Criterion-Referenced Fitness Standards Associated with Maintaining Functional Capacity in Chilean Older Adults

Abstract

The aim of the current study was to develop fitness standards associated with maintaining physical capacity in older adults at two different levels—that needed for advanced functioning and that needed for maintaining moderate (independent) functional ability. This was a cross-sectional study of 406 Chilean adults aged 60 and more. Functional capacity was measured through the Composite Physical Function (CPF) scale. A battery of validated fitness tests for this population was used. Based on the results of the CPF, two variables were created: “advanced physical capacity” (defined as those scoring 24 on the CPF scale) and “moderate (independent) physical capacity,” defined as those scoring between 14 and 23 on the CPF scale. Fitness cut-off values were calculated for each of the two created variables to evaluate the risk of losing the independence through Receiver Operating Characteristic (ROC) curves analysis and logistic regression. The developed cut-off points provide important information for professionals working directly with older adults, to detect the risk of losing functionality and independence.

Introduction

Aging is defined as a natural and unavoidable process, which generates gradual and sometimes irreversible changes in the organism over time. This process affects all living organisms, progressively degenerating physical, physiological, and psychosocial functions, and often leads to a decrease in quality of life and to the loss of autonomy in older adults.^1,2 Medical advances along with other factors have caused a progressive population aging with a consequent increasing of the prevalence of physically dependent people, which leads to huge costs for society.³ The aforementioned situation has caused an increase in scientific interest toward the assessment and detection of dependence in that population.

There are many definitions of the concept of dependence, all of which are focused on the loss of autonomy. Dependence is defined as the impossibility of conducting daily activities within “normal limits” and defines the parameters for its assessment.⁴ These activities are classified in Activities of Daily Living (ADLs), which are elemental tasks of personal self-care, universal in nature as they are not culture restricted (have a shower, get dressed, walk, eat, use the toilet, go to bed, and get out of bed)⁵ and Instrumental Activities of Daily Living (IADLs), defined as activities which allow a person to interact with their environment (do the shopping, cook, household cleaning, financial management, use transportation, responsibility for their medication, among others).⁶

Knowing the levels of functional independence allows professionals working with older adults to design programs and strategies to improve the health and quality of life of this age group. Currently, there are different instruments to assess independence, being Katz⁵ and Mahoney and Barthel⁷ indices the most frequently used. Nevertheless, these questionnaires demand time and qualified personnel for their application and are also limited to assessing ADLs. Composite Physical Function (CPF) scale, developed by Rikli and Jones,^8,9 is a simple instrument consisting of 12 items, which allows the assessment of both ADLs and IADLs.

Functional dependence is typically related to physical fitness.¹⁰ During the process of aging, a decrease in physical fitness is produced, mainly because of the deterioration of aerobic endurance, flexibility, strength, speed, agility, and balance.¹¹ Physical activity in this age group allows to maintain physical fitness conditions, which contributes to delay the loss of functionality.¹² Physical function is also linked to survival.¹³ Nevertheless, professionals working with older adults often do not possess information to identify the values of physical fitness, which might put them at risk of losing functionality. In recent years, studies have been published providing criterion-referenced fitness standards associated with the capability of maintaining functional independence in advanced ages.^9,14 However, these standards are defining fitness cut points needed for maintaining moderate (independent) functioning, thus not allowing to establish reference values which would determine different degrees of risk of losing functional independence. The objective of this study was to develop cut-off values of physical fitness, which estimate the levels of physical fitness needed by older adults to a) prevent the drop from high functionality (full physical independence), and b) avoid descending to low functionality (high level of physical dependence).

Methods

A cross-sectional study was conducted. Inclusion criteria for the study were: men and women aged 60 or more, living in the Maule region (Chile), and members of day clubs, older adult clubs, or assisted living residences in different cities of the region. Exclusion criteria were: severe cognitive impairment indicated through Pfeiffer test,¹⁵ severe motor disabilities, and uncontrolled hypertension.

