PHYSICAL EXERCISE AND WORKING EXTENDED HOURS

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1 PHYSICAL EXERCISE AND WORKING EXTENDED HOURS Kirsty J. Kerin, Ph.D. Acacia Aguirre, M.D., Ph.D. Introduction Physical exercise is the key to maintaining a healthy body and mind, but exercising can be difficult if you work the night shift. Of more than 10,000 shiftworkers asked about their exercise habits by Circadian, 42 percent reported not exercising regularly. The most common excuse cited was lack of time. Another common excuse is a failure to exercise due to not knowing when to exercise during their night shift. Most think that exercising will hinder their sleep when they finish the night shift and try to go home and go to bed in the morning. Not so, but timing is everything when it comes to exercising on the overnight shift. Exercise has three major benefits for an extended hours worker: it can improve health, increase alertness on the night shift, and even be used to influence a change in circadian body rhythms to help workers adapt to night work more quickly. Encouragement and support will be needed when you implement an exercise program in your facility, not only in providing access to exercise equipment, but in educating the workers about how and when to use the equipment to their best advantage. There are 168 hours (10,080 minutes) in every week. Cardiovascular health can be improved with only three 30-minute sessions a week. How many adults in North America could honestly fail to find three 30-minute sessions during this time? That s less than 1% of their week. The key is to perform the exercise at a time when it will not only benefit health, but also benefit alertness on the night shift without adversely affecting sleep when the night shift is over. This Circadian Alert is designed to provide you with easy-to-use knowledge and reference sources to design and establish a healthy exercise program in your extended hours operation. Encouraging an exercise routine will maximize the health and quality of life of your employees while reducing the operational and medical costs created by unfit and overweight employees Circadian Technologies, Inc. All rights reserved by Circadian Technologies, Inc. It is illegal to reproduce this information in any form without our consent.

2 When to Exercise on the Night Shift Exercise can produce minor changes in circadian rhythms. For example, a 30-minute session of exercise at a point in the range of four hours before to one hour after the circadian minimum body temperature delays the subsequent temperature rhythm by approximately one hour. Equally, a similar-length session of exercise between three and eight hours after the minimum body temperature advances the body rhythm by about an hour. Exercise at other times in the 24-hour period has no significant effect on the circadian temperature rhythm (Edwards, 2002). So what about the circadian rhythm of sleep? According to most research, moderate exercise has also been shown to slightly change the timing of sleep by up to an hour, and slightly improve the quality of sleep of the worker the following day. It is hypothesized that this improvement is due to the exercise promoting longer periods of deeper slow-wave sleep. Although researchers have investigated the effect of exercise on the circadian rhythm of sleep, most studies test extreme exercise, either for many hours duration or for shorter periods of intense-level physical activity. Little research has been done on the effects of low-level exercise (the type that shiftworkers are able to perform on their breaks) on sleep patterns after the night shift. In addition, interpreting some general results by incorporating each study can be difficult as the testing conditions are extremely varied. The amount and the type of exercise, and the amount of light exposed to the subjects, will have different effects on the results. Phase-Shifting the Timing of Sleep The timing of the onset of sleep can be slightly affected by exercise. Exercise has been shown to cause a small change in the timing of the release of melatonin, a substance the body releases to induce sleep. This can cause a small change in the timing of sleep for the employee. By timing the exercise correctly, the employee can use exercise to his or her advantage to increase alertness on the night shift and speed up the process of adapting to the block of night shifts. The timing of exercise throughout the night shift seems to affect how much, and in which direction, the sleep pattern is shifted. It would seem that exercise before midnight makes it difficult for an individual to fall asleep before 1 a.m. (maybe a minor delay in the onset of sleep), but it does not alter the onset of sleep after this time, even up to 7 a.m. (Mizuno, 1998). Performing exercise after midnight can affect the onset of sleep at the end of the night shift around 7 a.m. In one study, a delay in the release of melatonin was seen when light-restricted subjects were asked to exercise heavily for two hours on a rowing machine at midnight. A delay in the release 2 I CIRCADIAN TECHNOLOGIES, INC

