Trunk Movements in Older Subjects During Sit-to-Stand

Transcription

1 844 Trunk Movements in Older Subjects During Sit-to-Stand Gillian D. Baer, MSc, MCSP, Ann M. Ashburn, MPhil, MCSP ABSTRACT. Baer GD, Ashburn AM. Trunk movement in older subjects during sit-to-stand. Arch Phys Med Rehabil 1995;76: Sitting to standing (STS) is an activity that is performed many times during the course of a day and is an important prerequisite to the achievement of many functional goals. This article presents the results from a pilot study, the purpose of which was to develop a method for investigating the activity of sit-to-stand. The study describes STS timing and patterns of trunk movement during standing up in a population of 30 normal older adult subjects (mean age, 61.6 years; SD, 7.7 years). Data were gathered using a three-dimensional movement analysis system, CODA-3. Time taken to stand up was recorded, as were the trunk movements of pelvic and shoulder rotation, trunk lateral flexion, pelvic and shoulder lateral shift, and backward shoulder movement to achieve stance. Results show that normal subjects stood up quickly (mean, 1.67sec; SD,.27sec; range, 1.26 to 2.13sec), and despite large amounts of trunk forward flexion and upward motion necessary to achieve the task of standing up, only small amounts of trunk rotation, trunk lateral flexion, and trunk lateral shift were measured during the activity. The identification of these movement characteristics may be beneficial in assisting with analysis of the STS movement pattern by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation It is widely accepted by physiotherapists that control of normal alignment and trunk activity can positively influence the quality of peripheral and functional movement in people with neurological impairment. Although physical treatment aims for normality, treatment goals are based on many unsubstantiated assumptions about symmetry and ranges of normal trunk movement during functional activities. The underlying premise that normal people move symmetrically is inherent in some sit-to-stand (STS) studies ~'2 and not examined in others; however, no objective evidence of this symmetry has been documented in the literature. A greater knowledge and understanding of the essential components of normal movements are essential for developing strategies for treatment and evaluating efficacy of intervention. The normal gait cycle has been analyzed and studied in depth, producing considerable understanding of the activity. In contrast, limited knowledge exists about the process of achieving many other functional activities. A bank of normal data needs to be established for a range of functional tasks; rising to stand from a seated position is one of these activities. The relevance of STS as a quantitative measure of function has been highlighted, 3 yet limited documentation of this activity is available. This study focuses on trunk movement during STS in "normal" subjects. The word "normal" is used with caution throughout the discussion and reflects the fact that the sample group investigated in this study had to satisfy inclusion criteria. A major reason for the focus on trunk movement is that during the rehabilitation of people with neurological impairment, trunk alignment and trunk activity are From the Department of Physiotherapy, Queen Margaret College (Ms. Baer), Edinburgh, Scotland; and the University Rehabilitation Research Unit, Southampton General Hospital (Ms. Ashburn), Southampton, England. Submitted lor publication July 19, Accepted in revised form April 11, No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Ms. G.D. Baer, MSc, MCSP, Department of Physiotherapy, Queen Margaret College (Leith Campus), Duke Street, Edinburgh EH6 8HF, Scotland by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation /95/ $3.00/0 commonly regarded as having major implications for the "normality" of subsequent movement. 4 Previous studies investigating whole body movements have considered the trunk only as one segment and analyzed trunk activities as such. 5 There is, however, a move to investigate more complex trunk movement during various activities. 6 Further studies investigating how sections of the trunk relate to each other during STS are required. This article presents results from a study investigating the trunk movements of normal older adult subjects during STS. BACKGROUND Kelley and colleagues 7 were the first to define STS in phases, proposing two: forward flexion followed by extension. More recently, four phases have been suggested: flexion momentum, momentum transfer, extension, and stabilization. 3'5'8 In 1990, Kralj and associates 9 published a sixpoint STS cycle analogous to the gait cycle, with percentage timings for each event. Despite these proposals for defining the activity, there is still no consensus of terminology used for describing STS, making study comparisons difficult and complex. A key difference in methodologies has been whether prescribed rising times have been used or not. Prescribed rising times have varied from 1.15 seconds, 5"8 1.2 seconds, 3'~ 1.3 seconds, lj or 2 seconds] Studies using unrestrained protocols have reported mean STS times in normal subjects of between 1.8 and 3.3 secondsg'j2'j3; the variations in timings probably resulted, in part, from the different study methodologies. In elderly subjects, depending on the methodology used, a rising time of up to 11 seconds has been reported~4; however, particular attention to incorporate the stabilization phase in the reported measure was included, in contrast to other STS studies, making comparison difficult. Ikeda and associates s studied a group of elderly subjects and found that age does not influence timing, movement velocity, or body angular displacements, except for an increased head-to-trunk flexion during STS. Millington and

