I SAW a poster in a gym recently that listed the amazing power of exercise.
It claimed that exercise can 鈥渂enefit your self-esteem, reduce stress and
tension, enrich your sex life, improve your relationships at work鈥� and even
鈥渕ake you a better person鈥�. I began to wonder if there was anything exercise
couldn鈥檛 do.
That said, at least some of those claims fit well with my own experience as
an exercise psychologist who teaches aerobics. Dedicated exercisers tell me they
feel 鈥渁lert and alive鈥� or perhaps 鈥渢ired but happy鈥� after a work-out.
But not so long ago this 鈥渇eel-good factor鈥� was scorned by respectable
research psychologists and other medical professionals. Just 14 years ago, one
Harvard physician even suggested in the Journal of the American Medical
Association that 鈥渢he runner鈥檚 high鈥� was a ploy developed by marketing
wizards to boost sales of sportswear. Such scepticism all but evaporated
following a wave of studies showing that exercise can trigger feelings of
happiness, euphoria, calmness, and tranquillity for anything from a few minutes
to 24 hours.
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With the widespread acceptance that the runner鈥檚 high actually exists came a
host of experiments designed to discover its biological underpinnings. Much to
everyone鈥檚 surprise, the long-favoured hypothesis that exercise has its effect
by pumping up the body鈥檚 endorphins, substances that are chemically related to
opium and block pain receptors in the brain, is proving difficult to
substantiate. And in the absence of good biochemical explanations for exercise
euphoria, research psychologists are now testing alternative explanations. Among
the prime contenders are the 鈥渕astery鈥� hypothesis, the idea that exercise
enhances mood because it triggers a sense of achievement, and the 鈥渄istraction鈥�
hypothesis, the idea that exercise is a psychological upper because it
temporarily distracts from your everyday woes.
Exercise addiction
The key study to show that exercise has the power to change mood came from
psychologist Andrew Steptoe and his colleagues at St George鈥檚 Hospital Medical
School in London. In the late 1980s, they randomly assigned 109 sedentary adults
to one of four groups. The first two groups took 45-minute sessions of aerobics
at either a moderate or high intensity three times a week. The third group took
part in gentle stretching exercises and the fourth group did nothing. After 12
weeks, the moderate aerobic exercisers were the only people to show a marked
improvement in psychological 鈥渨ellness鈥�, as judged by tests that detected a
reduction in tension, anxiety and confusion, and an increase in how they
perceived their ability to cope with stressful situations (see 鈥淒on鈥檛 be so
尘辞辞诲测鈥�).
Steptoe鈥檚 findings have since been confirmed time and again. Some
psychiatrists are so convinced of the existence of the feel-good factor that
they are using it to treat clinical depression (see 鈥淜eep taking the
蝉颈迟-耻辫蝉鈥�).
But as with most things that make you feel good, there are those who believe
that exercise may also have a nasty downside: exercise addiction. One news
report described a 鈥渇itness fanatic鈥� who continued to run 100 miles a week even
after repeated bouts in hospital for running-related injuries. In another, a
woman divorced her husband because he was exercising 6 or 7 hours a day. In
fact, the incidence of exercise addiction, if such a phenomenon exists, is
likely to be low. Still, the idea that exercise is addictive lends support to
the idea that the feel-good factor is due to the release of endorphins.
Psychological highs
Certainly, opiate drugs, which include heroin and cocaine, can induce
profound psychological highs. And the negative feelings that exercise
enthusiasts report when they aren鈥檛 able to exercise are, arguably, like mild
cases of the withdrawal that drug addicts go through when they can鈥檛 get a fix.
More convincingly, a multitude of studies show that vigorous exercise, even as
little as a 30-second sprint, can cause blood endorphin levels to soar to seven
times their normal levels for several hours. Yet it鈥檚 still unclear exactly why
endorphins are released during exercise, although they may help to block the
pain caused by the build-up of acid by-products in muscle.
The evidence that the body鈥檚 own opiates cause exercise-induced euphoria
is even less clear cut. Some studies show that when drugs such as naltrexone and
naloxone, which block the action of endorphins, are injected before, during or
after exercise, they completely abolish its mood-enhancing effects.
Unfortunately, an equal number of studies show that these drugs have little or
no effect whatsoever.
