Download Correlation between prior exercise and present health and fitness

ORIGINAL CONTRIBUTION
Correlation Between Prior Exercise and Present Health
and Fitness Status of Entering Medical Students
D. Fred Peterson, PhD
Brian F. Degenhardt, DO
Carol M. Smith, MS
Four hundred forty-one students were tested for strength,
agility, flexibility, and endurance as well as for body fat,
heart rate, and blood pressure. Questionnaires estimated
prior exercise, sleep, diet, and leisure habits.
Students were more fit than published norms. Their
reported prior exercise habits correlated positively with
estimated VO2max. Positive results of endurance tests correlated with better eating habits and lower blood pressure. Strong correlation existed between reported exercise
and lower body fat, heart rate, and diastolic blood pressure.
Blood pressure was in the hypertensive range in 57 individuals, and high blood pressure correlated with higher
body weight, percent body fat, and resting heart rate.
The authors concluded that most incoming medical
students are fit and physically active. Positive correlations
exist between prior exercise habits, performance on fitness tests, and indicators of reduced health risks. There was
high correlation between risk factors for heart disease and
measured blood pressure.
A
s health care providers, physicians should be aware of
the relationship between health and physical fitness.
The American Heart Association states that “regular aerobic
activity plays a role in prevention of cardiovascular disease.”1
That report encouraged medical schools and graduate training
programs to prepare physicians to recommend exercise to
their patients.1 To maximize effectiveness, physicians should
be prepared to provide knowledgeable counseling and project a lifestyle consistent with good physical and emotional
health.2
The exercise and fitness habits of today’s entering medical students are not known. Additionally, there is no evidence
of a significant move on the part of medical schools to promote health and physical fitness in the curriculum. A general
From the Departments of Physiology (Peterson), Osteopathic Manipulative
Medicine (Degenhardt), and Student Affairs (Smith), Kirksville College of
Osteopathic Medicine, Kirksville, Missouri.
Supported by American Osteopathic Association Grants No. 97-04-447 and
No. 98-04-461.
Address correspondence to D. Fred Peterson, PhD, Department of Physiology, Kirksville College of Osteopathic Medicine, Kirksville, MO 63501.
increase in the number of health promotion programs for
medical students through the 1980s and early 1990s3 has
been followed by a decline.4 Currently, only 20% of all US and
Canadian medical schools offer any health promotion programs for their students, and few of these programs are comprehensive in design.4 Hence, habits practiced by students
before entering medical school may constitute the primary
basis for their own lifetime exercise and fitness habits as well
as the lifestyle that they will promote.
The preestablished lifestyle habits of entering freshman
medical students has not been evaluated. Recent studies
have evaluated the physical fitness of first-year medical students in the United States5,6 and Canada.7 The time during the
school year when data were collected was not specified in any
of these studies; therefore, changes in exercise habits due to
academic pressures may have already begun to influence
the results. We hypothesized that entering medical students,
through personal awareness and vocational choice, already
practice good health habits as reflected in their own level of
physical activity and fitness.
Methods
Subjects
Students in the classes of 2001 to 2003 at the Kirksville College
of Osteopathic Medicine (KCOM) participated in this study.
The group included 441 (94.8%) of the 465 students enrolling
between 1997 and 1999 and consisted of 320 male and 121
female students averaging 24.8 years of age (SD, 2.8 years). Subjects originated from 40 states, with 88 individuals describing
themselves as nonwhite. Nine of those were members of
underrepresented minority groups (black or Hispanic). The
other 79 listed themselves as Indian, Pakistani, Asian, Pacific
Islander, or other. Participation was voluntary, and all students signed an informed consent previously approved by
the institutional review board.
