Assessment of the musculoskeletal performance with squat tests and performance-oriented measurements in older adults

Abstract

BACKGROUND:

Balance and mobility impairments, declined musculoskeletal strength and performance, limited range of motion, and poor flexibility are fairly common among older adults.

OBJECTIVES:

To determine the lower extremity muscle force and to verify the correlation with the gait characteristics and balance in community dwelling older adults.

METHODS:

Seventy-five adults with a mean age of 75.07 $\pm$ 6.28 years were included in the study. All participants were evaluated with the following tests: half squat (HS), decline squat (DS), foot print analysis (step length, step wide, stride length, walking velocity and cadence) and Tinetti Performance Oriented Mobility Assessment (POMA).

RESULTS:

HS and DS test scores were significantly correlated with Tinetti Balance and Gait Assessment scores and gait characteristics, except step wide ( $p<$ 0.01). The results of this study showed that the participants who have higher scores in the squat tests, showed higher scores in terms of POMA ( $p<$ 0.01).

CONCLUSION:

Appropriate and direct assessment of lower limb power and performance in balance and gait tests should be done to identify functioning of the older adults. Half and eccentric decline squat tests used in this study were useful, cheap and easy. The squat tests can be used to determine the relationship between balance and gait characteristics, in addition to predicting the musculoskeletal performance in older adults.

Keywords

Half squat decline squat Tinetti Performance Oriented Mobility Assessment (POMA)foot print analysis older adults

1. Background

Balance disturbances and mobility impairments, musculoskeletal strength, limited range of motion, and poor flexibility are fairly common among older adults [1]. Inevitably, aging leads to some functional declines. Review studies have indicated that physical inactivity is related to accelerated depletion of functional reserves, and lead to deficits in muscle strength, neuromuscular activation, range of motion, and flexibility. This in turn leads to an increased incidence of functional problems, frailty, falls, and loss of functional independence, which ends with placing frail older people at risk for institutionalization [1, 2]. Additionally, the fear of falling can be so overwhelming that it frequently leads to subsequent self-imposed inactivity, whereby these limitations may lead to musculoskeletal restrictions [3].

In association with all these factors, the resulting gait disorders in older adults have a characteristic clinical picture, which includes small steps, shuffling, hesitation, poor balance, and unstable turns [4]. Although gait can be characterized in numerous ways, gait speed is a simple and valid concise measure that has been extensively used through the years. Gait speed stays comparatively stable until the seventh decade and thereafter slows 15% per decade. Diminished gait speed is associated with shorter stride length and single support time (single foot on the floor) as well as increased double support time (both feet on the floor). These changes represent a modest level decrease in these quantitative gait indices in healthy elderly who were capable of walking efficiently and relatively quickly [5, 6].

Multiple interacting factors are implicated in the deterioration of balance. It especially depends on sensory input, central processing (or motor control), and muscle strength and power. Muscle function, muscle strength or rate of joint torque development are being used to predict performance-challenging balance measures and falls, but not sway when standing [7]. There is extensive documentation, in cross- sectional studies, of a 20%–40% decrement of strength from the third through the eighth decades [5]. Additionally, the ability to generate muscle power of the lower body, which was recently recommended as the best measure of muscle quality, is involved in many tasks of daily living such as climbing stairs or rising from bed [8]. There are some daily living tasks and exercises performed in rehabilitation for older adults that require postural stability during a semi-flexed (mini-squat) knee posture. This is an essential posture to be performed during tasks like retrieving something from a low table or the floor, using the toilet or performing sitting and standing tasks. Thus, impaired postural control from aging during the mini-squat posture may compromise the functionality and social participation of older adults [9].

In the last decade much research has been performed to identify risk factors related to fall events. Both extrinsic and intrinsic factors play a role. The apparent relationship between balance control, age and risk of falling stimulated studies of the relation between age and balance, underlined the development of standardized procedures for measuring balance and studies to predict the risk of falling for older adults. Other investigators compared several psychological indicators of balance confidence in relation to physical performance [3, 10].

