05/16/2014 01:12 pm ET Updated Jun 27, 2014

3 Predictors of Whether You Will Win the Battle Against the Underrecovery Monster

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Recovery is your ability to meet or exceed performance in a particular activity.

I'll say that again.

Recovery is your ability to meet or exceed performance in a particular activity.

This means that if you walk into your workout and you can't achieve a marked improvement in how much you can lift or how fast you can move, you're battling the underrecovery monster. And if you're exercising in that underrecovered state, then you either don't care about performance or you're just exercising because it feels good or you're addicted to exercise or you don't mind prematurely destroying your body and joints. Perhaps all of the above.

So let's look at three predictors of whether you will win the battle against the underrecovery monster and meet or exceed performance week after week: your muscles, your nerves and your blood.

Predictor #1: Your Muscles

As you probably know, after you workout, your muscles look like a scarred battlefield, especially if it's an impact based workout or one that involves some deceleration, such as running or weight training. This is because every time you strain your muscles with exercise, there is trauma to the muscle fibers.

Of course, this is a good thing -- based on a phenomonon called "hormesis." Hormesis is a biological reaction whereby a beneficial effect (improved health, stress tolerance, muscle growth, longevity, etc.) results from exposure to low doses of an agent that could be otherwise toxic or lethal when given at higher doses. So sure, exercise could kill you if you do it enough, but in low, moderate or controlled doses, sane exercise exposure can give you hormetic benefits. Other examples of hormesis which I discuss in my new book include fasting, calorie restriction, cold temperature, heat shock, low level radiation and germs exposure. In other words: Things that are bad in high amounts can be good in low amounts.

So muscle injury is a form of hormesis and is something that is good in controlled amounts. This is because once a muscle fiber gets injured, muscle cell organelles respond with inflammation and activate satellite cells, which are located on the outside, but very near to your muscle fibers. A biological effort to repair or replace damaged muscle fibers begins with the satellite cells fusing to each other and fusing to the muscles fibers. This not only repairs the muscle, but can also lead to increases in muscle fiber cross-sectional area or even the create of new muscle protein strands, called myofibrils.
Some of these satellite cells serve as a source of new nuclei so you can synthesize more proteins and create even more contractile myofilaments in your muscle, known as actin and myosin.

Unfortunately, especially for anyone restricting calories, eating a low fat diet, or simply training too much, most of these repair adaptations are severely hampered, since you probably happen to be low in growth hormone or Insulin Like Growth Factor, both of which stimulate satellite cells to produce the gains in the muscle fiber size. Insulin also stimulates muscle growth by enhancing protein synthesis and facilitating the entry of glucose into cells. Your satellite cells actually use glucose as a fuel to enable their cell growth activities.

Testosterone also affects muscle fiber repair. This is because testosterone can stimulate growth hormone responses in your pituitary gland, which then enhances cellular amino acid uptake and protein synthesis in muscle. In addition, testosterone can increase the presence of neurotransmitters at the fiber site, which can also help to activate tissue growth, and interact with nuclear receptors in your DNA, resulting in protein synthesis. So low testosterone status, especially when it comes to growth hormone, testosterone and insulin means you're going to take way longer to recover.

So how long should all these mechanisms described above actually take? Researchers have found that muscle protein synthesis increases by about 50 percent for four hours after a workout. This is evidence that muscles are repairing damage accrued from the workout, and also building new material to make themselves stronger and more fatigue-resistant. This repair process appears to peak about 24 hours after a workout, at which point muscle protein synthetic rate goes up by a hefty 109 percent. By about 36 hours after a workout, the whole process is pretty much complete, and muscles are back to their normal status. So every time you beat up and tear down muscle fibers, especially with running and weight training, you're looking at an approximate 36-hour recovery time before another true high quality session is realistic.

Predictor #2. Your Nerves

When you need to contract a muscle, a message goes down your brain and spinal cord where it eventually connects to individual muscle motor units through a neuromuscular junction. The muscle then receives that contractual message and fires.

