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Validity and reliability of a
one‐minute half sit‐up test of
abdominal strength and endurance
a
Maria H. Diener , Lawrence A. Golding
a b
& Don Diener
a
a
Exercise Physiology Laboratory and Department of
Psychology, University of Nevada, Las Vegas, Las Vegas,
Nevada, 89154
b
Exercise Physiology Laboratory, University of Nevada,
LasVegas, Las Vegas, NV, 89154, U.S.A.
Published online: 08 Jul 2009.
To cite this article: Maria H. Diener , Lawrence A. Golding & Don Diener (1995): Validity
and reliability of a one‐minute half sit‐up test of abdominal strength and endurance, Sports
Medicine, Training and Rehabilitation: An International Journal, 6:2, 105-119
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VALIDITY AND RELIABILITY OF A ONE-MINUTE
HALF SIT-UP TEST OF ABDOMINAL STRENGTH
AND ENDURANCE
MARIA H. DIENER, LAWRENCE A. GOLDING, and DON DIENER
Exercise Physiology Laboratory and Department of Psychology, University of Nevada,
Las Vegas, Las Vegas, Nevada 89154
Downloaded by [UQ Library] at 19:36 22 June 2013
(Received May 27, 1994; accepted January 7, 1995)
Abdominal muscle strength and endurance are widely assessed by means of a timed 1-minute full sit-up test, despite the more accepted use of half sit-ups as a muscular strength and endurance exercise. In the present study,
the validity and reliability of a 1-minute half sit-up protocol was investigated. A total of 142 different subjects
participated in one of four studies designed to assess test-retest reliability, interapparatus reliability, intertester
reliability, and validity. Findings included very high test-retest reliability (r = 0.98), moderately high interapparatus reliability (r = 0.71), and high intertester reliability (r = 0.76). The correlation of the half sit-up test with
the full sit-up test of the National YMCA was 0.67 and the correlation with isometric abdominal strength was
0.38. The proposed half sit-up test was found to be reliable and is proposed as an alternative method of evaluating abdominal strength and endurance.
KEYWORDS: half sit-ups, abdominal strength and endurance, fitness testing
Among the reasons for concern about the condition of the abdominal musculature are the
aesthetic appeal of a flat, toned abdomen (Golding et al., 1989), the importance of strong
abdominal muscles to good posture (Flint and Diehl, 1960; Peterson and Wheeler, 1988;
Troup and Chapman, 1969), and the relationship between strong abdominal muscles and
the diminished incidence of low back pain (Donchin et al., 1990; Helewa et al., 1990;
Langrana and Lee, 1984; Rasch and Allman, 1972). A number of exercises have been designed for the abdominal muscles (Clarke, 1976; Flint, 1965; Sodeberg, 1966; Walters and
Partridge, 1956), but the sit-up is the most commonly used.
A full sit-up, in which the hips are flexed a full 90°, was for years the most widely used
form of sit-up despite the stress placed on the lower back due to anterior pelvic tilt and despite reliance on the hip flexor muscles in the late stage of the test after the spine has been
fully flexed by the abdominal muscles (Allsop, 1971; DeLacerda, 1978; Gilliam, 1976;
Kendall, 1965; Nelson, 1964; Ricci et al., 1981). Recruitment of the hip flexor muscle
group can be detected after the spine has been flexed 30° to 45° (Flint, 1964; LeVeau,
1973; Walters and Partridge, 1956). Support at the feet while performing a sit-up increases
hip flexor activity (Godfrey et al., 1977; LaBan et al, 1965) and decreases rectus abdominis activity (Halpern and Bleck, 1979; Walters and Partridge, 1956).
Half sit-ups (also called "abdominal crunches," "partial sit-ups," and "partial curl-ups")
in which the spine is flexed less than 30° do not recruit the hip flexors and, compared with
Correspondence to: Lawrence A. Golding, Exercise Physiology Laboratory, University of Nevada,
LasVegas, Las Vegas, NV 89154 U.S.A.
105
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106
M. H. DIENERcra/.
a full sit-up, places less stress on the lower back. Performing the half sit-up with the feet
unsupported and the knees flexed maximizes abdominal muscle activity and minimizes
hip flexor activity (Godfrey et al, 1977; Halpern and Bleck, 1979). Different researchers
have reported that abdominal muscle activity is maximized by different degrees of knee
flexion. On the basis of electromyographic (EMG) studies, the optimal angle of the knees
has been variously reported to be 45° (Flint, 1965), 65° (Walters and Partridge, 1956), and
90° (LaBan et al, 1965).
