Development of a Functional Bridge Test for Screening Impairments and Disabilities in Hemiplegic Patients with Acute Stroke while on the Bed

ABSTRACT

Objectives: To provide a safe and appropriate out-of-bed program for stroke patients, screening for stroke-related functional impairments and disabilities should be performed in advance. However, few tools are available for clinical assessment of out-of-bed mobility while patients are still on bed. We sought to establish the validity and reliability of a newly developed Functional Bridge Test (FBT) for hemiplegic patients with acute stroke.

Methods: This repeated-measures, observational study was conducted at a stroke care unit at an acute hospital. We assessed the validity of the FBT score, intra-rater and inter-rater reliabilities of the FBT, and concurrent validity of the FBT in stroke patients with hemiplegia. In addition to the original qualitative assessment, the FBT was also assessed quantitatively to evaluate the validity of the FBT score. Outcome measures included stroke severity, lower limb muscle strength, and basic mobility.

Results: We enrolled 32 patients with acute stroke. The newly developed FBT score had high validity. Intra-rater and inter-rater reliabilities (weighted kappa coefficient, 95% confidence interval) showed almost perfect agreement (0.95, 0.88–1.00; 0.98, 0.94–1.00, respectively). The FBT score was significantly associated with stroke severity, physical function, and basic mobility.

Conclusions: The FBT has sufficient validity and reliability for acute stroke patients with hemiplegia. The advantages of the FBT in a clinical setting are based on its ability to be quickly administered on a bed without the need for specialized equipment. The FBT may help in screening functional impairment and disability in hemiplegic patients with acute stroke before they resume out-of-bed activities.

INTRODUCTION

Although many patients with acute stroke have limited physical function and basic mobility limitations,¹⁾ appropriate management of patients in a stroke unit promotes their functional recovery.²⁾ Early mobilization, with an emphasis on out-of-bed interventions is an important component of stroke unit care.³⁾ However, to our knowledge, only a few methods of assessment have been shown to screen stroke-related impairments and disabilities in patients while they are still on bed.

Although patients with acute stroke are increasingly encouraged to resume out-of-bed activities as soon as possible,⁴⁾ behavioral observational studies have found that patients who experienced stroke and were admitted to acute hospitals are typically inactive and spend most of their time on bed.⁵⁾ A more recent study revealed that patients increased the time spent out of bed each day during the initial hospital stay after a stroke, but the time spent upright remained low throughout the study’s observation period.⁶⁾ In addition, the activity levels in patients after an acute stroke were reported to vary among hospitals.^7,8) These findings indicate a need to standardize interventions aimed at resuming out-of-bed activities.

To provide a safe and appropriate out-of-bed program, patients need to be screened for stroke-related functional impairments and disabilities in advance. However, only a few conventional assessments can be completed before patients resume out-of-bed activities. Moreover, there are several limitations to assessing patients with acute stroke; these include blood pressure changes, consciousness disorders, attention disorders, difficulty in maintaining a posture, low endurance, and medical treatments.

Therefore, we have developed a novel Functional Bridge Test (FBT), which involves the patient making a bridge movement while in the supine position on the bed. The bridge movement is elevation of the hips and trunk extension under gravity, and requires muscle activities of the hip and trunk extensors.^9,10) Other studies have used the bridge movement to evaluate the patient’s functional ability,^11,12) lumbar spine-stabilization capability,^13,14,15) and cardiopulmonary function.¹⁶⁾ The bridge maneuver may reflect the postural control function of proximal lower-extremity muscles and the trunk muscles required to get out of bed.

This study aimed to investigate the effectiveness of the FBT to screen impairments and disabilities in hemiplegic patients with acute stroke. The specific aims of the study were to determine the validity of the FBT score by quantitative evaluation, the intra- and inter-rater reliability of the FBT, and the concurrent validity of the FBT. We hypothesized that the FBT would show high reliability and would significantly correlate with scores of physical functions (stroke severity, lower limb hemiplegia, and lower extremity muscle strength) and basic mobility in hemiplegic patients with acute stroke.