The final sample was composed of 406 older adults (111 men and 295 women). Sample size calculation was performed for the area under the Receiver Operating Characteristic (ROC) curve (AUC) analysis. A sample of 200 from the positive group and 200 from the negative group achieve 99% power to detect a difference of 0.15 between the AUC under the null hypothesis of 0.60 and an AUC under the alternative hypothesis of 0.75 using a two-sided z-test at a significance level of 0.05.^16,17 All participants signed an informed consent form and the study was approved by the Universidad Autonoma de Chile Bioethics Committee (Ethical Application Ref. No. 028-15).

Functional ability level

Functional ability level was measured through the CPF scale, developed by Rikli and Jones,⁸ and translated and validated for its use in Chile.¹⁸

Sociodemographic and lifestyle characteristics

A sociodemographic and lifestyle questionnaire, which included marital status, educational attainment, and physical activity performed per week, was conducted.

Mean arterial pressure

Arterial pressure was assessed in two consecutive occasions through automated wrist sphygmomanometer, validated for its use in research studies (model HEM-6111; Omron). The results from this test were used in the criteria of exclusion “uncontrolled arterial hypertension.”

Cognitive impairment

Cognitive impairment was assessed through the Pfeiffer test,¹⁵ which assesses dementia through 10 questions. The results from this test were used in the criteria of exclusion “severe cognitive impairment.”

Weight and height

These data were gathered following standardized techniques and protocols.¹⁹ Body weight was measured using a body weight scale (model 803; Seca, Ltd.) with a precision of 0.1 kg. Height was assessed using a stadiometer (model 213; Seca, Ltd.) with a precision of 0.1 cm.

Physical fitness assessment

All participants conducted a warm-up before the application of the tests. This warm-up consisted of neuromuscular activation (joint mobility) and stretching exercises with a duration of 5 minutes. The total application time of the test was ∼45 minutes, and it was conducted during the morning, between 9:00 am and 1:00 pm. All measurements were made by physical education students who were trained.

The utilized tests for the assessment are described below.

Lower and upper limb strength

To measure the lower limb strength, the 30-second chair stand test was used.²⁰ This test measures the number of times a person can stand up from a sitting position in the timeframe of 30 seconds. For upper limb strength, handgrip strength test was applied.²¹ The test was conducted two times on each hand using the Jamar Plus digital dynamometer (Rolyan; Sammons Preston, Bolingbrook, IL) and subsequently, the average of each hand was calculated.

Lower and upper limb flexibility

Flexibility of lower limbs was measured through the Chair Sit-and-Reach test.²² This test measures the distance between the middle finger and the tip of the foot while maintaining a sitting position. To assess the flexibility of the upper body (shoulders), the Back Scratch test²³ was conducted. The test measures the distance between the middle fingers of both hands behind the back by passing a hand over the shoulder and the other up through the back. For measurement effects on flexibility in both tests, left and right were measured twice and the average of both was calculated.

Agility and dynamic balance

Timed up and go (TUG) test was conducted.²⁰ The test measures the time that participants take in standing up from a chair, walk 2.44 m, and go back to the original sitting position.

Aerobic endurance

The Six-Minute Walking test²⁴ was conducted. This test measures the amount of meters a person can walk during 6 minutes in a 20-m-long circuit.

Statistical analyses

For the presentation of sample characterization, descriptive analyses were conducted with all participants of the study.

The results of the CPF distinguish people with high functionality (scoring 24), moderate functionality (scoring 14–23), and low functionality (scoring 13 or less). To analyze the values of physical fitness associated with maintaining “advanced” and “moderate” (independent) functional capacity, two variables were created according to the three possible categories of the CPF. The first variable was “advanced physical capacity.” In this variable, the value “one” would be for those participants scoring 24 in the CPF, whereas the value “zero” would be for those participants scoring 23 or less in the CPF. The second variable was “moderate (independent) physical capacity.” In this variable, the value “one” was for those participants with moderate or high level of functionality according to the CPF score (scoring 14 or more), whereas the value “zero” was assigned to those participants with low functionality according to the CPF score (scoring 13 or less).

ROC curves were used to determine the cut-off values of physical fitness, which reached higher sensibility and specificity according to the results of the two created variables and sex. AUC was obtained to determine the overall precision of physical fitness values measured through the physical tests.

Subsequently, a binary logistic regression was carried out, considering the two created variables as dependent variable, and the results of the physical fitness tests and age as covariates, all these aimed to identify the variables associated with maintaining functional capacity. Statistical analyses were carried out using the IBM SPSS v21 software (SPSS, Inc., Chicago, IL), with a statistical significance of p < 0.05.

