Mind-set Matters: Exercise and the Placebo Effect
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Crum, Alia J., and Ellen J. Langer. 2007. Mind-set matters: Exercise and the placebo effect.
Psychological Science 18, no. 2: 165-171.

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http://dx.doi.org/10.1111/j.1467-9280.2007.01867.x

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PS YC HOLOGICA L SC IENCE

Research Article

Mind-Set Matters
Exercise and the Placebo EffectAlia J. Crum and Ellen J. Langer
Harvard University

ABSTRACT—In a study testing whether the relationshipbetween exercise and health is moderated by one’s mindset, 84 female room attendants working in seven different
hotels were measured on physiological health variables
affected by exercise. Those in the informed condition
were told that the work they do (cleaning hotel rooms) isgood exercise and satisfies the Surgeon General’s recommendations for an active lifestyle. Examples of how theirwork was exercise were provided. Subjects in the control
group were not given this information. Although actual
behavior did not change, 4 weeks after the intervention,
the informed group perceived themselves to be getting
significantly more exercise than before. As a result, compared with the control group, they showed a decrease inweight, blood pressure, body fat, waist-to-hip ratio, andbody mass index. These results support the hypothesis thatexercise affects health in part or in whole via the placebo
effect.
The placebo effect is any effect that is not attributed to an actual
pharmaceutical drug or remedy, but rather is attributed to theindividual’s mind-set (mindless beliefs and expectations). The
therapeutic benefit of the placebo effect is so widely acceptedthat accounting for it has become a standard in clinical drug
trials to distinguish pharmaceutical effects from the placebo
effect and the placebo effect from other possible confounding
factors, including spontaneous remission and the natural historyof the condition (Benson & McCallie, 1979; Brody, 1980; Nesbitt Shanor, 1999; Spiro, 1986). Kirsh and Sapirstein (1998), in ameta-analysis of 2,318 clinical drug trials for antidepressant
medication, found that a quarter (25.16%) of the patients’ responses were due to the actual drug effect, another quarter(23.87%) were due to the natural history of depression, and half
(50.97%) were due to the placebo effect.
Address correspondence to Alia Crum or Ellen Langer, Departmentof Psychology, Harvard University, 1330 William James Hall, 33
Kirkland St., Cambridge, MA 02138, e-mail: ajc@post.harvard.edu
or langer@wjh.harvard.edu.

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The placebo effect extends much further than medications ortherapy: Subjects exposed to fake poison ivy developed realrashes1 (Blakeslee, 1998), people imbibing placebo caffeine
experienced increased motor performance and heart rate (andother effects congruent with the subjects’ beliefs and not with thepharmacological effects of caffeine; Kirsch & Sapirstein, 1998),
and patients given anesthesia and a fake knee operation experienced reduced pain and swelling in their ‘‘healed’’ tendonsand ligaments (Blakeslee, 1998). More generally, studies suggest that 60 to 90% of drugs and other therapies prescribed byphysicians depend on the placebo effect for their effectiveness(Benson & Freedman, 1996; Nesbitt Shanor, 1999).
The placebo effect does not have to involve inert pills or
sham procedures. Symbols, beliefs, and expectations can elicit
powerful physiological occurrences, both positive and negative(Hahn & Kleinman, 1983; Roberts, Kewman, & Mercie, 1993).
For example, the mere presence of a doctor increases patients’blood pressure (the ‘‘white coat effect’’), reinterpreting pain in
nonthreatening ways (e.g., as sensations) prompts patients totake fewer sedatives and leave the hospital sooner; and thehealth decline of cancer patients often has less to do with theactual course of the illness and more to do with their negative
expectations regarding the disease (Langer, 1989).
EXERCISE AND THE PLACEBO EFFECTAs the most common health threats are now infectious rather
than chronic, remedies have also changed. Doctors now prescribe behavioral changes such as exercise for chronic diseases
like diabetes, heart disease, and even cancer. We wondered
whether the well-known benefits of exercise are in whole or inpart the result of the placebo effect. A positive finding would
speak to the potentially powerful psychological control people
have over their health.
There is evidence supporting the idea that the placebo effectplays a role in occasioning the psychological benefits associatedwith exercise (Desharnais, Jobin, Cote, Levesque, & Godin,
1

When negative expectations are met with negative results, the placebo effectis often called the nocebo effect (Hahn, 1997).

