There is, in both cases. We have already identified some of the biological factors that make certain athletes excel: a mutation that makes the body more resistant to lactate acidosis for example, or a certain bone/tendon structure specifically optimized for running and so on. We also know that there a threshold when additional muscle doesn't add to more efficacy anymore due to problems in blood circulation and so on. Drugs and surgery can only change some biological parameters, physical aids Like shoe forms have a limit of optimization as well. But people dominating their fields usually do so due to biological advantage. In modern high professionalized sports, there's little "fairness" involved.