The establishment of specific and sensitive functional measures is needed for clinical trials in older adults. Although the squat posture is often used in daily life tasks, to the best of our knowledge the relationship between balance and gait with this posture has not been previously investigated. Considering the above, the objectives of the present prospective cohort study were to determine the lower extremity muscle force with unilateral eccentric squats on a flat (half squat-HS) and a declined surface (decline squat-DS) and additionally to verify the correlation of these with the gait characteristics and balance in community dwelling older adults.

2. Methods

2.1 Study population

This is a prospective population-based cohort study performed in community dwelling older adults in Aydin, Turkey. The study was approved by the Ethical Committee of Pamukkale University. Participants provided written informed consent and were permitted to withdraw from the study at any time. The participants were aged between 65–95 years. Inclusion criteria were: (1) 65+ years, (2) could walk independently without walking-aids, and (3) more than 6 in the score of Hodkinson’s Abbreviated Mental Test. Thirteen subjects refused to participate, and one subject could not finish the tests. In total 78 (55 men and 23 women) participants were included in the study.

2.2 Measurements

Simple clinical measures on balance predicting falls, loss of independence functional status and sensitivity to change with training [7] were performed. Performance-orientated measurement of balance and gait were done using by the Turkish version of the Tinetti Performance Oriented Mobility Assessment (POMA). The inter-rater reliability, content validity and predictive validity were established by the test developers and showed good performance on inter-rater reliability and concurrent validity [11, 12, 13].

Table 1
Demographics

Parameters	Min. – Max.	Mean $\pm$ SD
Age (years)	65–94	75.07 $\pm$ 6.28
Height (cm)	145.00–181.00	162.47 $\pm$ 8.98
Weight (kg)	46.00–95.00	70.07 $\pm$ 13.73
BMI (kg/m ${}^{2}$ )	18.00–41.40	26.46 $\pm$ 4.83
Hodkinson’s mental test score	7.00–10.00	7.33 $\pm$ 0.43

BMI: Body Mass Index.

Performance-oriented gait measurements used in this study were done using the foot print method. Step width, step length, double step length, cadence and gait speed were recorded after a 20 m walking area [14]. Parameters were measured for the middle 10 meters and timed by a chronometer. The first and last meters, considered respectively warm-up and the deceleration phases, were not included in the calculation. Participants began the test on the word “start” and were instructed to “walk at a comfortable and secure pace”.

Lower extremities functioning level was measured by the unilateral eccentric squats on a flat (half squat-HS) and a declined surface (decline squat-DS). DS has been described as a method to maximally load the knee extensors in an eccentric manner. This functional test is considered a useful clinical assessment. Furthermore, it is used as an easy and effective rehabilitation exercise for knee extensors [15]. The HS performed on a flat floor with 20 ${}^{\circ}$ knee flexion and DS was done on a decline board with 25 ${}^{\circ}$ , on dominant lower extremity and with a little support [16]. The test performance was recorded as the repetition in one minute. Participants were instructed to squat down and then return to the starting position. This was repeated as many times possible within the timeframe. A 10 s rest period was given between the sets [17].

2.3 Data analyses

Descriptive analyses were performed for the demographics, Turkish version of Tinetti Performance Oriented Mobility Assessment (POMA), gait (foot print) variables, and strength measurement with half and declined squat (repetition/min). The prevalence and incidence of falls and recurrent falls were also recorded. To analyze linear relationship between two quantitative dependent or independent variables Pearson’s Correlation was used. $p<$ 0.05 was considered statistically significant.

3. Results

3.1 Baseline characteristics of subjects

The baseline information about participants’ demographics and clinical characteristics are shown in Tables 1 and 2.

Table 2
Clinical characteristics

Parameters	$n$	%
Medical diagnosis
No	7	9.0
Diabetes mellitus	47	60.3
Hypertension	14	17.9
Coronary heart disease	8	10.3
Osteoporosis	13	16.7
Urinary incontinence	16	20.5
Vision problems	38	48.7
Others	2	2.6
Medication
No	9	11.5
One	35	44.9
Two-three	31	39.7
Four or more	3	3.9
Previous fall history
No falls	58	74.4
Once	8	10.3
Twice	4	5
Three times or more	8	10.3
Fear of falling
Yes	18	23.1
No	60	76.9

3.2 Previous history of falls

The prevalence of previous falls within the past year was 10.3% for three times, while 74.4% of the subjects reported that they had never fallen down. Eighteen out of the 78 subjects revealed that they had subjective mobility problems and a fear of falling (Table 2).