Largely because of the stress placed on the lower back, the full sit-up is being replaced
by the half sit-up in exercise programs. Despite this fact, the full sit-up test continues to
be used to assess abdominal strength and endurance, probably because of the ease of its
administration and the availability of standardized protocols and established norms for it.
Currently, there are three full sit-up protocols in use: (1) the 1-minute full sit-up protocol
(AAHPERD, 1980; American College of Sports Medicine, 1991; Golding et al, 1989),
(2) various unlimited time full sit-up protocols (Johnson and Nelson, 1986; Mathews,
1973; Quinney et al, 1984), and (3) a "pass-fail" full curl-up test (Faulkner and Stewart,
1982) requiring the performance of only one full curl-up (a curl-up involves flexing the
neck, the spine, then the hips, with emphasis on keeping the spine rounded throughout the
movement).
For the same reasons that the half sit-up has replaced the full sit-up in most exercise programs, it would be valuable to develop a standard test of abdominal muscular strength and
endurance using the half sit-up. Two types of half sit-up protocols have been proposed: one
requiring unlimited repetitions (Faulkner et al, 1989; Jette et al, 1984), and a timed 1minute protocol (Macfarlane, 1993; Reebok, 1991; Robertson and Magnusdottir, 1987).
Conceptually, the criterion for proper performance of a half sit-up involves raising the
scapulae from the exercise surface. In practice, a commonly used criterion for a "legal"
half sit-up is to require the hands to slide forward a certain distance (Macfarlane, 1993;
Robertson and Magnusdottir, 1987). Although it is relatively easy to assess whether subjects have met this criterion, it is not clear whether a test based on sliding the hands forward measures the same thing as a test based on raising the scapulae a specific degree
from the horizontal position. It is possible, for example, that the "reach" criterion measures, in part, flexibility, putting the individual with poor upper spine flexibility at a disadvantage, while favoring those with good shoulder flexibility (Faulkner et al, 1989;
Robertson and Magnusdottir, 1987).
EXPERIMENT 1: TEST-RETEST RELIABILITY
Two testing instruments were constructed to standardize the half sit-up test. Apparatus A
was designed to ensure that a correct half sit-up was counted only when the scapulae were
raised from the exercise surface. Apparatus B, designed to be suitable for field testing, was
based on the criterion of sliding the hands forward 3.5 inches. In experiment 1, test-retest
reliability was investigated for both of these half sit-up devices.
Subjects
Subjects were recruited by a variety of means, including announcements posted on campus bulletin boards and published in the campus and city newspapers. As an incentive to
participate, subjects were offered a brief fitness evaluation. All subjects were in apparent
HALF SIT-UP TEST
107
good health. Volunteers with a history of low back pain were eliminated from the study.
Percent body fat (Jackson-Pollock sum of four sites, Golding et al, 1989), aerobic fitness
(3-minute step-test, Golding et al., 1989), and spine and hamstring flexibility (sit-andreach, Golding et al., 1989) were measured for all subjects. A description of the characteristics of the subjects participating in all of the experiments of the present study is
presented in Table I.
Fourteen women and 14 men, ranging in age from 18 to 72 years (median age, 21),
served as subjects for the test of apparatus A. Twenty-one women and 11 men 18 to 43
years of age (median age, 24) participated in the test of apparatus B.
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Apparatus and Procedure
Apparatus A. This apparatus consisted of an adjustable supporting arm with a contact plate
that triggered a common lap counter when a very light pressure was applied to it (Fig. 1).
The apparatus was adjusted so that the forehead touched the plate at the apex of each half
sit-up. The subject lay supine with the knee joint at right angles (90°), the feet flat on a neoprene mat (5/8 inch medium density), and the hands held across the chest. The head and
the spine were flexed until the inferior angle of the scapulae just left the mat. A 30° wedge
maintained the position while the apparatus was adjusted to the correct height. This guaranteed contact at the maximum reach of the half sit-up. The wedge was then removed and
the subject performed as many half sit-ups as possible in 1 minute. A correct half sit-up was
scored when the forehead contacted the plate and the scapulae returned to the mat.
