Journal of Aging and Physical Activity, 1994,2,206-220
O 1994 Human Kinetics Publishers. Inc.
Maximal Isometric Muscle Strength and
Socioeconomic Status, Health, and Physical Activity
in 75-Year-Old Persons
Taina Rantanen, Pertti Era, Markku Kauppinen,
and Eino Heikkinen
This study analyzes the associations of socioeconomic status (SES), health,
and physical activity with maximal isometric strength in 75-year-old men (n =
104) and women (n = 191). Maximal isometric strength was measured with
dynamometers; the forces were adjusted using body weight. The maximal
forces for women varied from 66% (trunk flexion) to 73% &nee extension)
of those of the men. SES was not associated with muscle force. For men the
trunk forces and elbow flexion force correlated negatively with the number
of chronic diseases, index of musculoskeletal pain, and self-rated health. For
women all the strength test results correlated with self-rated health; the other
health indicators showed significant correlation with trunk extension force
only. For both sexes the physically more active exhibited greater strength.
The index of musculoskeletal symptoms explained the variance on trunk force
factor in both sexes. It was concluded that a higher level of everyday physical
activity and good values in the state-of-health indicators were the most important variables explaining greater strength among the elderly.
Key Words: isometric force, education, occupation, population study, aging
Maximal muscle strength and locomotor abilities have been found to deteriorate with age (Asmussen, Fruensgaard, & Norgaard, 1975; Bassey et al., 1992;
Clement, 1974; Era, Lyyra, Viitasalo, & Heikkinen, 1992; Heikkinen et al., 1993;
Rikli & Busch, 1986; Viitasalo, Era, Leskinen, & Heikkinen, 1985; Young, 1986).
To be performed successfully, everyday motor tasks require a certain amount of
strength, and below this strength threshold functional impairment occurs (Astrand,
1992; Buchner, Cress, Wagner, & de Lateyer, 1992; Buchner & Lateyr, 1991;
Young, 1986). Eventually the well-being of an older individual as well as the
burden on the health care system are connected with the degree of dependence
a person has in everyday life.
Great interindividual variation in strength among the elderly has been
The authors are with the Department of Health Sciences and Gerontology Research
Centre, University of Jyvaskyla, Finland. Request reprints from T. Rantanen, Dept. of
Health Sciences, University of Jyvaskyla, PO Box 35, SF-40351 Jyvtiskyla, Finland.
Isometric Muscle Strength
207
observed (Heikkinen, ArajWi, Era, et al., 1984; Svanborg, 1988; Viitasalo et
al., 1985). Elderly women and men who have maintained a physically active
way of life have greater muscle strength compared to their sedentary peers
(Clement, 1974; Era et al., 1992; Rantanen, Parkatti, & Heikkinen, 1992; Rantanen, Sipila, & Suominen, 1993; Sipila, Viitasalo, Era, & Suominen, 1991).
The strength characteristics of older persons with health problems have
rarely been investigated, due partly to the potential risks attending maximal
performance. Chronic diseases are common among elderly people, however.
Those with no clinically diagnosed chronic diseases constitute a minority of their
age group, with proportions varying from 2% (80-89 years of age) to 8-9%
(70-79 years) (Jylha et al., 1992).
Education and occupation have also been found to correlate with maximal
strength. Young men in physically strenuous occupations exhibit greater strength
than those in more sedentary jobs (Era et al., 1992). Physically strenuous work
does not seem to maintain greater strength; on the contrary, middle-aged persons
doing heavy work (Nygird, LuopajWi, SuumWi, & Ilmarinen, 1988) or those
with less education (Rantanen et al., 1992) had lower muscle strength. Among
retired elderly persons, the results have been contradictory. Aniansson, Grimby,
and Rundgren (1980) found poorer quadriceps strength among 70-year-old men
who had had high occupational physical activity. Era et al. (1992) found no
association between strength and occupational status among 71- to 75-year-old
men, whereas among 70- to 81-year-old women a history of heavy work correlated
positively with trunk extension strength (Rantanen et al., 1993).
Educational background, occupational status, health, and physical activity
are interrelated. Leisure time physical activity was found to be more common
among people of high occupational status and more education who were doing
physically light work than among those doing heavy manual work and having
less education (Aro, Ras&en, & Telama, 1985; Vuolle, Telama, & Laakso, 1986).
