Do varicose veins temporarily become larger/protrude through the skin more when a muscle is contracted?

Varicose veins: when a muscle contracts it forces increased blood into the veins and the varicosities enlarge.

Yes. Don't worry. : The contracted muscle may force more blood into the vein. In addition muscle under vein bulges w contraction & may push the vein superficially, so its more visible. This isn't dangerous in any way & doesn't mean the veins the treatment. We treat varicose veins in people with legitimate pain,swelling, or skin issues associated w the veins. Otherwise the veins don't need treatment. Hope this helps.