I think posture would be more of an issue than the weight.
Think of it this way- if you weighed 45lbs more than you do right now and were on the treadmill, would that be a problem? Probably not. The vest is just a way for you to have more body weight so your resistance is more. Stand up straight, make sure the vest fits right... go see a doctor if you're really concerned about it.
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Sage knows our mythic history, King Arthur's and Sir Caradoc's
She answers hard acrostics, has a pretty taste for paradox
She quotes in elegiacs all the crimes of Heliogabalus
In conics she can floor peculiarities parabolous
-C'hi