2 TRUNK MOVEMENTS DURING SIT-TO-STAND, Baer 845 colleagues ~ studied 10 healthy elderly subjects and noted consistent patterns of trunk and lower limb movement during the phases of STS, although two different strategies of upper limb movements were identified. As most studies have used young subjects 1'2'3'5'j 1,12 and few studies have used more than 30 "normal" subjects, the generalization of findings to an older population is difficult. Nearly all previous studies of STS have described the movement from a sagittal plane. Researchers using this plane have been able to provide primarily kinematic data, eg, lower limb joint angles during the rising to stand j'5'7's'j 1,12,15,16; or they have added to the body of biomechanical data with respect to s tandin g up. 3.9, ~0. ~7-19 Resultant joint moments have been found to increase with increasing knee flexion at the starting position. Studies investigating the effect of different seat height in relation to knee height have shown a decrease in lower limb joint ranges of motion and a reduction of forces in lower limb joints and muscles as seat height increases, j'19 In elderly people, it has been shown that as seat height used decreases, the action of standing up becomes more difficult. 14 Studies investigating the distribution of weight during STS have noted that normal subjects exhibit a virtually symmetrical distribution. 16'2 In contrast, hemiplegic subjects show marked asymmetry, with increased weightbearing through the unaffected leg during STS. 16'21'22 It might be reasonable to assume that a marked asymmetry of weight distribution could be associated with marked asymmetrical movement pattern, although this has not been established. In general, researchers into STS can be criticized for controlling the task procedure too rigidly. Although strict procedures may result in a uniformity of action and facilitate analysis, they may also eliminate the natural variability of individuals during movement and, consequently, raise questions about generalizability of findings and may affect the practical relevance. A fixed starting position with arms crossed and feet precisely positioned 10.2cm apart has been adopted in some studies. 3'5'8 Manipulation of seat height has included its adjustment to 75% to 80% of subjects' floorto-knee height, 9'~7 or its alignment with the knee joint line. 6 Time taken to stand up has either been left to individual variation, 1 '~2 assigned to a number of "self-selected" speeds, 2 or regimented by metronome in an attempt to ensure repeatability of the action within a prescribed rising time. 3'5'7'8'1 j All these methods have manipulated the environment to match the individual, rather than requiring the individual to adapt to the environment, thereby eliminating aspects of natural variability that occurs both within and between subjects standing up under normal circumstances. Although a degree of standardization is of benefit if trying to investigate forces generated under specific conditions, strict standardization cannot reflect standing up under normal conditions in which the seat height is fixed and, therefore, subsequent movement has to adapt to it. Excessive constraints may hinder the movement to such an extent that the result is far from normal. In summary, most of the published literature describes studies concentrating on sagittal plane measurement of angular limb movements and lower limb force production during standing up. No published work describing trunk movements could be found, apart from a couple of studies undertaken in the sagittal plane and investigating the trunk as a complete segment. 2"~ It is clear that more knowledge is required about the STS activity and that testing by the least restrictive procedure might allow greater generalization of findings. STUDY AIMS This study was undertaken to collect a database of time taken to stand and movements occurring during STS in normal subjects. Specific aims were (1) to record the time taken to stand up from sitting, (2) to measure angular movements of lateral trunk flexion and trunk rotation during the STS cycle, and (3) to measure range of lateral shift at the pelvis and shoulders during the STS cycle. METHODOLOGY Subjects were volunteer workers at a community hospital or relatives of patients. Subjects with a history of gross neurological or musculoskeletal abnormality were excluded. Written consent was obtained from each subject and assessments were completed during one visit. Data was collected using a three-dimensional, computercontrolled, movement analysis system--coda-3 (CODA)." This system uses optical scanning techniques with 3 scanners to detect reflected light from prismatic, retro-reflective markers positioned on the subject. CODA is reported to be accurate to.05% of range. 