I have worn all -poly in the past and the issue with sweat is that if not washed off the poly [or any material, for that matter] it will eventually weaken it and cause holes and tearing . Having said that, it is a robust material and can withstand quite a bit of such abuse before going downhill. Agree fully with what mcnash has just said there --the hair itself will normally `go`before the base does, depending on how you treat your system overall. Oxidation and exposure to the sun, washing etc will all take their toll but look, having found Toplace, you can stay looking good always due to the reasonable cost of the systems --- a major issue [especially in the tough economic times in which we are all living ] for people concerned about their hair loss, is the cost of systems and the high prices charged by Salons generally --with Toplace you can easily keep your appearance at a fraction of the cost, and all you have to do is get used to doing your own attachments etc. The forum is full of tips and people`s real experiences, good bad and indifferent --- well worth reading through and forming your own plan of action. Why don`t you consider slightly altering your routine a little so that your work-outs can be done at a time when you can then go home afterwards and remove your system for a good cleaning of the scalp --consider one of those systems designed for such activities [shown on the style options section ] and wear a more `normal`one for everyday wear [ work etc ] I know that may not be practical --but in the world of wearing, sometime slight changes in lifestyle are sometimes required -- wearing is the next best thing to having your own hair, but will never be 100% the same, so there has to be a little `give` on all our parts in order to wear with confidence. I`m considering going full -cap for a while now and I realise that it will be different to a topper --not a lot, but still , a new area for me which will require changes to my `routine` --- it`s just something you adapt to. Why not order 2 systems -- one all poly/thin skin and one lace with maybe part of the perimeter done in poly --as mcnash said, when you`re younger you can get away with higher densities so no worries about the poly being obvious [I wear a medium/low density now and I can`t see any appreciable show through of the poly strip ] You can decide then which is best for you for any subsequent orders. I reckon for warmer climates most people find the lace systems just much lighter on the head and if you are sweating, the scalp won`t itch as much as it tends to with all -poly systems. The pros and cons have been fairly well discussed in a few recent posts--just have a look through them and hopefully that will help you with your choice--Paul.