Results

Participants' characteristics are displayed in Table 1. The mean (standard deviation [SD]) of age was 74.02 (6.71) in men and 71.56 (6.78) in women. Table 2 presents the results of the ROC curve according to the advanced physical capacity and moderate physical capacity variables, indicating the cut-off points for measured physical fitness in males and females. AUC for advanced physical capacity in men fluctuated between 0.73 and 0.88 and in women, between 0.58 and 0.70. Regarding moderate physical capacity, the fluctuation of the AUC in men was between 0.63 and 0.94, and in women between 0.69 and 0.85.

Table 1.

Characteristics of the Study Population

Variable	All participants (n = 406)	Males (n = 111)	Female (n = 295)
Age (years)	72.23 ± 6.842	74.02 ± 6.71	71.56 ± 6.78
Age categories, n (%)
60–69	153 (37.7)	28 (25.2)	125 (42.4)
70–74	119 (29.3)	38 (34.2)	81 (27.5)
75–79	61 (15)	21 (18.9)	40 (13.6)
80+	73 (18)	24 (21.6)	49 (16.6)
Education, n (%)
Not able to read or write	51 (12.7)	25 (22.9)	29 (9.9)
Primary school	218 (53.4)	55 (50.5)	160 (54.8)
Secondary	89 (22.2)	17 (15.6)	72 (24.7)
University	43 (10.7)	12 (11.0)	31 (10.6)
BMI
Normoweight	175 (43.1)	64 (57.6)	111 (37.6)
Overweight	131 (32.3)	29 (26.1)	102 (34.6)
Obese	100 (24.6)	18 (16.2)	82 (27.8)
Waist circumference (mean ± SD)	99.59 ± 12.53	100.77 ± 11.67	99.15 ± 12.83
Hip circumference (mean ± SD)	105.66 ± 11.34	102.56 ± 10.54	106.83 ± 11.42
Functional fitness
Upper body flexibility—back scratch (cm)	−20.71 ± 14.21	−26.68 ± 14.77	−18.46 ± 13.33
Lower body flexibility—chair sit-and-reach (cm)	−6.70 ± 10.29	−9.95 ± 12.16	−5.47 ± 9.22
Upper body strength Handgrip (kg)	45.49 ± 15.13	56.60 ± 18.15	41.31 ± 11.31
Lower body strength 30-second chair stand (No. of repetitions)	11.58 ± 4.08	11.35 ± 4.62	11.68 ± 3.86
Agility/dynamic balance 8-foot up-and-go (seconds)	8.55 ± 5.68	10.01 ± 9.41	8.01 ± 3.21
Aerobic endurance six-minute walking (m)	395.15 ± 119.58	388.10 ± 134.77	397.66 ± 113.86
CPF, n (%)
High functionality	166 (40.9)	57 (51.4)	109 (36.9)
Moderate functionality	183 (45.1)	39 (35.1)	144 (48.8)
Low functionality	57 (14)	15 (13.5)	42 (14.2)
Where you live, n (%)
Own home	341 (84.0)	80 (72.1)	261 (88.5)
Alleged	40 (9.9)	19 (17.1)	21 (7.1)
Institutionalized	25 (6.2)	12 (10.8)	13 (4.4)
Marital status, n (%)
Single	79 (19.7)	30 (27.5)	49 (16.8)
Married	178 (44.4)	49 (45.0)	129 (44.2)
Widow/separated/divorced	144 (35.9)	30 (27.5)	114 (39.0)
Living with …, n (%)
Alone	95 (23.7)	29 (26.6)	66 (22.6)
Not alone	306 (76.3)	80 (73.4)	226 (77.4)
Residence place, n (%)
Rural	91 (22.7)	27 (24.8)	64 (21.9)
Urban	310 (77.3)	82 (75.2)	228 (78.1)
Physical activity at week, n (%)
0 hours/week	139 (34.7)	45 (41.3)	94 (32.2)
<3 hours/week	133 (32.9)	34 (31.1)	99 (33.9)
≥3 hours/week	129 (32.1)	30 (27.6)	99 (33.9)

BMI, body mass index; CPF, Composite Physical Function; SD, standard deviation.

