Effects of Clenching Strength on Exercise Performance: Verification Using Spinal Function Assessments

The effects of lumbar stabilization exercises with and without jaw movements in non-specific low back pain (A randomized controlled trial)

Objective

This study aimed to investigate the added effect of jaw clenching on the efficacy of lumbar stabilization exercises to manage chronic non-specific low back pain.

Methods

This randomized controlled trial was conducted at the Sindh Institute of Physical Medicine and Rehabilitation (SIPM&R) Karachi from April 2021 to April 2023. Eighty patients with chronic non-specific low back pain participated in this study. Forty patients each were randomly allocated to the lumbar stability exercise (LSE) group' and the lumbar stability exercise with teeth clenching (LSETC) group. Patients in both groups performed respective exercises twice weekly for 12 weeks. The Numeric Pain Rating Scale (NPRS), Roland Morris Disability Questionnaire (RMDQ), and Pressure Biofeedback Unit (PBU) were used to assess pain, disability, and muscle endurance respectively. Data were collected at the baseline, after six weeks and 12 weeks of intervention. A p-value of <0.05 was considered statistically significant.

Results

Both groups showed statistically significant improvements in pain, disability, and muscle endurance. Upon further stratification, participants aged 20-30 years in the LSETC group showed significantly higher scores than the LSE group for NPRS, RMDQ, and PBU after 12 weeks. Overall, the LSETC group showed relatively higher improvement in mean scores for NPRS, RMDQ, and PBU than the LSE group.

Conclusion

Lumbar stabilization exercises with and without jaw movement are effective for the treatment of chronic non-specific low back pain. The addition of teeth clenching enhanced the effectiveness of lumbar stability exercises, especially in young adults. Trial Registration: Clinicaltrials.gov (NCT04801212), Prospectively registered on March 16, 2021.

The effects of jaw clenching and mouthpiece use on bat swing velocity in Division II athletes

Research assessing the effects of mouthpieces on an individual's aerobic, anaerobic, or muscular performance have attributed cited improvements to the participant's ability to jaw clench. Jaw clenching research finds positive outcomes with the task of jaw clenching with targeted muscle groups in a controlled laboratory setting. Thus, the study's goal was to determine if the addition of a mouthpiece would positively affect performance outcomes in a field-based whole-body muscle movement. Fourteen participants (8=F and 6=M) NCAA softball and baseball athletes completed 5 maximal bat swings with and without a mouthpiece in 4 conditions: no jaw clenching (NC), mouthpiece and jaw clenching (MP+C), mouthpiece only (MP), and jaw clenching only (C). Significant differences occurred in conditions, with the highest velocity noted in the combined condition of MP+C (71.9 mph) as compared to NC (67.9 mph), MP (68.6 mph), and C (70.9 mph). A repeated measures ANOVA demonstrated significant differences with bat swing velocity (F = 13.19, df 3, p < 0.0001). Pairwise comparisons revealed significant differences in MP+C with MP (p = 0.007); MP+C with NC (p = 0.001), and C with NC (p = 0.009). The results of this study provide evidence of jaw clenching's positive effects on the dynamic, whole-body explosive activity of a bat swing.

Relationship between a gum-chewing routine and oral, physical, and cognitive functions of community-dwelling older adults: A Kashiwa cohort study

AIM

As associations between oral function and general health have been reported in community-dwelling older adults, easily implementable preventive measures are urgently required. We focused on the health benefits of gum chewing, as no studies have been carried out on the impact of gum-chewing routines on the health of older adults. This cross-sectional study aimed to determine whether the gum-chewing routine is associated with oral, physical and cognitive functions in community-dwelling older adults.

METHODS

This study included 1617 community-dwelling older participants in a health survey carried out in 2021. The gum-chewing routine and weekly chewing time were assessed using a self-administered questionnaire. The outcome measures, including actual measurements of oral function, physical function, cognitive function, dietary intake and lifestyle, were evaluated using self-administered questionnaires or health surveys.

RESULTS

We analyzed 1474 (mean age 76.1 ± 5.8 years, 45% women) participants for whom all data were not missing, and 14% of them had a gum-chewing routine for more than 30 min weekly. Oral functions were significantly higher in older adults with a gum-chewing routine, and there were substantially fewer participants with oral frailty (adjusted odds ratio 0.581, 95% confidence interval 0.340-0.993). Additionally, cognitive and physical functions, including grip strength, were significantly higher in the gum-chewing routine group.

CONCLUSIONS

Community-dwelling older adults with a gum-chewing routine have higher oral, physical and cognitive functions. These findings indicate that a gum-chewing routine might contribute to maintaining oral function and preventing frailty. Geriatr Gerontol Int 2024; 24: 68-74.

