Systematic Review: Sling Exercise & Stroke

News Summary Sling Exercise Therapy (SET) has proven to significantly reduce walking impairment post stroke, according to a new systematic review and meta-analysis published in the reputable International Journal of Rehabilitation Research [1]. This study provides the strongest evidence yet that SET—the core of Redcord’s Neurac Method—is an effective and evidence-based treatment for walking impairment post stroke. Both the SET and Neurac method were firstly described by Redcord [2, 3].

Conclusion

The Chinese researchers concluded that SET can more effectively improve the walking ability of patients with stroke compared to conventional physical therapy or trunk strengthening. At least in East Asia, their findings support SET to properly manage the post-stroke walking impairment. 

Results

The review included 25 studies and 1 504 patients with stroke (753 and 751 in the experimental and control group) published from 2012 to 2021. SET significantly improved the following five walking functions (beyond active control therapy):

1) 10 m maximum walking speed (large effect: Standardized Mean Difference (SMD) 0.85 [95%CI 0.6 to 1.1])

2) Muscle activation of rectus femoris, biceps femoris, and gastrocnemius (RF Mean Difference (MD) 18.5 [95% CI 12.2 to 24.9], BF 26.7 [0.7 to 52.6], GC 4.5 [0.89 to 8.1] integrated EMG, mVs).

3) Functional ambulation category [FAC] (MD 1.2 [95%CI 1.0 to 1.4] points).

4) Timed up and go test (MD -4.9 [95% CI -6.4 to -3.5] sec).

5) Step length (MD 5.0 [3.4 to 6.5] cm).

Comparisons: 18 studies compared ‘SET combined with conventional physical therapy’ with ‘conventional physical therapy’, four studies ‘SET’ with ‘conventional physical therapy’, and three studies ‘SET combined with conventional physical therapy’ with ‘conventional trunk training combined with conventional physical therapy’.

Methodological Quality: Of the 25 studies, one scored excellent (10/10), 13 good (7-9/10), and 11 fair (4-6/10) on the PEDro-scale. None scored poorly.

Background

Walking impairment is a common consequence of stroke, resulting in long-term disability. Trunk muscle strength has long been proven to be positively associated with post-stroke walking performance [4]. As a type of trunk training, SET has been widely applied to improve the trunk function in stroke patients although the results (in the most recent systematic review) have been inconsistent [5]. The purpose of the present Long et al. (2022) systematic review was to investigate the efficacy of SET on post-stroke walking impairment.

Methods

The team of Chinese researchers conducted a systematic review and meta-analysis. Systematic searches were performed in 7 scientific databases - PubMed, Web of Science, EMBASE, Cochrane Library, Chinese national knowledge infrastructure, China science and technology journal database (VIP), and WanFang - from their inception up to 1 August 2021. They included all studies published in English or Chinese.

What This Means for Your Practice

The Long et al. (2022) review documented high SET compliance among patients. Further, about 70% of the studies did this SET this way: Therapy sessions from 20 to 40 minutes a day, frequency 5 days a week, over a period of 4 to 8 weeks. Although the time per session varied highly, the review did not find significant differences between the short (20-40 min) and long (40-90 min) sessions. Therefore, they recommended the short-sessioned SET plan in managing post-stroke walking impairment.

Bottom Line

With moderate evidence SET is clinically important more effective in improving walking function of patients with stroke compared to conventional physical therapy or trunk training. Long et al.’s (2022) findings support SET to manage post-stroke walking impairments, at least in East Asia.

References

1. Long, J., et al., Effects of sling exercise therapy on post-stroke walking impairment: a systematic review and meta-analysis. International Journal of Rehabilitation Research, 2022. 45(1): p. 12-23. https://pubmed.ncbi.nlm.nih.gov/34726197/

2. Kirkesola, G., Neurac - a new treatment method for long-term musculoskeletal pain. Fysioterapeuten, 2009. 76(12): p. 16-25. http://cdn1.sourze.se/cdn.zitiz.se/userfiles.cdn.zitiz.se/z/caea9cc5-b663-44ec-b91d-cccabcafc571/Neurac%20Article%20Fysioterapeuten%20200912.pdf

3. Kirkesola, G., Sling exercise therapy (S-E-T): a total concept for exercise and active treatment of musculoskeletal disorders. Fysioterapeuten, 2000. 12(6): p. 7.

