Influence of knee angle and individual flexibility on the flexion–relaxation response of the low back musculature

Shin, Gwanseob; Shu, Yu; Li, Zheng; Jiang, Zongliang; Mirka, Gary A.

doi:10.1016/j.jelekin.2003.12.001

Cited by 63 publications

(27 citation statements)

References 28 publications

(38 reference statements)

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“…Subsequent univariate ANOVA revealed that angle had a statistically significant effect on the multifidus activation during both the sudden loading phase of the trial as well as the steady state response ( Figure 3). These results indicate that the 60° condition was initiating the flexion-relaxation response of the multifidus muscles, as shown in previous studies (Shin et al, 2004) for both the steady state and sudden loading exertions. The lack of significance of support on these responses suggests that the loss …”

Section: Resultssupporting

confidence: 89%

“…The independent variables in this study were the lower extremity support condition with two levels (no support vs. with knee support) and torso flexion angle with two levels (45° vs. 60°). These two particular torso flexion angles were chosen for evaluation because of the expected changes in the relative contribution of the passive tissues to the total extensor moment (i.e., the flexion-relaxation response) as has been shown in previous research (e.g., Shin et al, 2004). The goal in the current study was to evaluate the potential interactive effects between this torso angle and knee support effects that might be generated.…”

Section: Experimental Designmentioning

confidence: 99%

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The Effect of a Knee Support on the Biomechanical Response of the Low Back

Shu

Jiang

et al. 2007

Journal of Applied Biomechanics

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Stooping and squatting postures are seen in a number of industries (e.g., agriculture, construction) where workers must work near ground level for extended periods of time. The focus of the current research was to evaluate a knee support device designed to reduce the biomechanical loading of these postures. Ten participants performed a series of sudden loading tasks while in a semisquat posture under two conditions of knee support (no support and fully supported) and two conditions of torso flexion (45 and 60°). A weight was released into the hands of the participants who then came to steady state while maintaining the designated posture. As they performed this task, the EMG responses of the trunk extensors (multifidus and erector spinae) were collected, both during the “sudden loading” phase of the trial as well as the steady weight-holding phase of the trial. As expected, the effects of torso flexion angle showed significant decreases in the activation of the multifidus muscles with greater torso angle (indicating the initiation of the flexion–relaxation response). Interestingly, the results showed that the knee support device had no effect on the activation levels of the sampled muscles, indicating that the loss of the degree of freedom from the ankle joint during the knee support condition had no impact on trunk extensor muscle response. The a priori concern with regard to these supports was that they would tend to focus loading on the low back and therefore would not serve as a potential ergonomic solution for these stooping/semisquatting tasks. Because the results of this study did not support this concern, further development of such an intervention is underway.

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Section: Resultssupporting

confidence: 89%

Section: Experimental Designmentioning

confidence: 99%

The Effect of a Knee Support on the Biomechanical Response of the Low Back

Shu

Jiang

et al. 2007

Journal of Applied Biomechanics

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“…Two types of extension moment generator including the active mechanism (muscle tissue) and the passive mechanism (ligaments, discs and fascia) were investigated in the static trials, because a pilot study revealed that the HEIGHT chosen in current study, specifically 55 cm and 70 cm, require over 60 degree trunk flexion where the passive tissues are in tension and begin to offset the external torque (i.e., initiation of flexion-relaxation phenomenon (FRP)) Silver, 1951 and1955;Shin et al, 2004). To capture the active muscle activity, the average (across muscle pairs), normalized EMG included five bilateral muscles: erector spinae (ES), latissimus dorsi (LD), rectus abdominis (RA), external oblique (EO) and gastrocnemius (GAS).…”

Section: Dependent Variablesmentioning

confidence: 99%

The effect of a lower extremity kinematic constraint on lifting biomechanics

Jin

Mirka

2011

Applied Ergonomics

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Leaning against a stationary barrier during manual materials handling tasks is observed in many industrial environments, but the effects of this kinematic constraint on low back mechanics are unknown. Thirteen participants performed two-handed lifting tasks using both a leaning posture and no leaning posture while trunk kinematics, muscle activity and ground reaction force were monitored. Results revealed that lifting with the leaning posture required significantly less activity in erector spinae (26% vs. 36% MVC) and latissimus dorsi (8% vs. 14% MVC), and less passive tissue moment compared with the no leaning posture. Peak sagittal accelerations were lower when leaning, but the leaning posture also had significantly higher slip potential as measured by required coefficient of friction (0.05 vs. 0.36). The results suggested that the leaning lifting strategy provides reduced low back stress, but does so at the cost of increased slip potential.

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“…To explain the observed reduction in lumbar flexion, possible factors influencing spinal stability have to be highlighted. Shin et al [40] demonstrated in their work that healthy subjects with the greatest lumbar flexibility had the highest activity levels of the LMM. Panjabi [41] described a model for spinal stability consisting of three subsystems (spinal column, spinal muscles and neural control unit) which together create optimal spinal flexibility and dynamic stability.…”

Section: Discussionmentioning

confidence: 99%

Correlation between lumbar dysfunction and fat infiltration in lumbar multifidus muscles in patients with low back pain

Hildebrandt¹,

Fankhauser²,

Meichtry

et al. 2017

BMC Musculoskelet Disord

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BackgroundLumbar multifidus muscles (LMM) are important for spinal motion and stability. Low back pain (LBP) is often associated with fat infiltration in LMM. An increasing fat infiltration of LMM may lead to lumbar dysfunction. The purpose of this study was to investigate whether there is a correlation between the severity of lumbar dysfunction and the severity of fat infiltration of LMM.MethodsIn a cross-sectional study, 42 patients with acute or chronic LBP were recruited. Their MRI findings were visually rated and graded using three criteria for fat accumulation in LMM: Grade 0 (0–10%), Grade 1 (10–50%) and Grade 2 (>50%). Lumbar sagittal range of motion, dynamic upright and seated posture control, sagittal movement control, body awareness and self-assessed functional disability were measured to determine the patients’ low back dysfunction.ResultsThe main result of this study was that increased severity of fat infiltration in the lumbar multifidus muscles correlated significantly with decreased range of motion of lumbar flexion (p = 0.032). No significant correlation was found between the severity of fat infiltration in LMM and impaired movement control, posture control, body awareness or self-assessed functional disability.ConclusionThis is the first study investigating the relationship between the severity of fat infiltration in LMM and the severity of lumbar dysfunction. The results of this study will contribute to the understanding of the mechanisms leading to fat infiltration of LMM and its relation to spinal function. Further studies should investigate whether specific treatment strategies are effective in reducing or preventing fat infiltration of LMM.

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Influence of knee angle and individual flexibility on the flexion–relaxation response of the low back musculature

Cited by 63 publications

References 28 publications

The Effect of a Knee Support on the Biomechanical Response of the Low Back

The Effect of a Knee Support on the Biomechanical Response of the Low Back

The effect of a lower extremity kinematic constraint on lifting biomechanics

Correlation between lumbar dysfunction and fat infiltration in lumbar multifidus muscles in patients with low back pain

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