Final answer:
An athlete with weakened obturator externus, gemellus superior, and piriformis muscles would have limited external rotation of the hip joint.
Step-by-step explanation:
The athlete with weaknesses in the obturator externus, gemellus superior, and piriformis muscles would likely experience limitation in the movement of external rotation of the hip joint. These muscles are part of the lateral rotators of the femur at the hip, which are responsible for external rotation. Therefore, if these muscles are weak, the athlete's ability to externally rotate the hip will be compromised.