Subliminal audio messages are messages that pass your conscious threshold. They may be viewed as covert messages because you do not consciously hear them. The subconscious mind on the other hand understands them, and is able to change your thoughts and feelings towards exercise because of their impact.
What they can't do
But, they can not change you unless you want them to. If you are not committed to exercising regularly, if you still plan on making excuses or just toying with the idea of exercising while all you will do is sit at home and read Reddit, subliminal audio is not for you.
The simple fact is that subliminal audio is recorded to help you deal with a lack of motivation when the exercise gets tough and muscles start to hurt, or when lungs start to burn during the long run. They are able to give you that extra push that you need.
What they feel like