Individuals on beta blockers will have a lowered blood pressure, resting heart rate, training heart rate, and maximal heart rate. An example is selection bias, which occurs when study subjects are chosen in a way that can misleadingly increase or decrease the strength of an association. Choosing experimental and control group subjects from different populations would result in a selection bias. It may be further defined as the use of living organisms to make a product or run a process. By this definition, the classic techniques used for plant and animal breeding, fermentation and enzyme purification would be considered biotechnology.
Some people use the term only to refer to newer tools of genetic science.
In this context, biotechnology may be defined as the use of biotechnical methods to modify the genetic materials of living cells so they will produce new substances or perform new functions. In a double blind experiment, neither the researchers nor the participants are aware of which subjects receive the treatment - until after the study is completed. Once the athlete's blood levels have returned to normal, adding back in the removed red blood cells gives the athlete an increased number of red blood cells. It is illegal in most competitions. Risks include blood coagulation in the arteries presenting a risk of death.