How can I reduce the appearance of bulging viens on my hands? (photos)

Your age is much too young for having bulging protruding veinson the dorsal side of your hands. However,  since you are in physical fitness and possibly doing weight lifting or push-ups, it can happen at your age too. I imagine being fit you have a healthy low percentage of body fat meaning that the layer of fat pad ( we all have) in your hands is low as well thus the veins bulge even more.Generally speaking, I see this condition much later in life the reasons being thinning (atrophy) of the skin as well as the already mentioned disappearing fat pad that this time, coming with the maturity that is inevitable; of course, flaunting, showing it is optional.There are three ways to take care of the condition. One is to use fillers, artificial ones, (Restylane, Juvederm,Sculptra, etc. etc.) or own fat transfers harvested by liposuction. Both will do nothing to the bulging veins, just puff up your hands in kind of make-believe, veins still there, less visible. The fat fillers will last longer, the artificial will need to be frequently repeated, and they are not inexpensive. 
Only two procedure target the veins directly. One is sclerotherapy, either chemical (liquid or foam) or heat ( laser) and the other removal of the bulging veins. I will not dwell on injections or heat; in both several sessions are needed weeks apart thus the convalescence is much too long, the results are questionable, many times not long lasting, skin pigmentation and distant deep ( arm) veins blood clots (especially after injections) could be unpleasant complications.Personally, I prefer to remove the veins. The procedure, "Rejuvanad," is a minimally invasive method, done in the office, both hands in the same session and in local anesthesia. No convalescence is needed, all my patients drive away if they have not requested a tranquilizer. The method is similar to the ambulatory phlebectomy I use for leg's varicose veins since 1989 (over 4000 cases) with excellent results.Through tiny entry points not more than 2 mm (1/16 of an inch) with the help of specially designed hooks the bulging veins are removed in entirety. No stitches are needed and the results are remarkable, indeed.In over 500 procedures of the kind, I have seen only one patient with recurrence. She was young, also an athletic; lifting weights, push-ups, you name it. I have certainly redone her (that was two years ago), and so far I have not seen her back, but I am sure I will. Based on this statistic I consider "Rejuvahand" the best and ONLY available permanent solution. Back to your specific case, not examining and talking to you, being young and an athlete, I would caution you if you can't change your athletic routine. Of course, the procedure can be done; you will be pleased with the immediate results, but you have to take in consideration that you are exposing yourself to early recurrences.

Thank you for your question. Sclerotherapy is one option to treat your veins. Sclerotherapy treatment involves an injection of a chemical that will cause your vein to contract and become scarred internally. The vein will disappear from your body after some time. Generally, it takes about 8-10 weeks for the vein to disappear. You could also try dermal fillers such as Radiesse to help plump the hands. For more information, I recommend getting a in person consultation from a board-certified dermatologist.