Detailed Instructions: In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
Q: What do gymnasts have to overcome with their muscle force?, Context: A higher flight phase results in a higher vertical ground reaction force. Vertical ground reaction force represents external force which the gymnasts have to overcome with their muscle force and has an impact on the gymnasts linear and angular momentum. Another important variable that affects linear and angular momentum is time the landing takes Gymnasts can alter the shape of the area by increasing the time taken to perform the landing. Gymnasts can achieve this by increasing hip, knee and ankle amplitude. With the increase of height, the amplitude in ankles knees and hips rise the bars.
A:
external force