3 of melatonin caused a delay in the onset of sleepiness. The change was minimal and was not noticeable to the subject on a daily basis, but it was evident after about six consecutive days of testing (Miyazaki, 2001). In this case, exercising heavily helped shift the sleep pattern to make it easier to work the night shift and sleep in the daytime. What about moderate exercise? The effects of different levels of exercise at 1 a.m. were tested using three protocols: no exercise, moderate exercise for three hours, or intense exercise for one hour. Melatonin release was delayed by 63 minutes in the moderate exercise group and 55 minutes in the intense exercise group. This means that moderate exercise shifted the sleep pattern as much as the intense exercise. But it s not easy for any shiftworker to exercise moderately for three hours while on duty. What about low-level physical activity? Unfortunately, few studies have looked at the effects of low-level exercise such as that available to a shiftworker on duty (e.g. 20 minutes on an exercise bike or treadmill). In a study of exercise over eight consecutive night shifts, subjects performed moderate regular exercise (15 minutes of cycling during every hour of each shift), and they wore heavy welding goggles during the commute home to restrict their exposure to natural light. By the end of the eight consecutive night shifts, subjects natural sleep time was delayed by nine hours (Eastman, 1995). So it would seem that low-level regular exercise during each work shift would assist the alertness of the worker and somewhat delay melatonin release, though not to the extremes seen when exercising for 15 minutes every hour. So let s pick a time of day that would boost alertness during the work shift and also help employees shift their sleep patterns forward in time, allowing them better sleep during the following day after the night shift is over. From the research to date, exercise performed between midnight and 1 a.m. seems to produce the most significant delay in melatonin release. The effect of exercise on melatonin release appears to be less extreme when the exercise occurs in the later hours of the night or early morning before the end of the night shift (Van Reeth, 1994). It s not a good idea to exercise within a couple of hours before bedtime (whatever time of day or night one s bedtime is), as exercise causes the body temperature to rise creates a hormonal response that excites the body systems and prevents an individual from falling asleep easily. So, sometime after midnight and before the last two hours of the shift is the best time to exercise. To be even more specific, exercising sometime between 12:30 a.m. and 2 a.m. will most likely achieve the maximum effect on alertness and sleep delay. As always, each worker will have an individual circadian clock and the natural timing of their sleep cycles will be different. Therefore, the natural best exercise time will also be individual and different. This is lucky for the facility that has just one piece of exercise equipment! Encourage your workers to start keeping track of when they exercise and how good they felt on shift, and after their sleep the following day. 3 I CIRCADIAN TECHNOLOGIES, INC

4 Improving the Quality of Sleep Exercise has been shown to alter the quality of sleep and also the individual s perception of the quality of their sleep. Again, the type and duration of the exercise affects the results of the studies, and so an overall consensus on the effects of exercise on sleep quality can be complicated. Exercise benefits sleep quality if performed at moderate levels. It has been shown using EEG recording techniques (recording of brain waves through electroencephalography), that time spent in deep sleep throughout the night is significantly longer after moderate exercise (Horne, 1976; Driver, 1988; Mizuno, 1998). The subjects also reported an increased perception of getting a good night s sleep after exercising the night before (Yoshida, 1998). A decent level of aerobic exercise should be performed in order to gain these benefits in sleep quality (20 to 30 minutes on an exercise bike, treadmill, or elliptical machine should suffice). The exercise intensity should be conversational workers should be able to hold a conversation comfortably, while still feeling they re working up a sweat. The effort is needed to feel the results in a study of low-level water aerobics, no significant differences in sleep EEG or perception were found between individuals in the exercise and non-exercise groups (Oda, 2001). This low-impact exercise did not seem to produce the same positive effect on sleep as the moderate exercise. Sleep quality is only negatively affected by exercise if it is completely physically exhausting (like a marathon or triathlon event!). In such cases, it was shown that the onset of rapid eye movement (REM) sleep was delayed (Driver, 1994). It s unlikely that any shiftworker will be running a marathon while they are on duty and if they have the time for that, then you should really take a look at your excess staffing levels! Increasing Alertness Exercise certainly increases the alertness of the worker on the night shift. Imagine sitting in a dimmed room, feeling your head nod and sleep waves rushing over you as you monitor a control screen. Should you get some coffee, or should you wheel the exercise bike over and cycle for 20 minutes while monitoring the screen? The benefits of a brief workout are obvious. How does exercise increase alertness? Even low-level exercise causes changes in the body. Movement of the muscles creates different demands on the rest of the body systems as it requires the use of energy sources, an increased oxygen supply, a system to get rid of waste products, and a method to get rid of the heat produced. In order to support the effort of exercising, the heart, blood vessels, nervous system, lungs, liver 4 I CIRCADIAN TECHNOLOGIES, INC

