The effect of acute back muscle fatigue on postural control strategy in people with and without recurrent low back pain

AbstractThe impact of aging on the back muscles is not well understood, yet may hold clues to both normal aging and chronic low back pain (cLBP). This study sought to investigate whether the median frequency (MF) surface electromyographic (SEMG) back muscle fatigue method—a proxy for glycolytic muscle metabolism—would be able to detect age- and sex-specific differences in neuromuscular and muscle metabolic functions in individuals with cLBP in a reliable way, and whether it would be as sensitive as when used on healthy individuals. With participants seated on a dynamometer (20° trunk anteflexion), paraspinal SEMG activity was recorded bilaterally from the multifidus (L5), longissimus (L2), and iliolumbalis (L1) muscles during isometric, sustained back extensions loaded at 80% of maximum from 117 younger (58 females) and 112 older (56 female) cLBP individuals. Tests were repeated after 1–2 days and 6 weeks. Median frequency, the SEMG variable indicating neuromuscular fatigue, was analyzed. Maximum back extensor strength was comparable between younger and older participants. Significantly less MF-SEMG back muscle fatigue was observed in older as compared to younger, and in older female as compared to older male cLBP individuals. Relative reliability was excellent, but absolute reliability appeared large for this SEMG-fatigue measure. Findings suggest that cLBP likely does not mask the age-specific diagnostic potential of the MF-SEMG back extensor fatigue method. Thus, this method possesses a great potential to be further developed into a valuable biomarker capable of detecting back muscle function at risk of sarcopenia at very early stages.

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Individuals with recurrent low back pain exhibit further altered trunk control in remission than when in pain

10.1101/2020.10.15.20213488 ◽

2020 ◽

Author(s):

Hai-Jung Steffi Shih ◽

Linda Van Dillen ◽

Jason Kutch ◽

Kornelia Kulig

Keyword(s):

Young Adults ◽

Low Back Pain ◽

Back Pain ◽

Control Strategy ◽

Frontal Plane ◽

Low Back ◽

Trunk Control ◽

Co Activation ◽

Symptom Remission ◽

Recurrent Low Back Pain

AbstractBackgroundMovement alterations due to low back pain (LBP) could lead to long-term adverse consequences if they do not resolve after symptom subsides. This study aims to determine if altered trunk control associated with recurrent low back pain persists beyond symptom duration.MethodsTwenty young adults with recurrent low back pain were tested once during an LBP episode and once in symptom remission, and twenty matched back-healthy participants served as controls. Participants walked on a treadmill with five prescribed step widths. Motion capture and surface electromyography were used to record frontal plane trunk kinematics and muscle activation. Thorax-pelvis coordination was calculated using vector coding technique, and bilateral longissimus activation and co-activation were analyzed.FindingsYoung adults with recurrent LBP exhibited a “looser” trunk control strategy in the frontal plane during gait that was persistent regardless of pain status across multiple step widths compared to back-healthy controls. This was demonstrated by a greater pelvis-only, less thorax-only coordination pattern, and decreased bilateral longissimus co-activation in individuals with recurrent LBP than controls. The looser trunk control strategy was further amplified when individuals with recurrent LBP were in symptom remission and exhibited greater trunk excursion and reduced in-phase coordination.InterpretationThe amplification of aberrant movement during symptom remission may suggest that movement patterns or anatomical factors existing prior to the tested painful episode underlie the altered trunk control in individuals with recurrent LBP. The symptom remission period of recurrent LBP patients may be a critical window into clinical evaluation and treatment.

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