Lifestyle Habits and Health History
During orientation each student completed a survey estimating personal exercise, sleep, leisure, and dietary habits
during the past year. Each question, except the one related to
diet, was followed by five choices on a sliding scale appropriate
to that question regarding frequency of occurrence or duration
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ORIGINAL CONTRIBUTION
Table 1
Characteristics and Fitness Status of Entering Medical Students
KCOM Men
Variable
Published Norms
or
50th Percentile*
Mean SD
KCOM Women
Mean SD
Published Norms
or
50th Percentile*
Age, y
25.0 2.7†
——
24.2 2.9
——
Age range, y
21-42
——
21-35
——
Married
129 (40%)†
——
17 (14%)
——
Height, cm
177.9 7.1†
——
163.7 6.9
——
Weight, kg
79.7 12.0†
——
62.6 12.1
——
Waist/hip ratio
0.87 0.04†
——
0.79 0.04
——
Body fat, %
13.1 15-2011
20.4 5.8
2511
Resting heart rate, beats/min
69.1 10.6
6711
71.8 12.3
6911
123
114 11
116
76
71 9
70
4.7†
Systolic blood pressure, mm Hg
125 Diastolic blood pressure, mm Hg
75 9†
VO2max (mL/min/kg)
42.1 11.4 (315)†
40-4411
35.6 10.7 (118)
37-4011
Sit and reach, in
3.3 3.2
0-111
5.4 2.7 (120)
3-411
Bench press (reps)‡
28.9 15.5 (313)
20-2211
32.3 18.4 (41)
17-2011
Grip strength, lb§
237.6 40.6
224-22510
135.4 25.8 (81)
106-10810
Vertical jump, in
21.2 3.5 (316)†
169
13.4 2.4 (118)
89
Curl ups (reps)
69.0 13.5 (317)†
458
61.9 18.3 (117)
408
Quad jump test score
25.1 4.6
13-249
23.5 3.9 (116)
14-269
13†
(317)v
(210)†
(316)†
* Average values for students are compared, by gender, to values found in published tables. A single number in the published norms column
signifies a single value existed for all ages represented in our study. A range of numbers in the published norms column indicates multiple
published values for the different age groups represented in our study. References for published norms are in parentheses. A total of 320 male
and 121 female subjects are represented in the table. Injuries prevented some subjects from performing some fitness tests. The number of subjects
who completed a given test is in parentheses.
† Men significantly different from women, P .001.
‡ Bench press was only obtained for women during 1999.
§ Grip strength was obtained in 1998 and 1999 only.
of the activity. The dietary habits question had a 5-point scale
of responses: 5, consistent well-balanced diet; 4, fewer than
three junk food meals per week; 3, at least half well-balanced
meals; 2, occasional good meals; and 1, mostly fast food, high
fat, and sugar.
Each student completed a comprehensive medical history questionnaire and underwent a medical examination,
which was conducted by KCOM physicians and upper class
students during the first week of classes. All subjects were
cleared to participate in physical activity and to undergo physical fitness testing.
Fitness Evaluation
Physical fitness assessment was conducted at the campus fitness center during the second or third week of classes. Resting
heart rate and blood pressure were measured before fitness
testing, with students lying supine for at least 4 minutes of rest.
Percent body fat was estimated by the 3-skinfold-thickness
method8 using Lang calipers. These measurements were all performed by one individual with more than 15 years’ experience
to ensure consistency. Waist and hip measurements were
made according to the technique described in Cotton8 while
subjects were standing. From these measurements, waist-tohip ratio was calculated.
Performance of each subject in areas of strength,
endurance, flexibility, and agility was evaluated using fitness
measures previously used in the campus wellness program.
The VO2max was predicted with the Astrand cycle test, a 6minute submaximal cycle ergometer test8 using calibrated
Monark stationary cycles. Vertical jump was measured by the
method of Johnson and Nelson9 counting the best of two
attempts using a Vertec apparatus (Sports Imports Inc).
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ORIGINAL CONTRIBUTION
Abdominal muscle strength was estimated with curl ups.8 Grip
strength was measured using a calibrated Jamar hand
dynamometer.10 Two trials were made with each hand, and the
best scores for each hand were added together for a total score.
Bench press repetitions were obtained using free weights with
the bar set at 80 pounds for men and 35 pounds for women. The
Young Men’s Christian Association protocol was followed at
a cadence of 60 repetitions per minute.11 Trunk flexion (flexibility) was measured using a sit and reach box (Novel Products).
