This study aimed to investigate the effects of different sitting postures and prolonged sitting on lumbosacral nerve root function by measuring the amplitude of the soleus (SOL) Hoffmann reflex (H-reflex).
Methods
This study included 30 healthy individuals who were selected through convenience sampling and divided according to daily sitting duration over the past year into a prolonged sitting group (≥6 h/day) and a control group (≤4 h/day). The SOL H-reflex amplitude was recorded in erect, slumped, slouched, and supine positions. Ischial pressure was evaluated in all sitting postures to assess spinal loading.
Results
Slouched sitting significantly lowered ischial pressure (p<0.0005) and produced higher H-reflex amplitudes (p<0.0005), which were not significantly different from those in the supine position (p=0.362). In contrast, (p<0.0005) erect and slumped (p < 0.0005) postures showed increased ischial pressure and significantly reduced H-reflex amplitudes (p<0.0005 for both postures). Participants in the prolonged sitting group demonstrated significantly lower SOL H-reflex amplitudes than those in the control group (p=0.008, ηp²=0.23).
Conclusion
Various sitting postures and durations exert different effects on the lumbosacral spine and nerve roots. Slouched sitting reduces spinal stress and lower nerve root compression compared to erect and slumped seated positions. Extended sitting duration may partially compress the lumbosacral nerve root, thereby potentially contributing to postural low back pain over time.
GBD 2019 Diseases and Injuries Collaborators. Global burden of 369 diseases and injuries in 204 countries and territories, 1990–2019: a systematic analysis for the global burden of disease study 2019. Lancet2020; 396: 1204–1222.
2.
Al AmerHS. Low back pain prevalence and risk factors among health workers in Saudi Arabia: a systematic review and meta-analysis. J Occup Health2020; 62: e12155.
3.
da SilvaTMillsKBrownBT, et al.Recurrence of low back pain is common: a prospective inception cohort study. J Physiother2019; 65: 159–165.
4.
LisAMBlackKMKornH, et al.Association between sitting and occupational LBP. Eur Spine J2007; 16: 283–298.
5.
De CarvalhoDGreeneRSwabM, et al.Does objectively measured prolonged standing for desk work result in lower ratings of perceived low back pain than sitting? A systematic review and meta-analysis. Work2020; 67: 431–440.
6.
BakerRCoenenPHowieE, et al.The short-term musculoskeletal and cognitive effects of prolonged sitting during office computer work. Int J Environ Res Publ Health2018; 15: 1678.
7.
ShinSSYooWG. Differences in regional and global lumbar angle during slumped sitting and upright sitting among global three subgroups. J Back Musculoskelet Rehabil2021; 34: 877–885.
8.
AxelssonPKarlssonBS. Intervertebral mobility in the progressive degenerative process. A radiostereometric analysis. Eur Spine J2004; 13: 567–572.
9.
LiJQKwongWHChanYL, et al.Comparison of in vivo intradiscal pressure between sitting and standing in human lumbar spine: a systematic review and meta-analysis. Life (Basel)2022; 12: 457.
10.
KettARSichtingFMilaniTL. The effect of sitting posture and postural activity on low back muscle stiffness. Biomechanics2021; 1: 214–224.
11.
SaiklangPChatpremTKaroonsupcharoenO, et al.The comparison of the effect of prolonged sitting on lumbar repositioning error in asymptomatic and chronic low back pain participants with seated sedentary behavior. Trends Sci2024; 21: 7332–7332.
12.
OdesolaDFKulonJVergheseS, et al.Smart sensing chairs for sitting posture detection, classification, and monitoring: a comprehensive review. Sensors2024; 24: 2940.
13.
FlomanYLiramNGilaiAN. Spinal manipulation results in immediate H-reflex changes in patients with unilateral disc herniation. Eur Spine J1997; 6: 398–401.
14.
AliAASabbahiMA. H-reflex changes under spinal loading and unloading conditions in normal subjects. Clin Neurophysiol2000; 111: 664–670.
15.
SabbahiMAOvak-BittarF. Electrodiagnosis-based management of patients with radiculopathy: the concept and application involving a patient with a large lumbosacral disc herniation. Clin Neurophysiol Pract2018; 12: 141–147.
16.
MakhsousMLinFBankardJ, et al.Biomechanical effects of sitting with adjustable ischial and lumbar support on occupational low back pain: evaluation of sitting load and back muscle activity. BMC Musculoskelet Disord2009; 10: 17.
17.
MakhsousMLinFHendrixRW, et al.Sitting with adjustable ischial and back supports: biomechanical changes. Spine (Phila Pa 1976)2003; 28: 1113–1121.
18.
EgawaKOidaYKitabatakeY, et al.Effect of weight bearing on the soleus H-reflex during upright standing under the head-out water immersion condition in humans. Environ Med2003; 47: 81–84.
19.
SabbahiMA. Fixing lumbosacral radiculopathy with postural modification: a new method for evaluation and treatment based on electrodiagnostic testing. J Neurol Orthop Med Surg1997; 17: 176–181.