Table 2.

Receiver Operating Characteristic Curve

	Advanced physical capacity				Moderate (independent) physical capacity
	AUC	Best cut-off value			AUC	Best cut-off value
		Cut-off	Sensitivity (%)	Specificity (%)		Cut-off	Sensitivity (%)	Specificity (%)
Males
Upper body flexibility—back scratch (cm)	0.748	−22.875	81.5	56.1	0.781	−36.500	73.3	85.4
Lower body flexibility—chair sit-and-reach (cm)	0.741	−11.250	63	86	0.632	−19.375	53.3	83.3
Upper body strength handgrip (kg)	0.726	57.325	70.4	61.4	0.714	48.077	66.7	66.7
Lower body strength 30-second chair stand (No. of repetitions)	0.794	12.50	90.2	59.6	0.785	8.50	66.7	77.4
Agility/dynamic balance 8-foot up-and-go (seconds)	0.876	7.8000	75.5	86	0.836	8.2800	93.3	71.6
Aerobic endurance six-minute walking (m)	0.864	417.00	87.5	72.7	0.944	308.00	100	87.8
Females
Upper body flexibility—back scratch (cm)	0.579	−17.375	54.8	60.2	0.697	−23.125	61.9	75.4
Lower body flexibility—chair sit-and-reach (cm)	0.605	−0.8750	56.5	57.8	0.712	−11.125	61.9	79.1
Upper body strength handgrip (kg)	0.633	41.925	62.4	63.3	0.693	36.075	54.8	72.7
Lower body strength 30-second chair stand (No. of repetitions)	0.699	11.50	59.8	67	0.850	10.50	90.2	69
Agility/dynamic balance 8-foot up-and-go (seconds)	0.691	7.380	58.9	72.5	0.791	8.480	65.9	78.7
Aerobic endurance six-minute walking (m)	0.666	409.50	57.9	71.3	0.820	309.00	62.5	89.6

AUC, area under the curve.

Tables 3 and 4 depict the results of the binary logistic regression, which identified the most significant physical tests associated with maintaining functional capacity. These results are presented with the two created CPF variables, “advanced physical capacity” and “moderate (independent) physical capacity,” according to sex. The associated variables for full advanced physical capacity in men were the chair sit-and-reach test, the six-minute walking test, and age; whereas for women, advanced physical capacity was associated with the 30-second chair stand test and TUG test. On the other hand, the model for moderate physical capacity in men included the results of the back scratch test, the handgrip strength test, and the six-minute walk test, whereas in the case of women, the significant variables were the chair sit-and-reach test, the 30-second chair stand test, and the six-minute walk test.

Table 3.

Logistic Regression Model and Respective Discriminative Capability for the Physical Independence in Males

	Advanced physical capacity β (SE)			Moderate (independent) physical capacity β (SE)
Logistic model	β (SE)	OR (95% CI)	p	β (SE)	OR (95% CI)	p
Males
(a) Constant	−3.053 (3.761)	0.047	0.417	5.346 (2.918)	209.813	0.067
(β₁) Upper body flexibility—back scratch (cm)				−0.086 (0.025)	0.917 (0.851–0.989)	0.039
(β₂) Lower body flexibility—chair sit-and-reach (cm)	−0.061 (.027)	0.941 (0.893–0.991)	0.022
(β₃) Upper body strength handgrip (kg)				−0.082 (0.040)	0.922 (0.852–0.997)	0.042
(β₄) Lower body strength 30-second chair stand (No. of repetitions)
(β₅) Agility/dynamic balance 8-foot up-and-go (seconds)
(β₆) Aerobic endurance—six-minute walking (m)	−0.13 (0.003)	0.987 (0.981–0.994)	0.000	−0.023 (0.007)	0.977 (0.963–0.992)	0.002
(β₇) Age	0.099 (0.046)	1.104 (1.009–1.208)	0.031
Probability criterion (%)	86.1			94.1
R² Cox and Snell	0.436			0.387
R² Negelkerke	0.582			0.723

CI, confidence interval, OR, odds ratio; SE, standard error.

Table 4.