METHODS

Study Design

This prospective, single-center study used a repeated-measures, observational design to investigate the validity of the FBT score, reliability of the FBT, and concurrent validity of the FBT. The study was explained to all patients, after which we obtained written informed consent from all participants. This study was approved by the Ethics Review Board of the Nippon Medical School Chiba Hokusoh Hospital (Approval number: 760) and was conducted in accordance with the principles of the Declaration of Helsinki.

Study Population

This study was conducted on all patients who were consecutively admitted to the stroke care unit at the Nippon Medical School Chiba Hokusoh Hospital from September 2019 to March 2021 and who were diagnosed with a stroke (except subarachnoid hemorrhage and bleeding from an arteriovenous malformation) based on neurological symptoms and X-ray computed tomography or magnetic resonance imaging. Patients eligible for participation in this study were those with acute stroke who were recruited within 10 days of onset of the stroke. Inclusion criteria were as follows: aged 20 years or older, no previous history of stroke, lower limb hemiplegia, awake or able to open eyes when wakened verbally, and the ability to independently perform activities of daily living (ADL) prior to the stroke. The following exclusion criteria were applied: insufficient comprehension or collaboration because of aphasia and/or cognitive dysfunction; progressive neurological disorders identified during the assessment period; previous cranial nerve disease; lesions on both sides of the cerebral hemisphere; ataxia of the lower limbs; a history of lower extremity amputation; and difficulty performing a bridge maneuver because of a disorder other than stroke (such as orthopedic disorders or unstable medical conditions). In this study, the sample size was set to 32 patients because we graded the FBT on four levels.¹⁷⁾

Raters

We developed a novel FBT for clinical use by physiotherapists with various levels of clinical experience. Accordingly, we selected two physical therapists with different clinical experience to act as raters: rater A had 7 years of clinical experience, and rater B had 2 years of clinical experience. Rater A created a manual regarding the standardized evaluation of the FBT. Rater B was familiarized with the FBT via a 10-minute session before the start of this study, during which rater A explained and demonstrated the FBT procedure using the standardized set of instructions.

Procedure

Each patient was tested three times (labeled Days 1, 2, and 3). Tests were conducted on consecutive days or at a maximum of 2 days apart, ensuring that each patient’s test data were collected within 1 week. Three test occasions were used to allow for the possibility of a learning effect between Days 1 and 2.¹⁸⁾ On Day 1, the patients were introduced and habituated to the FBT, whereas data collected on Days 2 and 3 were used for analysis. The validity of the FBT score was examined using the FBT score on Day 2 and two-dimensional data from video recorded during the FBT on Day 2. The intra-rater reliability was calculated by comparing the FBT score evaluated by the same rater (rater A) on Days 2 and 3. The inter-rater reliability was calculated for differences between raters A and B on Day 3. Then, the concurrent validity was calculated for the correlation between the FBT score and other outcomes on Day 2.

On the first test day, the FBT was administered by rater A. The FBT procedure was first explained to the patient by the rater according to the standardized set of instructions. Each patient then performed one trial of the FBT. On the second test day, the FBT was again administered by rater A, who was blinded to the previous evaluation results. Patients underwent the FBT only once on Day 2, although other outcome parameters were also measured. On the third and final test day, the patients performed two sets of the FBT; one set was administered by rater A (who was blinded to the previous evaluation results), whereas the other was supervised by rater B. Raters were blinded to each other’s findings. Patients performed the FBT once for each rater.

Outcome Measures

Characteristics of Patients

We recorded the patient demographic variables of age, sex, height, weight, and time of evaluation from the onset of stroke. The stroke details were also recorded, such as the type of stroke (infarction or hemorrhage), the side of hemiplegia, stroke severity according to the National Institutes of Health Stroke Scale (NIHSS) score,¹⁹⁾ the motor score for the leg on the affected side (NIHSS Subtest), and the modified Rankin Scale (mRS)²⁰⁾ as a measure of global outcome after stroke.

Functional Bridge Test

The main outcome measurement was the FBT, which we had developed for on-bed assessment of the patient’s ability to raise and hold the hips for 3 seconds (Fig. 1). The starting position for the FBT required the patient in the supine position on a bed, with the arms folded across the chest and the knees flexed at 120°. The rater supported two parts of the patient’s body so that the affected leg did not collapse from the starting position. The patient’s foot on the affected side was supported via the rater’s leg, and the patient’s knee on the affected side was supported by the rater’s hand. However, if the patient collapsed to the affected side during the bridge maneuver, the rater did not provide additional knee support. The rater gave each patient the following standardized instructions: “Please raise your hips as high as possible while trying not to collapse to this side (the affected side). Please keep your hips raised for 3 seconds.” When the hip elevation was insufficient or if the hips collapsed to the affected side, the rater encouraged the patient to raise his or her hips higher or to avoid collapsing to the affected side, within the same FBT.