20.
PipkinLSprigleS. Effect of model design, cushion construction, and interface pressure mats on interface pressure and immersion. J Rehabil Res Dev2008; 45: 875–882.
21.
SpyropoulosPPapathanasiouGGeorgoudisG, et al.Prevalence of low back pain in Greek public office workers. Pain Physician2007; 10: 651–659.
22.
BaeckeJABuremaJFrijtersJE. A short questionnaire for the measurement of habitual physical activity in epidemiological studies. Am J Clin Nutr1982; 36: 936–942.
23.
VosGACongletonJJMooreJS, et al.Postural versus chair design impacts upon interface pressure. Appl Ergon2006; 37: 619–628.
24.
NaltyTSabbahiM. Electrotherapy clinical procedures manual. New York: McGraw Hill Med. Pub. Div., 2001, p.312.
25.
Al AmerHSSabbahiMAOlsonSL. Reliability of the soleus H-reflex in different sitting postures. Med Sci (Basel)2020; 8: 48.
26.
Blanca MenaMJAlarcón PostigoRArnau GrasJ, et al.Non-normal data: is ANOVA still a valid option?Psicothema2017; 29: 552–557.
27.
KandethodyMRChrisPT. Mathematical statistics with applications in R. (3rd ed.). Hoboken, NJ, USA: Academic Press, 2021.
28.
RichardsonJT. Eta squared and partial eta squared as measures of effect size in educational research. Educ Res Rev2011; 6: 135–147.
29.
WilkeHJNeefPCaimiM, et al.New in vivo measurements of pressures in the intervertebral disc in daily life. Spine1999; 24: 755–762.
30.
AnderssonBJOrtengrenRNachemsonA, et al.Lumbar disc pressure and myoelectric back muscle activity during sitting. I. Studies on an experimental chair. Scand J Rehabil Med1974; 6: 104–114.
31.
ShinGMirkaGA. An in vivo assessment of the low back response to prolonged flexion: interplay between active and passive tissues. Clin Biomech (Bristol)2007; 22: 965–971.
32.
McGillSMBrownS. Creep response of the lumbar spine to prolonged full flexion. Clin Biomech1992; 7: 43–46.
33.
DunkNMCallaghanJP. Gender-based differences in postural responses to seated exposures. Clin Biomech (Bristol)2005; 20: 1101–1110.
34.
MiyoshiTNozakiDSekiguchiH, et al.Somatosensory graviception inhibits soleus H-reflex during erect posture in humans as revealed by parabolic flight experiment. Exp Brain Res2003; 150: 109–113.
35.
KawashimaNSekiguchiHMiyoshiT, et al.Inhibition of the human soleus hoffman reflex during standing without descending commands. Neurosci Lett2003; 345: 41–44.
36.
MorishitaYHidaSNaitoM, et al.Measurement of the local pressure of the intervertebral foramen and the electrophysiologic values of the spinal nerve roots in the vertebral foramen. Spine (Phil Pa 1976)2006; 31: 3076–3080.
37.
FujiwaraAAnHSLimTH, et al.Morphologic changes in the lumbar intervertebral foramen due to flexion-extension, lateral bending, and axial rotation: an in vitro anatomic and biomechanical study. Spine (Phil Pa 1976)2001; 26: 876–882.
AdamsMAMcMillanDWGreenTP, et al.Sustained loading generates stress concentrations in lumbar intervertebral discs. Spine (Phil Pa 1976)1996; 21: 434–438.
40.
HedmanTPFernieGR. Mechanical response of the lumbar spine to seated postural loads. Spine (Phil Pa 1976)1997; 22: 734–743.
41.
UrbanJPSmithSFairbankJC. Nutrition of the intervertebral disc. Spine2004; 29: 2700–2709.
42.
GrunhagenTShirazi-AdlAFairbankJC, et al.Intervertebral disk nutrition: a review of factors influencing concentrations of nutrients and metabolites. Orthop Clin North Am2011; 42: 465–477.
43.
CinottiGDe SantisPNofroniI, et al.Stenosis of lumbar intervertebral foramen: anatomic study on predisposing factors. Spine (Phil Pa 1976)2002; 27: 223–229.
44.
SabbahiMAKhalilM. Segmental H-reflex studies in upper and lower limbs of healthy subjects. Arch Phys Med Rehabil1990; 71: 216–222.
45.
StinsonMDPorter-ArmstrongAEakinP. Seat-interface pressure: a pilot study of the relationship to gender, body mass index, and seating position. Arch Phys Med Rehabil2003; 84: 405–409.
46.
BodofskyEB. Contraction-induced upper extremity H reflexes: normative values. Arch Phys Med Rehabil1999; 80: 562–565.
47.
WilliamsMMHawleyJAMcKenzieRA, et al.A comparison of the effects of two sitting postures on back and referred pain. Spine (Phil Pa 1976)1991; 16: 1185–1191.
