Circadian Rhythms and the Effect of Jet Lag on Human Performance Mike Plyley, Ph.D., Brock University National Coaching Institute NCCP Level 4/5 Task 5 - Environmental Factors

Statement of the Problem Global village leads to competition across many time zones Global village leads to competition across many time zones Leads to disruption of the body’s natural circadian rhythms Leads to disruption of the body’s natural circadian rhythms Symptoms include: Symptoms include: Fatigue during the day inability to sleep at nightFatigue during the day inability to sleep at night Decreased mental performanceDecreased mental performance Loss of stamina and coordinationLoss of stamina and coordination Loss of appetite, headachesLoss of appetite, headaches

Circadian Rhythms Normally set to a 25 hour rhythm, but light cues reset the rhythms to a 24 hour period Normally set to a 25 hour rhythm, but light cues reset the rhythms to a 24 hour period Circadian rhythms include body temperature, hormones, electrolytes, muscle strength Circadian rhythms include body temperature, hormones, electrolytes, muscle strength Affects performance, alertness, fatigue Affects performance, alertness, fatigue Centre for control is located in the front tip of the hypothalamus, and is linked by nerves to retina Centre for control is located in the front tip of the hypothalamus, and is linked by nerves to retina

How your body keeps time The "pacemaker" is called the suprachiasmatic nuclei, an area that regulates the firing of nerve cells that seem to set your circadian rhythms. The "pacemaker" is called the suprachiasmatic nuclei, an area that regulates the firing of nerve cells that seem to set your circadian rhythms. Scientists can't explain precisely how this area in your brain "keeps time." They do know your brain relies on outside influences, "zeitgebers", to keep it on a 24h schedule. Scientists can't explain precisely how this area in your brain "keeps time." They do know your brain relies on outside influences, "zeitgebers", to keep it on a 24h schedule. The most obvious zeitgeber is daylight. When daylight hits your eyes, cells in the retinas signal your brain. Other zeitgebers are sleep, social contact and even regular meal times. They all send "timekeeping" clues to your brain, helping to keep the circadian rhythms running on schedule. The most obvious zeitgeber is daylight. When daylight hits your eyes, cells in the retinas signal your brain. Other zeitgebers are sleep, social contact and even regular meal times. They all send "timekeeping" clues to your brain, helping to keep the circadian rhythms running on schedule.

Bodily Rhythms Sleep and wake - Your sleep follows a circadian rhythm. You're most likely to sleep soundly when your temperature is lowest, in the wee hours of the morning. You're also most likely to awaken when your temperature starts to rise around 6 to 8 a.m. As you age, your brain's "pacemaker" loses cells. This changes your circadian rhythms, especially noticeable in how you sleep. You may nap more, have disrupted sleep and awaken earlier. Temperature - Temperature is lowest when you're inactive. Although activity makes temperature rise, it still follows a definite circadian rhythm. In the late afternoon, your temperature can be as much as 2 degrees Fahrenheit higher than in the morning, and it will rise and fall even if you never see daylight.

Bodily Rhythms To some extent, most hormones are regulated by circadian rhythms, e.g., cortisol affects many body functions, including metabolism and regulation of your immune system. Its levels are highest between 6 and 8 a.m. and gradually decline throughout the day. If you change your daily sleeping schedule, the peak of cortisol's cycle changes accordingly. Growth hormone stimulates growth in children and help maintain muscle and connective tissue in adults. Sleep triggers hormone production, regardless of when you go to bed; however, production peaks during the first two hours of sleep. If you're sleep deprived, production drops.

Bodily Rhythms Cardiovascular System More strokes and heart attacks occur in the morning than at any other time of day. Blood clots most rapidly at about 8 a.m. Blood pressure also rises in the morning and stays elevated until late afternoon, then drops off to its lowest point during the night. These changes occur independently of physical activity. Exercise at any time of the day is beneficial. On the other hand, if you're training for athletic competition, you may have reason to schedule that event later in the day. Athletes seem to perform best in the late afternoon, when strength, body temperature and flexibility peak.

Bodily Rhythms Pain tolerance Athletes who compete late in the day may perform better because they can "gain" without as much "pain." Pain tolerance is highest in the afternoon. One study shows tooth pain is lowest in the late afternoon, a consideration when you schedule your next dental appointment!

Circadian Rhythms – Mental Component

Circadian Rhythms – Mental Alertness

Circadian Rhythms – Body Temperature Other effects include HR, VE, BP

Melatonin Hormone known to control the generation of the various circadian rhythms Hormone known to control the generation of the various circadian rhythms Natural surge from 11 pm – 7 am Natural surge from 11 pm – 7 am Exogenous administration of melatonin causes hypothermia Exogenous administration of melatonin causes hypothermia Chronobiotic - can reset internal circadian rhythms Chronobiotic - can reset internal circadian rhythms

Recommendations – Before Travel Set departure time to permit one day of adjust- ment at the new site for each time zone traveled Alternate one day of fasting and one day of eating prior to departure – this make the body more sensitive to time cues in the new zone Use meal times closer to the new zone on the day before departure Train for 2-3 days close to the time of the new zone Can, if necessary, adjust bed and wake times prior to departure Be careful of disrupting living patterns at home

Recommendations – During Travel Fast or eat sparingly on the flightFast or eat sparingly on the flight Avoid alcohol, drink 1.5 L water per hour of flight timeAvoid alcohol, drink 1.5 L water per hour of flight time Stretch and move regularly during the flight Stretch and move regularly during the flight Eat low fat foodsEat low fat foods

Recommendations – Upon Arrival Eat all meals at meal time of arrival site Expose to light in the morning at arrival site waking time Eat high protein meals for breakfast and lunch to stimulate adrenaline Eat high carbohydrate foods at dinner to initiate serotonin release and relaxation 2-3h post-meal Do light aerobic activity as soon as possible upon arrival and in the mornings Match bed time immediately to new zone – can use short naps in the afternoon Extra sleep on first night can speed adaptation

Recommendations – Upon Arrival Avoid the use of sleeping pills For other medication - scientists are looking at how circadian rhythms affect the way your body uses medications. One finding is that less anesthesia is needed to cause analgesia or drowsiness when administered in the afternoon. Experiments with cancer medications have shown that there are particular times of the day that the drugs are more effective, and show fewer side effects. Stay on schedule as changes in one’s daily habits such as a short night's sleep can disrupt your circadian rhythm. You may be able to stay "in sync" by keeping a consistent daily schedule.

Resources A jet lag calculater can be found at jet lag calculater can be found at A well written primer on jet lag by Thomas Reilly can be found at sportsci.org/encyc/jetlag/jetlag.htmlA well written primer on jet lag by Thomas Reilly can be found at sportsci.org/encyc/jetlag/jetlag.htmlhttp:// sportsci.org/encyc/jetlag/jetlag.htmlhttp:// sportsci.org/encyc/jetlag/jetlag.html Ask Suzy about the “anti jet lag” dietAsk Suzy about the “anti jet lag” diet