Sleep And Exercise

Sleep  is  critical  to  normal  physiological  and  psychological  function,  and  people  spend  nearly  one third of their lives asleep. Usual sleep duration is considered to be between 7 and 9 hours per night for  healthy  adults.  The  different  stages  of  sleep have  historically  been  defined  according  to  the 1968 classification rules of Alan Rechtschaffen and Anthony Kales (R&K) as wakefulness, one of four stages of non-rapid eye movement (NREM) sleep (S1, S2, S3, and S4), or rapid eye movement (REM) sleep.  The  American  Academy  of  Sleep  Medicine (AASM)  modified  these  standard  guidelines  and recommended that NREM sleep be referred to as N1, N2, and N3, with N3 reflecting R&K stages S3  and  S4,  and  Stage  REM  to  be  referred  to  as Stage R. A normal sleep cycle (consisting of all the sleep  stages)  lasts  for  approximately  90  minutes and is repeated throughout the night.

Sleep can be measured by several different methods.  Self-reports  such  as  sleep  logs  or  diaries  are helpful  to  determine  trends  over  time.  However, these are subjective and rely on accurate recollection by the individual. Actigraphy is a method of measuring  body  movement.  For  the  purpose  of measuring  sleep,  these  devices  are  typically  worn on  the  wrist  and  periods  of  low  activity  scored as  “sleep”  and  periods  of  high  activity  scored  as “awake.”  Due  to  its  noninvasive  nature,  actigraphy  has  been  used  widely  as  a  tool  to  measure sleep quantity and quality over lengthy periods of time  and  in  the  normal  (home)  sleeping  environment,  although  the  method  cannot  determine  the different stages of sleep or transient arousals from sleep.  Polysomnography  is  acknowledged  as  the gold  standard  method  of  measuring  sleep,  as  it allows  assessment  of  all  sleep  stages  and  is  used widely to assess the presence and severity of sleep disorders.  Polysomnography  requires  many  electrodes to be attached to the scalp and face in order to  measure  brain,  eye,  and  chin  muscle  activity, and sensors on the chest, finger, and face to monitor cardiorespiratory parameters.

Effects of Acute Exercise on Sleep

Normally,  core  body  temperature  peaks  in  the early  evening,  starts  decreasing  prior  to  bedtime, and reaches its minimum in the early hours of the morning. Exercise in the evening is known to raise core temperature, which could potentially oppose the normal pre-bedtime decrease and interfere with sleep onset. This is one factor underlying the current  recommendations  that  exercise  should  only be  performed  5  to  6  hours  before  bedtime  and no  closer  than  3  hours  prior  to  sleep.  However, data  supporting  this  widely  accepted  recommendation  are  scarce.  Indeed,  a  study  reported  that high-intensity  exercise  performed  in  the  evening has little effect on sleep in healthy young people. Similarly,  a  meta-analysis  of  the  literature  on  the effect of exercise on sleep, accounting for time of day, showed that acute exercise increased Stage 2 and  slow  wave  sleep,  decreased  REM  sleep,  and increased total sleep time.

Effects of Chronic Exercise on Sleep

There  is  little  research  investigating  the  effect  of chronic exercise among athletes on sleep, although it  has  been  reported  that  those  athletes  who become  overtrained  report  disrupted  sleep  patterns.  In  the  general  population,  regular  physical exercise  is  recommended  as  a  way  to  reduce  the effects of other contributing factors to poor sleep such  as  smoking,  ingesting  too  much  caffeine, overeating, and consuming alcohol.

Effects of Acute Sleep Loss on Exercise

Good  sleep  is  considered  essential  for  optimum athletic  performance  and  is  regarded  as  the  primary  method  of  recovery  from  physical  activity (PA).  Acute  sleep  deprivation  has  been  shown  to negatively  impact  sport  performance.  However, the magnitude of this detrimental effect appears to depend on the specific athletic activity. A literature review  by  Thomas  Reilly  and  Ben  Edwards  concluded  that  the  effects  of  acute  sleep  deprivation or an altered sleep pattern had a marginal impact on  predominantly  aerobic  or  anaerobic  sports (e.g., sprints, power events, running 3,000 meters, swimming  400  meters)  but  a  negative  impact  on sports that required high concentration, consisted of  a  mixture  of  anaerobic  and  aerobic  activities, or  required  multiple  anaerobic  efforts  (e.g.,  field sports,  sailing,  road  cycling,  aiming  sports,  combat  sports,  swimming,  middle  distance  running, jumping events, weight training). The specific performance  decrements  included  poorer  decision making  (DM),  increased  errors,  decreased  power output, and increased fatigue.

Effect of Chronic Sleep Loss on Exercise

Very  little  is  known  about  the  effects  of  chronic sleep  loss  on  athletic  performance.  Case  studies of  ultraendurance  cycling  events,  which  require sustained  periods  of  wakefulness,  report  that,  in order  to  maintain  optimal  athletic  performance, at  least  2  hours  of  sleep  per  night  are  required. Similarly,   a   cluster   napping   technique   (multiple  short  naps)  is  reportedly  adopted  in  ultraendurance sailing to achieve an average total sleep time of 5.5 hours per day, presumably as a method to maintain optimal vigilance.

Jet Lag and Exercise

One of the most common transient sleep disorders experienced by athletes is jet lag due to travel across multiple  time  zones.  Symptoms  of  jet  lag  include disorientation,  light-headedness,  impatience,  and lack of energy. Westward travel tends to be accompanied by less severe jet lag than eastward travel. Athletic performance can be compromised due to jet  lag  as  the  body’s  circadian  rhythms  adjust  to the new time zone.

Undiagnosed Sleep Disorders and Exercise

Undiagnosed  sleep  disorders  have  the  potential to  reduce  athletic  performance.  One  such  prevalent  disorder  among  the  general  population  is obstructive  sleep  apnea  (OSA),  which  is  characterized by repetitive narrowing and/or collapse of the  pharyngeal  airway  during  sleep,  resulting  in reduced blood oxygen levels and multiple arousals from sleep. The repetitive arousals fragment sleep and  have  been  associated  with  decreased  motor function  and  increased  fatigue.  While  usually associated  with  a  sedentary  lifestyle  and  obesity, anatomically predisposed athletes (e.g., high body mass index and large neck circumference) can also be  affected  by  OSA.  One  example  of  this  is  the increased  prevalence  of  OSA  among  American football players, particularly offensive and defensive linemen.

Conclusion

Sleep is critical to both physiological and psychological  function.  Sleep  loss  has  a  negative  impact on athletic performance; hence, education of athletes  and  coaches  on  sleep  hygiene  principles  is needed to minimize sleep loss-related performance decrements.  Sleep  disorders  are  surprisingly  common  among  athletes  and,  if  suspected,  should  be investigated  and  treatment  initiated  in  order  to optimize athletic performance.

References:

  1. Atkinson, G., & Davenne, D. (2007). Relationships between sleep and physical activity and human health. Physiology and Behaviour, 90, 229–235.
  2. Driver, H. S., & Taylor, S. R. (2000). Exercise and sleep. Sleep Medicine Reviews, 41, 387–402.
  3. Reilly, T., & Edwards, B. (2007). Altered sleep-wake cycles and physical performance in athletes. Physiology and Behaviour, 90, 274–284.
  4. Youngstedt, S. D. (2005). Effects of exercise on sleep. Clinics in Sports Medicine, 24, 355–365.
  5. Youngstedt, S. D., O’Connor, P. J., & Dishman, R. K.(1997). The effects of acute exercise on sleep: A quantitative synthesis. Sleep, 20(3), 203–214.

 

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