The Lunge.
Benefits of the Lunge
1. Balance / coordination
2. Promotes healthy metabolism
3. Strengthens muscles throughout the knee and hip structures
4. May lengthen tight muscles
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Most people will find sufficient training effect from bodyweight alone. From there, you may want to advance and hold some sort of weight.
Why medicine balls are effective is because you can get a positive training effect from relatively light weights. It’s great for core stuff also.
To Lunge or not to Lunge…
Verdictum: To Lunge, my friends.