23 A digital timer connected to a pressure pad, mounted on a standard height stool of 51cm was used to record the point of "seat off." CODA was set to commence recording in conjunction with the digital timer. Reliability of CODA measurements were established by repeated blind testing of distances and angular goniometer positions and found to be accurate with an intraclass correlation coefficient (ICC) of.98. Marker Placement Subjects stood with their arms by their side during marker placement. Markers were placed on the spine of the scapula 9cm medial to the acromion process, over the sacro-iliac joints, and on the heel at the point of tendo-achille insertion (fig 1). Intratester reliability of marker placement-replacement was found to be highly accurate (ICC,.99 on 8 subjects). Sit-to-Stand Cycle Data were obtained at the 6 points in the STS cycle shown in figure 2. Features of STS Examined The key aspects of the STS cycle used for analysis were as follows: (1) the time and rhythm; (2) lateral shift at the shoulders and pelvis, measured as the mean total lateral excursion of the 2 shoulder or sacro-iliac markers; (3) lateral trunk flexion, measured as an angular value between the shoulder and pelvic markers; (4) backward shoulder movement to achieve stance, which was examined because it has not received detailed investigation, despite being noted as a feature of STS 12; and (5) rotation at the shoulders and pelvis. The term rotation used here does not refer to rotation about

3 846 TRUNK MOVEMENTS DURING SIT-TO-STAND, Baer ) Point I Point 2 Point 3 Point 4 ( Point 5 Point 6 Fig 2--Diagrammatic representation of points in the sit-tostand cycle. Point 1, quiet sitting: 0.1see before movement initiation. Point 2, initiation: first discernible body movement. Point 3, seat off: thighs leave seat. Point 4, mid-stance: peak vertical acceleration changes to vertical deceleration. Point 5, stance: shoulders move back to achieve upright position. Point 6, quiet standing: lsec after achieving stance. to avoid a loss of the initial data. The mean of 3 separate trials was used in data analysis for each subject. RESULTS Sit-to-stand activity was measured in 30 volunteers, 14 men and 16 women. Mean age was 61.6 years (SD, 7.7 years; range 50 to 80 years); mean height was 1.69m (SD 0.09m; range 1.56 to 1.9m); weight was 70.3kg (SD, 11.5kg; range 51.5 to 90kg). Anthropometric data were also recorded. Fig 1--Marker placement. a central vertical axis (which was not possible to compute), but to rotation of either the shoulder or pelvic girdle in relation to the horizontal plane of CODA. This means that only an indication of rotation rather than true rotation values were obtained. Testing Procedure To observe subjects standing up in their normal way, few constraints were placed on the STS procedure and a standard height seat was used. The only restrictions imposed were that subjects were not allowed to use their hands to push up and that the feet stayed on the floor. On the command " l 2-3-stand," subjects were asked to stand up in their normal manner. Recording commenced on the count " 3, " in order STS Time and STS Cycle The time taken for completion of STS was calculated from the point of movement initiation to Stance. The mean time to achieve stance was 1.67sec (SD 0.27sec) with a range of 1.26 to 2.13sec. One-way analysis of variance (ANOVA) of STS time over the 3 trials showed a statistically significant between-subject difference (F = 6.8, p <.05). A N O V A of STS time within subjects showed no difference (table 1), suggesting that there may be a consistency to an individual's timing of the movement, although variations in timing may be utilized by different subjects. Table 2 summarizes the time taken by normal subjects to complete one STS cycle. Using the points of the STS cycle, allows an indication of the rhythm of the STS cycle by calculation of phase percentage timing. Table 2 shows that the STS cycle was split into 3 phases from the start of movement and that the phases were approximately equal in timing. To reach "Seat O f f " from initiation took just over a third of the cycle, and "mid-stance" was achieved just under two thirds of the way through the cycle. Lateral Shift Measurements were obtained for both shoulder and pelvic lateral shift (measured as the mean lateral excursion of the Table 1: Summary of One-Way ANOVA for STS Time Source df SS MS F p F crit Between subjects Within subjects

