Improvement

[Bunx]

A low growl curls in mirror
at the discount gym.  Rec center

The drawstring of your sweats
will not be untied, lacking proper form
has languished the loops I'd cut has and the 
into clumps.

There is no banana in your smoothie. Maybe start at "no" your clearly missing the fancy gym

The woman on the stair climber
might not be crying
about your lack of progress. Ok narrator missing attention from women. Trust fund bro ran out of trust??

Trembling in plank,
you don’t have the strength
to keep your body still.

The only destination is collapse. "Collapsed destination frustration" perhaps?

The floor is speckled black rubber
and you lie prone on a thin red mat.

You must shower.

Flip flops condom your feet,
but nothing protects your lungs
from black mold and assorted fungus.

A low growl curls.

Just some ideas my friend