The best of three trials was counted. Each participant was
tested twice for agility using the quadrant jump test described
by Johnson and Nelson.9 Occasionally, a student chose not to
participate in a particular test due to an existing acute or chronic
physical limitation.
Statistical Analysis
All data were compared using correlation statistics in an SPSS
statistical package. Spearman’s correlation coefficient was used
to account for survey questions and demographic information, such as gender and marital status, which were not normally distributed. Interaction between two variables was considered significant if P .05. Values in tables and text are
reported as mean plus or minus SD.
Results
Subjects
Characteristics of subjects are indicated in Table 1 and in
Methods. Men were significantly older than women and were
more likely to be married. Married students were significantly
older than the unmarried ones (26.0 0.3 years versus 23.7 0.2 years; P .01).
Health Status
General physical characteristics are listed in Table 1. None of the
subjects had a chronic condition that would prevent participation in physical activity. Men had higher systolic and diastolic blood pressure than women. Fifty-four men and three
women had systolic blood pressure of 140 mm Hg or greater
and/or diastolic blood pressure of 90 mm Hg or greater. Resting
heart rate was similar between genders. Ten men and 12 women
had resting heart rates of 90 beats/min or greater.
Prior Lifestyle Habits
Thirty-five (7%) students reported that they had not exercised
during the preceding year. The group as a whole averaged
exercising 2.5 to 3 times per week, spending between 40 and 50
minutes per session at a moderately intense level (3.7 on a scale
of 1 to 5; ranging from no exercise to sustained, high-aerobic
activity). There were no differences in any of these variables
between men and women or between white and nonwhite
groups. Subjects reported sleeping 7 to 8 hours per night. Students indicated that they averaged slightly more than 50%
well-balanced meals during the previous year and took four to
five leisure breaks per week lasting 1 to 1.5 hours each.
Physical Fitness
As a group, these students exceeded published national norms
for their age and gender-matched peers for our measures of
strength, flexibility, and agility (Table 1). Collectively, men and
women were at or slightly below published norms for estimated endurance (VO2max). Subjects were substantially better
than average for percent body fat, and waist-to-hip ratios averaged well below the high-risk range for heart disease.8
Correlations
Gender—Men scored higher on measures of strength, agility,
and endurance when compared directly with the women.
Men also had lower percent body fat but higher waist-to-hip
ratio than women (Table 1). Women were more flexible. No
gender differences were found for past exercise, sleep, leisure,
or dietary habits.
Marital Relationships—Correlations between exercise history, physical measurements, and fitness scores are indicated
by gender in Table 2 (men lower left, women upper right).
Married men spent less time exercising, exercised less vigorously during the preceding year, and were heavier than single
men. Married women exercised less often than single women.
There were no identifiable differences in fitness measurements
between married and single individuals of either gender.
Personal Lifestyle and Fitness—Prior regular exercise was
positively correlated with lower resting heart rates and lower
percent body fat in both genders. Bench press, curl ups, and
VO2max were all highly correlated with past exercise frequency
in both genders. In general, positive fitness measures were
more strongly associated with frequency and intensity of exercise than with duration. Good dietary habits correlated with
lower diastolic blood pressure and lower body fat. Leisure
breaks and sleep correlated with some other variables (Table 2),
but no pattern was apparent.
Fitness Interactions—Numerous measures were correlated
with weight. In both genders, blood pressure was positively
correlated with body weight, percent body fat, and heart rate,
but negatively correlated with estimated VO2max (Table 2).
The VO2max was also negatively correlated with body weight,
resting heart rate, and percent body fat in both genders.
VO2max correlated positively with numerous other fitness
measures, and most measures of strength were positively correlated with one another (Table 2).