Fig. 1.

The Functional Bridge Test (FBT). (a) The starting position of the FBT. The patient lies in the supine position on a bed with arms folded across the chest and the knees flexed at 120°. The rater supports the patient’s foot and knee on the affected side. If the patient collapses to the affected side during the bridge maneuver, the rater does not add any additional knee support. (b) The lift-off position of the FBT. The patient strives to hold the hips raised at a maximum height for 3 seconds.

Qualitative evaluation of the FBT included a manual measurement of the height of the lowest part of the hip on the affected side. The rater used his or her hand to evaluate the minimum grading of the hip, while counting to three, using a four-point grading scale after the hip had been elevated to the maximum height. Grade 1 was defined as a difficulty in lift-off (less than 3 seconds). Grade 2 was defined as lift-off for 3 seconds or more, with insufficient hip elevation [higher than or equal to the height of a hand on the bed (approximately 2 cm high)]. Grade 3 was defined as lift-off for 3 seconds or more, with slightly insufficient hip elevation [higher than or equal to a vertical fist on the bed (approximately 8 cm high)]. Grade 4 was defined as lift-off for 3 seconds or more, with sufficient hip elevation [higher than or equal to the distance from the tip of the index finger that was positioned with finger abduction and the intermediate forearm to the bed (approximately 14 cm high)]. These hand-based measures use to evaluate the height of the lowest part of the hip are shown in Fig. 2.

Fig. 2.

The handshapes used in the FBT. The rater uses each handshape to assess the patient’s hip-to-bed height during the bridge maneuver. The grade is determined by whether the handshape of each grade can pass between the lowest part of the patient’s hip and the bed. After the hip elevation has reached maximum height, the rater evaluates the minimum grading during a count to three. The scale is a four-point grading: Grade 1, difficulty in lift-off; Grade 2, insufficient hip elevation; Grade 3, slightly insufficient hip elevation; Grade 4, sufficient hip elevation.

Although the FBT was originally designed as a qualitative evaluation, this study also used a quantitative evaluation to verify the validity of the FBT score based on the manual measurement. Quantitative evaluation was performed using videos recorded during the FBT performed on Day 2. A video camera (HC-W570M; Panasonic, Osaka, Japan) was positioned on a tripod 120 cm from the anterior superior iliac spine on the affected side. In addition, an inclinometer (GL-300; Nippon Seiki, Nagaoka, Japan) was used to maintain the video camera in a plane parallel to the floor at a height of 60 cm. Prior to performing the maneuver, reflective markers were placed on the patient’s acromial angle, crista iliaca (between the anterior superior iliac spine and the posterior superior iliac spine), anterior superior iliac spine, greater trochanter of the femur, and lateral condyle of the femur on the affected side. These markers were used to analyze the hip elevation and hip joint angle via a two-dimensional video analysis (Kinovea two-dimensional video software, Version 0.8.26; https://www.kinovea.org/). The elevation of the hip was defined as the lowest height of the hip within 2 seconds of when the maximum height was reached. A larger hip elevation indicated that the patient had higher bridge function. The height of the hip elevation was determined using the reflective marker on the anterior superior iliac spine. The anterior superior iliac spine at rest was set to 0 cm. The hip joint angle was defined as the maximum hip joint angle within 2 seconds of when the maximum height was reached. A smaller hip joint angle indicated that the patient had higher bridge function. The hip joint angle was determined using the angle formed by the line connecting the acromion angle and the crista iliaca with the line connecting the greater trochanter of the femur and the lateral condyle of the femur. Rater A performed these calculations.

Prior to this study, a preliminary study was conducted to validate the platform bed (Fig. 1) used in present test. The FBT scores for the ordinary bed (used by patients in hospital wards) and scores for the platform bed showed excellent agreement [weighted kappa coefficient=0.91; 95% confidence interval (CI), 0.85–0.97; P <0.001]. The platform bed was used in the present study because of its consistency with the ordinary bed and for reasons of accuracy in video recording.

