Difference in the recruitment of intrinsic foot muscles in the elderly under static and dynamic postural conditions

Effects of somatosensory-stimulating foot orthoses on postural balance in older adults: A computerized dynamic posturography analysis

BACKGROUND

Foot orthoses (FO) with protruding knobs designed to stimulate the mechanoreceptors on the glabrous skin of the foot have been proposed to enhance proprioception, thereby improving postural balance and stability. This study aimed to investigate the effects of these FO with stimulating knobs on the postural balance in the elderly using computerized dynamic posturography (CDP).

RESEARCH QUESTION

Do FO with stimulating knobs enhance postural balance in the elderly by improving scores related to sensory organization, motor control, and adaptation in response to different static and dynamic perturbation conditions?

METHODS

Twenty-three healthy elderly participants performed the CDP, which includes Sensory Organization Test, Motor Control Test, and Adaptation Test in both flat FO and stimulating FO. The Bertec Balance Advantage System with force plates was employed to collect comprehensive CDP data.

RESULTS

Our results indicated a significant improvement in the composite equilibrium score (MD=1.44, p = 0.048) and weight symmetry (MD=-1.85, p = 0.024) between the two limbs when using the stimulating FO compared to the flat FO condition. The latency and amplitude scaling during backward translation as well as sway energy during toes down perturbations were lower in females than males with stimulating FO (Latency: MD=-6.62, p = 0.044; Amplitude scaling: MD=-1.75, p = 0.011; Sway energy: MD=-40.08, p = 0.007).

SIGNIFICANCE

These findings highlight the potential of stimulating FO to provide enhanced somatosensory feedback for better postural control and coordination, underscoring their potential clinical application in improving balance and sensory integration.

Comparison of subdermal needle and surface adhesive electrodes for intraoperative neuromonitoring during spine surgeries

BACKGROUND

This study aimed to further compare subdermal needle electrodes (NE) and surface adhesive electrodes (SE) during intraoperative neuromonitoring (IONM) in spine surgeries.

METHODS

We analyzed data from forty consecutive patients undergoing spine surgery. The data mainly included impedance, Root Mean Square (RMS), Tc-MEP and free-run EMG characteristics of NE versus SE with (left foot) and without (right foot) conductive paste (CP) during IONM.

RESULTS

Results indicated that SE with CP exhibited significantly lower impedance than SE without CP and higher impedance than NE. The RMS of free-run EMG recorded by SE were found to be higher than the NE, but no significant differences were found between SE with CP and SE without CP. Furthermore, NE yielded higher MEP amplitudes and superior signal-to-noise ratios (SNR) than SE. The ratios of MEP amplitude and SNR recorded by SE to NE were not significantly different between the left and right foot. The success rate for MEP induction was significantly higher with NE than SE.

CONCLUSION

This research advocates for prioritizing NE in IONM during spine surgeries due to their favorable performance characteristics.

Role of motor unit activity in flexor digitorum brevis to maintain balance during forward leaning

Our purpose was to compare the influence of motor unit activity in Flexor Digitorum Brevis (FDB) and Soleus (SOL) on force fluctuations during three forward-leaning tasks. Ground reaction forces and high-density EMG signals were collected from 19 males when leaning forward at 25%, 50%, and 75% of maximal forward leaning force. EMG amplitude increased with percent of leaning and was greater for SOL than FDB, but there were no differences in force fluctuations across tasks. Differences in motor unit activity indicated that the relative contribution of the two muscles to the control of balance varied across tasks as confirmed by the association between the fluctuations in neural drive [standard deviation of the filtered cumulative spike train (SD of fCST)] and force [coefficient of variation (CoV) for force]. Specifically, the correlation values were greater for FDB at the lower target forces. Correlation analyses revealed that synaptic noise (CoV for interspike interval) was weakly correlated with the CoV for force, whereas the variability in shared synaptic input (SD of fCST) was strongly correlated with the CoV for force. This finding suggests that the relative influence of the two muscles on the fluctuations in force during forward leaning varied with task requirements.

The Effects of Ankle and Foot Exercises on Ankle Strength, Balance, and Falls in Older People: A Systematic Review and Meta-Analysis

OBJECTIVE

Ankle-foot control is essential to maintain balance and gait stability. However, there has been limited evidence on the effect of ankle-foot exercises on balance and falls in older people. This study aimed to summarize the effects of ankle-foot exercises on ankle flexibility and strength, balance, mobility, and falls in older people and to identify determining factors for ankle-foot exercises to improve balance and mobility.

METHODS

Cumulative Index to Nursing and Allied Health Literature, Embase, PubMed, and Physiotherapy Evidence Database (PEDro) were searched to identify randomized controlled trials that studied the effects of ankle-foot exercises on ankle control, balance, and falls in older people. The PEDro scale was used to evaluate the methodological quality of the studies. Meta-analyses were done for similar outcomes. The quality of evidence was rated by GRADE.