Comment
Our results indicate that most subjects were in good health and
most (93%) had engaged in some form of regular physical
activity during the previous year. There were no reported differences in degree of physical activity between genders. Collectively, they performed particularly well on tests of agility,
flexibility, and strength. Our subjects were on average leaner
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ORIGINAL CONTRIBUTION
Table 2
Correlations Between Measured Variables*
Married
Exercise
Frequency
Exercise
Duration
Exercise
Intensity
Nightly
Sleep
Leisure
Breaks
Diet
Height
Weight
Resting
Heart
Rate
Married
—–—
F† (N)
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
Exercise
frequency
M§ (N)
—–—
F§
F§
—–—
—–—
—–—
—–—
—–—
F‡ (N)
Exercise
duration
M§ (N)
M§
—–—
F§
—–—
—–—
—–—
—–—
—–—
F† (N)
Exercise
Intensity
M‡ (N)
M§
M§
—–—
—–—
—–—
—–—
—–—
—–—
F§ (N)
Nightly
sleep
—–—
—–—
—–—
—–—
—–—
F‡
—–—
—–—
—–—
—–—
Leisure
breaks
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
Diet
—–—
M†
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
Height
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
F§
—–—
Weight
M†
—–—
—–—
M‡ (N)
—–—
—–—
—–—
M§
—–—
F†
Resting
heart
rate
—–—
M† (N)
—–—
M§ (N)
—–—
—–—
—–—
—–—
—–—
—–—
Systolic
blood
pressure
—–—
—–—
—–—
—–—
—–—
—–—
—–—
M§
M§
M§
Diastolic
blood
pressure
—–—
—–—
—–—
M‡ (N)
—–—
—–—
M† (N)
—–—
M‡
M§
Percent
body
fat
—–—
M§ (N)
M‡ (N)
M§ (N)
—–—
M†
M§ (N)
—–—
M§
M§
Waist/
hip
ratio
—–—
—–—
—–—
M‡ (N)
—–—
—–—
—–—
M† (N)
M§
M†
Bench
press
—–—
M§
M‡
—–—
—–—
—–—
M† (N)
—–—
M§
M†(N)
Grip
strength
—–—
—–—
—–—
—–—
—–—
—–—
—–—
M§
M§
—–—
Curl ups
—–—
M‡
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
Vertical
jump
—–—
—–—
M§
—–—
—–—
—–—
—–—
M§
—–—
—–—
Agility
—–—
—–—
—–—
—–—
—–—
—–—
—–—
M‡
—–—
—–—
Sit and
reach
—–—
M†
—–—
M†
—–—
—–—
—–—
—–—
—–—
M†(N)
VO2max
—–—
M§
M‡
M§
—–—
—–—
—–—
—–—
M§ (N)
M§ (N)
*This table identifies areas of significant correlation between each measured variable as it relates to every other variable.
Variables that are correlated among the female (F) subjects are illustrated in the upper right half of the table. Correlations
among male (M) subjects are in the lower left half of the table.
†P.05
‡P.01
§P.001
(N) indicates that the relationship is negative. For example, the interaction between exercise frequency and resting heart rate
for women indicates a negative relationship, ie, high exercise frequency correlates with low resting heart rate at P.01.