4. Van Criekinge, T., et al., SWEAT2 Study: Effectiveness of Trunk Training on Gait and Trunk Kinematics After Stroke: A Randomized Controlled Trial. Phys Ther, 2020. 100(9): p. 1568-1581.

5. Chen, L., et al., Effect of Sling Exercise Training on Balance in Patients with Stroke: A Meta-Analysis. PLoS One, 2016. 11(10): p. e0163351.

Scientific Summary Original Title: Effects of Sling Exercise Therapy on Post-Stroke Walking Impairment: A Systematic Review and Meta-Analysis Published in: International Journal of Rehabilitation Research 2022;45(1):p.12-23. By: Junzi Long, Yasu Zhang, Xiaomin Liu, and Xiaoqin Jin From: School of Rehabilitation Medicine, Henan University of Chinese Medicine, Zhengzhou, Henan, China.

1. Background 

Stroke is a leading cause of adult disability, with walking impairment being a common consequence. Post-stroke, people often experience reduced gait speed and walking endurance, as well as loss of independence. A systematic review (SR) (2011) [1] found that after three months of rehabilitation, 60% of non-ambulatory stroke survivors regained independent walking ability, compared to only 39% of those treated in an acute care unit—highlighting the critical role of rehabilitation in restoring such mobility.

Trunk control is frequently impaired after a stroke, hampering walking performance. A randomized controlled trial (RCT) (2020) [2] demonstrated a positive association between trunk muscle strength (core stability) and post-stroke walking ability. Furthermore, a SR in healthy individuals (2020) [3] reported that sling exercise therapy (SET) leads to greater activation of trunk muscles than conventional trunk training. Given its benefits for trunk control, SET has been introduced into stroke rehabilitation. However, previous meta-analyses have yielded inconsistent results (e.g., [4]), warranting further investigation.

Purpose

This SR by Long et al. (2022) [5] aimed to evaluate the efficacy of SET in improving post-stroke walking impairment and to provide evidence-based recommendations for clinical practice.

2. Methods

The Long et al. (2022) systematic review and meta-analysis were conducted in accordance with the respected PRISMA guidelines. A comprehensive literature search was performed across seven scientific databases, including PubMed, Web of Science, EMBASE, Cochrane Library, Chinese National Knowledge Infrastructure (CNKI), China Science and Technology Journal Database (VIP), and WanFang, covering studies published up to August 1, 2021. The most central search terms were stroke, sling exercise, and trunk training.   

Methodological quality assessment of the studies was rated by the physiotherapy evidence database (PEDro) scale (0-10, worst to best). Studies were scaled ≤ 4, 4-6, 7-9, and 10 as poor, fair, good, and excellent, respectively.

Outcome Measures

Primary outcomes assessed the therapeutic effects of SET, including:

1) Total Effective Cases Rate (TECR): [(significantly effective cases + effective cases) / total cases]

2) 10-meter Maximum Walking Speed (10mMWS): Measured in meters/second

3) Lower limb muscle function (activation): Measured via integrated electromyography (iEMG) [mVs] of the rectus femoris (RF), biceps femoris (BF), and gastrocnemius (GC)

Secondary outcomes focused on functional mobility, gait, and walking safety, evaluated using:

1) Functional Ambulation Category (FAC): 0–5 or 6-point scale

2) Timed Up and Go Test (TUGT): Measured in seconds

3) Step Length (SL): Measured in centimeters

3. Results

The SET groups showed significantly greater case effectiveness than groups receiving conventional physical therapy or trunk training (TECR: RR 1.28, 95% CI: 1.15–1.42, P < 0.00001).

SET significantly improved walking function beyond active control therapy, including:

• 10-meter Maximum Walking Speed: Large effect (Standardized Mean Difference, SMD 0.85 [95% CI: 0.6–1.1], ref. Cohen’s d scale [6]).