TABLE 1
Statistics describing the 142 subjects from all experiments
Statistics
Variables
Age (yr)
Height (inches)
Weight (pounds)
Body Fat (%)
Recovery heart rate* (b • min')
Cardiorespiratory fitness levelT
Flexibility (inches)
Women (n = 82)
Age(yr)
Height (inches)
Weight (pounds)
Body Fat (%)
Recovery heart rate* (b • min')
Cardiorespiratory fitness level'
Flexibility (inches)
Men (n = 60)
Age(yr)
Height (inches)
Weight (pounds)
Body Fat (%)
Recovery heart rate* (b • min ')
Cardiorespiratory fitness level?
Flexibility (inches)
Mean
28.88
66.70
147.11
18.93
106.73
3.93
17.24
SD
11.92
3.98
26.84
7.00
19.39
1.89
4.32
Minimum
16
57
103
4.4
58
1
6
28.96
64.81
133.22
22.42
111.38
3.92
18.62
10.97
3.15
18.60
5.24
20.30
2.01
3.82
16
58
103
12.3
67
1
9
67
78
186
34.7
145
7
27
28.77
69.28
166.10
14.21
100.16
3.96
15.42
13.21
3.52
24.73
6.29
15.99
1.73
4.30
18
57
120
4.4
58
1
6
72
76
230
29.9
151
7
25
•Kasch 3 minute step test.
^1 = excellent; 2 = good; 3 = above average; 4 = average; 5 = below average; 6 = poor, 7 = very poor.
Maximum
72
78
230
34.7
151
7
27
108
M. H. V1ENER etal.
:WMQNUTS
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HOLES
KNEES AT RIGHT ANGLES
PIATFOMM
FIGURE 1 Apparatus A: Detail and correct positioning of subject performing a half sit-up. See text
for caution in using this apparatus.
A caution about the use of apparatus A is warranted. It is possible that a highly motivated subject, especially on fatigue of the abdominal muscles, might attempt to activate
the counter mechanism by an exaggerated forward head lean and thus risk hyperflexion of
the cervical spine. In practice, this type of motion is not effective and none of the subjects
of the present study were observed to attempt to reach the counter by an exaggerated head
lean. Nevertheless, it is prudent to caution a subject not to attempt to reach the trigger
mechanism by thrusting the head forward and experimenters should monitor subjects
carefully for any motion that risks hyperflexion of the spine.
Apparatus B. Apparatus B consisted of a plywood board covered with a neoprene pad.
Two strips of self-adherent Velcro were placed, rough side up, perpendicular to the body
(Fig. 2). The strips were placed 3.5 inches apart. A pilot study revealed that shorter distances, including the 3 inches (7.62 cm) suggested by Robertson and Magnusdottir (1987),
allowed highly motivated subjects to reach the goal distance by depressing their shoulders
without actually performing spine flexion. When the goal distance was set at 3.5 inches,
subjects were forced to flex the spine. Subjects lay supine with the hands pronated and the
fingertips on the first strip of Velcro. The subjects were instructed to maintain the shoulders in a relaxed position (neither depressed nor elevated). Compliance with this instruction was verified visually by the experimenter. A subject flexed the spine so that the
fingertips of each hand reached the second strip of Velcro, then returned to the starting position. A subject performed as many repetitions as possible in 1 minute.
A subject was randomly assigned to apparatus A or apparatus B and given a half sit-up
test as already described. A subject was given no instructions about stretching or warm-up
but was allowed to do so briefly if desired. Following recovery from the first sit-up test (return to resting heart rate), a subject was given, in sequence with no rest periods, the step
test, the flexibility test, and skinfold test. Following these tests a subject was given the second sit-up test. The interval between the first and second sit-up test was 10 to 15 minutes.
HALF SIT-UP TEST
109
Top View
rnywOOQ R1SX
Neoprene mat
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4a1
1*x«rVelcro strip
1* x 8* Velcro strip
Side View
KNSES AT f«QHT ANGLES
FIGURE 2 Apparatus B: Detail and correct positioning of subject performing a half sit-up.
