One of the number one mistakes runners make when training for a goal time is they go all out all the time. It is an easy trap to fall into. You are training, your endurance is getting better it makes sense to try to up and up the speed on the treadmill or hit a pace on your garmin on each run. There are a couple problems though with this training strategy.
1. It isn’t maintainable: Without easier days we are always pushing our bodies to the max. Training programs are set up to create a pace range that you fall into over the week. Without easier days (that still work on building mitochondria our CO2 eating bacterial friends that live in our muscles) we don’t develop a stimulus/recovery curve. When we do a workout we tear down our body telling it to rebuild stronger. If you go 100% all the time all you have is stimulus. Therefore each workout you are breaking down your body more and more until you can’t even run anymore. People who go all out all the time are perfect candidates for stress fractures, plantar faciitis, and achilles tendonitis.
2. Improvements in speed are marginal when we go all out all the time.: So maybe you are an injury resistant person. Maybe your body is tough. Maybe the above argument isn’t enough to convince you to slow down. (You will get hurt btw. Maybe it will take a couple years but you WILL get hurt!) However, even if you are made of steel going all out will leave your legs feeling like lead every day and most detrimental on your speed days. If you go all out all of the time you will be behind in your training than the person who is fresh for their speed work.
Think about every speed workout you do like buying stock. This speed “stock” will mature for you roughly every two weeks helping you move faster then. If you go all out every day you won’t be able to hit your times during speed work. (and if you can hit prescribed times going 100% every day that means you could be going even faster!) If you don’t hit a speed workout you won’t have any stock to mature. Your daily runs may begin to be faster by 5 to 10 seconds a mile if you push hard every day, but good speed work can increase your race pace by minutes!
Overall a training program is like a game of mother may I and your body is the mother. We all want to sprint to the end, but that never works. Eventually the mother turns around sees us moving too fast, and sends us back to the start. Train hard, but train smart. Keep your easy run days easy. Your body and finish time will thank you!