3.3 Performance-orientated measurements

The mean of half and decline squat tests’ repetition number in one minute, the Turkish version of the Tinetti Performance Oriented Mobility Assessment (POMA) scores, and gait characteristics with foot print method are listed in Table 3. The repetition in the DS (20.73 $\pm$ 13.47) was less compared to the HS (31.75 $\pm$ 15.60).

Table 3
Performance-oriented measurements of balance, gait and strength

Scores	Min. – Max.	Mean $\pm$ SD
Tinetti Balance and Gait Scale
Balance (max. $=$ 16)	8–16	14.94 $\pm$ 2.05
Gait (max. $=$ 12)	5–12	10.94 $\pm$ 1.71
Total (max. $=$ 28)	16–28	25.91 $\pm$ 3.37
Foot print analysis
Step length (cm)	16–82	43.39 $\pm$ 12.40
Double step (cm)	36–126	85.66 $\pm$ 23.57
Step width (cm)	1–19	9.84 $\pm$ 3.53
Cadence (step/min)	40–129	90.17 $\pm$ 16.68
Pace (m/min)	19–111	65.51 $\pm$ 23.57
Strength
Half squat (repetition/min)	0–65	31.75 $\pm$ 15.60
Decline squat (repetition/min)	0–50	20.73 $\pm$ 13.47

3.4 Relationship between variables

The relationship between half and decline squat tests, the Turkish version of the POMA and gait characteristics are shown in Table 4. There were high level positive correlations between the balance score and gait characteristics including step length, double step length and gait speed both squats. The correlation between gait and total score of the Turkish version of the POMA and DS were stronger than the HS (Table 4).

Table 4
Relationship of the half and decline squat with gait characteristics and the Tinetti Balance and Gait Scale

Variables	HS		DS
	$r$	$p$	$r$	$p$
Gait characteristics
Step length (cm)	0.436	0.000 ${}^{**}$	0.393	0.000 ${}^{**}$
Double step (cm)	0.426	0.000 ${}^{**}$	0.406	0.000 ${}^{**}$
Step width (cm)	0.087	0.447	$-$ 0.079	0.492
Cadence (step/min)	0.303	0.007*	0.207	0.069
Pace (m/min)	0.484	0.000 ${}^{**}$	0.430	0.000 ${}^{**}$
Tinetti Balance and Gait Scale
Balance	0.407	0.000 ${}^{**}$	0.397	0.000 ${}^{**}$
Gait	0.446	0.000 ${}^{**}$	0.512	0.000 ${}^{**}$
Total score	0.481	0.000 ${}^{**}$	0.515	0.000 ${}^{**}$

HS: Half squat; DS: Decline squat, ${}^{*}p<$ 0.01, ${}^{**}p<$ 0.001.

4. Discussion

About one third of the community dwelling older adults above age 65 fall every year, while 40% of those over age 80 experience one or more falls. Every year, an estimated 30–40% of patients over the age of 65 will fall at least once [5, 12, 18]. The most consistent predictors of future falls are clinically abnormal gait or balance disorders, aging and gait speed, while previous falls, medications and impairments in strength are risk factors that are most highly correlated with fall risk [1, 2, 4, 5, 12, 18]. Although review studies indicate that the deficits in muscle strength are important risk factor for falls, no previous published study has examined the relationship of knee strength (measured with eccentric contraction) on gait and balance in a population-based sample of community dwelling adults. It remains unknown why therapeutic managements using decline eccentric squats offer superior clinical efficacy compared to standard horizontal eccentric squats [19]. In association with the literature highlights we studied, the lower extremity muscle force measured with unilateral eccentric squats on a flat (half squat-HS) and on a declined surface (decline squat-DS) and its relationship with the gait characteristics and balance in community dwelling older people was examined in this prospective cohort study.

