Page 139 - Petelin, Ana, ur. 2024. Zdravje delovno aktivnih in starejših odraslih / Health of Working-Age and Older Adults. Zbornik povzetkov z recenzijo ▪︎ Book of Abstracts. Koper: Založba Univerze na Primorskem/University of Primorska Press

Changes of lumbar muscle stiffness following spinal flexion exposure

Rok Vatovec, Nejc Šarabon, Matej Voglar
1 University of Primorska Faculty of Health Sciences, Izola, Slovenia
Introduction: Spinal flexion exposure (SFE) is considered as an important risk factor for
the occurrence of low back pain in working-age adults. Evidence suggests that longer
durations of SFE lead to increased intrinsic trunk stiffness. Authors of previous stud-
ies have speculated that the latter is a consequence of increased muscle stiffness. To
the best of our knowledge, there are currently no available studies on the changes in
lumbar muscle stiffness following SFE. Furthermore, the comparison of the response
between genders warrants investigation. Therefore, the aim of our study was to eval-
uate the effect of SFE on lumbar muscle stiffness and to compare the response be-
tween genders.
Methods: Our study sample included 16 healthy young volunteers. Erector spinae and
multifidus resting shear modulus was measured bilaterally using shear wave elastog-
raphy. The participants completed a 60-min intermittent SFE protocol, which consist-
ed of 40 repetitions of static spinal flexion (60 s) interspersed with 30 s of unsupport-
ed upright sitting. The measurements were completed prior to and following the SFE
protocol. Data were analysed using a mixed-method repeated measures analysis of
variance with two within- (time and muscle) and one between- (gender) subject fac-
tor. For statistically significant interactions, post-hoc tests were completed using the
Bonferroni correction.
2
Results: Our results did not show a significant time × muscle × gender (p = 0.60; η =
2
0.05), time × gender interaction (p = 0.78; η = 0.01) or gender effect (p = 0.46; η =
2
0.04). On the other hand, we found a significant time (p < 0.01; η = 0.65), muscle (p
2
2
2
< 0.01; η = 0.58) and muscle × gender effect (p = 0.01; η = 0.25). The post-hoc tests
revealed marginally significantly higher right multifidus stiffness in males compared to
females (p = 0.05). Following SFE, left and right erector spinae shear modulus in-
creased by 8.17 and 6.43 %, respectively, whereas left and right multifidus shear mod-
ulus increased by 15.38 and 8.76 %, respectively.
Discussion and conclusions: The main finding of our study is that SFE leads to increased
lumbar muscle stiffness. Furthermore, this response appears to be comparable be-
tween genders. The exact mechanism for increased lumbar muscle stiffness remains problemi, izzivi in priložnosti na področju zdravja ... | concerns, challenges and opportunities in the health ...
debatable. Although this finding may be related to isometric loading of the trunk ex-
tensors, evidence suggests that isometric fatigue leads to a reduction in resting lum-
bar muscle stiffness. Increased lumbar muscle stiffness may serve as a compensation
for reduced connective tissue stiffness, which has been frequently reported in previ-
ous studies. Higher lumbar muscle stiffness may result in increased compressive load-
ing of spinal tissues, thus elevating the risk for the development or persistence of low
back pain in working-age adults.
Keywords: muscle mechanical properties, bending, shear modulus, erector spinae,
multifidus, elastography

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