What鈥檚 more, attempts to correlate mood with blood levels of endorphins have
also drawn a blank. For instance, in 1994, Elizabeth Klonoff, a psychologist at
California State University in San Bernadino, examined &bgr;-endorphin levels and
mood in 23 women over 8 weeks while they embarked on an exercise programme from
scratch. She found that while &bgr;-endorphin levels increased in some women, they
were not necessarily the ones who experienced the biggest exercise highs.
Magic elixir
鈥淭here鈥檚 still work to be done, and until it鈥檚 been done [the endorphin
theory is] still a possibility,鈥� says Steven Petruzzello, an exercise
psychophysiologist at the University of Illinois at Urbana-Champaign. 鈥淏ut
endorphins are [not] the magic elixir that some people think.鈥�
But if endorphins don鈥檛 hold the key to the feel-good factor, what else
might? One contender is the 鈥渢hermogenic hypothesis鈥�. This draws on the idea
that saunas, which raise body temperature without a person having to go to the
trouble of moving, make you feel good, so perhaps exercise has its effect in the
same way鈥攂y raising the body鈥檚 temperature.
But when Petruzzello and researchers from Arizona State University in Tempe
and the University of Costa Rica in San Jos茅, Costa Rica, persuaded 20
healthy volunteers to run on a treadmill in warm, cool, or normal conditions
with a temperature probe inserted in their rectums, they discovered that
volunteers whose body temperature increased showed an increase in anxiety. When
their body temperature returned to normal, the volunteers鈥� anxiety levels fell.
However, Petruzzello warns that the study does not 鈥渃ompletely rule out
temperature [because] brain temperature is regulated differently from the rest
of the body鈥�.
So much for physiological explanations for the feel-good factor. Some suspect
that the mood-boosting aspects of exercise have nothing to do with physical
exertion at all.
Last year, psychologists Jane Harte of James Cook University in Townsville,
Australia, and Georg Eifert of West Virginia University in Morgantown monitored
mood in 10 experienced outdoor athletes before and after they ran once on an
outdoor track, and once on a treadmill in the lab. After the outdoor run, the
athletes鈥� scores on a mood test indicated that they were less depressed,
anxious, hostile and fatigued, and more invigorated than before the
run鈥攆indings entirely consistent with the existence of the feel-good
factor. But the treadmill run only made the athletes feel tired, even though
they had worn headphones and listened to a tape of outdoor noises, including the
sound of wind, birds and traffic.
Clearly energy expenditure alone doesn鈥檛 improve mood. The exercisers have
got to like what they are doing to get a psychological lift. And if that鈥檚 the
case, consider some of the stranger experimental designs that鈥攕urprise,
surprise鈥攆ailed to find any psychological benefits of exercise. One
research team monitored mood in volunteers riding a bicycle while submerged in a
tank of water. And researchers routinely attempt to discover an improvement in
mood in exercisers who are wired to a mass of recording equipment, measuring
everything from heart rate and breathing to brain activity.
Still, there seems to be more to the exercise high than just having fun.
Another suggestion, the 鈥渄istraction鈥� hypothesis, predicts that any activity (so
long as it is not itself too unpleasant) that diverts people鈥檚 attention from
the daily hassles of life will improve their mood. The seed for this idea comes
from the observation that although quiet rest or meditation make people feel
less anxious, they don鈥檛 provide the psychological charge that exercise
does.
鈥淓xercise has a dual effect,鈥� says Don Saklofkse, an educational psychologist
at the University of Saskatchewan in Saskatoon. 鈥淚t decreases tense arousal, the
feeling of being mentally uptight. But exercisers also feel energised and ready
to go. Relaxation and deep breathing only cut tension, they don鈥檛 alter energy
濒别惫别濒蝉.鈥�
And what you think about while you exercise can subtly alter the feelings of
wellbeing, according to a study by Kathryn Goode and David Roth, psychologists
at the University of Alabama at Birmingham. They looked at the moods of 150
experienced runners before and after a training run. The runners also completed
a questionnaire about their thoughts during the run. Those who reflected on
their external surroundings tended to feel more invigorated after exercise,
while the runners who contemplated their relationships with partners, children
or friends felt less tense and anxious.