5 and skin respond. Exercise prompts the release of adrenaline into the bloodstream, which causes increased brain activity. Exercise may increase alertness by raising the body temperature of the worker during the overnight period. The body temperature naturally drops by about two degrees Fahrenheit over the nighttime hours in order to induce and maintain restful sleep. By exercising, the body temperature is maintained and perceived sleepiness decreases (Matsumoto, 2002). The type of exercise performed should be carefully considered, as humans tend to have reduced physical performance during the overnight hours. In particular, balance and hand-eye coordination are reduced, so employees should remember to pay special attention when working out. Exercise bikes or elliptical machines with hand-holds can be easier than treadmills for workers in the nighttime hours. Naturally, individual preferences will vary. One study has shown that if workers have been awake for extremely long hours (e.g. those failing to prepare for the first night shift and staying awake for 24 hours or more) their perception of function can improve, but their actual brain activity fails to improve due to the extreme fatigue. In this case, workers may be overconfident and have an increased risk of human error (Matsumoto, 2002). Encouraging employees to prepare adequately for the night shift is important in any extended hours operation. Low- to moderate-level exercise should be encouraged, as it is extremely unlikely that workers on duty have time to overexert themselves. Starting an exercise program slowly will help ease workers into the habit of working out, and supplying information about warming up, cooling down and stretching will promote safe exercise practices. Obviously, all workers should be encouraged to consult their physicians before starting significant exercise programs if they are concerned about their health. Not only does exercising on the shift create an immediate boost in alertness, improve sleep quality, and speed the transition to the block of night shifts, research has shown that workers who exercise are also more alert the following day after waking from sleep (Yoshida, 1998). This is probably due to the increased sleep quality they had following night-shift exercise. It s a win-win for the workplace and the family if the health and happiness of the worker improves. 5 I CIRCADIAN TECHNOLOGIES, INC

6 Cost-Effectiveness of Exercise In an effort to evaluate the cost-effectiveness of providing exercise facilities or programs at companies, the Health Management Research Center at the University of Michigan collated a number of research papers and studies. Their findings include: Twenty percent of employees must participate in order for a program to be cost-effective (this value may be lower in an extended hours operation, where health is generally worse than the U.S. average). Running or jogging programs are the most cost-effective. A summary of 14 studies revealed cost/benefit ratios of $1.07 to $5.58 per dollar invested (again, the performance enhancement and decrease in fatigue in extended hours employees may provide a cost/benefit ratio at the higher end of this range). Indirect benefits (not included in the cost savings calculation above) can include improvements in absenteeism, productivity, stress, recruitment, retention, corporate image, satisfaction, and employee morale. These are areas where extended hours operations often experience problems. Lifestyle training may be more cost-effective than structured fitness programs. Conclusions Circadian s overnight exercise tips: Low-level exercise will improve individuals overall health and mood. While three 30-minute sessions per week or more is ideal for improving cardiovascular fitness, any activity will improve alertness. Any exercise will boost alertness by activating multiple body systems and releasing adrenaline which stimulates the brain. Exercise on the bike or treadmill should be conversational an individual should be able to hold a conversation comfortably (maintains the correct aerobic zone). 6 I CIRCADIAN TECHNOLOGIES, INC