But in the same way that muscles can fatigue, or become torn and injured, training can also damage your nervous system. This is called neural fatigue, and can drain both your central nervous system, or the local nerves at the muscle sites themselves (the neuromuscular junctions), that join your nervous system and the muscle together.

The main reason for this is because your body releases inflammatory cytokines (chemical messengers) in response to muscle damage induced by your training. These inflammatory messengers dock on receptors in your central nervous system and thus hamper neural recovery. But unlike muscle damage, nerve fatigue doesn't just result from training, but can also be due to other nervous system stressors such as lack of sleep, drugs, stimulants, alcohol or lifestyle and relationship stress (yes, an argument with your significant other can cause massive cytokine releases, an issue I discussed in a recent anxiety podcast).

Since your nervous system is basically the "battery" that fires all your muscles, if your nervous system is under-recovered, then the strength and function of your muscles is negatively affected. So your muscles could be primed and ready to rumble, but if your nervous system is under-recovered, you're still screwed -- and this is why you can still get overtrained or underrecovered even if you're not exercising excessively, but perhaps partying too much, working too much, not sleeping enough, or experiencing poor relationships.

And it's important to know that your central nervous system doesn't differentiate between muscle groups. If it's fatigued, it's fatigued. So if you do a hard run today, then head to the gym tomorrow, you may find that your strength on an overhead press is negatively effected -- and unless your run on your hands and shoulders, that's not muscle fatigue -- it's nervous system fatigue. When it comes to this issue, low-level, aerobic cardio don't really create as much neural fatigue as high intensity cardio and sprints, which is why you can intelligently stack your week to alternate aerobic and anaerobic sessions if you want to allow for prime neural recovery.

So how long does that neural recovery actually take? In most cases, when your nervous system is drained from high intensity efforts or too much stress, it needs 48 hours to fully recover. Any intense training you do within that 48-hour window simply drains the nervous system even more. So this is why you can't simply do hardcore workouts day after day, even if they're performed for different muscle groups, or with different activities. Eventually, your nervous system will simply poop out.

Of course, you can also drain the local nerves that feed into specific muscles as well -- which are those neuromuscular junctions I mentioned earlier. And when it comes to local neuromuscular fatigue, it can take up to four days before that links between your muscles and nervous system is fully recovered, which means that workouts which heavily stress the same muscle group may need as many as four days before having complete neural recovery.

This completely explains why you can have a crappy workout even if you're not sore -- either your central nervous system or your neuromuscular junctions simply haven't recovered.

Predictor #3. Your Blood

Finally, if you're banging your head against a brick wall because you've been giving your muscles and nervous system adequate recovery, but still aren't performing at your desired capacity, then you may want to take your blood into consideration.

Angiogenesis is the process via which new blood vessels form from pre-existing vessels. Increased muscle activity and contractions increase angiogenesis -- so during the recovery period after a workout, you produce new blood vessels and capillaries that feed into the working tissue. Numerous studies have shown that the capillary density, expressed as the number of capillaries per muscle fiber, do indeed increase in response to training and recovery.

Researchers have also found increases in reticulocyte counts (new red blood cells) as a response during the tapering period from hard workout blocks, which suggests an increased erythropoiesis (red blood cell production) during recovery.

Another adaptation that takes place in your blood in response to training is an increase in eosinophils, the white blood cell components that can detox some of the inflammation inducing substances in the body, and destroy allergen-antibody complexes, as well as an increase in lymphocytes, the white blood cells that fight infection. Interestingly, this is why people who are under-recovered may not only get sick more, but could also tend to be more susceptible to food allergies and food intolerances. So if you're getting sick much, short of breath often, or experiencing lots of issues with digestion, it could be a blood under-recovery issue -- even if your muscles and nerves are just fine.

So that's it -- the three predictors that will determine whether you'll win the battle against the underrecovery monster -- or whether you'll just keep banging your head against a brick wall every time you step into your workout. Now that you know the importance of these three parameters, you can read about how to optimize your recovery after a workout. If you have your own tips about recovery, or questions about muscles, nerves and blood, then leave your thoughts below.