION)
The body should not enjoy comfort and service but should live a basic living and working things out by yourself.
The ego and temper should never be there and emotions, desires should be in control and they should practice "bramachariyam".
The more deeper practice of prayanama and hatta yoga, meditations and service to mankind should be performed.
At the end of 48 days the mind, body, emotions will be balanced and well tuned towards the superconcious state of the mind. This is the state where we can experience the state of bliss and union with the absolute. And having to carry a kavadi in this state is completely a joyful experience and there will be no pain, tiredness, input from any of the 5 senses and you will see the grace them and the "dance" they will perform in the joy of the union. The goal is this.
The other things that you see are somehow is not a complete experience (shall not elaborate on this).
Kavadi is not to torture the body or did never GOD asked you to do that or did HE never ask you for anything and HE will never ask. It is you that promise to offer something that he never asked for . HE is all giving and has that unconditional love towards the creation that HE never ask any in return for something that you ask for. If HE in any state ask for something then you are "working" with so called demi GOD.
(thats my personal view)
Try asking HIM with the pure heart and one mind and one thought and in selfless mode....for sure you will get it even if you don't say "I will do this and that". But remember, you have taken this birth to complete a task and you may have to face challenges to complete that ....and that you will have to face it.
Click the link for the purana story about the origin of Kavadi
The cave...at about 5 am on the 1st Feb
And it made me laugh when i heard the commentator who said "Murugan has 6 padai veedu" and Batu caves is the 7th padai veedu" it is already said there are only 6 such places for Lord Murugan .... who authorised the new 7th Padai veedu?