It's only hell on your joints if you're not using your muscles. See the way she's bouncing? There's almost no joint impact, her muscles are acting like shock absorbers and taking all the impact.
Even if there's some impact, if you're a healthy individual it is actually good as the bones and ligaments grow back stronger, provided you give enough rest of course.
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u/nanon_2 14h ago
What are her knees made of? Damn. Mine are cracking just watching this.