Related Clues:

• Humans, among others
• See 30-Across
• Speed
• Move it
• It starts and ends with a line
• Derby, for one
• Derby, e.g.
• Mudder's day event
• Hustle
• Census datum
• 440 or 10K
• 100-meter, e.g.
• Hurtle
• 10K, e.g.
• Three-legged endeavor