Copyright r 2007 Association for Psychological Science

165

Exercise and the Placebo Effect1993; Plante, Lantis, & Checa, 1998; Plante & Rodin, 1990).
Desharnais et al. conducted an experiment on 48 healthy young
adults engaged in a supervised 10-week exercise program. Halfof the subjects (the experimental condition) were led to believethat the program was specifically designed to improve psychological well-being. The other half were not told anything about
these benefits; instead, the emphasis was on the biological aspect of the program. Although the results showed similar increases in fitness in the two conditions, the subjects in theexperimental condition showed a significant increase in selfesteem.
Although studies have yet to investigate whether the perception of physical activity and resulting beliefs about one’s
health have effects on the physiological benefits associated withphysical activity, several studies allude to the possibility. Healthperceptions have been related to actual health. For example,
Kaplan and Camacho (1983), in a cohort study of 6,928 adults,
found that perceived health was a better predictor of mortality
than actual health. Idler and Kasl (1991) concluded that elderly
persons who perceive their health as poor are 6 times more likely
to die than those who perceive their health as excellent, regardless of actual health status.
Further support for the possibility of the placebo effect in thebenefits of exercise comes from the fact that the numerous
studies linking exercise to health have generally relied on selfreported information to measure physical activity (Plante &Rodin, 1990); the results of these studies therefore reflect therelationship between health and perceived levels of physicalactivity, rather than actual levels. This raises the question ofwhether some of the positive gains of physical activity are due
more to the perception of exercise and its association with healththan to the actual performance of exercise.
In the study we report here, we investigated the role of theplacebo effect (the moderating role of mind-set) in the relationship between exercise and health. We hypothesized that theplacebo effect plays a role in the health benefits of exercise: thatone’s mind-set mediates the connection between exercise andone’s health. If this hypothesis is true, increasing perceived
exercise, independent of actual exercise, would be expected toresult in subsequent health benefits (a placebo effect).

complete), and engage in exerting activities that require walking, bending, pushing, lifting, and carrying, clearly meeting andexceeding the Surgeon General’s requirements. Room attendants may not perceive their work as exercise. If they do not, andif the relationship between exercise and health is moderated bymind-set as we hypothesize, then these workers may not be receiving the full health benefits of their exercise. Similarly, if
their mind-sets are shifted so that they become aware of theexercise they are getting, then health improvements would be
expected to follow.

DesignEach of seven hotels was randomly assigned to one of two conditions: informed or control.
Subjects in the informed condition received a write-up discussing the benefits of exercise and were informed that their
daily housekeeping work satisfied the CDC’s recommendations
for an active lifestyle. Specifically, they were told that exercise
does not need to be hard or painful to be good for one’s health,but that it is simply a matter of moving one’s muscles andburning calories (accumulating approximately 200 calories per
day to meet the recommendations). They were given specificdetails of the average calorie expenditure for various activities(changing linens for 15 min burns 40 calories, vacuuming for 15
min burns 50 calories, and cleaning bathrooms for 15 min burns
60 calories), and they were told that although these figures werebased on results for a 140-pound woman and each of them would
burn calories at a different rate, it was clear that they were easily
meeting and even exceeding the Surgeon General’s recommendations.2 This sheet, written in both English and Spanish,
was read and explained to the subjects and then posted on thebulletin board in their lounge.3
The subjects were told we were interested in getting information on their health so that we could study ways to improve it,
and in return for helping, they would receive information about
research on health and happiness.
Subjects in the control group were given all the same information as those in the informed group except they did not receive information about how their work is good exercise until
after the second set of measures was taken (see Procedure).

METHOD

Logic
The Surgeon General has stated that all adults should accumulate at least 30 min of physical exercise per day for a healthy
lifestyle (Centers for Disease Control and Prevention, CDC,
1996). Everyday moderate physical activity can be achieved bytaking a brisk walk, climbing the stairs, or performing active
housework (CDC, 1996). Although many people today havesedentary jobs, there are some jobs that are intrinsically physical. Hotel room attendants, for example, clean on average 15
rooms a day (each room taking between 20 and 30 min to166

Subjects
Subjects were recruited through hotels. To prevent information
contamination, we assigned all room attendants within a hotel tothe same condition. Four hotels were assigned to the informed
2This information is based on extensively researched recommendations forexercise and calorie expenditure made by the CDC, American College of Sports
Medicine, and Surgeon General (Pate, Pratt, Blair, et al., 1995, as cited in CDC,
1996).
3
All of the written information was translated into Spanish, and each hotel
had a designated and qualified supervisor to translate the verbal informationand instruction to the subjects.