In addition, the greater prevalence of chronic diseases and poorer values in stateof-health indicators was associated with a heavy work history, less education,
and lower social status (Cunningham & Kelsey, 1984; Hasan, 1989; Heikkinen
et al., 1993). No studies have examined the simultaneous associations of these
background factors with strength in a representative sample of older people.
The purpose of the present study was to investigate the levels of maximal
isometric strength as well as the associations between socioeconomic status,
health, and physical activity and strength among all the 75-year-old residents of
Jyvaskyla, a medium-sized town in central Finland. Uni- and multivariate analyses
were used to study the significance of the intercorrelated background factors
with respect to maximal strength.
Participants and Methods
This study was implemented as part of a larger gerontological research program
known as the Evergreen project. The study group comprised all those born in
1914 (N = 388) who were permanent residents of the city of Jyvkkyla in August
1989. Six persons had died or moved away before the measurements took place.
A total of 350 persons (92%) were interviewed in their homes and 5 were
interviewed through a family member. In all, 104 men (83%) and 191 women
(75%) subsequently participated in the laboratory examinations. The participation
208
Rantanen, Era, Kauppinen, and Heikkinen
rate for the strength tests among the men was 81%, and among the women it
was 75% of the total eligible population.
BACKGROUND INFORMATION
The home interview dealt with education, occupation, self-rated health, symptoms of
the musculoskeletal system, and physical activity. A 6-point scale was used to assess
level of physical activity in the past year. On this scale a short period of moderate
physical activity is considered equal with a longer period of easy physical activity
(Grimby, 1986; Mattiasson-Nilo et al., 1990). The scale was as follows:
1. Hardly any physical activity;
2. Mostly sitting, sometimes walking, easy gardening or similar tasks, sometimes
light household tasks such as heating up food, dusting, or "clearing away";
3. Light physical exercise around 2 to 4 hours a week such as walking, fishing,
dancing, ordinary gardening; main responsibility for light domestic work such as
cooking, dusting, clearing away, and making beds,taking part in weekly cleaning;
4. Moderate exercise 1to 2 hours a week such as jogging, swimming, gymnastics, heavier gardening, home repairs, or easier activities more than 4 hours
a week; responsible for all domestic activities light and heavy; weekly
vacuum cleaning, washing floors, and window cleaning;
5. Moderate exercise at least 3 hours a week;
6. Hard or very hard exercise several times a week such as jogging or skiing.
An index (range 0-6)describing overall musculoskeletal pain during the
past 2 weeks was calculated as the sum total of symptoms at three localities:
shoulders and neck, back and hips, arms and legs. A 3-point scale was used: 0 =
no pain; 1 = some pain; 2 = a lot of pain. Weight and height were measured using
conventional methods. Body composition was assessed through bioelectrical
impedance (Spectrum 11, RJL Systems, Inc., Detroit) (Lukaski & Bolonchuk,
1987; Lukaski, Johnson, Bolonchuk, & Lykken, 1985).
Information about diagnosed chronic diseases was elicited through a questionnaire that the participant completed at home and brought to the laboratory.
There it was checked during the medical examination and, when necessary,
completed by the physician, who also obtained information about chronic diseases
through clinical observation and questions.
Contraindicationsto the strength tests were evaluated by a physician according to the criteria of the American College of Sports Medicine (1986). Due to
symptoms of the musculoskeletal system, heart problems (recent cardiac infarction or systolic blood pressure over 200 mmHg), or lack of cooperation, 1 woman
and 4 men were excluded from the strength tests.
STRENGTH MEASUREMENTS
The maximal isometric strength of hand grip, arm flexion, and knee extension were
measured on the side of the dominant hand with the subject sitting in an adjustable
dynamometer chair constructed at the Department of Health Sciences (Heikkinen et
al., 1984; Sipila et al., 1991; Viitasalo et al., 1985). Hand grip strength was measured
by a dynamometer fixed to the arm of the chair. Elbow flexion strength was measured
at an angle of 90" in a neutral position (thumb up) with the elbow supported
Isometric Muscle Strength
209
comfortably and the wrist attached by belts to a strain-gauge system. Knee extension
strength was measured at an angle of 60"from full extension. The ankle was fastened
by a belt to a strain-gauge system. Maximal isometric trunk flexion and extension
strengths were measured in a standing position according to Viitasalo, Viljarnaa,
and Komi (1977). The subject was allowed two or three practice trials, after which
three formal trials were performed with a 1-min interval between each. The best
result of the three actual trials was accepted as the result. The strength results
were adjusted for body weight. Relative rather than absolute strength gives a better
indication of mobility in the performance of daily motor tasks.