Results and Discussion
An alpha level of 0.05 was adopted for all statistical tests. The mean number of sit-ups performed with each apparatus for all subjects and for men and women separately is reported
in Table II. Test-retest reliability was assessed by both Pearson's r and the intraclass corre-
110
•
M. H. DIENER et al.
TABLE II
Number of half sit-ups* performed in experiment 1
Session 1
Session 2
Mean
SD
Mean
SD
All subjects
Apparatus A (contact plate)
Apparatus B (reach 3.5 inches)
Men
Apparatus A (contact plate)
Apparatus B (reach 3.5 inches)
Women
Apparatus A (contact plate)
Apparatus B (reach 3.5 inches)
No.
53.9
50.8
19.8
12.7
56.6
53.2
21.8
13.2
28
32
61.4
56.5
15.4
11.8
63.5
59.5
18.8
12.1
14
11
46.5
47.8
21.6
12.4
49.7
50.0
23.1
12.8
14
21
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•One-minute test, maximum effort
lation. Reliability was high for both devices but slightly higher for apparatus B than for apparatus A (apparatus A, r = 0.941, p < 0.001; intraclass correlation was 0.961; apparatus B,
r = 0.978, p < 0.001; intraclass correlation was 0.980). The tests were similar in reliability
for the male (apparatus A, r = 0.906, p < 0.001; apparatus B, r = 0.982, p < 0.001) and the
female subjects (apparatus A, r = 0.955, p < 0.001; apparatus B, r = 0.973, p < 0.001).
A paired-sample t test was computed, comparing the number of half sit-ups performed
in each set for each apparatus. Subjects performed significantly more half sit-ups in the
second session using either apparatus (apparatus A, / = -2.25, p < 0.05; apparatus B, t =
-2.89, p < 0.01), possibly due to a learning effect. Because the apparatus and protocol
were both new to the subjects, it seems likely that learning, familiarity, and pacing allowed
them to perform slightly better in the second session. This may have been especially true
of apparatus A because of a subject's initial apprehension about triggering the counter
with the forehead, accounting for the slightly higher difference between sessions for this
device. It is also possible that a subject remembered the number of repetitions performed
in the first session and was motivated to better the performance in the second session.
Women showed greater improvement on apparatus A than did men, possibly because of
their greater initial apprehension about triggering the counter. Men, on the other hand, for
unknown reasons, showed a greater improvement on apparatus B.
EXPERIMENT 2: INTERAPPARATUS RELIABILITY
In experiment 2, a subject performed the half sit-up test with both of the testing devices
used in experiment 1. The two devices were compared on the degree to which they produced similar results. A high correlation between performance on the two devices would
confirm that sliding the hands forward 3.5 inches (apparatus B) caused the subject to raise
the scapulae from the exercise surface (apparatus A).
Method
Subjects. Subjects for experiment 2 were drawn from the same pool as those who served
in experiment 1, comprising 18 women and 12 men from 18 to 63 years of age (median
age, 31).
HALF SIT-UP TEST
111
Apparatus and Procedure
The apparatus and testing procedures were the same as used in experiment 1. Half of the
subjects were randomly assigned to begin testing with apparatus A, the other half with apparatus B. Subjects performed one of the two protocols for the 1-minute half sit-up test.
Following recovery of resting heart rate to baseline after the first sit-up test a subject was
given, in sequence, with no rest period, between, the step test, the flexibility test, and skinfold test. The subject was then given the second sit-up test. The interval between the first
and second sit-up test was 10 to 15 minutes.
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Results and Discussion
The mean number of half sit-ups performed with apparatus A and apparatus B was 54.6
(19.3 SD) and 50.3 (15.8 SD), respectively. A correlated t test revealed no significant difference between the number of sit-ups performed on both test instruments (t(29) = 1.74,
p > 0.05). Women performed somewhat fewer sit-ups than men on both instruments (A,
51.3 and B, 49.0 for women; A, 59.7 and B, 52.3 for men). Interapparatus reliability was
assessed with both Pearson's r (r = 0.712, p < 0.001) and the intraclass correlation
(0.810). The moderately high correlation and lack of a significant difference between apparatus A and apparatus B indicate that the two devices measure the same sit-up characteristic of the subjects. Interapparatus reliability was higher for women (r = 0.826, p <
0.001) than for men (r = 0.574, p > 0.05). It is difficult to understand why this should be
the case.
