Your fitness routine is in full swing two months into the year: You're eating right and you're exercising, but you're not yet seeing the results you want.
What's missing? It might be sleep.
"You can have two people who are doing the exact same workout and eating the same good nutrition, but one is seeing huge progress and the other isn't. A lot of the time, good sleep is the difference," said Mansur Mendizabal, a personal trainer and kettlebell instructor in Washington.
"Sleep is the only time the body is fully recovering and rebuilding," he said.
Sleep — specifically deep sleep — is the difference when it comes to such things as muscle recovery, mental acuity, and reaction time, another important aspect of sports performance.
"It's during the deep stages of sleep that all the tissues of the body repair," said John Broussard, a sports medicine doctor in Washington. "But you have to get into all the stages of sleep in the proper sequence to get those restorative benefits."
There are four parts of the sleep cycle: Stage 1 (nearawake), Stage 2 (onset of sleep), Stage 3 (deep and restorative sleep) and Stage 4 (deep REM or dream state), which occurs at about 90 minutes into each cycle.
Lack of sleep affects our cognitive and motor performance, Broussard said.
"We are performing every day no matter what the setting is."
But let's say the setting is the gym. What are the recommendations for adequate sleep, and what exactly does that sleep do for our muscle tissue?
"Many people think you build (muscle) in the gym, but you actually build when you sleep," says Chirjeev Sawhney, a personal trainer and fitness manager at a Gold's Gym in Arlington, Virginia.
This is because, during deep sleep, the body uses the protein you consumed the day before and the growth hormone is produced (also in deep sleep) to repair the muscle tissue you tore up during your workout, Sawhney said.
"It's when you repair that broken tissue that you get stronger," he said.
In fact, when Sawhney gets a new client, he makes sure sleep is discussed at some point during the first few sessions.
Mendizabal agreed that sleep needs to be addressed.
"Sleep needs to be made a priority. If you don't sleep, your body is stressed, you crave food, your immune system is compromised," Mendizabal said. But he recognizes that it isn't possible for everyone to get the seven to eight hours recommended by the National Institutes of Health.
"Six hours is more realistic. But on a report card, that would be the equivalent of a D," he said.
For those who want to improve their grade to an A, Broussard recommends the following measures:
Make sure you have a bright work environment during the day.
Try to spend at least one hour outside every day.
Try to create stress-free evenings.
Take magnesium or melatonin, both of which have been shown to lessen muscle tension and anxiety, before bedtime. Warm milk can also help.
Make sure your bedroom is cool and dark, with no TV or other electronics (especially no blue screens, as they make it harder for the pineal gland to produce melatonin).
Don't keep your phone by the bed unless you use it as an alarm clock (if so, turn on the do-not-disturb function and don't check texts or emails).
Gabriella Boston is a fitness trainer and freelance writer. She can be found at gabriellaboston.com.