Runway,
Running can be detrimental to a sprinter, but perhaps for better reasons than reported in Procycling! Running becomes more detremental as the type of cycling goes from endurance to pure sprinting, remember that even sprinters in road races are fundamentaly aerobic beasts!
Realising that running can be beneficial to cycling at times (e.g. cyclo cross, cross training, MTB, etc.), for a sprinter running is unlikly to be of any benefit at all. This is due to 'transfer', activities that are beneficial to another activity (e.g. driving a car and driving a bus) have positive transfer, while other activities have no transfer (e.g. dancing and driving) or negative transfer (e.g. activities are damaging to each other).
Many of the adaptations to running have no transfer or negative transfer to sprinting. Pure sprinting (i.e. track sprinting) requires neuromuscular skill, strength, technique, anaerobic capacity, etc. and running can have a negative effect on all of these characteristics. Sprinting in road races requires less strength, greater aerobic capacity, economy (or efficency), etc. and running is again likely to have a negative effect on these.
If you are not very fit, you may benefit from running because it will improve your aerobic capacity and help you lose weight. However as you become more trained gains will come slower and greater gains will be made by on the bike training only.
Many people forget that training needs to be specific; running will make you run faster, sprint training will make you sprint faster, endurance training will allow you to ride faster for longer, weight training will help you lift bigger weights. The issue of transfer does mean that at times aerobic training will help you sprint faster, so will weight training (for pure sprinters) and sprint type training, but unfortunatly not running.
Hope this makes sense and answers the question.