Short Form of Postural Assessment Scale for Stroke Patients

We used the Short Form of the Postural Assessment Scale for Stroke patients (SFPASS)²¹⁾ to evaluate the basic mobility of each patient. The SFPASS is a shortened version of the PASS²²⁾ and has good reliability, validity, and responsiveness.²¹⁾ The SFPASS consists of five items: moving from sitting to supine, supine to sitting, sitting to standing, standing to sitting, and one-leg stance on the non-paralyzed leg. The ability to perform each item is graded on a three-level scale. The total score ranges from 0 to 15, with higher scores indicating a greater postural control ability. As a measurement condition for this study, the affected side of the patient was located at the edge of the bed, which was 43 cm high and did not have handrails.

Muscle Strength of Lower Limb

Isometric muscle strength of the knee and hip extensor was assessed on both legs with a hand-held dynamometer (μTas F-1; Anima, Tokyo, Japan). The patients were tested with standardized testing positions and dynamometer placements.^23,24,25,26) Given that some patients were not stable in the sitting position, all measurements were repeated in the supine position. The measurements of knee extensor and hip extensor isometric strength by hand-held dynamometer in neurologically affected patients have been reported as reliable (intra-class correlation coefficient: 0.87–0.99).²³⁾ The test was performed twice and mean values were obtained. A third trial was performed when the difference between the two measurements exceeded 10%. The test parameters involved calculating the torque to body weight ratio (Nm/kg) and the percentage of body weight (%). The former was calculated by multiplying strength (N) by lever arm length (m), divided by body weight (kg).²⁷⁾ The latter was calculated by dividing strength (N) by body weight (N), multiplied by 100 (%).^28,29) The muscle strength on the affected and unaffected sides combined was estimated as the sum of the test parameters on both legs.^27,28,29)

Statistical Analysis

All statistical analyses were conducted using the Statistical Package for Social Sciences (SPSS) version 26.0 for Windows (IBM, Armonk, NY, USA), and the threshold for significance was P <0.05. Data were analyzed in three stages: validity of the FBT score, reliability, and concurrent validity.

First, to examine the validity of the FBT score in patients with acute stroke, one-way analysis of variance and Tukey’s honestly significant difference test were used to determine the difference between the FBT score and the quantitative FBT data. The value of the quantitative evaluation was presented for each bridging ability classified by the FBT score. Second, the intra-rater and inter-rater reliabilities were assessed using weighted Cohen’s kappa (quadratic weight). The levels of the kappa coefficient (κ) were classified using the Landis standards: fair agreement, 0.21–0.40; moderate agreement, 0.41–0.60; substantial agreement, 0.61–0.80; and near-perfect agreement, ≥0.81.³⁰⁾ Last, the concurrent validity was evaluated using Spearman’s rank correlation coefficient (ρ), which tested the relationship between the FBT score and the NIHSS score, the motor score of the leg on the affected side (NIHSS Subtest), the lower limb muscle strength, and the SFPASS score.

RESULTS

Characteristics

Of the 291 consecutive patients with acute stroke admitted during the study period, 32 patients were included in the analysis based on the inclusion and exclusion criteria (Fig. 3). No data were missing. Table 1 shows the demographic and clinical characteristics of the study participants. The mean duration from stroke onset to Day 1, Day 2, and Day 3 were 5.1 days (SD=2.2), 6.7 days (SD=2.3), and 8.7 days (SD=2.5), respectively.

Fig. 3.

Participant flow diagram for FBT study.