When asked which apparatus they preferred, 91% of the subjects reported a preference
for apparatus A (contact plate), whereas only 9% preferred apparatus B (reach, 3.5
inches). When asked to explain their preference, a number of subjects reported discomfort
around the neck and shoulder area when forced to hold their arms by their sides, others
reported that they were unaccustomed to performing sit-ups with their arms extended, and
still others stated that the contact plate provided better feedback regarding the completion
of a sit-up than did the Velcro strips. Table III shows a comparison of selected features of
each apparatus reported by subjects and experimenters.
TABLE III
Comparison of the two testing devices on selected variables
Variable
Apparatus A
Apparatus B
Somewhat involved
Very easy
Ease of construction
Time of construction
3-4 hours
1 hour
Material cost (approximately)
$30.00
$ 10.00
Subject preference
91%
9%
Field test applicability
Portable
Very portable
Test-retest r
0.941
. 0.964
Advantages
Subjects prefer
Low cost
Easy to administer
Easiest to administer
Disadvantages
Adjustment must be precise
Experimenter monitors
scapulae, hands, and counter
Counter may malfunction
Subjects may cheat
Concern about possible
cervical hyperflexion
112
M. H. DIENER el al.
EXPERIMENT 3: INTERTESTER RELIABILITY
Because of the greater ease of construction and portability of apparatus B, the high interapparatus reliability, and similar test-retest reliability for both devices, further testing was limited to apparatus B. In experiment 3 the intertester reliability of apparatus B was assessed.
Method
Subjects. Ten women and 10 men participated in experiment 3. The subjects ranged in
age from 18 to 49 years, with a median age of 28 years. None of these subjects participated in the other experiments.
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Apparatus and Procedure
The apparatus and testing procedures were the same as those used with apparatus B. Two
naive testers (one male and one female) administered the half sit-up test. Neither tester had
any fitness testing experience, although both were exercise leaders. The testers were not
told the purpose of the experiment. A tester read a set of precise written instructions for
administering the test to a subject and administered the test without further explanation.
Each tester was randomly assigned half of the subjects for the first session and tested the
other half 1 week later.
Results and Discussion
The correlation between the testers was high (r = 0.762, p < 0.001; intraclass correlation
was 0.853). The intertester reliability was somewhat greater for the female subjects (r =
0.840 p < 0.01) than for the male subjects (r = 0.761, p < 0.05).
As in experiment 1, there was a significant difference between the number of repetitions
performed in the first and second session (t = 3.69, p < 0.01). More repetitions were performed in the second session. The group mean half sit-up score performed in sessions 1
and 2 for both testers combined was 49.6 (11.6 SD) and 55.5 (13.4 SD), respectively. The
increase between sessions was twice that found in experiment 1, probably because the
longer interval between retests (1 week versus 10 to 15 minutes) allowed full recovery
from the acute fatigue of a test session or more complete learning of the motor skill
needed to perform the test. The intersession difference undoubtedly resulted in an understatement of intertester reliability by confounding tester and session effects. Thus, subjects
measured first by tester 1 might be expected to perform more sit-ups when examined by
tester 2, whereas those tested last by tester 1 might be expected to perform fewer sit-ups
than when measured by tester 2.
EXPERIMENT 4: CONCURRENT VALIDITY
Concurrent validity was assessed by correlating the scores obtained on the proposed 1minute half sit-up test with a number of other fitness measures, including the YMCA bentknee full sit-up test, an isometric test of abdominal strength, percent body fat, and
recovery heart rate on the step test.
HALF SIT-UP TEST
113
Method
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Subjects. Twenty-one women and 15 men participated in experiment 4. The subjects
ranged in age from 17 to 68 years, with a median age of 23 years. Ten of the subjects of
experiment 4 also participated in either experiment 1 or 2 of the present study, although
their results were not included in the analyses for these experiments. Experiments 1, 2,
and 4 were run concurrently and subjects were initially assigned to these experiments in
order of appearance. Subjects were given the opportunity to participate in other experiments at a later date. Records allowed identification of a subject repeating a test item but
not the experiment that was completed first. Of the 10 subjects who participated in other
experiments, it might be expected that two thirds (roughly 6) participated in prior experiments before their participation in experiment 4.
Apparatus and Procedure
Half Sit-Up Test. The half sit-up test was conducted using apparatus B and procedure previously described.
