The UKK Walk Test, developed by the Urho Kaleva Kekkonen Institute for Health Promotion Research (the UKK Institute), measures the most important factor of a person's fitness, endurance, or cardiorespiratory capacity. It suits almost anyone between the ages of 20 and 65 years who does not have a disease or disability thah prohibits brisk walking or who is not taking a medication that affects heart rate. The UKK Walk Test also provides reliable test results for people who are overweight. However, its is not recommended for those who are extremely fit. The test is performed by walking 2 kilometers on a flat surface at as briks pace as possible. The results of the test are recorded as a fitnees index, which takes into consideration the person's age, gender, height, weight, time taken to walk 2 kilometers, and heart rate at the end of the test. The index has been used to form five „fitness classes“, which can be used to compare the individual result with the fitness of others of the same age. By performing the test at suitable intervals a preson can reliaby follow the changes that occur in his/her own fitness. The test should be performed under guidance, because then the results are reliable. Many different factors can cause an incorrect result and therefore affect the success of the test. Such factors are, for example, incorrect measurement of the distance, a non-flat surface or hilly terrain, and an incorrect recording of the time or heart rate. In addition unsuitable clothing or careless preparation for the test can spoil the results. The results can also be distorted by walking too slow, health factors that limit brisk walking or medication that affects heart rate. The UKK Walk test was developed especially to assess cardiovascular fitness by measuring its gold standard, maximal aerobic power (VO2 max). In later studies it was also found that the test reflects the functional capacity of the musculoskeletal system. Therefore the UKK Walk Test is well suited for assessment of health-related fitness among the general population.