Workouts generate stress, which we athletes feel as fatigue. Later, as we rest, our body shifts into repair mode. It is during this time that the rewards for all that hard work are received.
If fatigue leads to improvement, then more is better, right? Wrong! When we carry too much fatigue, our body spends all of its resources trying to catch up. There will be no improvement in fitness, and quite possibly a decline. Your goal should be to walk along the narrow path between too little and too much stress, to do just enough. Stay on the path and your fitness will improve. Go off course either way and there will be no improvement.
A popular term for this concept is minimal effective dose, which is the smallest input required to produce the desired result. In our case, the result we desire is a successful race performance. What is the minimal dose, the least stress, necessary to achieve that result?
The amount of stress a person can absorb is highly individual. One of the characteristics of world class athletes is their ability to tolerate a lot of training stress without breaking down. This is not a matter of will power, or grit, or toughness. The ability to absorb stress starts with the genes you were born with and can be extended, quite a bit, by how carefully you increase your training load.
A good rule of thumb is to never feel seriously fatigued during training. Should you find yourself dragging through your day, take it as a signal that you have been working too hard. You need to back off, or risk an overuse injury that will sideline you for weeks and possibly ruin your year. Remember, stress is stress. Work, family, training. It all piles on. Control what you have control over, and that most likely will be your training.
The principle of doing just enough applies to a lot more than training. One activity it does not apply to is sleep. I said at the start of this piece that when we rest is when our body responds to the stress we have applied by making us stronger. The most effective rest is sleep, and for that, you can’t get too much.