• Your effort
• Your shoes
• Whether you have any external weight on you, such as a hydration vest
• The terrain you're running on
• The weather conditions
• Your hydration status
• If you had adequate rest the night before
• Your training volume
• The type of training you do. (E.g. weightlifting or cross-training.)
• How much running experience you have
• Genetics and physical factors, such as the length of your legs
• Your mood and the music you listen to can affect your running performance

Run training that can help you become a faster runner:

• Tempo runs help to develop your anaerobic or lactate threshold. Run at an easy pace for five to 10 minutes, then run about 10 seconds slower than your 10K pace for 15 to 25 minutes, then finishing up with another five to 10 minutes of easy running.
• Interval runs include segments of fast running followed by segments of easy running or walking.
• Fartlek runs are like interval running, except that it's based more on how you feel.

• Hill runs. Running up and down hills helps to strengthen your legs and lungs.
• Trail runs allow for a varied terrain that can make you a faster runner on roads.
• Distance runs sprinkled here and there will improve your endurance.
• Sprinting sessions once or twice a week can improve your speed.
• Easy runs help you to adapt to all the training you are doing.