YMCA Full Sit-Up Test. From a supine position with the knees flexed at 90°, the feet flat
on the ground, and the hands behind the head, subjects flexed the spine and hips until the
left elbow touched the right knee, alternating on each repetition. Subjects performed as
many sit-ups as possible in 1 minute (Golding et al., 1989).
Strength Test. A strength table was used to measure isometric strength of the hip flexors
and the spine flexors (Fig. 3) by isolating and maximizing the pull of these muscle groups
(Clarke, 1966). The tension was measured by a calibrated load cell. A subject's score on
this test was the highest of two trials. Hip strength was defined as the mean of the left and
right hip strength.
Each subject performed a half sit-up test and the YMCA full sit-up test. One of these
tests was conducted at the beginning of each session, the other at the end (about 30 minutes later). Half of the subjects were randomly assigned to take the half sit-up test first;
the other half began with the full sit-up test. The test of abdominal and hip flexor isometric strength was conducted following the first sit-up test. Tests of aerobic fitness (3-minute
step-test, Golding et al, 1989), spine and hamstring flexibility (sit-and-reach, Golding et
al, 1989), and percent body fat (Jackson-Pollock sum of 4 sites, Golding et al, 1989)
were conducted following the isometric strength test in an order that varied unsystematically among subjects. A subject was allowed to rest briefly (2 to 5 minutes) between tests.
Results and Discussion
Table IV presents the mean and standard deviation of each important measure from experiment 4. A matrix of (Pearson) correlations among the measures from experiment 4 is
presented in Table V. A correlation matrix similar to Table V was computed excluding
each subject who had participated in another sit-up experiment. This matrix was similar
to Table V. The greatest difference between any two of the 45 different pairs of correlation
made was the correlation between the full sit-up measure and abdominal strength (0.13 for
the full sample versus -0.15, excluding repeaters). No other pair of correlations differed
by more than 0.18.
114
M. H. DIENER et al.
DETAIL
.-
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DIBECTION OF MOVEMENT
NON-TESTED LEG
DIBECTION OF MOVEMENT
TESTED LEG
FIGURE 3 A: Strength table: Positioning of subject during isometric abdominal strength test, and
detail of load cell. B: Positioning of subject during isometric hip flexor strength test.
HALF SIT-UP TEST
115
TABLE IV
Group mean scores for the half sit-up, full sit-up, and isometric strength from experiment 4
All subjects
Men
Women
Mean
SD
Mean
SD
Mean
SD
Half sit-up (rep)*
59.07
14.25
53.75
15.55
49.95
15.65
Full sit-up (rep)*
37.20
8.27
34.50
9.02
32.57
9.23
Total hip strength (kg)
103.43
41.76
91.46
34.38
82.91
25.75
Abdominal strength (kg)
21.73
8.48
17.26
8.01
14.07
6.02
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*One-minute test, maximum effort.
Variable
10.
l.Age
2. Height
3. Weight
4. Body fat (%)
5. Step test
6. Flexibility
7. Abdominal
strength
8. Full sit-ups
9. Hip strength
10. Half sit-ups
TABLE V
Correlation matrix among variables from all experiments.
Variable
1.
2.
3.
4.
5.
6.
7.
1.00
-O.10
0.04
0.19
-0.13
-0.23
0.10
1.00
0.75*
-0.01
0.15
-0.19
0.09
-0.11
0.22
0.03
0.07
-0.07
0.08
1.00
0.08
0.25
-0.07
0.21
0.03
0.16
-o.oo
8.
9.
1.00
-0.07
0.67*
1.00
0.13
1.00
-0.27
-0.52*
1.00
-0.25
-0.31
1.00
0.20
1.00
-0.58*
-0.16
-0.59*
-0.40*
-0.20
-0.57*
0.10
-0.01
0.11
0.14
0.63*
0.38*
0.44t
1.00
•p £ 0.001; tp £ 0.01; *p £ 0.05.
The correlation between the number of half sit-ups and the number of full sit-ups
(YMCA protocol) performed was moderately high for the entire sample (r = 0.669, p <
0.001). This relationship was somewhat stronger for men (r = 0.736; p < 0.01) than for
women (r = 0.589; p < 0.01). The absence of a higher correlation may be attributable to the
different muscle groups and the greater range of motion necessary to perform the full situp. The correlation was sufficient to conclude that there is a moderately strong relationship
between the current standardized full sit-up test and the proposed half sit-up protocol.