Statistical Methods
The statistical significance of differences between means was analyzed by the Student
t test or one-way analysis of variance. The associations of strength measures with
the continuous background variables were analyzed by Pearson product-moment
correlations. The associations between muscle force and the discrete variables were
determined by estimating the polyserial correlation coefficients. The chi square test
was used with the cross-tabulation. Multivariate linear structural equation models
were used to analyze the simultaneous associations of the background variables with
the indicators of maximal isometric strength. The models were constructed with the
help of the LISREL VI program (Jiireskog & Sorbom, 1986).
Results
BACKGROUND INFORMATION
All the participants were retired. Some 78% of the men and 90% of the women
had received an elementary education or less. The majority had worked in blue
collar jobs (61% of the men and 58% of the women), and 24% of the women
had been housewives (Table 1).
At the time of the measurements, 63% of the men and 71% of the women
were engaged in light physical activities at most for 2 to 4 hours a week, such as
light walking, dancing, easy gardening, or similar tasks. Another 11% of the men
and 3% of the women claimed to be moderately active at least 3 hours a week,
such as playing tennis, swimming, or jogging (Table 2). The physical characteristics
of the subjects are summarized in Table 3. The men were taller and heavier than
the women. The women had greater body mass index and fat content.
Five men (5%) and 15 women (8%)were found to be free of chronic diseases.
Diseases of the cardiovascular, musculoskeletal, and nervous system were most
common. That is, 49% of the men and 51% of the women had a disease in one of
these systems, 31% of both sexes had two of these diseases, and 4% of the men
and 3% of the women had a disease in all three systems (Figure 1). The prevalence
of these diseases and their combinations did not differ between the sexes. Twelve
men and 18 women had diseases other than those mentioned above, such as mental
disorders, tumors, diseases of the digestive system, and diabetes. Men had on
average 2.0 and women had 2.3 chronic diseases. The majority of the participants
rated their health as average (Table 4). No differences were observed between the
sexes in self-rated health or musculoskeletal symptoms. Among both sexes, self-
210
Rantanen, Era, Kauppinen, and Heikkinen
Table 1 Educational and Occupational Background Among
75-Year-Old Men and Women
Variable
Women
(n = 236)
Men
(n = 119)
Less than elementary school
Elementary school
Lower secondary school
Upper secondary school
Housewife
Farmer
Manual worker
Managerial (higher and lower)
Table 2 Intensity of Physical Activity Among 75-Year-Old Men and Women
Variable
1. Hardly any physical activity
2. Mostly sitting, sometimes walking, light
tasks
3. Light physical exercise about 2-4 hrs/
week, walks
4. Moderate exercise 1-2 hrslweek or easier exercise more than 4 hrslweek
5. Moderate exercise at least 3 hrslweek
6. Hard or very hard regular exercise several
timestweek
Men
(n=104)
Women
(n=191)
9%
3%
20%
22%
34%
46%
26%
11%
26%
3%
0%
0%
x2
13.6**
rated health, index of musculoskeletal symptoms, and number of chronic diseases
were significantly intercorrelated (Table 5).
MUSCLE STRENGTH
The absolute and body-weight-adjusted maximal isometric forces for both sexes are
shown in Figure 2. The smallest difference between the sexes in the body-weightrelated results was observed in leg extension force, with the women able to produce
on average 73% of the mean force exhibited by the men. The greatest difference
was seen in trunk flexion force, in which the corresponding ratio was 66%.
Isometric Muscle Strength
21 1
Table 3 Physical Characteristics of 75-Year-Old Men and Women (mean, SD)
Men
(n = 104)
M
Body height (cm)
Body weight (kg)
Body mass index (kg/m2)
Body fat content (%)
Men
Cardiovascular
169.5
74.1
25.8
21.9
SD
6.2
10.6
3.6
5.9
Women
(n = 191)
M
SD
155.8
67.6
27.8
32.8
5.5
11.6
4.7
7.0
Women
rn
Cardiovascular
Figure 1. Prevalence of diseases in the cardiovascular, musculoskeletal, and nervous
systems and combinations of them among 75-year-old men (n = 102) and women (n =
199). Five men and 15 women had no diagnosed diseases, and 12 men and 18 women
had diseases other than those mentioned above.
First, the associations between background factors and strength were studied
by correlation analyses or by comparing the strength levels between subgroups.