4 TRUNK MOVEMENTS DURING SIT-TO-STAND, Baer 847 Table 2: Total STS Time and STS Phase Percentage Timing--Normal Subjects Initiation Seat Off Mid-Stand Stance Mean time taken (see) STS cycle percentage % 64.7% 100% 2 shoulder or pelvic markers); the results are summarized in table 3. The direction of both lateral shoulder and lateral hip shift occurred randomly to either side both within and between subjects. The data for amount of shoulder shift showed a slightly positive skew, indicating that of the range used, there was a trend toward using a slightly smaller amount of shoulder shift. Data for lateral hip shift showed a negatively skewed distribution, implying that the majority of the group demonstrated a larger amount of lateral hip shift. The amount of lateral hip and shoulder shift was further analyzed to see if there was an association between the range of shift shown in the upper and lower trunk during STS. Spearman's rank correlation showed a positive association (rs =.732; p <.01), which could indicate that the more lateral shift there is at the shoulders during rising to stand, the more lateral shift there is at the hips. Trunk Rotation As previously stated, rotation values are given as rotatory movements of either the shoulder or pelvic girdle in relation to the horizontal plane of CODA. Counter-clockwise rotation, or rotation to the left from the horizontal axis (right shoulder or hip forwards) was assigned a positive value and rotation to the right assigned a negative value. The results of trunk rotation findings are presented in table 4. The total range of motion observed for rotation was similar at the shoulder (4.83 ) and the pelvis (5.69 ). It was interesting to note that during STS, this population had a tendency to demonstrate a shoulder position rotated to the right (-3.07 ), in contrast to the position of the pelvis, which was only minimally rotated (-0.35 ). An ANOVA demonstrated that there was a statistically significant difference between the shoulder and pelvis rotation positions (F = 9.62; p <.05). Lateral Trunk Flexion This value was measured as an angular value between the shoulder and pelvic markers. Thus if the markers were parallel, a value of 0 would be recorded. Lateral flexion to the right (a shortening of the right side of the trunk) was assigned a positive value; lateral flexion to the left was assigned a negative value. The total mean range of motion demonstrated for trunk lateral flexion was 3.56 (SD, 1.4; range 1.41 to 7.42 ). During STS, the population exhibited only small amounts of lateral flexion; mean position, 0.57 (SD, 2.9; range -5.5 to 5.9 ). A one-way t test showed that there was no statistically significant difference between the lateral flexion positions and 0 degrees (t =-.909; p -=.185), thus confirming that the amount of lateral flexion was small. Table 3: Amount of Lateral Shift at the Shoulder and Pelvis (mm) Mean Range of Lateral Shift During STS in mm (SD) Total Ranges of Lateral Shift During STS Shoulders 36.1 (12.6) Hips 29.6 (7.3) Backward Shoulder Movement The CODA traces demonstrated that nearly all subjects in this study (n -=- 28) commenced STS by moving the shoulders forward; the shoulders then continued to move forward, followed by an upward and backwards motion to achieve stance. Two features of backward shoulder movement on achieving stance were considered: the mean backward movement of the two shoulders and the difference between right and left shoulder movements on each trial of STS. The mean backward shoulder movement was 58.2mm (SD, 42.3 lmm; range, to 164.5mm [a negative value indicates forward shoulder movement]). The data for backward shoulder movement was found to follow a normal distribution. It was found that a minority of subjects (6%, n = 2) demonstrated a slight forward rather than backward movement to achieve stance, indicating either an almost upright posture during standing up, or possibly a slightly backwards inclination of the trunk. There were virtually no discrepancies between left and right backward shoulder movement with the mean value for left-right difference being 2.3mm (SD, 14.4ram; range 0 to 22mm). DISCUSSION This study investigated sit-to-stand in a group of "normal" adults between the ages of 50 to 80 years. The prime aim of the work was to collect "normative" data related to trunk movements and time for STS. The activity was examined under conditions as near normal as possible, with few restraining conditions. Overall, the results show that normal subjects stand up quickly and use a small amount of trunk activity during STS. Although the sample size of 30 was limited, there are few studies in the published literature that have larger samples. The numbers, however, did not allow comparisons between subjects of similar ages, heights, or weight. Furthermore, the testing procedure differed from those used in previously published studies, which limits strict comparisons but does allow inferences to be drawn. A minority of the measures showed a slightly skewed distribution, and in future studies, a larger sample group should allow for a more comprehensive analysis of the findings. Table 4: Trunk Rotation Values at the Shoulder and Pelvis (in Degrees) Mean Range Total Mean Rotation Total Range of Rotation Ranges Position of Rotation During of Amount During Positions STS (SD) of Rotation STS (SD) During STS Shoulder 4.83 (2.63 ) (3.00 ) Pelvis 5.69 (1.96 ) ,35 (3.74 ) A negative value indicates rotation to the right.