In the literature it was reported that the incidence of falls increases with age [12, 18, 20]. All subjects included in this study were 65 years or older. The mean age was 75.07 $\pm$ 6.28 years. The presence of depression and cognitive problems were associated with a five-fold fall risk increase amongst depressed older adults on multiple medications [18, 21]. To eliminate this all subjects were assessed with Hodkinson’s Abbreviated Mental Test. The mean was 7.33 $\pm$ 0.43. As a general concept while assessing older adults, a history of the patient’s falls with a detailed description of the circumstances of the fall, frequency, and symptoms at the time of the fall, injuries, and other consequences should be obtained [12, 18, 21]. Assessments should also include the individual’s perceived functional ability and fear related to falling [18]. 23.1% of our subjects were afraid of falling; this might be because of the high proportion of subjects who reported that they had not fallen before (74.4%).

In the related literature it was stated that the physical exam should include measurements in terms of balance, lower extremity function, gait and mobility [3, 4, 12, 18, 21]. This is why performance-orientated measurements of balance and gait were done with the Tinetti Performance Oriented Mobility Assessment (POMA) [11, 12]. The foot print method done on 20 m was the other performance-oriented gait measurement used in this study. These assessments gave us a more detailed description of gait abnormalities in comparison to classic physical examination alone. Although gait can be characterized in numerous ways, gait speed is a simple yet valid summary measure that has been extensively used throughout the years. Gait speed stays comparatively stable until the seventh decade and thereafter slows 15% per decade. Sixty-two years coincided with an accelerated decline in self-selected speed of walking [4, 5]. Our subjects’ mean of gait speed was 65.51 $\pm$ 23.57 m/min (range 19–111 m/min), which is a quite slow walking velocity. Especially, diminished gait speed is associated with decreased stride length and single support time (single foot on the floor) as well as increased double support time (both feet on the floor) [5, 18, 20]. The other differences could be seen as slower cadence, shorter step length, shorter stride length, reduced hip and knee range of motion, and greater stride width with greater propensity of landing flat-footed vertical oscillation, and lateral sway of the head [18]. In addition, fallers had increased variability of kinematic measures compared with non-fallers. We did not separate the subjects according to their fall history, but we observed that gait characteristics are different from young persons and that the ranges were quite broad for all parameters (Table 3). The cadence was 90.17 $\pm$ 16.68 step/min., while the step width was recorded as 1 to 19 cm (9.84 $\pm$ 3.53 cm). These results show that some of the subjects have a great risk of falling, while as a whole they have a low fall risk according to the mean score. Based on previous studies, gait disorders are defined as either gait velocity equal or below 0.8 m/s or POMA Gait Test score below nine [21]. Our subjects’ mean Tinetti Balance Test score was 14.94 $\pm$ 2.05 (low fall risk), POMA Gait Test score was 10.94 $\pm$ 1.71 (medium fall risk) and a total score was 25.91 $\pm$ 3.37 (low fall risk). According to all performance-oriented balance and gait tests, we noted that our subjects have a medium fall risk during walking activities, whereas they have a low risk during balance activities. The remarkable result for us was that the manner in which a certain activity is performed is a reflection of how the subject attempts to maximize comfort and endurance, and represents the best compromise between parsimony in energy utilization and safety, as was also stated by Fukagawa et al. [6].

Motor adaptations and the motor task being performed muscle control and strength is essential to maintain trunk and pelvic stability and to control balance [2, 5, 17]. In particular, the rate at which muscle power declines is even more rapid than the concomitant loss of muscle strength and mass [8]. Such temporal discrepancies reveal more intricate musculoskeletal deficits, especially lower extremity power and strength, and are recognized as an important underlying cause of the onset of frailty, balance impairment and increased incidence of falls with age as well as difficulties performing daily and leisure activities [2, 4, 5, 8, 10, 12, 18, 22]. Kuo et al. stated that, during the accelerating phase of squat to prevent the body from falling forward, increased muscle activity of the erector spinae and biceps femoris is required to increase hip extensor moment, and increased muscle activity of the rectus femoris and biceps femoris is needed for co-contraction to maintain knee stability, in addition to the co-activated plantar flexors and the tibialis anterior. They observed that older adults had increased head motion and required increased activity of the posture muscles to compensate for insufficient knee flexion during accelerating and decelerating squat phases and to maintain lateral stability [23]. Therefore, assessing lower extremity strength is essential for the balance and activities of daily living in older adults.