Intensity and frequency of physical activity correlated with greater maximal isometric forces for both sexes (Table 5). Among the men, poorer values in the state-ofhealth indicators (number of chronic diseases, index of musculoskeletal symptoms,
and self-rated health) were associated with low elbow flexion and trunk forces.
Among the women, poor self-rated health correlated with poor values in all the
force variables, but number of chronic diseases and index of musculoskeletal
symptoms correlated negatively with trunk extension strength only. A comparison
of the strength levels between the healthy women (no diseases) and those having
a disease of the musculoskeletal, nervous, or cardiovascular system or a combination
of these (see Figure 1) revealed no systematic differences between the means. The
sole exception was elbow flexion force: the group of Eyomen with both nervous
and musculoskeletal diseases performed worse ( p < .05) than the healthy women.
212
Rantanen, Era, Kauppinen, and Heikkinen
Table 4 Health Variables Among 75-Year-Old Men and Women (SD)
Variable
Number of chronic diseases
Index of musculoskeletal
pain, range 0-6
Self-rated health (%)
Good
Average
Poor
Men
(n = 105)
Women
(n = 200)
t value
2.0 (1.4)
2.3 (1.7)
-0.37 (ns)
2.2 (1.8)
2.4 (1.7)
-1.09 (ns)
13
76
12
15
72
13
x2
0.65 (ns)
Among the men such comparisons were not possible, as only 5 of them were free
of chronic disease.
No differences in the maximal forces were observed between those with
various education levels or between groups according to occupational background.
Because the background factors were interconelated, multivariate analyses were
performed so that their simultaneous associations with maximal strength could
be studied. The construction of the multivariate LISREL models was based on
information received from earlier literature as well as from previous correlation
analyses between the force and background variables.
Force factors were constructed in the interest of combining the original
test results into two factors describing the maximal strength as an entity. The
structure of the force factors differed somewhat between the sexes. Among the
men, the limb force factor was based on the measurements of hand grip, elbow
flexion, and knee extension strength (Figure 3). Knee extension strength also
had a loading on the trunk force factor together with the measurements of trunk
extension and flexion. Among the women the limb force factor was based on
the upper limb strength measurements (Figure 4). The trunk force factor was based
on measurements of knee extension and trunk flexion and extension strengths. For
both sexes the limb and trunk force factors were interconelated.
The regression analysis sections of the LISREL models also differed between the sexes. Initially, physical activity, number of chronic diseases, selfrated health, and index of musculoskeletal pain were introduced into the models
for both sexes in order to study their explanatory power simultaneously. The
variables that had statistically significant effects can be seen in Figures 3 and 4.
In both sexes the level of physical activity explained the variation in the
limb and trunk force factors. Among the men the trunk force factor was explained
by number of chronic diseases and index of musculoskeletal pain, whereas
among the women the explanatory variables were self-rated health and index of
musculoskeletal pain. In the model for the men, the determination coefficient
(R2)for the trunk force factor was 0.60 and for the limb force factor it was 0.50,
indicating that 60% of the variation in the trunk force factor and 50% of the
variation in the limb force factor were explained by the independent variables.
The determination coefficient (D) of the whole model for the men was 0.59, and
Table 5 Correlations Between Health, Physical Activity, and Force Variables Among 75-Year-Old Men and Women
Variable
1.
2.
3.
4.
5.
6.
7.
8.
Men (n = 91-1 19)
1 . Number of chronic diseases
2. Index of musculoskel. symptoms
3. Self-rated health
4. Intensity of physical activity
5. Hand grip force
6. Elbow flexion force
7. Knee extension force
8. Trunk extension force
9. Trunk flexion force
Women ( n = 175-263)
1 . Number of chronic diseases
2. Index of musculoskel. symptoms
3. Self-rated health
4. Intensity of physical activity
5. Hand grip force
6. Elbow flexion force
7. Knee extension force
8. Trunk extension force
9. Trunk flexion force
Note. Depending on the level of measurement for each pair of variables, product moment or polyserial correlation coefficients are used.
***p < 0.001; **p < 0.01; * p < 0.05.
!W
2
214
Rantanen, Era, Kauppinen, and Heikkinen
1000
N
Hand
grip
Absolute values
Elbow
flexion
Knee
Trunk
extension extension
Body weight
12
Trunk
flexion
- adjusted values
10 -.
Hand
grip
~lbow
Knee
Trunk
flexion extension extension
Trunk
flexion
Figure 2. The body-weight-related maximal isometric strength of five muscle groups
among 75-year-old men (n = 95-101) and women (n = 178-186) (mean SD).