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Alia J. Crum and Ellen J. Langer

condition, and three were assigned to the control condition. The
hotels were matched for similarity: The two same-franchise
hotels, the two condominium-type hotels, and the two unique,luxury hotels were in different conditions. The hotels did not
differ with respect to managerial structure, and all followed theEqual Employment Opportunity (EEO) codes and did not discriminate on the basis of age, gender, ethnic background, religious background, or sexual orientation, although all subjects
in this study were female. No information regarding subjects’characteristics (age or ethnicity) was known when the hotels
were assigned to the conditions.
In total, 84 subjects completed both sets of measures (44 in
the informed group, 40 in the control group). The subjects’ ages
ranged from 18 to 55 years, and most were Hispanic, althoughsome were Caucasian, African American, and Asian. All worked
32 to 40 hr per week and cleaned approximately 15 rooms perday. Statistical analysis revealed that at the onset of the investigation, the groups did not differ significantly except in age.4
This unexpected difference was controlled for in all analyses.
Procedure
All subjects were told that the purpose of the study was to findways to improve the health and happiness of women in a hotel
workplace. Each subject was given a questionnaire, and while
the subjects were filling it out, they were taken one at a time tocomplete their physiological measures. The informed group wasthen given the information about how their work is good exercise; this information was conveyed in the form of a verbal
presentation, through individual handouts, and on larger posters
tacked to the bulletin boards in their lounge in the hope that theywould be reminded of how much exercise they were getting eachday. The control group was not given this information.
Four weeks later, we returned to take the same measures, andall subjects were debriefed both orally and in writing. Eachsession took approximately 1 hr.
Measures
Self-Reported Exercise
The study was designed to instigate an increase in perceived
exercise independent of actual exercise. Self-reported exercise
was assessed through a series of questions. First, subjects wereasked to check ‘‘yes’’ or ‘‘no’’ to indicate whether or not they
exercised regularly ( perceived regular exercise). Second, theyused a scale from 0 to 10 to rate how much exercise they got( perceived amount of exercise). Following these questions, they
were asked to describe how they got their exercise. These descriptions were used for the measures of perceived work as exercise (i.e., whether or not subjects referenced their work) and4
Subjects in the informed group (mean age 5 34.12, SD 5 9.23) were significantly younger than subjects in the control group (mean age 5 42.40, SD 5
12.54), F(1, 81) 5 11.86, prep 5 .986.

Volume 18—Number 2

exercise outside of work (i.e., whether or not subjects named
activities such as swimming, running, doing sit ups, or othernon-work-related activities). Additional questions asked how
often subjects attended a gym and whether or not they walked towork each day.
It was assumed, and later confirmed by the hotel housekeeping managers, that the workload of the room attendants
remained constant in the 30 days prior to and the 30 days during
the study. Therefore, if there was no increase in reported exercise outside of work, any increase in perceived regular exercise,
perceived amount of exercise, or perceived work as exercise
would be assumed to reflect a change in mind-set initiated by theintervention and not due to an increase in actual exercise.