Logistic Regression Model and Respective Discriminative Capability for the Physical Independence in Female

	Advanced physical capacity β (SE)			Moderate (independent) physical capacity β (SE)
Logistic model	β (SE)	OR (95% CI)	p	β (SE)	OR (95% CI)	p
Female
(a) Constant	0.715 (0.481)	2.043	0.000	2.536 (0.878)	12.633	0.004
(β₁) Upper body flexibility— (cm)
(β₂) Lower body flexibility—chair sit-and-reach (cm)				−0.065 (0.023)	0.937 (0.896–0.980)	0.004
(β₃) Upper body strength handgrip (kg)
(β₄) Lower body strength 30-second chair stand (number of repetitions)	−0.141 (0.045)	0.869 (0.795–0.950)	0.002	−0.257 (0.076)	0.774 (0.667–0.898)	0.001
(β₅) Agility/dynamic balance 8-foot up-and-go (seconds)	0.202 (0.082)	1.224 (1.041–1.438)	0.014
(β₆) Aerobic endurance—six-minute walking (m)				−0.007 (0.002)	0.993 (0.989–0.998)	0.002
(β₇) Age
Probability criterion	66.6			89.7
R² Cox and Snell	0.140			0.249
R² Negelkerke	0.192			0.451

Discussion

The present study developed criterion-referenced fitness standards associated with maintaining physical capacity in older adults at two different levels—that needed for advanced functioning and that needed for maintaining moderate functional ability.

The training of all components of physical fitness may cause a delay in the process of aging and in the loss of functionality of people.²⁰ Over time, the loss of strength, flexibility, aerobic endurance, agility, and balance reduce the ability to autonomously perform ADLs and IADLs in older adults. It is up to the professionals who work directly with this group of people to improve their physical fitness through physical activity and recreation to delay functional dependence.¹⁴ Having physical fitness cut-off values based on maintaining functional capacity would help those professionals who work with older adults in their daily work. By conducting a physical fitness assessment, these professionals will be able to compare each physical capacity of older adults with the cut-off points reported in the current article, which may help to elaborate programs of physical activity, directly focused on maintaining functional capacity avoiding the risk of losing functionality

The CPF questionnaire offers two options. The first classifies the functionality into three levels: high, moderate, and low functionality and is based on the amount of activities a person can perform by himself. The second option classifies the functionality adjusted to age and classifies functionality into two levels: high functionality and low functionality (values by age range >90, 80–89, 70–79, 60–69).⁹ The fitness cut-off values associated with maintaining functional capacity developed in the present study were obtained from three options, CPF assessment scale (high, moderate, and low functionality), in contrast to the criterion references developed by Rikli and Jones⁹ and Sardinha et al.¹⁴ who performed with the CPF results, adjusted for age. We chose this option to identify values of fitness that may risk losing functionality, both moving from a state of full physical independence to nonfull physical independence (changing from a score of 24 to a score lower than 24 in the CPF), and from low dependence to high level of physical dependence (changing from a score of 14 or more to a score of 13 or less). Through this, more precise and detailed levels of fitness should be known by professionals working with older adult values.

The previous fitness cut-off values^9,14 used the senior fitness test (SFT) as an instrument to assess physical condition. In this study, we decided to replace the arm curl test by manual dynamometry to be more precise and cause less impact on the older adults test. Dynamometry is one of the most widespread and simplest test application for assessment of strength in the upper extremities in older people.^25
–27

Another novel aspect of this work is the inclusion of the flexibility component as a variable associated with dependence. This component was not included in previous studies for establishing fitness cut-off values based on dependence.^9,14 Lower limb flexibility maintenance is an important predictor of functional dependence and disability in the elderly.²⁸ Additionally, lower and upper limb flexibility is related with the Health-Related Quality of Life.²⁹ Therefore, lower and upper limb flexibility assessments were included through the back scratch test and the chair sit-and-reach test. The results showed that maintaining of functionality was associated with avoiding the decrease of flexibility. Specifically, flexibility of the lower limbs in men was directly associated with advanced physical capacity, and low upper limb flexibility was directly associated with moderate physical capacity. In the case of women, the decrease in lower limb flexibility was associated with losing moderate physical capacity.

