You keep up your gym membership and, however time-crunched your lifestyle, never fail to squeeze in some activity to your daily routine. But your fitness levels hit a plateau, you feel sluggish and you can't understand why. If this sounds like you, the chances are you are neglecting a vital but often overlooked aspect of your workout routine: sleep. Recent studies by sport scientists have begun to unravel the complex relationship between sleep and exercise performance and many experts now believe that fitness levels can be boosted simply by getting more shut-eye.
In recent research conducted at Stanford University's sleep disorders clinic, Dr Cheri Mah, who presented her findings at the annual meeting of the Associated Professional Sleep Societies, analysed the sleep/wake patterns of five sporty females over three weeks. She asked them to perform a series of athletic tests that included sprinting, tennis serves and other drills. On average, the women were getting between six and eight hours of sleep a night, which, considering their active lifestyles, could have meant they were in "sleep debt", Mah suggested.
Sure enough, when the same subjects were asked to extend their sleeping hours to 10 per night, their performance in the drills improved significantly and they were able to run faster and hit tennis balls more accurately. They also exhibited greater arm strength. The results were similar to those obtained by the Stanford researchers in a 2008 study of swimmers which showed that extra sleep enhanced alertness and fitness levels. Mah says that getting enough sleep is as important as aerobic and strength training, diet and conditioning in a fitness programme. "Sleep is an important contributing factor in fitness and sport performance," she says. "Many do not realise that optimal or peak performance can occur only when someone's sleep habits are optimal."
At the English Institute of Sport, physiologists are working with elite athletes to improve their sleeping patterns in the hope that it will raise the bar for performances by the Great Britain team at the London Olympic Games in 2012. But it is not only top athletes and the seriously sporty who benefit from better sleep habits. "Sleep is very important to fitness and general well-being," says Bob Richards, the national fitness training manager for Fitness First in the Middle East. "It is the time the body recovers from exercise and from the general stresses of the day. It is also the time when several major hormones in the body are released which help the body repair." It is known, for instance, that sleep reduces stress and anxiety (both a result of rising levels of the hormone cortisol being produced by the adrenal glands) by triggering the release of hormones that act as an antidote to anxiety. "Just feeling slightly tired can affect your hormonal stress levels which can alter your mood and make everything seem like it's too much more physical effort," says Matthew Walters, a certified personal trainer with www.keepfitdubai.com.
How much sleep you need to benefit your exercise regimen is a matter of debate among experts. Most recommend getting between seven and nine hours a night, although they concede that some people manage on more or less. But if you get less sleep than you need for a month or more, your workouts - and your health - will begin to suffer. "Tiredness affects exercise performance in many ways," says Walters. "Cardiovascular performance, or aerobic fitness, can be reduced by over 10 per cent when you are tired while performance in activities involving mental input or tactics such as golf, tennis or squash can really go downhill if you aren't getting sleep." Beyond fitness, general health can be adversely affected. Recent findings have shown that the sleep-deprived are less efficient at work, fatter, more likely to take time off sick, can struggle with relationships and are at increased risk of being involved in traffic or other accidents. The sleep-deprived are also at risk of heart disease, strokes and depression.
One approach many top athletes use to catch up on sleep is to take a regular lunchtime power nap lasting 10-20 minutes. "A lot of people do find they benefit from naps," says Professor Derk-Jan Dijk, the director of the Sleep Research Centre at the University of Surrey in England. "If you feel you don't get enough sleep at night, it can definitely be helpful to catch up with a 20-minute siesta. You will feel less tired and stressed and countless studies have shown that lowering stress levels has benefits in disease prevention." Studies by Nasa have shown that alertness increases by as much as 100 per cent after a brief nap, even in well-rested subjects. However, the overtired and chronically fatigued are likely to benefit most from a catch-up nap.
Professor Sarah Mendick, a Harvard University researcher who has studied the benefits of sleep, looked at the effects of napping compared with drinking caffeine. While one group of subjects was allowed to nap for 90 minutes, another drank 200mg of caffeine (the amount in a regular mug of coffee) and a control group took a placebo. When she tested her subjects on several tasks, including typing and spatial skills, such as remembering the layout of a room or a map, the coffee drinkers performed much worse than the placebo group, while the nappers performed best of all. In another, Mendick put 30 well-rested people through the same set of tasks four times in the course of day, starting at 9am and ending at 7pm. Performance dropped by more than 50 per cent in the subjects who stayed awake the whole time while the people who napped for an hour in the early afternoon were able to restore their performances.
If you have trouble dropping off to sleep at night, exercise can be helpful - just make sure it is not too demanding. Vigorous exercise - aerobics, circuits and running - within four hours of going to bed can be counter-productive and should be saved for earlier in the day. But a recent study at the University of Sao Paulo in Brazil found that people who did some gentle exercise before bedtime were 54 per cent less likely to have trouble getting to sleep and 36 per cent less likely to wake up during the night. But if you become chronically fatigued, it can be more help to skip exercise altogether and focus on resting instead. "If you are overtired and don't have the energy, then just skip the workout. It's your body's way of telling you to slow down," says Walters. "Allow yourself the luxury of resting. Don't then try to catch up on the missed workout. Your body needs at least one rest day a week to recover from exercise."
Walters adds that squeezing in a workout just to say that you did can be detrimental if it is leaving you exhausted for the wrong reasons. "Exercise is supposed to make you tired, but in a positive way. If you push yourself when you are too tired it will drain you mentally," he says. "Before a workout ask yourself if you will be able to maintain or improve on your previous session. If the answer is no because you are simply too drained of energy and are fatigued to the point it seems like a chore, then leave it and chill. It will recharge your batteries and allow you to work harder next time around."
