Also this is the first I have heard of "exercising" Bettas prolonging their life.
I would not think it would seeing as you are stressing Bettas out when you exercise them.
I also think that the mirror method would be the least stressful method of "exercising" a Betta as the Betta can just swim away if it does not like the mirror, some of the other methods mentioned (powerhead, swirling the water, etc.) do not give the Betta this freedom and in my opinion even sound like they could be considered on the verge of being cruel!
When you think about it it must stress the Betta out greatly to have a whirlpool in the tank that it has to swim against. A low flow filter would be a much better option because it filters the water and as long as you provide a place or two where the Betta can get out of the current and the filter does not create a whirlpool the Betta will not be nearly as stressed and can swim against the current of the filter at will rather than being forced to.
I would not think it would seeing as you are stressing Bettas out when you exercise them.
I also think that the mirror method would be the least stressful method of "exercising" a Betta as the Betta can just swim away if it does not like the mirror, some of the other methods mentioned (powerhead, swirling the water, etc.) do not give the Betta this freedom and in my opinion even sound like they could be considered on the verge of being cruel!
When you think about it it must stress the Betta out greatly to have a whirlpool in the tank that it has to swim against. A low flow filter would be a much better option because it filters the water and as long as you provide a place or two where the Betta can get out of the current and the filter does not create a whirlpool the Betta will not be nearly as stressed and can swim against the current of the filter at will rather than being forced to.