system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If our muscles become stronger after repeated use, why does our neck always get sore after looking down at our phone for too long?
gpt
Because you're not using your neck muscles when you stare down at a phone, you're keeping them static and stretched for long periods of time. Muscles benefit from repeated contraction, while static prolonged stretching weakens them over time.