Table 1.  Demographic and clinical characteristics of the study population

Characteristics	n=32
Age, years	68.6 ± 12.6
Sex (male/female), n	17/15
Type of stroke (infarction/hemorrhage), n	15/17
Hemiplegic side (right/left), n	13/19
Height, cm	161.4 ± 7.9
Weight, kg	66.0 ± 15.1
NIHSS
Total score, points	4.0 (2.3–8.8)
Motor leg with affected side, points	1.0 (1.0–2.0)
mRS, points	4.0 (4.0–5.0)
Knee extensor strength
Torque to body weight ratio, Nm/kg
Unaffected side	1.3 (0.9–1.7)
Affected side	0.6 (0.2–1.2)
Combined	1.9 (1.1–2.7)
Percentage of body weight, %
Unaffected side	41.7 (30.6–49.4)
Affected side	17.4 (4.7–37.4)
Combined	61.6 (31.9–83.5)
Hip extensor strength
Torque to body weight ratio, Nm/kg
Unaffected side	1.2 (0.9–1.3)
Affected side	0.8 (0.4–1.2)
Combined	2.0 (1.3–2.5)
Percentage of body weight, %
Unaffected side	34.0 (26.4–39.5)
Affected side	24.0 (12.0–34.0)
Combined	57.0 (36.1–72.8)
SFPASS, points	12.0 (3.4–13.5)

Data are given as mean ± SD, number, or median (interquartile range).

Validity of FBT Score

The quantitative data in each FBT score are presented in Fig. 4. The hip elevation and hip joint angle revealed significantly higher bridge function with higher FBT scores. The mean hip elevation in each grade was as follows: Grade 1, −0.8 cm (SD=1.6); Grade 2, 3.7 cm (SD=1.1); Grade 3, 9.0 cm (SD=1.5); and Grade 4, 15.2 cm (SD=1.8). The mean hip joint angle in each grade was as follows: Grade 1, 56.4° (SD=7.5); Grade 2, 44.6° (SD=4.3); Grade 3, 32.4° (SD=7.0); and Grade 4, 17.7° (SD=5.5).

Fig. 4.

The validity of the FBT score. (a) Mean hip elevation for each FBT score during the FBT. Higher values indicate better bridge function. (b) Mean hip joint angle for each FBT score during the FBT. Lower values indicate better bridge function. P values were calculated using one-way analysis of variance, followed by Tukey’s honestly significant difference test. Error bars show standard deviation. Asterisks indicate significant difference: * P <0.05; ** P <0.01.

Reliability

The weighted kappa coefficient for intra-rater reliability was 0.95 (95% CI, 0.88–1.00; P <0.001), indicating almost perfect agreement. Similarly, the weighted kappa coefficient for inter-rater reliability was 0.98 (95% CI, 0.94–1.00; P <0.001), also indicating strong agreement.

Concurrent Validity

The relationships between the FBT score and other variables are presented in Table 2. A higher FBT score was significantly associated with lower stroke severity, higher physical function, and higher basic mobility.

Table 2.  Concurrent validity of the Functional Bridge Test

Variable	Functional Bridge Test
	ρ
NIHSS
Total score	−0.72**
Motor leg with affected side	−0.82**
Knee extensor strength
Torque to body weight ratio
Unaffected side	0.85**
Affected side	0.88**
Combined	0.91**
Percentage of body weight
Unaffected side	0.81**
Affected side	0.88**
Combined	0.90**
Hip extensor strength
Torque to body weight ratio
Unaffected side	0.66**
Affected side	0.77**
Combined	0.75**
Percentage of body weight
Unaffected side	0.65**
Affected side	0.73**
Combined	0.71**
SFPASS	0.89**

ρ, Spearman's rank correlation coefficient.

* P <0.05; ** P <0.01.

DISCUSSION

This study investigated the effectiveness of the new FBT scale for screening stroke-related functional impairments and disabilities in hemiplegic patients with acute stroke before they resume out-of-bed activities. The results showed that the FBT had high validity and reliability. Our findings suggest that the FBT is a sound psychometrical measurement tool for screening physical functions and basic mobilities in individuals with acute hemiplegic stroke.

The validity of the FBT score, which was graded based on hand-based measurements, was tested to determine whether these handshapes could be used to grade quantitative data on bridge movements. We found that the FBT score reflected the quantitative evaluation of the bridge maneuver. Therefore, the hip elevation and hip joint angle could be differentiated according to handshape, providing validity for grading each patient’s bridge movement. Essentially, a rater could distinguish the level of a bridge movement by means of each handshape.

