1. Your Performance Will Be Less Than Average
Even one night of little sleep can affect your workout. Reaction times decrease and performance on tasks like driving and even handling heavy weights declines. That means your cognitive function (your ability to think straight, put in layman terms) is also affected greatly. It becomes harder to make decisions and memory is impaired. Plus, sleeplessness increases sensitivity to pain. That means your workout will feel all the harder even when you arent working as hard as usual, and your sore muscles boy will they be sore!
2. Your Risk for Injury Increases a Lot
You need to make sure that when you step into the gym, even if the workouts are very easy to you, you can stay focused. Like with driving, even if its something you are very much used to, you need to focus because one bad moment can hurt you. When you suffer from sleep deprivation your reaction time is slower, and your thinking skills and judgment are clouded by fatigue, so your risk for injury goes up a mile. Why should you risk an injury just to get bragging rights about having been to the gym for the day? It is better to rest and approach your workout with fresh enthusiasm because you are rested and operating at peak efficiency.
3. It messes up your immune system too
It does not take a lot of accumulated sleep deprivation to cause damage. Even if its been a few days of little sleep your health will be influenced. Your cortisol levels will grow- and if youre not sure, cortisol is a stress hormone. Because of this, your ability to fight infections will decrease. Combine that with the added stress of a hard workout, and you put yourself at greater risk for whatever virus happens to be super popular in that period. Wink wink, brace yourself winter is coming, you know? When youre exhausted, you need rest to lower your cortisol levels and get your immune system back up.
4. The effects add up whether we like it or not, and are hard to erase
One bad night of sleep cannot be erased by one extra night. We all know this, and yet we all try to prove Mother Nature wrong when it comes to sleep deprivation. The truth is that if we skip a beat with our sleep, we have to get a lot of rest to make up for it. If it wasnt so, we would get no sleep during the week, and then in the weekend just sleep for 2 full days, and be super-fresh on Mondays. But our bodies work differently, so proper sleep needs to be a consistent habit if we want to stay healthy and fit.