+
for the women it was 0.55. Among the women as well, a greater amount of the
variation in the trunk force factor (64%) than that in the limb force factor (56%)
can be explained by the background factors.
Discussion
The present study was undertaken to determine the associations of socioeconomic
status, health, and physical activity with maximal isometric strength among
75-year-old men and women. A higher intensity of physical activity and good
health was associated with greater maximal force in both sexes. Socioeconomic
status, however, was not associated with maximal strength.
Isometric Muscle Strength
215
-.38(.06)
Self-rated
health
force
factor
Education
R=.60
1.o"
Trunk
.20
r
Occupation
2
D=.59
1) Fixed to equal
2) Fixed
Fixc to 1.0
'
GFln.958
AGFIm.883
RMR-.037
Figure 3. Determinants of isometric muscle force among 75-year-old men. Factor
variance is explained by a regression model using the background variables as independent variables. RZ indicates the determination coefficient for each force factor separately, and D the corresponding coefficient for the whole model. Mutual correlations
between force factors and background factors shown. Explanatory variables (broken
lines) not significant and not incorporated into the final model. GFI = goodness-of-fit
index, AGFI = adjusted goodness-of-fit index, RMR = root mean square residual.
The measurement of maximal physical performance in elderly persons is
problematic and may be contraindicated. However, maximal isometric strength
can be tested with a low dropout rate even among an unselected elderly population,
as demonstrated here. The participation rates were 81% for the men and 75%
for the women, as calculated from the total eligible population. A study by
Larsson, Grimby, and Karlsson (1979) across age groups found that isometric and
dynamic measurements reveal a similar pattern of strength differences. Moreover,
there is evidence that isometric strength is positively correlated with a person's
ability to manage routine motor activities (Era, 1990; Rantanen, Era, & Heikkinen,
in press). Isometric testing does not of course provide information about force
production across the entire range of motion in a joint. However, it has proven
to be a good indicator of the ability of the knee extensors to emit torque throughout
the range of motion in healthy and injured knee joints (Kannus & Jawinen, 1990).
It has been suggested that relative rather than absolute measures of strength
are more cIoseIy related to the ability to perform physical movements (Buchner
et al., 1992). Consequently, since muscles act to move weight, the strength results
were adjusted for body mass. Moreover, greater absolute strength is usually
associated with greater body weight. The body-weight-related values of the
women varied from 66 to 73% of those of the men, depending on the muscle
group studied. Previous strength comparisons (Aniansson et al., 1980) between
Rantanen, Era, Kauppinen, and Heikkinen
216
&.56
Hand grip
-
activity
-.I7
Number of
.15
Education
Occupation
1) Fixed to equal
2) Fixed to 1.0
AGF1=.891
RMR=.045
Determinants of isometric muscle force among 75-year-old women. The explanatory variables marked with broken lines were not significant and were not incorporated into the final model. For details and definitions, see Figure 3.
Figure 4.
the sexes have shown the absolute values for quadriceps strength among healthy
70-year-old women to average 56% as against a variation in upper extremity
strength values from 48% (elbow extension) to 60 and 67% (hand grip and
elbow flexion).
In this study 5 men (5%) and 15 women (8%) had no medically diagnosed
chronic diseases. Generally only healthy (= no diagnosed disease) elderly people
have been selected for studies of strength or physical performance capacity
(Clement, 1974; Murray, Duthie, Gamberts, Sepic, & Moliinger, 1985; Rice,
Cunningham, Paterson, & Rechnitzer, 1989; Young, Stokes, & Crowe, 1984).
Hence relatively little is known about strength levels or changes among older
people with chronic conditions. In the present study no consistent statistically
significant differences in strength were observed between the healthy women
and those having one or more chronic diseases. In addition, the correlations
between number of chronic diseases and the force variables were not statistically
significant except for trunk extension force. These data suggest that chronic
disease as such is not necessarily connected with lower muscle strength among
elderly women. Because only 5 of the men were healthy, their strength levels could
not be compared. However, for men the number of chronic diseases correlated
negatively with the elbow flexion and trunk flexion and extension forces.