The lower limits of the 95% CI for intra- rater and inter-rater reliabilities were 0.88 and 0.94, respectively, which indicated that the test was very good for use in individual clinical assessment. Our result for the intra-rater reliability is consistent with that reported in a previous study of frail older adults that found the maximum height of a pelvis in two identical evaluation sessions, separated by a 48-hour interval, showed almost perfect agreement.¹²⁾ In addition, the standard error of measurement ranged from 1.38 to 1.62 cm.¹²⁾ This suggests that the bridge performance itself is stable, with little variation. The inter-rater reliability of the FBT was excellent, even though one rater was an inexperienced therapist and had only received a 10-minute lecture on how to administer the test. The high intra-rater and inter-rater reliabilities of the FBT may be attributed to the use of a simple method, using the rater’s handshape. A previous study reported that the reliability of a unilateral bridge maneuver was poor because of the difficulty in making a precise visual evaluation of whether the pelvis was being lowered.¹⁴⁾ Although the pelvis often tilts towards the affected side during the bridge movement in hemiplegic patients, as in the unilateral bridge, the handshape-based assessment may have resulted in higher reliability.

The FBT was strongly associated with other validated and established measures of stroke severity, lower limb muscle strength, and basic mobility, indicating good concurrent validity. This may be clinically plausible because a patient who achieves higher hip elevation during the bridge movement may have a higher level of physical function and mobility. In particular, the knee extensor strength on the affected and unaffected sides (combined) and the SFPASS score showed strong correlation with the FBT score. Previous studies reported that the former predicted sit-to-stand independence,²⁹⁾ while the latter was associated with the Barthel Index and the Fugl-Meyer motor test.²¹⁾ These findings suggest that the FBT can screen patients with acute stroke hemiplegia for their level of residual function before they resume out-of-bed activities. Furthermore, a previous observational study reported that one of the reasons for not using standardized outcome measures was the length of time they took for patients to complete.³¹⁾ However, the FBT took less than 1 minute from introduction to measurement, even in acute stroke patients with various limitations to assessment. Therefore, the FBT may be clinically useful because it not only reflects stroke-related disability and impairment but also is a simple and feasible assessment tool.

Several limitations of this study should be acknowledged. First, our results may not be generalizable to all acute stroke patients with hemiplegia. This study included a large proportion of patients with mild to moderate stroke severity and excluded patients with ataxia of the lower limbs or with orthopedic disorders. Second, although the height of the lowest part of the hip on the affected side was assessed using the rater’s handshape for clinical convenience, there may be errors because of differences in the sizes of raters’ hands and the heights of subjects. Given that hand size may vary between raters, it may be necessary to evaluate hand size, as shown in this study, before performing an assessment. In broader use of the FBT, further investigation may be necessary if the height distribution of subjects is different from that of the present study. However, the use of a clinical assessment tool without any special equipment is clinically very useful in an acute setting, where simplicity is desirable. Third, although the SFPASS was used to measure mobility and showed a strong relationship with the FBT in this study, the relationship between the FBT and actual ADL is unclear in the inpatient setting. Finally, there are differences in firmness between the ordinary bed used by patients in hospital wards and the platform bed used in this study. Although we previously confirmed high agreement of FBT scores between ordinary hospital beds and the platform bed used in the study, further validation of the FBT will be required for situations in which acute stroke patients get out of bed.

CONCLUSION

The results of this study suggest that the FBT is a valuable clinical tool because of its simplicity and it has sufficient validity and reliability. Currently, the timing and treatment used to assist patients to resume out-of-bed activities are based on the clinical experience of physiotherapists and nurses. The use of a standardized tool that can screen functional impairment and disability in acute stroke hemiplegic patients before they resume out-of-bed activities may help to provide safer and better optimized out-of-bed programs. Future studies on the FBT should focus on the applicability of this test to stroke patients in general and the predictive validity with regard to discharge outcomes.

CONFLICTS OF INTEREST

The authors report no conflicts of interest.

