Newswise — Athletes regularly feel mentally fatigued. Mental fatigue impairs sport performance and could lead to a higher injury risk. Yet, the current functional performance tests (FPTs) do not include important mental aspects for sports. The medical staff in sports often use FPTs for several reasons like determining if an athlete has a higher risk injury. Traditional FPTs are usually very simple (e.g., jumping as far as you can on one leg). More recently, researchers built a new FPT that contains mental aspects. This test is the reactive balance test. Yet, it is unknown if mental fatigue can affect traditional FPTs or the new reactive balance test. This is important since mental fatigue could influence the test scores without anyone knowing. In this study, researchers found that mental fatigue did not influence traditional FPTs but impaired the new test. This means that mental fatigue can be present when athletes are performing traditional FPTs without anybody knowing. The reactive balance test can be key in detecting the impact of mental fatigue during physical testing. Thus, it is important to make new FPTs that add mental aspects to physical testing to better help athletes and medical staff.