The correlation between isometric abdominal strength and the number of half sit-ups
was not high for the entire sample (r = 0.382, p < 0.05). The correlation was substantially
lower for the men (r = 0.142, p > 0.05) than for the women (r = 0.433, p < 0.05) in the
sample. It seems possible that abdominal strength is not a major limiting factor on the
number of sit-ups that a subject can perform, especially for men. A similar correlation between abdominal strength and other sit-up tests has been obtained in previous studies
(Berger, 1965; Harvey and Scott, 1965; Wedemeyer, 1945). Because sit-up tests require
both strength and endurance, it cannot be expected that all of the variance in the sit-up test
may be accounted for by the strength test alone. In addition, the half sit-up score was measured from an isotonic (dynamic) contraction, whereas the measure of abdominal strength
was an isometric test. The variance shared by isometric and dynamic strength has been reported to be 48% (Knapik et ai, 1983), leaving 52% of the variance due to error or other
factors. The correlation between the full sit-up test and isometric abdominal strength was
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116
M. H. DIENERefa/.
not significant for the entire sample (r = 0.135, p > 0.05) or for men (r = 0.043, p > 0.05)
or women (r = 0.067, p > 0.05) analyzed separately.
The relationship between several measures of fitness and performance on the half situp test was also explored. The correlation with recovery heart rate on the step test was
moderately high for the entire sample (r = -0.566, p < 0.001) as well- as for men (r =
-0.602, p < 0.05) and women (r = -0.582, p < 0.01) separately, suggesting that cardiorespiratory fitness is a component of the half sit-up test. The correlation between performance on the half sit-up test and the sit and reach flexibility test was not significant (all
subjects, r = 0.109, p > 0.05; men, r = 0.205, p > 0.05; women, r = 0.165, p > 0.05). There
is thus little indication that individuals with greater hamstring and lower back flexibility
have an advantage on the test.
The correlation between the number of half sit-ups performed and percent body fat was
moderately high for all subjects (r = -0.591, p < 0.001) and for men (r = -0.565, p < 0.05)
and women (r = -0.539, p < 0.05) separately. The correlation for the entire sample is
slightly higher than the correlation for either men or women separately because, in the entire sample, low body fat tends to identify men, who also perform a greater number of situps than women. Body fat might affect the performance of sit-ups in several ways,
including greater body weight and mechanical interference with the sit-up movement.
Because men tend to accumulate a greater portion of excess fat on the abdomen, one might
expect men to be more susceptible to both on increased body weight and mechanical resistance to movement than women and thus show a greater negative correlation between
body fat and performance on the sit-up test. The small difference between the correlation
for men and women does not provide support for the idea that the relationship between
percent body fat and the number of sit-ups performed is primarily a matter of either mechanical resistance or of increased upper-body weight.
It is possible that the relationship between percent body fat and performance on the situp test is partly affected by cardiorespiratory fitness or by general fitness. Highly fit people tend to have a low percent body fat, a low recovery heart rate, and perform well on the
sit-up test. The correlation between percent body fat and recovery heart rate on the step test
(r = 0.439) does not, however, seem large enough for this indirect relationship to account
for much of the correlation between percent body fat and performance on the sit-up test.
A stepwise multiple regression was performed to investigate the relationship of percent
body fat, cardiorespiratory fitness, and other variables to performance on the half sit-up
test. Variables available to enter the regression equation were age, gender, percent body
fat, recovery heart rate on the step test, abdominal strength, hip strength, and flexibility.
Only percent body fat and recovery heart rate on the step test contributed significantly to
the prediction of performance on the half sit-up test and were used in the equation. The
independent contribution of the latter two variables to the prediction of the half sit-up
score was roughly equal, assuming a standardized regression weight of-0.424 for percent
body fat and -0.380 for the step-test measure. Together these variables accounted for 47%
of the variance in the half sit-up test (multiple R = 0.68, p < 0.001).