REFERENCES

• 1.  Jørgensen HS, Nakayama H, Raaschou HO, Vive-Larsen J, Støier M, Olsen TS: Outcome and time course of recovery in stroke. Part I: outcome. The Copenhagen stroke study. Arch Phys Med Rehabil 1995;76:399–405. PMID:7741608, DOI:10.1016/S0003-9993(95)80567-2
• 2.  Langhorne P, Ramachandra S, Stroke Unit Trialists’ Collaboration: Organised inpatient (stroke unit) care for stroke: network meta-analysis. Cochrane Database Syst Rev 2020;4:CD000197. , PMID:32324916, DOI:10.1002/14651858.CD000197.pub4
• 3.  Indredavik B, Bakke F, Slørdahl SA, Rokseth R, Håheim LL: Treatment in a combined acute and rehabilitation stroke unit: which aspects are most important? Stroke 1999;30:917–923. PMID:10229720, DOI:10.1161/01.STR.30.5.917
• 4.  AVERT Trial Collaboration group: Efficacy and safety of very early mobilisation within 24 h of stroke onset (AVERT): a randomised controlled trial. Lancet 2015;386:46–55. PMID:25892679, DOI:10.1016/S0140-6736(15)60690-0
• 5.  Bernhardt J, Dewey H, Thrift A, Donnan G: Inactive and alone: physical activity within the first 14 days of acute stroke unit care. Stroke 2004;35:1005–1009. PMID:14988574, DOI:10.1161/01.STR.0000120727.40792.40
• 6.  Norvang OP, Hokstad A, Taraldsen K, Tan X, Lydersen S, Indredavik B, Askim T: Time spent lying, sitting, and upright during hospitalization after stroke: a prospective observation study. BMC Neurol 2018;18:138. PMID:30180819, DOI:10.1186/s12883-018-1134-0
• 7.  Bernhardt J, Chitravas N, Meslo IL, Thrift AG, Indredavik B: Not all stroke units are the same: a comparison of physical activity patterns in Melbourne, Australia, and Trondheim, Norway. Stroke 2008;39:2059–2065. PMID:18451351, DOI:10.1161/STROKEAHA.107.507160
• 8.  Hokstad A, Indredavik B, Bernhardt J, Ihle-Hansen H, Salvesen Ø, Seljeseth YM, Schüler S, Engstad T, Askim T: Hospital differences in motor activity early after stroke: a comparison of 11 Norwegian stroke units. J Stroke Cerebrovasc Dis 2015;24:1333–1340. PMID:25906937, DOI:10.1016/j.jstrokecerebrovasdis.2015.02.009
• 9.  Kavcic N, Grenier S, McGill SM: Quantifying tissue loads and spine stability while performing commonly prescribed low back stabilization exercises. Spine 2004;29:2319–2329. PMID:15480148, DOI:10.1097/01.brs.0000142222.62203.67
• 10.  Ekstrom RA, Donatelli RA, Carp KC: Electromyographic analysis of core trunk, hip, and thigh muscles during 9 rehabilitation exercises. J Orthop Sports Phys Ther 2007;37:754–762. PMID:18560185, DOI:10.2519/jospt.2007.2471
• 11.  Millisdotter M, Strömqvist B, Jönsson B: Proximal neuromuscular impairment in lumbar disc herniation: a prospective controlled study. Spine 2003;28:1281–1289. PMID:12811273, DOI:10.1097/01.BRS.0000066458.43883.17
• 12.  Pilon M, Nadeau S, Piotte F: Intertrial and test-retest reliabilities of Timed Bridge tests among frail older adults. Physiother Theory Pract 2009;25:507–515. PMID:19925173, DOI:10.3109/09593980802664851
• 13.  Schellenberg KL, Lang JM, Chan KM, Burnham RS: A clinical tool for office assessment of lumbar spine stabilization endurance: prone and supine bridge maneuvers. Am J Phys Med Rehabil 2007;86:380–386. PMID:17303961, DOI:10.1097/PHM.0b013e318032156a
• 14.  Tidstrand J, Horneij E: Inter-rater reliability of three standardized functional tests in patients with low back pain. BMC Musculoskelet Disord 2009;10:58. PMID:19490644, DOI:10.1186/1471-2474-10-58
• 15.  Andrade JA, Figueiredo LC, Santos TR, Paula AC, Bittencourt NF, Fonseca ST: Reliability of transverse plane pelvic alignment measurement during the bridge test with unilateral knee extension. Braz J Phys Ther 2012;16:268–274. PMID:22899181, DOI:10.1590/S1413-35552012000400007