• Lower limb muscle activation (iEMG, mVs):

  • Rectus femoris (RF): Mean Difference (MD 18.5 [95% CI: 12.2–24.9])

  • Biceps femoris (BF): MD 26.7 [95% CI: 0.7–52.6]

  • Gastrocnemius (GC): MD 4.5 [95% CI: 0.89–8.1]

• Functional Ambulation Category: MD 1.2 [95% CI: 1.0–1.4] points

• Timed Up and Go Test: MD -4.9 [95% CI: -6.4 to -3.5] sec

• Step Length: MD 5.0 [95% CI: 3.4–6.5] cm

Methodological Quality

The overall level of evidence was rated fair to good. Specifically, the studies were rated as follows:

• One excellent (10/10)

• 13 good (7–9/10)

• 11 fair (4–6/10)

• None poor

Seventeen studies did not report the type of SET device, and four studies used the device called 'Redcord sling' from Norway, cf. [7-10].

Effect Magnitude Interpretation

The present author (KV) interpreted the results according to the scales of Hopkins [11] and Cohen [6], as well as minimum clinical important difference (MCID) [12] (see the Discussion below). 

4. Discussion - What Does the Results Mean 

Results abstracted: Long et al. (2022) summerized, based on SR data from 1 504 patients, that SET was significantly more effective than conventional physical therapy or trunk training in managing post-stroke walking impairment. SET improved the rate of effective cases (TECR), maximal waking speed, muscle activation of the of lower limbs, functional ambulation category, balance-speed during raising, walking, cutting, and turning (TUGT), and step length. However, how may putting the effect magnitudes of these findings' into benchmarked contexts illuminate their meaning?

Effect Magnitude Interpretation

Total Effective Cases Rate (TECR):

The effect size for clinically significant cases was small in point estimate and ranged from trivial to small based on the confidence interval (CI), as interpreted using Hopkins' scale [11]. The increased "risk" of being an positive responder corresponds to 28% (95% CI: 15% to 42%). Most of the included studies defined treatment effectiveness based on lower limb muscle strength, spasticity reduction, and functional recovery, suggesting that while the effect size is small for the majority, it remains important and generalizable to the broader stroke population.

10-Meter Maximum Walking Speed (10mMWS):

The effect size for walking speed improvement was classified as large, ranging from moderate to high (CI) according to the highly respected Cohen’s d scale [6]. Walking speed is a critical outcome for post-stroke individuals, influencing their ability to safely cross busy streets, participate in social walks, and maintain overall cardiovascular and physical health through walking.

Muscle Activation (iEMG):

No established MCID exists for iEMG in post-stroke individuals, making it challenging to determine the clinical significance of the observed changes. Millivolt-seconds (mVs) of integrated EMG only represent the area under the curve of the rectified EMG signal over time. Despite this lack of benchmark (i.e., MCID), the findings are generalizable to the broader stroke population and support the more clinically meaningful outcomes related to activities of daily living and social participation, such as TUGT and FAC.

Functional Outcomes and Clinical Relevance

Functional Ambulation Category (FAC)

A difference greater than 1 point in the FAC scale represents a MCID because:

1) Each functional category in the FAC scale is separated by one point.

2) Such a change typically signifies a meaningful improvement in walking ability [13].

Timed Up and Go Test

The Mean Difference of -4.9 seconds (95% CI: -6.4 to -3.5 sec) exceeds both:

1) The Minimally Detectable Change (MDC) of 2.9 sec for individuals post-stroke [14], and  

2) The MCID of 3.4 sec established for individuals with spinal disc disease [15].

Given the strong association between TUGT dynamic balance performance and independence in daily and social activities, this improvement seems highly meaningful for post-stroke mobility.

Step Length

A mean step length increase of 5.0 cm (95% CI: 3.4–6.5 cm) is statistically significant, meaning it is likely to be observed in the broader post-stroke population. Although no established MCID exists for step length in stroke rehabilitation, a 5.0 cm increase is likely to be clinically meaningful because:

1) It represents a clear, measurable improvement in gait.

2) Even the lower confidence limit (3.4 cm) suggests a notable increase in step length.

An increase in step length directly supports improvements in walking speed, making it a moderate to highly clinically relevant outcome.

