[pedalpete]

yes and no.

Cycling puts an unnatural curve in our lower back, very similar to sitting in a chair, and due to the way the muscles work, cyclist end up with tight hip flexors and hamstrings and stretched spinal erectors (sorry, I've been out of Physiology for a while so can't remember the exact names of the muscles) which can further exacerbate the problem. Compare a cyclist with a runner, and you can see a noticeable difference in posture.

However, I wouldn't call it a 'negative health impact', as the activity is improving your health. Just be sure to stretch, and counter the muscle imbalances that the sport produces.

Many sports have similar results because they are unnatural. For example, snowboarders in big mountain areas end up with a unnaturally strong/tight oblique muscle on one side and one stronger leg. Surfers likely don't have this issue because the majority of their exertion occurs during the paddling phase and the length of time actually spent riding the wave is quite short.