• 16.  Tsuji T, Liu M, Tsujiuchi K, Chino N: Bridging activity as a mode of stress testing for persons with hemiplegia. Arch Phys Med Rehabil 1999;80:1060–1064. PMID:10489009, DOI:10.1016/S0003-9993(99)90061-8
• 17.  Cicchetti DV, Fleiss JL: Comparison of the null distributions of weighted kappa and the C ordinal statistic. Appl Psychol Meas 1977;1:195–201. DOI:10.1177/014662167700100206
• 18.  Hertel J, Miller SJ, Denegar CR: Intratester and intertester reliability during the Star Excursion Balance Tests. J Sport Rehabil 2000;9:104–116. DOI:10.1123/jsr.9.2.104
• 19.  Lyden P, Brott T, Tilley B, Welch KM, Mascha EJ, Levine S, Haley EC, Grotta J, Marler J, NINDS TPA Stroke Study Group: Improved reliability of the NIH Stroke Scale using video training. Stroke 1994;25:2220–2226. PMID:7974549, DOI:10.1161/01.STR.25.11.2220
• 20.  van Swieten JC, Koudstaal PJ, Visser MC, Schouten HJ, van Gijn J: Interobserver agreement for the assessment of handicap in stroke patients. Stroke 1988;19:604–607. PMID:3363593, DOI:10.1161/01.STR.19.5.604
• 21.  Chien CW, Lin JH, Wang CH, Hsueh IP, Sheu CF, Hsieh CL: Developing a short form of the Postural Assessment Scale for people with stroke. Neurorehabil Neural Repair 2007;21:81–90. PMID:17172558, DOI:10.1177/1545968306289297
• 22.  Benaim C, Pérennou DA, Villy J, Rousseaux M, Pelissier JY: Validation of a standardized assessment of postural control in stroke patients: the Postural Assessment Scale for Stroke Patients (PASS). Stroke 1999;30:1862–1868. PMID:10471437, DOI:10.1161/01.STR.30.9.1862
• 23.  Bohannon RW: Test-retest reliability of hand-held dynamometry during a single session of strength assessment. Phys Ther 1986;66:206–209. PMID:3945674, DOI:10.1093/ptj/66.2.206
• 24.  Aguiar LT, Camargo LB, Estarlino LD, Teixeira-Salmela LF, Faria CD: Strength of the lower limb and trunk muscles is associated with gait speed in individuals with sub-acute stroke: a cross-sectional study. Braz J Phys Ther 2018;22:459–466. PMID:29588151, DOI:10.1016/j.bjpt.2018.03.001
• 25.  Dorsch S, Ada L, Canning CG, Al-Zharani M, Dean C: The strength of the ankle dorsiflexors has a significant contribution to walking speed in people who can walk independently after stroke: an observational study. Arch Phys Med Rehabil 2012;93:1072–1076. PMID:22464738, DOI:10.1016/j.apmr.2012.01.005
• 26.  Dorsch S, Ada L, Canning CG: Lower limb strength is significantly impaired in all muscle groups in ambulatory people with chronic stroke: a cross-sectional study. Arch Phys Med Rehabil 2016;97:522–527. PMID:26615792, DOI:10.1016/j.apmr.2015.10.106
• 27.  Akazawa N, Okawa N, Tamura K, Moriyama H: Determining the cut-off value for knee extensor strength for identifying independence in gait in chronic stroke survivors. J Rehabil Med 2017;49:765–767. PMID:28949369, DOI:10.2340/16501977-2279
• 28.  Eriksrud O, Bohannon RW: Relationship of knee extension force to independence in sit-to-stand performance in patients receiving acute rehabilitation. Phys Ther 2003;83:544–551. PMID:12775200, DOI:10.1093/ptj/83.6.544
• 29.  Bohannon RW: Knee extension strength and body weight determine sit-to-stand independence after stroke. Physiother Theory Pract 2007;23:291–297. PMID:17934969, DOI:10.1080/09593980701209428
• 30.  Landis JR, Koch GG: The measurement of observer agreement for categorical data. Biometrics 1977;33:159–174. PMID:843571, DOI:10.2307/2529310
• 31.  Jette DU, Halbert J, Iverson C, Miceli E, Shah P: Use of standardized outcome measures in physical therapist practice: perceptions and applications. Phys Ther 2009;89:125–135. PMID:19074618, DOI:10.2522/ptj.20080234