Wednesday, October 16, 2013

Can Strength Training Help You Sleep?

About one-third of Americans sleep less than six hours per night [1]. Just a few days of sleep loss increases blood sugar, and long-term deprivation greatly increases the risk of diabetes. Due to a variety of causes, many struggle with consistently attaining at least seven hours of sleep per night. Thankfully, strength training helps...but only for some.

Research shows that strength training improves sleep quality and quantity in less than three months. My personal experiences with clients suggest that people can start sleeping better in less than two weeks. However, this doesn't happen for everyone. Some people are unaffected, and some are partially affected.

As far as why it may work for some, strength training improves growth hormone levels, and growth hormone is linked to the quantity of REM sleep. Strength training also may benefit sleep-preventing respiratory issues.

Strength Training and Sleep

Thanks to inactivity, increased sensitivity to light, elevated autonomic nervous system activity, changes in Circadian rhythm, medication side effects, hormonal changes, and illnesses, sleeping becomes increasingly more difficult with age [2]. It only makes sense that strength training is considered as a sleep aid: it does not require a lot of time, it's an intense activity that could increase fatigue at night, and inactivity is a contributor to sleep loss.

Fortunately, strength training does help, but the effects are not universal. A 1997 study lead by a Harvard researcher found that strength training was able to improve sleep quality in 40% of the group [2]. The other 60% did not digress, but also did not improve.

The study placed older adults with sleeping issues into one of two programs for 10 weeks: strength training or a health education group. The strength training group lifted highly challenging weights, involving all of the major muscle groups, for three workouts per week. The other group served as a control, focusing on health education and socializing during twice-weekly visits. The strength training program was about two-to-three-times more effective for improving sleep, which was assessed through detailed questionnaires. 

A more recent study from Texas Tech University also supported strength training's benefit for sleeping, showing a 38% improvement in self-rated sleep quality after three months of training [3]. This study was performed with people who were "good sleepers" to begin with. This demonstrates that strength training can also help those who already have good sleep habits. 

Both studies showed that there were no differences between genders - strength training should aid sleep quality with men and women equally.

Experiences in My Practice and Underlying Reasons

As mentioned, the 1997 study showed that a strength training program either improves sleep or has no effect. This is consistent with what I have found in my training practice. I typically find one of three scenarios occur:
  1. Strength training improves ability to fall and stay asleep, and this happens within two or three weeks. 
  2. The trainee sleeps better on workout nights, but no differently otherwise.
  3. No effect whatsoever.
The researchers offered no explanation for why weight training is beneficial for some, but the reason could be hormonal. Growth hormone levels are connected to REM sleep [4], and strength training increases growth hormone. In addition, many struggle to sleep due to respiratory issues and strength training may improve sleep apnea. A friend of mine is a physician with the Mayo Clinic in Scottsdale, AZ, and she has noticed her patients with sleep apnea begin to sleep better after starting intense strength training programs. Many of these patients do not lose weight, so the improvement can't be attributed to obesity changes. She now refers her sleep apnea patients to facilities with such programs.

As detailed in the 1997 study, strength training poses no detriment to sleep quality. I highly recommend those who struggle getting quality rest to start strength training. If it doesn't work, the consolation prize will be better physical appearance, more strength, and thicker bones.

*Thank you to Dr. Ben Bocchicchio, who contributed to the information presented in this post.

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