To determine advanced physical capacity, the AUC was always higher than 0.73 in men and higher than 0.58 in women. On the other hand, for moderate physical capacity the lower AUC was 0.63 in men and 0.69 in women. The aforesaid indicates that the analyzed physical tests can be associated with functional capacity by having a higher curve value in both analyzed variables. The results obtained in this study differ from those obtained in previous ones,^9,14 because the age was considered as a covariant, and thus, it is not present in the results according to age groups.

It is not possible to compare the cut-off points obtained through this study with those conducted by American and Portuguese research,^9,14 because in both studies, these were made age adjusted and only the Portuguese distinguished those values based on gender. However, this study developed fitness standards associated with maintaining moderate physical capacity (moving from a state of high level of physical dependence to a state of low dependence) and advanced physical capacity based on gender, which may be easily used by therapists and researchers.

Given the current demographic changes, professionals who work with older adults should shift from a welfare mentality toward one focused on the preservation or improvement of all dimensions of quality of life during the process of aging.³⁰ Due to the increase in life expectancy, the effort should be aimed at analyzing how people live the last years of their lives to achieve successful old age and to delay the process of aging.³ This would result in a reduction of dependence and the huge associated cost. The present study provides relevant information for the assessment and contribution to the adjustment of exercise programs, oriented to delay the loss of functionality and independence.

Further studies should analyze the impact of economic status or education level, since both factors are commonly associated with dependence and autonomy.^31,32 The notion of successful aging is controversial, although all evidences suggest that the presence of disability and level of physical functioning are the main factors to define it.³³ Successful aging is associated with a reduction in healthcare costs, thus strategies aimed to improve physical functioning in older adults are required from institutions and governments.

Conclusions

This study presents fitness standards which older adults should possess to prevent the drop from high functionality (full physical independence), and to avoid descending to low functionality (high level of physical dependence). The fitness tests more related with advanced physical capacity were chair sit-and-reach (lower body flexibility) and six-minute walking (aerobic endurance) for men; and 8-foot up-and-go (agility/dynamic balance) and 30-second chair stand (lower body strength) for women. The fitness test more related with moderate physical capacity were back scratch (upper body flexibility), handgrip (upper body strength), and six-minute walking (aerobic endurance) for men; and 30-second chair stand (lower body strength), chair sit-and-reach (lower body flexibility), and six-minute walking (aerobic endurance) for women.

Limitations

The present study has certain limitations. The size of the sample is smaller to that present in previous studies, and thus limits the possibility of conducting the analyses by age groups. Nevertheless, age has been included in the analyses as a covariant to adjust the results by this variable. Furthermore, technicians and researchers may benefit from having a single and simpler result, which is not divided by the age groups' physical activity. There are other tests to measure fitness; however, the tests we used in this investigation are widely applied in research and clinic practices in older adults. Due to the cross-sectional nature of the study, the results cannot determine the cause and effect.

Strengths

The incorporation of handgrip as a measure of upper body strength and the inclusion of upper and lower body flexibility are two of the most important strengths of the present study. Handgrip measure is one of the most widespread and simplest test for assessing strength in the upper extremities in older people and it is more precise and cause less impact than the arm curl test included in previous studies. The maintenance of the lower limb flexibility is an important predictor of functional dependence and disability in the elderly, and both, lower and upper body flexibility are related with quality of life in this population. Previous studies did not include the assessment of flexibility.

Additionally, we have calculated fitness cut-off values for both advanced physical capacity and moderate physical capacity. Previous studies calculated fitness cut-off values only for physical dependence.

Perspective

This information should be used by professionals working with older adults, by periodically detecting those individuals who are at risk of losing functional independence and by selecting those exercise routines which best fit each individual's needs.

Footnotes

Acknowledgments

This study was supported by Internal Research Grants from the Universidad Autonoma de Chile (DIUA115-2017), Biomedical Research Networking Center on Frailty and Healthy Aging (CIBERFES), and FEDER funds from the European Union (CB16/10/00477). The author D.C.M. is supported by a grant from the Spanish Ministry of Education, Culture, and Sport (FPU14/01283). He was previously supported by a Predoctoral Fellowship from the Fundación Tatiana Pérez de Guzmán el Bueno.

Author Disclosure Statement

No competing financial interests exist.

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