Dependent Variables: Physiological Measures
Weight and percentage of body fat were measured using theTanita Body Fat Monitor/Scale (Model UM-026, Tanita Manufacturing Co., Tokyo, Japan). In addition to giving a normal
weight reading (to the closest 1/10 pound), this model measures
body fat using a simplified version of bioelectrical impedance
analysis that uses leg-to-leg bioimpedance analysis. After
weight and impedance are measured, computer software (amicroprocessor) embedded in the product uses the measured
impedance, the subject’s weight, and the subject’s gender,height, and age (which are entered in) to determine the percentage of body fat and body water, according to equation formulas. Tanita’s standard formulas have been derived by multiple
regression analysis, using the institutional standard, dual-energy x-ray absorptiometry (DEXA), as a reference.5
Body mass index (BMI) was calculated after the fact using thefollowing equation: [(weight in pounds)/(height in inches height in inches)]  703. BMI expresses weight as adjusted forheight.
Waist-to-hip ratio (WHR) was measured by a tape measure
and calculated as the waist circumference divided by the hip
circumference. Waist measurements were taken at the midpoint
between the upper iliac crest and lower costal margin in the
midaxillary line (the narrowest point of the waist). Hip circumference was measured at the largest point around the buttocks or gluteofemoral fold.
Blood pressure (BP) was measured using the HEM-711AC
OMRON Automatic Blood Pressure Monitor with IntelliSense(Omron Co., Tokyo, Japan). The OMRON monitor uses theoscillometric method of BP measurement, detecting blood’s
movement through the brachial artery and converting it to adigital reading of systolic and diastolic blood pressure.
5
Initial and final measurements were taken at the same time of day (morning).
(Body-fat readings are normally highest in the morning; therefore, because
measures were taken in the morning, these readings may be higher than normal.) In addition, measures were taken 4 weeks apart to eliminate the hydration
fluctuation involved in a woman’s menstruation cycle. Clothing weight was
accounted for by virtue of the fact that the women wore the same uniforms at thetwo sessions.

167

Exercise and the Placebo EffectDependent Variables: Behavioral Measures
In addition to assessing changes in exercise outside of work
(including gym attendance, walking to work, or other non-workrelated physical activities), we assessed substance abuse anddiet through questions asking subjects to reflect on their habits
over the past 30 days, including how much they ate relative totheir normal intake, how many cigarettes they smoked, howmany servings of vegetables and sugary foods they ate, and how
many glasses of caffeinated beverages, alcoholic beverages, andwater they drank.
RESULTS

Change in Self-Reported Exercise
Subjects’ self-reported exercise was examined using 2 (time:
Time 1, Time 2; within subjects)  2 (condition: control, informed; between subjects) repeated measures analyses of variance (ANOVAs). These analyses yielded no significant effects
for exercise outside of work. Perceived amount of exercise,
however, showed main effects of time, F(1, 65) 5 6.80, prep 5.955, Z2 5 .10, and condition, F(1, 65) 5 4.79, prep 5 .910, Z2
5 .07, which were qualified by a significant interaction, F(1, 65)
5 6.34, prep 5 .955, Z2 5 .09 (see Table 1). Simple effects tests
demonstrated that subjects in the informed condition reported
higher levels of perceived amount of exercise at Time 2 than did
subjects in the control condition, t(38) 5 6.72, prep > .99,
whereas there were no significant differences between conditions at Time 1, t(52) 5 0.40, prep 5 .749. Similar results were
found for perceived regular exercise and perceived work as
exercise. Thus, the experimental group increased their perceived exercise over the course of the study, whereas the control
group did not, and neither group increased their actual levels ofactivity. Table 1 shows the means and standard deviations forthese changes, which are illustrated graphically in Figure 1.
Change in Dependent Variables: Physiological Measures
Repeated measures 2 (time: Time 1, Time 2; within subjects)  2(condition: control, informed; between subjects) ANOVAs
yielded a significant interaction effect for weight, F(1, 71) 5
10.89, prep 5 .984, Z2 5 .13; percentage of body fat, F(1, 49) 5
7.31, prep 5 .958, Z2 5 .13; BMI, F(1, 67) 5 7.344, prep 5 .958,
Z2 5 .10; WHR, F(1, 67) 5 7.46, prep 5 .961, Z2 5 .10; andsystolic BP, F(1, 67) 5 7.34, prep 5 .958, Z2 5 .10. No significant differences were found in diastolic BP. Table 1 presents themeans and standard deviations of these variables, which areillustrated graphically in Figure 2.
Change in Dependent Variables: Behavioral Measures
As mentioned, repeated measures ANOVAs yielded no significant effects for subjects’ responses regarding exercise outside ofwork. Similarly, there were no significant changes in subjects’
substance abuse and diet.

