Head Posture Influences Low Back Muscle Endurance Tests in 11-Year-Old Children

Does difficulty in chewing induce subjective musculoskeletal symptoms? A case-control study

OBJECTIVES

Risk factors associated with the development of musculoskeletal disorders and symptoms remain an important issue worldwide. This study aimed to investigate the relationship between oral health problems such as difficulty chewing and the occurrence of stiff neck/shoulders (SN/S) and low back pain (LBP).

DESIGN

Case-control study.

SETTING AND PARTICIPANTS

This study was conducted from 1 April 2018 to 31 March 2020. The subjects were 77 341 workers among 646 281 workers from several employers in Japan.

OUTCOME MEASURES

Participants were asked to evaluate their subjective SN/S and LBP symptoms using a self-administered questionnaire.

METHODS

We defined the chewing condition using a questionnaire, and workers who responded with 'I can chew anything' were classified as the good condition group (GCG), and those who responded with 'Sometimes I have difficulty chewing due to problems with the teeth, gums, or bite' or 'I can hardly chew' were classified as the poor condition group (PCG). Setting the year 2018 as the baseline, we performed a logistic regression model using propensity score and inverse probability weighting (IPW) methods and chewing condition groups as explanatory variables and SN/S and LBP as objective variables.

RESULTS

The IPW-adjusted logistic regression model showed that the OR of SN/S was approximately 1.25 (95% CI 1.17 to 1.33) times higher in the PCG than that in the GCG (p<0.001). Similarly, the OR of LBP was about 1.37 (95% CI 1.27 to 1.48) times higher in the PCG than that in the GCG in the IPW-adjusted logistic regression model (p<0.001).

CONCLUSIONS

Our study suggests that the occurrence of SN/S and LBP symptoms in workers could be predicted depending on the presence of difficulty in chewing. Therefore, oral health and health guidance are gaining importance for the prevention of subjective musculoskeletal symptoms.

Correlation Between Central Sensitization and Remote Muscle Performance in Individuals With Chronic Low Back Pain

OBJECTIVE

The purpose of this study was to examine associations between the degree of central sensitization (CS) and remote muscle performance in people with chronic low back pain (CLBP).

METHODS

The 2011 fibromyalgia (FM) criteria and severity scales (2011 FM survey) were used as a surrogate measure of CS to divide the participants into 2 groups: FM-positive CLBP and FM-negative CLBP. Measures related to central sensitization included the 2011 FM survey and pressure pain threshold of the thumbnail. Measures related to muscle performance included neck flexor muscle strength and endurance and plantar flexor muscle strength. Between-groups and correlation analyses were performed.

RESULTS

Sixty people with CLBP were enrolled (30 FM-positive, 30 FM-negative). There was no significant difference between the subgroups in age, sex, or pain duration (P > .05). The FM-positive CLBP group showed poorer neck flexor muscle endurance (P = .01) and plantar flexor muscle strength (P = .002) than the FM-negative CLBP group, whereas neck flexor muscle strength was not different between the groups (P = .175). Scores for FM and values for pressure pain thresholds of the thumbnail were associated with neck flexor muscle strength (respectively, r = -0.320, P = .013, and r = 0.467, P < .001), endurance (r = -0.242, P < .001, and r = 0.335, P = .009), and plantar flexor muscle strength (r = -0.469, P < .001, and r = 0.500, P < .001).

CONCLUSION

We found associations between the degree of CS and remote muscle strength and endurance, suggesting that poor remote muscle performance is possibly a clinical sign of CS in people with CLBP.

Back Muscle Function in Older Women With Age-Related Hyperkyphosis: A Comparative Study

OBJECTIVE

The purpose of this study was to compare static maximal back extensor muscle force, endurance, and characteristics of flexion relaxation phenomenon (FRP) in older women with and without age-related hyperkyphosis.

METHODS

Maximum back extensor force and endurance measured in a sitting position with a designed load cell setup; appearance, onset, and offset angles of FRP; and extension relaxation ratio (ERR) during a dynamic flexion-extension task were compared between 24 older women with hyperkyphosis (thoracic kyphosis angle ≥50°), mean age 65 ± 4.4 years, and 24 older women without hyperkyphosis (thoracic kyphosis angle ≪50°), mean age 63 ± 4.3 years. Variables of force, endurance, angles of FRP, and ERR were analyzed using an independent sample t test. A χ² test was used to identify differences between groups in FRP appearance.

RESULTS

Static back extensor force and endurance were significantly lower among those with versus those without hyperkyphosis (P ≪ .001). Although the 2 groups did not differ in FRP appearance and ERR in the superficial erector spinal muscles (P ≫ .05), FRP in the hyperkyphosis group started sooner and ended later than in the group without hyperkyphosis (P ≪ .05).

CONCLUSION

Our study indicates that women with age-related hyperkyphosis had decreased static maximal force and endurance of the back extensor muscles and prolonged myoelectrical silence of the superficial erector spinal muscles. Reduced endurance of the superficial erector spinal muscles may trigger early onset of FRP and prolonged relaxation of these muscles.

Neck posture during lifting and its effect on trunk muscle activation and lumbar spine posture

Neck and head posture have been found to have a significant influence on the posture of the lower spine region during lifting and both an extended/upward gaze and a flexed/downward gaze have been hypothesized to lead to increased pain and/or overuse of the neck musculature. As a result, strength training recommendations have turned to the use of a retracted neck posture as being the safer posture to assume during lifting. This study examined trunk and neck muscle activity and lumbar spine posture in seven participants while performing moderate load lifts using a retracted neck posture (chin drawn in posteriorly; recently gaining popularity among coaches, trainers, and physical therapists to reduce neck pain during lifting, and freestyle neck posture (no instructions given). The retracted neck resulted in less lumbar spine flexion and increased lumbar erector spinae, external oblique, and sternocleidomastoid activity. The retracted posture also resulted in decreased activity in the thoracic erector spinae and dorsal neck musculature. The increased trunk and sternocleidomastoid activity and decreased spine flexion observed in the seven participants of this study when lifting with a retracted neck may have the potential to help lower the risk of spine pain/injury.