Heading for goal
Yet another possible reason why exercise, but not a quick lie-down, provides
a psychological high is that exercise often requires some degree of skill, or
the exerciser has some goal in mind鈥攆or example, running a certain
distance or doing a number of sit-ups. According to the 鈥渕astery鈥� hypothesis,
part of the feel-good factor is due to a sense of achievement: usually, the
greater the challenge of the exercise, the better people feel when they
finish.
鈥淚f you can expose people to a task that they can do well in, it instils
confidence in them and increases their outlook on life. They become more
positive about themselves,鈥� says clinical exercise physiologist Kerry Stewart of
Johns Hopkins School of Medicine in Baltimore.
And the ability of 鈥渕astery鈥� experiences to improve mood appears to have
little to do with endorphins. Albert Bandura and co-workers at Stanford
University in California devised an ingenious experiment to investigate
self-confidence and endorphin activity. Half a group of volunteers performed
maths problems at a gentle pace designed to enhance their confidence. The other
half had to work so quickly that it was impossible for them to get the answers
right. Immediately after the two groups had finished the sums, the volunteers
received injections of naloxone, the endorphin blocker, or saline. Then, the
length of time they could withstand the pain of holding their hand against a
cold surface was measured.
Tolerating pain
The low-confidence group, whose members had been forced to do badly in the
maths test, tolerated the pain better鈥� unless they also received a
naloxone injection. In this case they fared no better than people who had become
confident in their ability to do maths problems. Those results suggest that the
stress of failure had boosted the volunteers鈥� endorphin levels. If the same
holds true for exercisers鈥攁nd at this stage that鈥檚 a very big
鈥渋f鈥濃�攖hen failure to achieve an exercise goal, rather than success, should
trigger an increase in endorphins. The feel-good factor, on the other hand, is
always associated with exercise success, not failure.
That may make the endorphin theory seem even more shaky, but in reality even
the most ardent supporters of the psychological explanations for the feel-good
factor admit that it is likely to be due to some combination of both
psychological and biochemical factors. After all, says Stewart, 鈥渦ltimately
everything you do can be explained on a biochemical basis鈥�.
* * *
Don鈥檛 be so moody
Sweating is one of the physical correlates of being hot. But unlike body
temperature, mood doesn鈥檛 have a direct physical correlate, so if psychologists
want to know how someone feels they can only ask.
To make it possible to get an objective snapshot of peoples鈥� moods in
different situations, psychologists have created tools such as the Profile of
Mood States (often referred to as the POMS) and the State Anxiety Inventory.
POMS and the State Anxiety Inventory are actually lists of adjectives such as
鈥渞esentful鈥�, 鈥渃heerful鈥�, and 鈥減eeved鈥� that the people being studied are asked to
rate according to how they feel at that particular moment. For example, 1 =
鈥渧ery much鈥�, 2 = 鈥渁 bit鈥�, 3 = 鈥渘ot at all鈥�.
The mood questionnaires that are most widely used today are geared towards
negative moods because they were originally designed to help pick up anxiety
disorders and depression. Now, psychologists are coming up with a new breed of
questionnaires鈥攆or example the Subjective Exercise Experiences
Scale鈥攖hat are designed to pick up positive mood swings.
* * *
Keep taking the SIT-UPS
Exercise has long been touted as a way to reduce blood pressure, and the risk
of heart disease. Now, some people are arguing that its mood-enhancing powers
can also be harnessed to treat鈥攐r even prevent鈥攃ertain mental
disorders.
Back in 1985, psychiatrists Marjorie Klein, John Greist and their colleagues
at the University of Wisconsin, Madison, showed that exercise was as effective
for treating mild to moderate clinical depression as group psychotherapy.
Studies since then have echoed this result and shown that exercise, like both
counselling and certain types of psychotherapy, can alleviate depression within
about eight weeks.
Egil Martinsen, a psychiatrist at the Central Hospital in F rde in Norway,
prescribes as little as three one-hour sessions per week of brisk walking or
jogging for eight weeks. One advantage, he says, is that moderate exercise has
none of the side effects that drugs have, such as muscle cramps and headaches.
Another is that most of his patients say that they prefer exercise to
psychotherapy.
One in four people in the West suffers from a major depressive bout at some
point during their lives. Some psychologists, like William Morgan of the Sport
Psychology Laboratory at the University of Wisconsin, Madison, are promoting
exercise as a means of reducing the number of people who suffer clinical
depression.