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TABLE 1
Self-Reported Exercise and Significant Dependent Variables byTime and Condition
Dependent measure and groupSelf-reported exercise
Perceived amount of exercise
Informed
Control
Perceived regular exercise
Informed
Control
Perceived work as exercise
Informed
Control
Physiological variables
WeightInformed
Control
Body mass index
Informed
Control
Body-fat percentage
Informed
Control
Waist-to-hip ratio
Informed
Control
Systolic blood pressure
Informed
Control
Diastolic blood pressure
Informed
ControlTime 1Time 2

3.76 (3.41)
3.17 (3.42)

5.74 (3.48)nnn
3.21 (2.67)

0.42 (0.5)
0.39 (0.5)

0.68 (0.5)nn
0.36 (0.5)

0.29 (0.4)
0.23 (0.4)

0.45 (0.5)nn
0.15 (0.4)

145.5 (22.4)
146.92 (23.2)

143.72 (22.7)nnn
146.71 (23.0)

26.05 (3.8)
26.89 (4.8)

25.70 (3.8)nnn
26.86 (4.8)

34.84 (6.3)
35.71 (4.9)

34.34 (6.3)n35.89 (4.79)

0.834 (0.05)
0.853 (0.06)

0.826 (0.06)nn
0.855 (0.06)

129.55 (24.3)
128.87 (22.1)

119.9 (19.8)nn
127.27 (21.73)

79.55 (17.48)
77.80 (12.85)

74.88 (14.47)n
75.03 (11.60)

Note. Standard deviations are given in parentheses. Paired-sample t tests
indicated that on each of these variables, the informed group differed significantly between Time 1 and Time 2 (np < .05, nnp < .01, nnnp < .001).

DISCUSSION

Mind-Set Matters
This study did not test the placebo effect in the traditionalmanner, in which expectations are aroused through inert pills or
sham procedures. Rather, subjects were actually engaging in a
behavior that is clinically proven to have positive effects on thephysiological variables measured (e.g., CDC, 1996; Hubert,
Feinleib, McNamara, & Castelli, 1983; Lee, Manson, Hennekens, & Paffenbarger, 1993; Press, Freestone, & George, 2003;
Raglan & Morgan, 1987; Schnohr, Scharling, & Jensen, 2003;
Tipton, 1984). To determine if the placebo effect plays a role inthe benefits of exercise, this study investigated whether subjects’ mind-set (in this case, their perceived levels of exercise)
could inhibit or enhance the health benefits of exercise independently of actual exercise.
Although it is clear that the room attendants studied met or
exceeded the Surgeon General’s recommendations for physicalVolume 18—Number 2

Alia J. Crum and Ellen J. Langer

Fig. 1. Changes in self-reported exercise as a function of time and group. Bars denote standard errors of the means.

activity, initial measures suggest that the subjects were notaware that their work is good exercise. At the onset of the experiment, 66.6% of subjects reported not exercising regularly,
and 36.8% reported not getting any exercise. Interestingly, thehealth of the room attendants reflected their perceived levels of

exercise rather than their actual levels: According to their initialphysiological measures, the subjects were at risk with respect toBP, BMI, percentage of body fat, and WHR—all important indicators of health. These results suggest the possibility that at
the onset of the study, the room attendants were not receiving the

Fig. 2. Changes in physiological dependent variables as a function of time and group. Bars denote standard errors of the means. BMI 5 body massindex.

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169

Exercise and the Placebo Effectfull benefits of their exercise because they were not aware thatthey were getting exercise at work. Of course, there may havebeen many confounding reasons (e.g., genetics or diet) why these
women were unhealthy despite their intense activity levels.
Over the course of the study, the percentage of informed
subjects who reported exercising regularly (perceived regularexercise) doubled (39.4% to 79.4%), and the average amount of
exercise that subjects in the informed group believed themselves to be getting (perceived amount of exercise) increased bymore than 20%. It is important to note that although the informed room attendants did report higher levels of exercise at
the end of the study, they did not report getting any additional
exercise outside of work. In addition, although the subjects in
the informed group showed a significant increase in recognizing
their work as a form of exercise, their actual workload did notchange. Thus, the changes in reported physical activity appear
to be attributable not to actual increases in physical activity, but
to a shift in mind-set initiated by the information given to them in
the intervention.
This shift in mind-set in the informed group was accompanied
by remarkable improvement in physiological measures associated with exercise. After only 4 weeks of knowing that their work
is good exercise, the subjects in the informed group lost an average of 2 pounds,6 lowered their systolic BP by 10 points,7 andwere significantly healthier as measured by body-fat percentage, BMI, and WHR. These were small but meaningful changes
given the state of health the subjects were in, especially considering that the change occurred in just 4 weeks. All of thesechanges were significantly greater than the changes in thecontrol group. These results support our hypothesis that increasing perceived exercise independently of actual exercise
results in subsequent physiological improvements.