Multiple regression analysis indicated that the -0.591 correlation between percent body
fat and performance on the half sit-up test is substantially (-0.424) direct, but partially attributable to the correlation of percent fat with recovery heart rate (r = 0.439) and an independent correlation (-0.380) of recovery heart rate with performance on the half sit-up test
(0.439 x -0.380 = -0.167 + (-0.424) = -0.591). Despite the absence of a significant gender difference in the correlation between percent body fat and number of half sit-ups per-
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HALF SIT-UP TEST
117
formed, the greater portion of this correlation does not seem to be affected by cardiorespiratory or general fitness and thus seems most likely to be due to mechanical factors.
Similarly, the greater portion (-0.380) of the -0.566 correlation between recovery heart rate
on the step test and performance on the half sit-up test is independent of body composition.
Robertson and Magnusdottir (1987) have argued the case for the validity of the sit-up
test as a measure of abdominal muscle strength and endurance based largely on logical
considerations. A sit-up, especially the half sit-up, clearly requires strength of the abdominal musculature, and a test based on a repetition score obviously requires endurance.
Providing empirical assessment of the relative validity of various sit-up tests is not an easy
matter. Isometric and dynamic abdominal strength can be assessed independently of a situp test by procedures described in the present study. It is difficult, however, to propose a
means of assessing the endurance of the abdominal musculature sufficient to provide a criterion against which to assess the validity of a sit-up test. Assessing the endurance of the
abdominal muscles must involve repeated contraction of these muscles. The motion produced by contracting the abdominal muscles is that of a sit-up. Variations in initial posture and criteria for completion are possible, but it is not clear why a specific test should
serve as a criterion against which to measure others.
Besides examining whether a score on a test is correlated with a criterion, it is possible
to assess the validity of a test by examining the degree to which a score on it is correlated
with a measure that is conceptually unrelated to the phenomenon of interest. Finding, for
example, that a score on a sit-up test was more highly correlated with hip strength than
with abdominal strength would raise a question about the validity of such a test. In the present study, a significant correlation was found between performance on the half sit-up test
and measures of cardiorespiratory fitness and body fat, neither of which is directly related
to abdominal strength and endurance.
It may not be possible to devise a test of abdominal muscle strength and endurance that
is free of the effects of cardiorespiratory fitness and body composition. Any test that involves repeated contraction of major muscle groups seems likely to be influenced by cardiorespiratory fitness, although the use of a short test period (such as the 1-minute interval
used in the present test) should minimize this effect. It might be possible to devise a test
based on flexion of the spine from an upright position against an external source of resistance that would be less influenced by the weight of the upper body than a sit-up test, but
any effect of the mechanical resistance of abdominal fat can probably not be eliminated.
Even if the direct influence of body composition and cardiorespiratory fitness could be
eliminated from a test of abdominal muscle strength and endurance, there might well still
remain a correlation among these variables because of a difference between individuals in
overall fitness. Subjects who, for example, exercise regularly tend to have lower body fat,
greater cardiorespiratory fitness, and greater abdominal muscle strength and endurance.
The proposed half sit-up test is reliable, easy to administer, and is at least as well validated as the full sit-up test currently in widespread use. The choice of use of the former
over the latter, however, must be based on more substantial grounds than the demonstrated
difference in reliability and validity of a test. The problem that led to the abandonment of
the full sit-up as a recommended exercise—reliance on the hip flexors and stress on the
lower back—is, of course, a problem to some extent for the half sit-up test as well.
Additionally it may be difficult for the public to take seriously a call to abandon the full
sit up as an exercise when professionals continue to rely on a full sit-up test as a measure
of fitness.
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M. H. DIENER etal.
SUMMARY OF FINDINGS
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1. The proposed protocol for testing abdominal strength and endurance, using a 1-minute
half sit-up test, showed high test-retest reliability (r = 0.98).
2.There was a high correlation (r = 0.71) between the number of half sit-ups performed
using the 3.5 inch hand reach criterion and the number performed using a contact plate
criterion for the completion of a valid half sit-up movement.
3.The intertester reliability of the proposed 1-minute half sit-up test is high (r = 0.76).
4.The 1-minute half sit-up test showed a moderately high correlation with the 1-minute
full sit-up test (r = 0.66).
5. The 1-minute half sit-up test showed a low to moderate relationship with isometric
abdominal strength (r = 0.38), higher than that of the full sit-up test (r = 0.135).
6.There was a moderate correlation between performance of the half sit-up test and percent body fat (r = -0.59) and recovery heart rate on the step test (r = -0.57).
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