Q: Why is it difficult to throw a ball while treading water (as in water polo)?
⚙️ Biomechanical Insight
When throwing a ball on solid ground, a person relies heavily on a stable base — particularly the legs — to generate force. The throw involves a complex kinetic chain beginning from the ground, moving through the legs, hips, trunk, shoulder, and arm.
On land:
- The legs act as a firm anchor.
- They provide a reaction force necessary for rotational torque.
- This stability helps generate speed and accuracy in the throw.
🌊 In Water: Why It’s Difficult
When treading water, especially in water polo, the mechanics change entirely:
- The legs are continuously moving to keep the player afloat.
- This movement prevents them from providing a stable base for pushing off.
- As a result, the body lacks reaction force from the legs.
- This makes hip and trunk rotation less effective, weakening the power and accuracy of the throw.
🔍 Key Point: It is hard to generate the required reaction force through the legs while treading water, which significantly reduces throwing effectiveness.
✅ Final Answer
The correct reason why it is difficult to throw a ball while treading water is:
D. It is hard to generate reaction force with the legs
Because the legs cannot anchor and push against a solid surface, the kinetic chain is disrupted and power generation is significantly diminished.