But How?
How exactly did the change in mind-set bring about such significant physiological changes? Conventional science assumes
that in order for weight to be lost and body fat to be reduced,
certain biological and physiological events must also take place.
In the case of BP, it is assumed that it is lowered during exercise
because the peripheral blood vessels are dilated, and that, overtime, the attenuating effect of exercise on the sympathetic
6
The fact that these subjects significantly reduced body-fat percentage in
addition to significantly losing weight makes the weight loss even more important because it indicates that these women lost body fat rather than water
weight.
7
In an effort to make BP readings as reliable as possible, we controlled forseveral variables that are known to cause fluctuation: substance abuse (subjects
reported no significant changes in alcohol, caffeine, or tobacco use during thestudy), diet (subjects reported no significant change in diet), time of day (BPwas taken at the same time of day in the two sessions), hormonal regulation (BPwas taken 4 weeks apart to control for fluctuation due to menstruation), heart
rate (there was no significant difference in heart rate between Time 1 and Time2), and immediate physical activity (BP was measured both times after subjects
had been sitting for at least 10 min, to ensure that resting BP was measured).

170

nervous system’s activity helps to reduce rennin-angiotensin
system activity, reset baroreceptors, and promote arterial vasodilation (which helps to control BP; CDC, 1996). In the case ofweight, it is assumed that exercise helps to reduce body fat byincreasing energy expenditure: To the extent that energy expenditure exceeds caloric intake, the result is weight loss
(theoretically, about 1 pound of fat energy is lost for each
additional 3,500 kilocalories burned; CDC, 1996).
Given this knowledge, one interpretation of our results regarding the relationship between increased perceived exercise
and improved health would be that they were mediated by achange in behavior. The data collected in this study, however, do
not support this conclusion. As mentioned, the room attendants
did not report any increase in exercise outside of work, nor did
they experience any increase in workload over the course of thestudy. In addition, the subjects reported their habits had notchanged over the past 30 days with respect to how much they ate(including servings of sugary foods and vegetables) and how
much they drank (caffeine, alcohol, and water). Thus, neither
increased exercise nor decreased caloric intake was reportedby the subjects.
Of course, it is possible that the room attendants actually didchange their behavior—actually did cut back on calories, improve the quality of the food they ate, or work harder or moreenergetically—but did not report such changes.8 However,previous research has found it very difficult to change behaviorof this sort (Deutschman, 2005). Thus, even if these behavioral
changes did occur as a result of the intervention, that too would
make these results interesting.
In summary, the data collected in this study, coupled withprevious research indicating the difficulty of changing behavior,
make it unlikely that the relationship between mind-set andimprovements in health was mediated by a change in behavior.
In either case, whether the change in physiological health was
brought about directly or indirectly, it is clear that health issignificantly affected by mind-set.
IMPLICATIONS AND FUTURE RESEARCH

The results of this study provide another example of the power ofthe placebo effect. The moderating role of mind-set and its
ability to enhance health should be identified further, substantiated, and utilized. The present results may have particular
relevance for treating diseases associated with a sedentary
lifestyle.
There is still no generally accepted, scientifically groundedmodel substantiating the relationship between mind-set andhealth, although several models have been proposed (see Lovallo, 2005). The present findings warrant investigation in thisarea.
8
Future research might benefit from using measures (e.g., pedometers, foodjournals, or other people’s assessment of diet and activity levels) to enhancecontrol for these variables.

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Alia J. Crum and Ellen J. Langer

People have mindlessly overlooked what it means that placebos are inert. Ultimately, each individual is responsible for
their effects. Recognizing this suggests that it is time for us all to
explore more direct means of controlling our health, such as
pursuing mindfulness (see Langer, 1989) as a tool to actively anddeliberately change our mind-sets.
Acknowledgments—The authors wish to thank Cathy Crum,
Maja Dijikic, Adam Grant, and Carey Morwedge for theircomments on this manuscript.
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(RECEIVED 1/3/06; REVISION ACCEPTED 5/1/06;
FINAL MATERIALS RECEIVED 5/23/06)

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