In light of other SRs

Other SRs support the results of the current SR (Long et al., 2022). For example, Chen et al. (2016) concluded that SET could improve the balance function of stroke patients by increasing degrees of Berg balance scale, Barthel index score and Fugl-Meyer Assessment [4]. However, Chen et al. [4] also cautioned against the limited evidence of 9 RCTs and suggested future large and strong RCTs to add confirmation. In addition, a more recent SR on low back pain (2021) [16] demonstrates that SET is more effective for the improvement of trunk control through restoring normal muscle strength, activation, and cross-sectional area than all active comparisons. However, also in the latter SR the methodological quality could have been better.

Methodological Quality

The methodological quality of the included studies (Long et al.) ranged from fair to good. Hence, Long et al. (2022) noted that the overall quality was unsatisfactory, emphasizing the need for future studies to improve their PEDro scores and standardize intervention protocols to possibly enhance replication, effects, and interpretability.

5. Conclusion

Long et al. (2022) concluded that SET is more effective than conventional physical therapy or trunk training in improving walking ability in post-stroke patients, particularly in East Asia. However, the present author (KV) emphasizes that the evidence remains somewhat uncertain. To strengthen the findings and provide more reliable effect estimates, future research must uphold higher methodological standards and refine the standardization of the most effective SET protocols (presented in the studies with the highest PEDro scores). 

References

1.Preston, E., et al., What is the probability of patients who are nonambulatory after stroke regaining independent walking? A systematic review. Int J Stroke, 2011. 6(6): p. 531-40.

2.Van Criekinge, T., et al., SWEAT2 Study: Effectiveness of Trunk Training on Gait and Trunk Kinematics After Stroke: A Randomized Controlled Trial. Phys Ther, 2020. 100(9): p. 1568-1581.

3.Aguilera-Castells, J., et al., Muscle activation in suspension training: a systematic review. Sports Biomech, 2020. 19(1): p. 55-75.

4.Chen, L., et al., Effect of Sling Exercise Training on Balance in Patients with Stroke: A Meta-Analysis. PLoS One, 2016. 11(10): p. e0163351.

5.Long, J., et al., Effects of sling exercise therapy on post-stroke walking impairment: a systematic review and meta-analysis. International Journal of Rehabilitation Research, 2022. 45(1): p. 12-23.

6.Cohen, J., Statistical power analysis for the behavioral sciences. 1988, Hillsdale, N.J.: Lawrence Erlbaum Associates.

7.Liu, Y.J. and C. A.L., Study on application of Neurac suspension therapy in rehabilitation of stroke patients with hemiplegia. Tianjin Med J, 2021. 49: p. 878-882.

8.Rong, J.F., et al., Effects of sling exercise training for core stability on balance function and walking ability in patients with stroke in recovery period. Chinese J Rehabilitation, 2017. 32: p. 109-112.

9.Sun, Z.X., Effect of sling exercise therapy on trunk function of stroke hemiplegia patients. 2012, Hebei Normal University.

10.Zhang, T.M. and J.W. Pan, Effect of sling exercise therapy on lower limb function in patients with stroke. J Shenyang Sport University, 2015. 34: p. 101-103.

11.Hopkins, W.G. A New View of Statistics: A Scale of Magnitudes for Effect Statistics. 2002  [cited 2023 Dec 26]; Available from: https://www.sportsci.org/resource/stats/effectmag.html.

12.Abilitylab, S.R. Shirley Ryan Abilitylab: Rehabilitation Measures Database. 2023  [cited 2023 Dec 26]; Available from: https://www.sralab.org/rehabilitation-measures.

13.Hayward, K.S., et al., Clinically important improvements in motor function are achievable during inpatient rehabilitation by stroke patients with severe motor disability: a prospective observational study. NeuroRehabilitation, 2014. 34(4): p. 773-9.

14.Flansbjer, U.B., et al., Reliability of gait performance tests in men and women with hemiparesis after stroke. J Rehabil Med, 2005. 37(2): p. 75-82.

15.Gautschi, O.P., et al., Assessment of the Minimum Clinically Important Difference in the Timed Up and Go Test After Surgery for Lumbar Degenerative Disc Disease. Neurosurgery, 2017. 80(3): p. 380-385.

16.Drummond, C., et al., Sling Exercise in the Management of Chronic Low Back Pain: A Systematic Review and Meta-Analysis. J Strength Cond Res, 2021.