7 Exercise can improve the sleep quality of individuals by increasing the amount of slowwave deep sleep. It is difficult for employees to negatively affect their sleep patterns the day after the night shift by exercising. Timing the exercise to occur after midnight will maximize the delay in melatonin release (optimal time is between 12:30 a.m. and 2 a.m.) Workers should refrain from exercise in the last two hours of a night shift if they plan to sleep in the morning. Exercise can be used to speed up the transition to getting used to working nights on a block of night shifts. It takes more than six days to significantly alter the onset of sleep through exercise alone light is far more influential. For more information about exercise in extended hours operations, or details about how to implement an exercise program in your workplace, please call Circadian Technologies, Inc. at CTI-5001 or a specialist at info@circadian.com. References Buxton OM, Frank SA, L'Hermite-Baleriaux M, Leproult R, Turek FW, Van Cauter E. American Journal of Physiology 1997 Sep; 273(3 Pt 1):E Roles of intensity and duration of nocturnal exercise in causing phase delays of human circadian rhythms. de Zwart BC, Bras VM, van Dormolen M, Frings-Dresen MH, Meijman TF. International Archives of Occupational Environmental Health 1993; 65(4): After-effects of night work on physical performance capacity and sleep quality in relation to age. Driver HS, Meintjes AF, Rogers GG, Shapiro CM. Acta Physiologica Scandinavica (Suppl.) 1988; 574:8-13. Submaximal exercise effects on sleep patterns in young women before and after an aerobic training programme. Driver HS, Rogers GG, Mitchell D, Borrow SJ, Allen M, Luus HG, Shapiro CM. Medicine and Science in Sports and Exercise 1994 Jul; 26(7): Prolonged endurance exercise and sleep disruption. Eastman CI, Hoese EK, Youngstedt SD, Liu L. Physiology and Behavior 1995 Dec; 58(6): Phase-shifting human circadian rhythms with exercise during the night shift. 7 I CIRCADIAN TECHNOLOGIES, INC

8 Edwards B, Waterhouse J, Atkinson G, Reilly T. Journal of Sports Sciences 2002 Sep; 20(9): Exercise does not necessarily influence the phase of the circadian rhythm in temperature in healthy humans. Horne JA, Porter JM. Electroencephalography and Clinical Neurophysiology 1976 Feb; 40(2): Time of day effects with standardized exercise upon subsequent sleep. Matsumoto Y, Mishima K, Satoh K, Shimizu T, Hishikawa Y. Neuroscience Letters 2002 Jun 28; 326(2): Physical activity increases the dissociation between subjective sleepiness and objective performance levels during extended wakefulness in human. Miyazaki T, Hashimoto S, Masubuchi S, Honma S, Honma KI. American Journal of Physiology: Regulatory, Integrative and Comparative Physiology 2001 Jul; 281(1):R Phase-advance shifts of human circadian pacemaker are accelerated by daytime physical exercise. Mizuno K, Asano K, Okamoto K. Psychiatry and Clinical Neurosciences 1998 Apr; 52(2): Effect of night exercise on the following partially deprived sleep. Oda S. Psychiatry and Clinical Neurosciences 2001 Jun; 55(3): The effects of recreational underwater exercise in early evening on sleep for physically untrained male subjects. University of Michigan. Health Management Research Center. Cost Benefit Analysis and Report Van Reeth O, Sturis J, Byrne MM, Blackman JD, L'Hermite-Baleriaux M, Leproult R, Oliner C, Refetoff S, Turek FW, Van Cauter E. American Journal of Physiology 1994 Jun; 266(6 Pt 1):E Nocturnal exercise phase delays circadian rhythms of melatonin and thyrotropin secretion in normal men. Yoshida H, Ishikawa T, Shiraishi F, Kobayashi T. Psychiatry and Clinical Neurosciences 1998 Apr; 52(2): Effects of the timing of exercise on the night sleep. Youngstedt SD, Kripke DF, Elliott JA. American Journal of Physiology: Regulatory, Integrative and Comparative Physiology 2002 Jan; 282(1):R Circadian phase-delaying effects of bright light alone and combined with exercise in humans. 8 I CIRCADIAN TECHNOLOGIES, INC

Shift Work and Fatigue

Shift Work and Fatigue SHIFT WORK What is Shift Work and why is it Important? It is: Groups of people working together alternating with other groups to create a cohesive and productive workplace 24 hours