5 848 TRUNK MOVEMENTS DURING SIT-TO-STAND, Baer The time to stand up ranged from 1.26 to 2.13 seconds. This is similar to the results found by Nuzik and colleagues ~2 (1.3 to 2.5 seconds), who also used a study design with very few constraints. The mean time to achieve stance was 1.67 seconds, which compares closely to Nuzik,~2 who quotes a mean time of 1.8 seconds. Interestingly, this is almost half the mean time of 3.3 seconds quoted by Kralj 9 and is about 15% of the time quoted by Hughes and colleagues.14 Possible explanations for the discrepancy of findings could be the use of different methodologies and the utilization of different data acquisition systems. Furthermore, the period for stabilization to occur after stance was not accurately measured in the present study, although an attempt to consider this aspect of STS was made by both Kralj 9 and Hughes.14 In retrospect, improved definition of the stabilization process at the end phase of the STS cycle is required. It is interesting that the mean time to stand up (1.67 seconds) in this study challenges those studies that have regulated rising time to between 1.15 to 1.2 seconds by the use of a metronome. 3'5'8'j '~ Although some of the subjects in those studies were younger, it is possible that the enforced faster time would alter the STS pattern and, as speculated, prevent a natural pattern of movement. This point should be considered and the information taken into account with older adult subjects who require rehabilitation of STS. Events in the early part of the STS cycle established in this study were similar in percentage timings to those found by Kralj 9 and Nuzik, ~2 although the timing of later events differed. The point of "seat off" was reached at 37.7% of the cycle, which closely matched the findings of Kralj 9 (34%) and Nuzik, 12 who showed the flexion phase--time to "seat off"--to last 35% of the cycle. Time to achieve "midstand" was found to be 64.7% of the cycle, which is 20% greater compared with the findings of Kralj. 9 The discrepancy of findings between the studies may well have been confounded by the different methodologies. This aspect of STS certainly requires further investigation, in particular to see whether there is a consistency to the STS rhythm. The lateral shift of the shoulders and the hips during the process of STS was not an aspect mentioned in the published literature, although this could have ramifications for therapy with respect to assessment arid the monitoring and training of weight bearing. The findings from the current study showed that "normal" older adult subjects used a range of lateral shoulder shift of up to 65ram and up to 48mm of lateral hip shift. In addition the direction of shift followed no particular pattern. This minimal amount of shift is barely perceptible to the human eye, and the resultant smooth movement is presumably energy efficient. It would have been interesting to examine whether amounts of lateral shift correlated with weight distribution during STS, but the requisite force-plate equipment to allow these measurements was not available to the investigator during this study. The relationship between range of lateral shoulder and hip shift showed a positive association for the subjects in this study. This may occur because the trunk under normal neuromuscular control moves as linked segments during STS; therefore, movement at one segment is mirrored at another segment either higher or lower. During STS, the subjects studied only used small ranges of rotation at the shoulder (4.8 ) and pelvis (5.7 ). There was a slight tendency during STS for the shoulders to rotate more toward the left than the right as demonstrated by a mean value of -3. Rotation of the pelvis, however, generally showed much less rotation. The figures obtained are small and probably virtually indiscernible to the human eye. Knowledge that when normal subjects stand up there is a small degree of trunk rotation is important, however, particularly for those patients that have lost this rotatory component because of pathological changes. It suggests that during rehabilitation, the successful use of strategies to regain trunk rotation may be important in ultimately determining whether success in achieving STS is obtained. It was not anticipated that large amounts of trunk lateral flexion would be observed during STS in "normal" subjects, because this was not apparent during clinical observation. It is, however, a phenomenon observed clinically in subjects with neuromuscular impairment and therefore would be an important feature to monitor in this group. Further work on this aspect has been carried out with a group of subjects with hemiplegia (unpublished data). It is well recognized that the trunk moves forward and upwards during STS; there is also a small amount of backward shoulder motion to complete STS. This study investigated the backward shoulder movement to achieve stance and studied whether there was any discrepancy between the movement of left and right shoulders. To achieve stance after the initial forward flexion phase, most subjects (n = 28) showed some backward shoulder movement (mean, 58.2mm [SD, 42.31; range, 16.2 to 164.5mm]), although 2 subjects appeared to stand up with minimal if any forward flexion component to the movement (ie, as they stood up, the trunk moved vertically). There was very little disparity between the two shoulders as they moved backwards, which probably suggests that any shoulder rotation component during STS did not occur at this stage in the cycle. CONCLUSION In conclusion, this article has described trunk movement during STS, time taken for STS, and the rhythm of STS in a population of 30 normal adult subjects. Overall, the results show that normal subjects stand up quickly and demonstrate a small amount of trunk lateral flexion, trunk lateral shift, and trunk rotation despite large amounts of trunk forward flexion and upward activity during the task of STS. The parameters of STS time are in agreement with previous investigators, ~2'j3 and it is recommended that this information could be used as a measure of progress for people with difficulty in performing STS. The ranges of lateral trunk flexion, lateral shift, and trunk rotation during STS were all found to be small and probably appear to be negligible to the human eye. It is hoped that this information can be applied by physiotherapists during the analysis of STS activity and in the rehabilitation of an individual with an altered pattern of movement. Future studies in this area should include a larger number of subjects and should develop a measurement system more appropriate for the clinical setting. The rhythm of STS should be examined in greater detail to determine a more accurate end point of STS activity. Therapeutic interventions Arch Phys Med Rehabi! Vol 76, September 1995

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