A new study published in GeroScience investigated whether the median frequency (MF) surface electromyographic (SEMG) back muscle fatigue method – a proxy for glycolytic muscle metabolism, could detect age- and sex-specific differences in neuromuscular and muscle metabolic functions in individuals with chronic low back pain (cLBP) in a reliable way, and if it would be as sensitive as when used on healthy individuals.

Here, participants were seated on a dynamometer (20° trunk anteflexion) and the 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 six weeks. Median frequency, the SEMG variable indicating neuromuscular fatigue, was analyzed.

The results revealed that maximum back extensor strength was comparable between younger and older participants. Whereas, 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. The relative reliability was excellent, but absolute reliability appeared large for this SEMG-fatigue measure.

The findings indicated that cLBP, probably does not mask the age-specific diagnostic potential of the MF-SEMG back extensor fatigue method. Therefore, 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.

Source: Gerold E, Richard H, Sara Z, Josef K, Patrick M, Thomas K. Age- and sex-specific effects in paravertebral surface electromyographic back extensor muscle fatigue in chronic low back pain. Geroscience. 2019. doi:10.1007/s11357-019-00134-7