Walking is an important element of various daily living activities. Gait properties that can characterize walking quantitatively may be simple indicators of overall human health.1 In old age, various physical functions, including lower limb strength, joints, and visual acuity, decrease and greatly affect gait. Researches have was reported that a gait change with age also relates to falls.2–4 In addition, gait has been used as a predictor of disease and death in older adults.3
As concrete parameters of gait stance time, swing time, step length, and step width including walking speed and cadence, have been used.5,6 The following changes have been reported to occur in walking with aging: a decrease in walking speed,5,7 an increase in single lower limb support time and a decrease in double lower limb support time during total contact time,8 and shortness of step length.9
The main factors related to gait change in old age include lower limb muscle function,10–12 vision function,13,14 and knee joint function.15,16 Among others, many reports are related to the effect of a decrease in lower limb strength on gait.10–12
Visual information is important for stable walking, and a decrease of visual function (eg, low visual acuity) produces disadvantage in achievement of daily living activities.17 In the case of older adults, researchers have reported that a decrease in visual acuity increases the risk of falls.18–20 Elliott et al21 confirmed that walking speed and cadence decreased when young healthy persons with simulated cataracts walked in dim light, and Moe-Nilssen et al22 reported that a sudden reduction from normal to marginal lighting while walking induced gait change.
In addition, lower limb joints play an important role in gait as walking is a movement that primarily requires the use of the lower limbs. In old age, knee joint function decreases, and patients with knee osteoarthritis have slower walking speed, and slower cadence, or shorter step length, and longer stance time.23,24 Kaufman et al25 confirmed that compared with healthy subjects, patients with knee osteoarthritis walk with a lower knee extension moment to reduce knee strain. Generally, older adults have suppressed joint function. About 25% of older adults aged 55 years or older, including patients with knee osteoarthritis, complain of knee joint pain.26,27 Knee joint pain greatly affects walking.28
In this way, it is considered that vision problems and knee joint pain, in addition to decreased lower limb strength, are important factors affecting gait.
In old age, it is commonly the case that many physical functions decrease simultaneously. In short, older adults generally have some problems (eg, decrease of lower limb strength and vision function, and knee joint pain) that affect gait. When examining older adults with vision problems and knee joint pain in addition to lower limb strength, it is difficult to identify the specific factor that affects gait. Not only lower limb strength but also vision problem or knee joint pain may be involved in gait limitations.
This study aimed to examine the effects of knee extension strength, visual acuity, and knee joint pain on gait parameter in older adults by considering synergies among these factors.
MATERIALS AND METHODS
The subjects who participated in this study were 181 healthy, community-dwelling female older adults. Table 1 shows their age and physical characteristics. All subjects participated in health class or social educational activities that were hosted by municipal governments. In addition, their “activities of daily living” score was very high (Ministry of Education, Culture, Sports, Science & Technology). Hence, they were judged to have high independence in daily activities because many of them engaged in leisure activity and work. Before the measurements, the purpose and procedure of this study were explained in detail and informed consent was obtained from all subjects. In addition, this study was approved by the Ethics Committee on Human Experimentation of Faculty of Education, Kanazawa University, Ishikawa, Japan (Ref. No. 19-17).
Gait properties were measured by a gait analysis system Walk Way MG-1000 (Anima, Japan) referenced to Demura and Demura's6 method. The MG-1000 with plate sensors can determine time, dimensions, and the distance of the foot or feet when the foot touched its surface and can measure grounding/nongrounding on the bearing surface as an on/off signal. Data were recorded into a personal computer at 100 Hz. Subjects walked 12-m path (wooden floor) with sensors mentioned previously with voluntary maximum speed. The analysis interval was from 4 to 8 m.