Apart from the direct effect of specific muscular and neurological diseases
on muscle, the loss of strength may at least in part be a result of the restricted
mobility caused by various symptoms (such as in cardiovascular disease), or
required for the care of the disease. For example, Sinaki, Khosla, Limburg,
Rogers, and Murtaugh (1993) suggest that the poorer back extension strength
Isometric Muscle Strength
* 2 17
among women ages 40 to 85 with diagnosed osteoporosis and previous vertebral
fractures was the result of pain caused by the injury, leading in turn to the
improper recruitment of back muscles and the ensuing disuse of the muscles.
The present study also showed that those with more musculoskeletal pain had
lower strength values in the trunk muscle tests.
The shortcoming here is the lack of information concerning the seriousness
of disease. In a population based study design, number of diseases and combinations of diseases may be found. This approach does not ensure that either healthy
persons or persons with specific diseases are found in sufficient numbers to
enable comparisons in even a relatively extensive data set. The benefit, on the
other hand, is that the results may be considered descriptive of the general
population within the area.
Good self-rated health correlated with greater strength in both sexes. The
ability to manage daily life has been found to be a significant determinant
of self-rated health (Jylh$ Leskinen, Alanen, Leskinen, & Heikkinen, 1986).
Consequently, the association between self-rated health and maximal strength
may be due to the superior ability of those with greater strength at managing
daily tasks (Rantanen et al., in press; Young, 1986). The results of this study
also suggest that the amount of everyday physical activity correlates with strength
among elderly persons. Those who keep busy in their daily activities show greater
strength. Greater maximal strength has also been observed in several earlier
studies of habitually physically active persons or athletes (Bassey, Bendall, &
Pearson, 1988; Borkan & Norris, 1980; Era et al., 1992; Holloway & Baechle,
1990; Rantanen et al., 1992; 1993; Sipilii et al., 1991).
In the present study, socioeconomic status (occupational background, level
of education) was not associated with strength. According to previous studies
the association between occupational workload and muscle strength seems to
vary by age group and sex. Among young persons physically heavy work is
associated with greater strength (Era et al., 1992), whereas middle-aged persons
in blue collar occupations have poorer strength than those in white collar jobs
(Nygibd et al., 1988; Rantanen et al., 1992). Toward the higher age groups the
association between heavy work and poorer strength seems to disappear, probably
due partly to selective mortality. Mortality has been found to be greater among
individuals in the lower socioeconomic categories, and in general the weaker are
more likely to die earlier (Clement, 1974; Phillips, 1986).Gender is also associated
with mortality. According to the Finnish census data, 24.2% of the men and
48.0% of the women born in 1914 were alive in 1989 when the study began.
This should be considered when comparing men and women.
The simultaneous associations of the background variables with the force
factors were studied with the aid of LISREL models. For both sexes rhe amount
of physical activity explained the variation in both the limb and trunk force
factors, whereas the state-of-health indicators explained the variance only in the
trunk force factors. Some difference between the sexes was also observed with
respect to the health variables in explaining trunk force. Number of chronic
diseases among the men and self-rated health among the women explained the
variation in the trunk force factor. Self-rated health and number of chronic
diseases were significantly intercorrelated in both sexes. In multivariate analysis
the intercorrelation of two independent variables may cause an effect to be
transmitted through one or the other.
218
Rantanen, Era, Kauppinen, and Heikkinen
Although the determination coefficients of the models were relatively high,
59% in the men and 55% in the women, other factors in addition to health status
and level of physical activity may also help explain the variation in maximal
strength. For example, genetics have an influence on strength (Pkrusse et al.,
1987). According to a review of the literature by Holloway and Baechle (1990),
the beliefs and expectations that individuals have about their behaviors, including
the ability to perform feats of strength and the propriety of doing so, as well as
the association of strength with masculinity, are powerful determinants for both
sexes in strength performance. Thus the elderly may be unfamiliar with the
meaning of maximal strength performance or may consider it improper for their
sex or age. These learned psychological responses may be limiting factors in the
expression of maximal strength.
It was concluded that the most important explanatory factors for greater
maximal strength were more habitual physical activity and better health. The
health variables explaining the variation in maximal strength were somewhat
different for the women than for the men. Chronic disease was not associated
with lower maximal strength in the women, whereas among the men multimorbidity was connected with lower maximal strength. It is also worth noting that despite
chronic diseases, the majority of the elderly subjects were able to participate in
the measurements of maximal isometric strength.
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Acknowledgments
This study was financially supported by grants from the Academy of Finland, the Ministry
of Health and Social Affairs, the Research Council for Sport and Physical Culture
of the Ministry of Education, and the City of Jyvaskyla. Our gratitude is also
expressed to all the 75-year-olds who participated in the study.