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ORIGINAL CONTRIBUTION
Table 2
Correlations Between Measured Variables*
Systolic
Blood
Pressure
Diastolic
Blood
Pressure
Percent
Body
Fat
Waist
Hip
Ratio
Bench
Press
Grip
Strength
Curl
Ups
Vertical
Jump
Agility
Sit and
Reach
VO2max
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
F† (N)
—–—
F§
—–—
F§
F†
—–—
—–—
F§
—–—
—–—
—–—
—–—
—–—
—–—
F‡
—–—
—–—
—–—
—–—
—–—
—–—
F† (N)
—–—
—–—
—–—
—–—
—–—
—–—
—–—
F†
—–—
—–—
F†
F‡
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
F†
(N)
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
F†
F†
—–—
—–—
—–—
—–—
F§
—–—
—–—
—–—
—–—
—–—
F§
F§
F§
F§
—–—
F§
—–—
—–—
—–—
—–—
F§ (N)
F‡
F§
F§
—–—
—–—
—–—
—–—
—–—
—–—
—–—
F§ (N)
—–—
F§
F†
—–—
—–—
—–—
—–—
—–—
—–—
—–—
F‡ (N)
M§
—–—
F‡
—–—
—–—
F‡
F†(N)
—–—
—–—
—–—
F§ (N)
M†
M‡
—–—
F§
—–—
—–—
—–—
—–—
—–—
F‡ (N)
F§ (N)
—–—
—–—
M§
—–—
—–—
—–—
—–—
F†
—–—
—–—
—–—
M§
—–—
M§ (N)
M†
—–—
F†
F§
—–—
—–—
—–—
—–—
—–—
—–—
—–—
—–—
M§
—–—
—–—
F†
—–—
—–—
—–—
M‡
—–—
F‡
F†
F‡
F†
—–—
—–—
—–—
—–—
M§
—–—
M† (N)
M§ (N)
—–—
M§
M§
M†
—–—
F‡
F‡
—–—
—–—
—–—
—–—
—–—
M§
M§
—–—
M§
—–—
—–—
F†
—–—
—–—
M‡ (N)
—–—
M§
—–—
M†
M§
M‡
—–—
—–—
M‡ (N)
M§ (N)
M§ (N)
M§ (N)
M§
—–—
M‡
M‡
—–—
—–—
—–—
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ORIGINAL CONTRIBUTION
than the general population. Their body fat values fell between
“fit” and “athletic” according to Cotton.8 We cannot account
for many of the 24 students who enrolled in medical school
during these 3 years but did not participate in the study. Several had acute conditions that prevented their participation, that
is, pregnancy, recent appendectomy, or sports injury. Because
of the high percentage of students participating, there was
minimal concern for self-selection bias by individuals who
would perform better on the tests that were administered.
Among the 24 who did not participate, several students were
not cleared for physical activity during the prerequisite physical examination screening. Others chose not to attend the
physical examination screening and were, therefore, ineligible
to participate in the fitness assessment. Remarkably, only two
of our subjects had a percent body fat in the obese range.8
Aerobic fitness was the area of poorest performance
among our subjects. Similar performances have been reported
for medical students.5 Values reported from three medical
schools in the United States and South Africa indicated that
most individuals tested in the first 3 years of medical school performed below the 50% level.5,12,13 This suggests that academically competitive premedical students may not be as involved
in aerobic activity as individuals tested by the Young Men’s
Christian Association.11 This contradicted our subjects’ good
performance on measures of strength and flexibility and suggests that many students had preferentially chosen strength
building but less aerobic exercise activities. Because aerobic
exercise is specifically implicated in prevention of cardiovascular disease,1 some of these students may have inadvertently
begun to make physical activity choices with minimal cardiorespiratory value.
Group averages for blood pressure were comparable to
averages compiled from over 40,000 Americans between 1960
and 1991.14 The percentage of our subjects in the clinically
hypertensive range (16.3% of men, 2.5% of women) is less
than most surveys during that time but greater than the most
recent survey, which included 1988 to 1991.14 Our findings
confirm that even among young adults highly motivated to
become health care professionals and who otherwise appeared
to be healthy, those having higher blood pressure also had a
greater likelihood for other risk factors known to be associated
with cardiovascular disease. Higher resting blood pressures
were positively related to higher resting heart rates, higher
percent body fat and body weight, as well as lower estimated
VO2max. Additionally, lower VO2max was strongly associated
with those who exercised less. This suggests that currently
accepted cardiovascular disease risk factors may already be
influencing the less aerobically active individuals in this otherwise asymptomatic young adult population of future health
care providers.
Conclusion
exercise habits (especially frequency and intensity of exercise)
led to positive relationships with lower heart rate, lower percent body fat, higher estimated VO2max, and better scores on
many measures of strength and flexibility. If these results are
representative of entering medical students nationwide, some
students are already practicing poor health habits, and medical schools should become more involved in educating future
physicians so that they are prepared to model good habits
and recommend exercise to their patients.1,2
Acknowledgments
The authors thank Dan Martin, MA, Lynda Grossgrove, MEd,
Bonnie King, and the staff at the Thompson Campus Center for their
assistance in fitness data collection
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Most of these students seem to have incorporated healthy
exercise habits in the past. Our data indicated that established
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