Lower Limb Strength: The Effect of Knee Extension Strength
Knee extension strength was selected for characterizing lower limb strength.29 During measurement of isometric knee extension strength, the subjects were seated upright in a rigid chair with knees flexed at an angle of 90° and with the lower lower limbs strapped in a pad just above the ankle, attached by a backward rigid bar to a tension meter attachment (T.K.K.1269f; Takei Scientific Instruments Co Ltd, Niigata, Japan). In addition, the subjects folded their arms on their chest. The subject was asked to extend the knee as hard as possible and to maintain it for 3 seconds. Each of the subjects' lower limbs was measured twice at intervals of greater than 30 seconds. It was difficult to adequately judge whether knee extension strength of older adults is superior or inferior because little data was available on their knee extension strength measured with the same method. Hence, superior and inferior groups in knee extension strength were made up among subjects measured in this study. In short, on the basis of mean value (mean) and standard deviation (SD), subjects were divided into 3 groups with different knee extension strength (inferior group: inferior < Mean − 1 SD; middle group: mean − 1 SD < middle < mean + 1 SD; superior group: mean + 1 SD < superior).
Visual Acuity: The Effect of Subjective Visual Acuity Problems
In old age, a decrease in visual function greatly affects gait. Persons who were selected in this study for visual acuity found it difficult to read characters or see people's faces, and felt hindered in their gait. Many of older adults have a narrowed visual field even if having normal eyesight. Hence, in this study, we simply asked older adults if they felt their walking was affected by their vision. Such an indicator of visual acuity has been used in a fall risk survey.30
Knee Joint Pain: The Effect of Subjective Knee Joint Pain
Having knee joints with orthopedic disorders affects walking.23,24 It was also assumed that subjective knee pain affects walking.28 Referring to Sugiura and Demura's31 method, persons with knee joint pain were divided into those who had pain in one knee joint or those who had pain in both knee joints.
Gait Variables (Temporal and Spatial Parameters)
The following 9 gait parameters were selected in reference to previous studies6: walking speed, cadence, stance time, swing time, double support time, step length, step width, walking angle, and toe angle.
Walking speed: walking distance per second (cm/s).
Cadence: the number of steps per minute (steps/min).
Stance time: the duration that the body is supported by 1 or both feet; that is, the phase in which one foot or both feet contact the floor.
Swing time: the duration that one foot swings; that is, one foot leaves the floor. This time agrees with a single support time (seconds).
Double support time: the duration in which both feet contact the floor (seconds).
Step length: the distance between anterior-posterior patterns (one step length).
Step width: the distance between both feet (centimeters).
Walking angle: the angle between the direction of movement and bilateral pattern line (°).
Toe angle: the angle between the direction of movement and the foot axis (°).
Older adults usually have a decrease in knee extension strength and vision problems or else knee joint pain simultaneously. The effect of the other factors was controlled to examine the unique effect of each factor.
The Effect of Knee Extension Strength on Gait (F1)
To examine the effect of lower limb strength on gait, mean differences of gait parameters among 3 groups with different knee extension strength (inferior, middle, and superior, divided by mean and SD) for subjects without visual acuity problems and knee joint pain were tested using 1-way analysis of variance (ANOVA).
The Effect of Subjective Visual Acuity Problem on Gait (F2)
To examine the effect of the visual acuity problem on gait, mean differences in gait parameters between groups with/without visual acuity problems for subjects without knee joint pain were tested using a t test.
The Effect of Subjective Knee Joint Pain on Gait (F3)
To examine the effect of knee joint pain on gait, mean differences of gait parameters between groups with/without knee joint pain for subjects without visual acuity problems were tested using 1-way ANOVA.
In addition, if significant differences were found in age, height, weight, and knee extension strength, gait parameters were tested using analysis of covariance. A Tukey HSD (Honestly Significant Difference) method was selected for multiple comparisons. The probability level of .05 was indicative of statistical significance.
The Effect of Knee Extension Strength on Gait (F1)
Table 2 shows the basic statistics and results of 1-way ANOVA for gait parameters among 3 groups with different knee extension strength (inferior, middle, and superior, divided by mean and SD) for subjects without visual acuity problems and knee joint pain. Walking speed and step length were significantly larger in the superior group than in the middle and inferior groups.