Effects of jaw clenching and mental stress on persistent inward currents estimated by two different methods

Spinal motoneuron firing depends greatly on persistent inward currents (PICs), which in turn are facilitated by the neuromodulators serotonin and noradrenaline. The aim of this study was to determine whether jaw clenching (JC) and mental stress (MS), which may increase neuromodulator release, facilitate PICs in human motoneurons. The paired motor unit (MU) technique was used to estimate PIC contribution to motoneuron firing. Surface electromyograms were collected using a 32-channel matrix on gastrocnemius medialis (GM) during voluntary, ramp, plantar flexor contractions. MU discharges were identified, and delta frequency (ΔF), a measure of recruitment-derecruitment hysteresis, was calculated. Additionally, another technique was used (VibStim) that evokes involuntary contractions that persist after cessation of combined Achilles tendon vibration and triceps surae neuromuscular electrical stimulation. VibStim measures of plantar flexor torque and soleus activity may reflect PIC activation. ΔF was not significantly altered by JC (p = .679, n = 18, 9 females) or MS (p = .147, n = 14, 5 females). However, all VibStim variables quantifying involuntary torque and muscle activity during and after vibration cessation were significantly increased in JC (p < .011, n = 20, 10 females) and some, but not all, increased in MS (p = .017-.05, n = 19, 10 females). JC and MS significantly increased the magnitude of involuntary contractions (VibStim) but had no effect on GM ΔF during voluntary contractions. Effects of increased neuromodulator release on PIC contribution to motoneuron firing might differ between synergists or be context dependent. Based on these data, the background level of voluntary contraction and, hence, both neuromodulation and ionotropic inputs could influence neuromodulatory PIC enhancement.

Relationship between oral frailty and locomotive syndrome in working-age individuals: a cross-sectional survey of workers in Japan

BACKGROUND

Although the relationship between oral and physical frailty in older adults has been investigated, few studies have focused on the working-age population. This study examined the relationships of the number of remaining teeth and masticatory ability, i.e., signs of oral frailty, with locomotive syndrome (LS) in the working-age population.

METHODS

The number of remaining teeth, masticatory ability, and presence of LS in 501 participants from four companies were examined. The relationships between the number of remaining teeth groups (≥ 20 teeth or ≤ 19 teeth) and LS and between the masticatory ability groups (high or low) and LS were examined. A binomial logistic regression analysis was conducted using LS from the stand-up test as the objective variable and the two subgroups based on the number of remaining teeth and potential crossover factors as covariates.

RESULTS

The analysis included 495 participants (354 males and 141 females; median age, 43 years). The median number of remaining teeth among the participants was 28, and 10 participants (2.0%) had ≤ 19 teeth. The mean masticatory ability values were 39.9 for males and 37.7 for females, and 31 participants (6.3%) had low masticatory ability. In the stand-up test, those with ≤ 19 teeth had a higher LS rate than those with ≥ 20 teeth. The odds ratio for LS in the group with ≤ 19 remaining teeth was 5.99, and the confidence interval was 1.44-24.95.

CONCLUSIONS

The results confirmed signs of oral frailty in the working-age population. Further, the number of remaining teeth possibly affects standing movement. Thus, oral frailty is associated with LS in the working-age population.

Effects of remote facilitation on ankle joint movement: Focusing on occlusal strength and balance

Background

Remote facilitation refers to teeth occlusion-activated spinal cord activity resulting in increased trunk and limb muscle strength. Facilitation depends on dentition-related pressure during occlusion and masticatory muscle contraction strength.

Aims

This study aimed to clarify the neurophysiological phenomenon and mechanisms by which occlusal strength and balance affect leg muscle activity and smooth joint movement execution.

Materials & Methods

To examine occlusal strength, three conditions were set: no contact between teeth and Moderate- and Maximum-strength occlusion (No-bite, Moderate, and Max conditions, respectively). To assess occlusal balance, we measured occlusal forces and calculated the left-right force ratio. We designated the sides with higher and lower occlusal pressure as hypertonic and hypotonic, respectively. We assessed ankle dorsiflexion movements with joint movement and isometric tasks.

Results

The rate of joint development and peak ankle dorsiflexion torque were significantly higher under occlusion (moderate and max compared to No-bite conditions), and the joint movement performance time was significantly shorter under Moderate compared to No-bite conditions. The joint movement execution time change rate from No-bite to Moderate condition was significantly lower on the Hypertonic side. Joint movement function was most improved under Moderate conditions.

Discussion

While remote facilitation improves with higher occlusal strength, leading to increased muscle strength, there is optimal occlusion intensity in joint movement. Moreover, an occlusal balance-dependent imbalance exists in remote facilitation between the Hyper- and Hypotonic sides.

Conclusion

Thus, low-intensity occlusion is optimal for smooth joint movement, and unbalanced occlusion results in asymmetrical motor function facilitation.