The single-leg squat performed on a decline board has been described as a method to maximally load the knee extensors in an eccentric manner. This functional test is considered an easy and effective rehabilitation exercise and assessment tool for knee extensors [15]. It was also declared that there is an association between knee extension strength, ankle dorsiflexion strength, chair stands and falling [18]. Keeping previous literature in mind, we chose half squat and decline squat tests to assess the lower extremity strength, especially knee extensors, which are more often used in daily living. Kongsgaard et al. found that normalized mean electromyography amplitudes of the knee extensor muscles were significantly greater during the decline compared to the standard squat [19]. As a first step to compare changes among measures, squats, especially the decline squat, may provide new additive information to the more commonly accepted measures. Previous studies have shown that lower body muscular power is more adversely affected by aging [8], so we would like to emphasize that the decline squat could provide a clinical estimate of lower body muscular power. As hypothesized we noted that subjects had done less repetition in eccentric decline squat (Table 3). Superior effectiveness of the eccentric decline squat, compared to half squat on a flat floor, may be the result of the fact that standing in the decline position reduces the contribution of the calf to the squat. In this manner, knee extensors and the patellar tendon are maximally loaded by reducing calf muscle tension, allowing better isolation of the knee extensor mechanism [15, 19].

In both cross-sectional and longitudinal studies, authors reported on the influence of aging on normal gait, which is attributed by the fact that aging-related neuromuscular impairment is associated with a significant decline in muscle strength, secondary to a loss of muscle mass [6, 22]. Fukagawa et al. demonstrated that older subjects needed a longer time for performing a squat, especially in the descending phase with more anterior inclination of the thorax and pelvis, more flexion in the hip joint, and less flexion in the knee and ankle joint [6]. Meanwhile, the relationship between impairments in muscle force generation and balance, however, has not been extensively investigated, e.g. for other activities such as a deep squat [6]. The purpose of this study was to determine whether there is a relation between the lower extremity muscle force tests (half squat and eccentric decline squat) with the Tinetti Performance Oriented Mobility Assessment (POMA) and gait parameters. Furthermore, we aimed to decide if these tests could be used as predictive scores on balance and gait in community dwelling older people. The relationship of the half squat test and decline squat test with POMA and gait characteristics are shown in Table 4.

The current results show that there was a high-level positive correlation with step length, double step length and gait speed and POMA Balance Test score in both HS and DS test ( $p=$ 0.000). Although step width is essential for maintenance of postural control and a correlation between muscle weakness and widen step width was expected, just in step width we did not find any relation for both squat tests ( $p>$ 0.05). While there was a high positive correlation with POMA Gait Test score ( $r=$ 0.446, $p=$ 0.000) and the POMA’s total score ( $r=$ 0.481, $p=$ 0.000) in HS, the correlation was stronger in DS ( $r=$ 0.512 and $r=$ 0.515 respectively, $p=$ 0.00) (Table 4). Due to deterioration of the musculoskeletal system and balance, older adults have more rigid coordination strategies for rapid changes in body direction in comparison to young subjects. When performing functional tasks, older adults require substantially greater effort than young adults relative to their available maximum capacity [23]. Use of a 25 ${}^{\circ}$ decline board during the performance of eccentric unilateral squats would decrease force generation of the calf muscles and thereby increase the load imposed on the knee extensor mechanism including the patellar tendon [19]. Thus, the feasibility, sensitivity and reliability of squat tests make them an informative and potentially useful tool for clinical and interventional assessments of the functional status associated with aging. Future studies are needed to determine whether the results are due to adaptations or functional capacities translated to and from daily living, especially for the decline squat. In regard to the sample size, a larger group might be important for adequately powering all balance and gait variables in order to identify other factors that might be of influence.

5. Conclusions

Falls in older adults are common but are not an inevitable by-product of aging. Appropriate and direct assessment of lower limb power and performance in balance and gait analysis should be done to identify those subjects. The performance-based functional assessment measurements (e.g. half squat and eccentric decline squat tests, gait characteristics and balance tests) could be potent predictors of balance impairments resulting with falls and recurrent falls. In order to evaluate the kinematic performance using the knee squat tests, especially the decline squat, as a motor task and understanding these could be beneficial to physiotherapists for utilizing squatting as a task to assess and improve motor function and balance in older adults.

Footnotes

Acknowledgments

The authors would like to thank all participants for their support.

Conflict of interest

None declared.

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