Impact of Sleep on Athletic Performance

Impact of Sleep on Athletic Performance

Conventional wisdom suggests that if you take a good athlete and give them frequent practice and repetition they will be successful at improving their performance and they will be able to continue to perform at a high level. More recently athletes have become more aware of the connection between diet and athletic performance.

However, there are times when no matter what you do in practice and what food you put in your body you struggle to perform. Sometimes the key to improving athletic performance is to examine your sleep habits. This is even true for professional athletes.

Carlos Gonzalez’s 2017 Season

Carlos GonzalezMajor League Baseball outfielder Carlos Gonzalez, a three-time All-Star, had one of the worst stretches of his career during the first half of the 2017 season with the Colorado Rockies. He hit a meager .221 in the first half with a poor .299 on-base percentage to go along with a .388 slugging percentage. His batting average in June was just .172 and went homerless during the entire month of July.

During this time Carlos tried doing everything he could to get out of his slump, but nothing seemed to work. Then in late August, he went to see a sleep specialist. With the help of the sleep specialist, Gonzalez was sleeping better and was able to turn his season around as he went on a tear in the month of September hitting .377 with a .484 on-base percentage, a .766 slugging percentage, and 6 home runs to go along with 16 RBI.

Gonzalez reported to USA Today Sports that, “It turned out that my sleep was the biggest issue all year for me.” He went on to say, “I had no idea. But once they [the sleep specialist] told me what to do, it completely changed everything for me.” It’s amazing what sleep can do for you, Gonzalez said.

The key for Gonzalez was to keep the TV off when he returned home after night games and tried to get to bed by midnight. He also closed all of the blinds to keep his sleeping environment as dark as possible.

This was a big change for Gonzalez since he was in the habit of staying up until 3 or 4 in the morning watching baseball highlights (like many other ballplayers do) after getting back from night games. This habit made it hard for him to get enough sleep and left him especially sleep deprived going into day games.

Consistently going to bed earlier, combined with avoiding electronics (TV), sleeping in a dark environment, and getting enough sleep, which are all tips we support, had a huge impact on Carlos Gonzalez’s athletic performance.

So is this unique to Carlos Gonzalez?

Where is the evidence the suggests sleep plays an important role in the performance of other athletes? Luckily, there are 2 studies that help address this issue.

Effect of Fatigue on MLB Players Strike-Zone Judgment

Researchers from Vanderbilt University found that strike-zone judgment was worse in September than in April for 24 of 30 MLB teams during the 2012 season. When this data was averaged across all teams it was found that Strike Zone judgment was significantly worse in September than it was in April.

Plate discipline, which was measured by a hitter’s tendency to swing at pitches outside of the strike zone got progressively worse as the season progressed. This decline in plate discipline followed a linear pattern that could be predicted by the data from the 2006 through 2011 seasons. In other words, the data from 2012 does not appear to be a fluke one-time occurrence.

The researchers theorized that the decline in plate discipline that occurs over the course of the season is related to fatigue and disrupted sleep patterns associated with playing a grueling 162 game schedule, the frequency of travel, and the small number of days off. This theory suggests that lack of sleep and fatigue trumps the traditional expectation that plate discipline should improve during the season through frequent practice and repetition.

So it seems that athletic performance can be negatively impacted over the course of a season, but how does lack of sleep impact athletes over the course of their careers.

Relationship Between Sleepiness of MLB Players & Longevity in the League

A study was done to examine the relationship between the sleepiness of MLB players and their longevity in the league. Before the 2010 season, 80 players were asked to self-report scores of sleepiness using the Epworth Sleepiness Scale, with lower scores indicating lower levels of sleepiness. Three seasons later the researchers followed up with these players checking their status to see if they were still in the league

The findings showed a very linear relationship between levels of sleepiness and the likelihood a player was still in the majors. The results found that 72% of players with a baseline ESS score of 5 were still in the majors 3-years later, compared with only 39% of players with a score of 10, and 14% of players with a score of 15.


Regardless of an athlete’s training regimen, it is becoming increasingly clear that ignoring their sleep needs will negatively impact their performance. Proper sleep habits appear to be the next frontier in athletic training and performance.