The Effect of Subjective Visual Acuity Problems on Gait (F2)
Table 3 shows the basic statistics and results of the t test for gait parameters between those with and without visual acuity problems for subjects without knee joint pain. Persons with visual acuity problems as compared with those without them showed a larger value in cadence and a less value in stance time.
The Effect of Subjective Knee Joint Pain on Gait (F3)
Table 4 shows the basic statistics and results of 1-way ANOVA for gait parameters among the 3 groups with different knee joint pain (one knee, both knees, and none) for subjects without visual acuity problems. Because significant differences were found in body mass and knee extension strength, analysis of covariance was used. Walking speed is faster in persons with pain in both knees as compared with persons without knee pain. Persons with pain in both knees showed a larger value in stance time and double support time than persons with pain in 1 knee or no pain.
The Effect of Knee Extension Strength on Gait
In examining for older women without visual acuity problems and knee joint pain, those with superior knee extension strength had significantly larger values in walking speed and step length than those with inferior knee extension strength. Researchers have reported that gait properties in older adults include a decrease in step length and an increase in double support time and step width.32,33 Patla34 reported that these gait properties in older adults, which differ from younger people, may contribute to increased walking stability.
A decrease in lower limb strength is closely related to a decrease in walking speed and is considered to be a main cause of gait change with age.35,36 Ferrandez et al37 reported that if walking speed is the same, gait movements in older adults will not be largely different from those of young adults. From the text given previously, similarly to results of previous studies,10–12 it is judged that knee extension strength contributes closely to a decrease in walking speed and step length.
The Effect of Subjective Visual Acuity Problem on Gait
Researchers have reported that fall risk in older adults increases with a decrease in visual acuity.18,38,39 However, studies also report no relationship between visual acuity and the fall risk when considering factors such as age.3,40
On the contrary, walking speed decreased when young persons with simulated cataract walked in dim light.21 Furthermore, a sudden change from normal to marginal lighting induces gait change, but gait characteristics are nearly normalized because of the adaptation to darkness during the first 90 seconds, suggesting that the darkness itself does not cause the gait changes.22 Also, in this study, cadence was higher and stance time was shorter because of visual acuity problem. However, the above-mentioned will be necessary to examine carefully because older women with visual acuity problems as compared with older women without them showed faster walking speed and wider step length, although significance was not found. In addition, the following may affect also the present result; there was no task in which subjects recognize an obstacle in which visual acuity is affected because of using a flat walkway in this study.
The Effect of Subjective Knee Joint Pain on Gait
Al-Zaharni and Bakheit23 and Bejek et al24 reported that patients with osteoarthritis show a decrease in walking speed and step length, and an increase in stance time. In addition, an increase in step width is found as one of the features of abnormal gait in people with disorders.33 Gehlsen and Whaley41 reported that older adults with fall history have significantly larger step width than those without it. Hence, step width may be an efficient means of judging abnormal gait.
Moreover, Bejek et al24 reported that patients with osteoarthritis, when walking with fast speed compared with slow speed, show a more prominent gait change due to the effects of pain.
In this study, older women with pain in both knees showed slow walking speed and long stance time and double support time. This gait changes are similar to those reported by Bejek et al.24 In addition, it is considered to be one of characteristics in persons with subjective knees joint pain because the parameters discussed previously are mainly ones regarding time.
This study examined the effects of knee extension strength, subjective visual acuity, and subjective knee joint pain on gait change in older adults.
Older adults with superior knee extension strength can walk at a faster speed and with longer step length than older adults with inferior knee extension strength. Persons with visual acuity problems had higher cadence and shorter stance time. In addition, persons with pain in both knees showed slower walking speed and longer stance time and double support time.
In conclusion, a decrease of knee extension strength and visual acuity and knee joint pain are factors affecting gait in the female older adults. Decreased knee extension strength and knee joint pain mainly affect respective distance and time parameters of the gait.
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