Abstract

BackgroundThe root mean square surface electromyographic activity of lumbar extensor muscles during dynamic trunk flexion and extension from a standing position and task specific spine ranges of motion objectively assess muscle function in healthy young and middle age individuals. However, literature on neuromuscular activation and associated spine and hip kinematics in older individuals is sparse. This cross sectional study sought to examine the sex and age (<40 versus >60 years) related differences in the neuromuscular activation profiles of the lumbar extensors and the related spine and hip kinematics from healthy individuals during a standardized trunk flexion-extension task.MethodsTwenty five older (13 females, 60–90 years) and 24 younger (12 females, 18–40 years) healthy individuals performed trunk flexion-extension testing by holding static positions at half-flexion way and full range of motion between standing and maximum trunk flexion. The associated lumbar extensor muscle activity was derived from measurements at standing, half, and maximum flexion positions. The range of motion at the hip and lumbar spine was recorded using 3d accelerometers attached to the skin overlying the multifidus and semispinalis thoracis muscles lateral to the L5 and T4 spinous processes, respectively. Statistical calculations were performed using a permutation ANOVA with bootstrap confidence intervals.ResultsThe muscle activity in the half related to the maximum flexion position (half flexion relaxation ratio) was significantly smaller in older males when compared with younger males. Moreover, measurements revealed smaller activity changes from standing to the half and from half to the maximum flexion position in older compared to younger individuals. Older males displayed smaller gross trunk range of motion from standing to maximum flexion than any other group.ConclusionsGender and normal aging significantly affect both the activation patterns of the lumbar extensor muscles and the kinematics of the trunk during a standardized trunk flexion-extension task. Measurement results from healthy young and middle age individuals should not be used for the assessment of individuals older than 60 years of age.Electronic supplementary materialThe online version of this article (doi:10.1186/1743-0003-12-3) contains supplementary material, which is available to authorized users.

Highlights

  • The root mean square surface electromyographic activity of lumbar extensor muscles during dynamic trunk flexion and extension from a standing position and task specific spine ranges of motion objectively assess muscle function in healthy young and middle age individuals

  • Mean root mean square (RMS) surface electromyographic (SEMG) half flexion relaxation ratio (HFR) of lumbar extensor muscles The ratio recorded at half and maximum trunk flexion (HFR) revealed significantly lower values in older males in comparison to all other subgroups and in older females compared to younger males (Table 2) meaning that the flexion relaxation phenomenon was less marked in these groups

  • Increments of the amplitudes from standing to the half and the respective decrements from half to the maximum flexion position were significantly smaller in older when compared to younger volunteers

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Summary

Introduction

The root mean square surface electromyographic activity of lumbar extensor muscles during dynamic trunk flexion and extension from a standing position and task specific spine ranges of motion objectively assess muscle function in healthy young and middle age individuals. Back muscle reflex latency of older individuals has been found to be delayed in response to loading of the spine along with less activity among trunk muscles in older adults performing functional tasks [13]. Such neuromuscular activation changes become dominant starting at 50 years of age when restrictions of range of motion start to manifest [14,15,16,17]. One can speculate that age associated changes likely have an impact on measurement results of kinematics and neuromuscular activation of lumbar extensors in trunk flexion-extension testing

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