RESULTS

Sixteen papers (n = 651) were included. Meta-analyses showed that ankle-foot exercises significantly improved ankle plantarflexion strength (SMD = 0.35, 95% CI = 0.04 to 0.65, low-quality evidence), ankle flexibility (SMD = 0.48, 95% CI = -0.01 to 0.96, low-quality evidence), and balance in an eyes-open condition (SMD = 0.41, 95% CI = 0.19 to 0.70, low-quality evidence). There was no significant change in ankle dorsiflexion strength (SMD = 0.29, 95% CI = -0.24 to 0.82, very low-quality evidence), balance under eyes-closed condition (SMD = 0.41, 95% CI = -0.1 to 0.92, very low-quality evidence), and gait speed (SMD = 0.36, 95% CI = -0.24 to 0.96, very low-quality evidence). Two studies reported insignificant findings on fear of falling, fall incidence, and risk of falls.

CONCLUSIONS

Very low- to low-quality evidence showed that ankle-foot exercises effectively improve ankle plantarflexion strength, flexibility, and balance with eyes open, whereas no effect on falls was found. Improvements in balance and gait tend to be associated with improvements in ankle strength and flexibility. Toe-strengthening exercise and training 3 times per week appear to be important for improving balance.

IMPACT

This review suggested that ankle-foot exercises might improve balance in older people. Determining factors leading to improvement in balance and mobility were identified. It paves the ground for further research to study the effect of ankle-foot exercises on fall prevention.

LAY SUMMARY

Ankle and foot exercises appear to be effective in improving ankle plantarflexion strength, flexibility, and balance performance in an eye-open condition. If you are an older adult who wants to improve your balance, your physical therapist may prescribe ankle and foot exercises as a supplemental component in a fall prevention program due to the observed improvements in balance and the safety and ease of the exercise.

Age-Related Reduction of Foot Intrinsic Muscle Function and the Relationship with Postural Stability in Old Adults

Introduction

The risk of falls among the elderly significantly increases, which has become a serious public health concern. Falls can not only lead to serious complications such as fractures and brain injuries but also limit their mobility function, reducing quality of life. Foot intrinsic muscles (FIMs) are an essential part of foot core stability even overall postural stability. This study aimed to investigate the effects of aging on the function of FIMs and to explore the influence of FIMs on postural control in the elderly.

Materials and Methods

56 healthy old participants (60-75 years) and 57 healthy young participants (18-29 years) joined this study. An ergoFet dynamometer was used to determine foot muscle strength (Doming, T1, T23 and T2345), and ankle muscle strength (plantarflexion and dorsiflexion). The morphology of FIMs and extrinsic foot muscle was determined using a Doppler ultrasound system, whereas the postural stability was assessed through Limits of Stability test. Independent samples t-test was used to determine the differences in strength and morphological parameters and Spearman correlation analysis was used to determine whether an association existed between muscle strength and postural stability parameters in the elderly.

Results

Compared with young adults, foot muscle strength and ankle muscle strength (Doming, T1, T23, T2345, dorsiflexion, and plantarflexion, all p <0.05) and the morphology of foot muscles (all p <0.05) were significantly reduced in the elderly. The strength of FIMs and the limit of stability (r = 0.302-0.424, all p <0.05) were significantly correlated in the elderly.

Conclusion

Compared with young adults, the weakness of strength as well as the morphological decline of the intrinsic and extrinsic foot muscles were found in the elderly. In addition, a correlation was observed between FIM's strength and postural stability in the elderly, suggesting their potential role in posture stability.

Age-Related Dysfunction in Balance: A Comprehensive Review of Causes, Consequences, and Interventions

This review delves into the multifaceted aspects of age-related balance changes, highlighting their prevalence, underlying causes, and the impact they have on the elderly population. Central to this discussion is the exploration of various physiological changes that occur with aging, such as alterations in the vestibular, visual, proprioceptive systems, and musculoskeletal degeneration. We examine the role of neurological disorders, cognitive decline, and medication side effects in exacerbating balance issues. The review underscores the significance of early detection and effective intervention strategies in mitigating the risks associated with balance problems, such as falls and reduced mobility. It discusses the effectiveness of diverse intervention strategies, including exercise programs, rehabilitation techniques, and technological advancements like virtual reality, wearable devices, and telemedicine. Additionally, the review stresses the importance of a holistic approach in managing balance disorders, encompassing medication review, addressing comorbidities, and environmental modifications. The paper also presents future research directions, emphasizing the need for a deeper understanding of the complex mechanisms underlying balance changes with aging and the potential of emerging technologies and interdisciplinary approaches in enhancing assessment and intervention methods. This comprehensive review aims to provide valuable insights for healthcare providers, researchers, and policymakers in developing targeted strategies to improve the quality of life and ensure the well-being of the aging population.