Megan Brooks

June 14, 2016

DENVER — Three days of sleep restriction slows metabolism and impairs performance in elite cyclists, a new study shows.

Elite athletes often don't get enough good-quality sleep, but little is known about the effect of this on physiology and exercise performance, Cheri D. Mah, from the Human Performance Center, University of California, San Francisco, noted in her presentation of this late-breaking study here at SLEEP 2016: 30th Annual Meeting of the Associated Professional Sleep Societies.

To investigate, her team enrolled 12 healthy 18- to 35-year-old elite male cyclists in a randomized crossover study. The cyclists had their sleep restricted from 8 hours to 4 hours for 3 days or extended to 10 hours for 2 weeks, with a 2-week washout period in between. Dr Mah presented only the sleep restriction findings here.

Outcome measures before and after the intervention included a 20-minute submaximal exercise test, a 1-minute incremental maximal exercise test, and a maximal time to exhaustion test on a bicycle ergometer and metabolic collection system, as well as the Psychomotor Vigilance Task (PVT).

After 3 days of sleep restriction, time to exhaustion decreased by 51 seconds, a difference of 14.4% from baseline, at which time they were getting 7.4 hours of reported sleep, Dr Mah reported.

In addition, maximal aerobic power decreased 2.8% (P < .05). Dr Mah noted that maximum volume of oxygen did not change with sleep restriction, "and this is consistent with our hypothesis that their aerobic capacity would not change with restricted sleep but that they would have a performance decrement, which is what we observed."

Submaximal heart rate also decreased after sleep restriction, as did peak heart rate (both P < .01). Metabolism also took a hit with short sleep; energy expenditure during 20 minutes of submaximal exercise decreased by about 4% (P < .001). There was also a slowing of response time of 15.5% on the PVT (P < .05).

"These findings suggest that sleep loss results in performance impairments, including decreased peak power and endurance performance, as well as decreased response speed in elite athletes," Dr Mah said.

Strong Study, Important Findings

"This is a strong study, with consistent findings that complement our research," Namni Goel, PhD, a sleep researcher at the University of Pennsylvania Perelman School of Medicine in Philadelphia, who wasn't involved in the study, told Medscape Medical News.

"What we've found in the laboratory working with healthy adults who don't necessarily exercise a lot is that with chronic sleep restriction people overeat and their energy expenditure drops. So even in people who are exercising a lot, you see this, and that is a very important finding because it means the changes might be even bigger in people who are not as fit," Dr Goel said.

She's not surprised by the findings. "You can't work at your potential when sleep deprived. It would be interesting to see how fast they recover," Dr Goel said.

In her research, she noted, "recovery depends on the kind of sleep loss, if you just lose one night of sleep when you're up all night, performance comes back after 1 day of sleep recovery, that's what we find, but if you are chronically sleep deprived some of the measures don't come back even after 4 nights of recovery."

The study was supported by the National Center for Advancing Translational Sciences, National Institutes of Health. The authors have disclosed no relevant financial relationships.

SLEEP 2016: Annual Meeting of the Associated Professional Sleep Societies. Abstract LBA3. Presented June 13, 2016.

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