Effect of Treadmill Perturbation-Based Balance Training on Fall Rates in Community-Dwelling Older Adults: A Randomized Clinical Trial.

Importance: Falls are common and the leading cause of injuries among older adults, but falls may be attenuated by the promising and time-efficient intervention called perturbation-based balance training (PBT). Objective: To evaluate the effects of a 4-session treadmill PBT intervention compared with regular treadmill walking on daily-life fall rates among community-dwelling older adults. Design, Setting, and Participants: This 12-month, assessor-blinded randomized clinical trial was conducted from March 2021 through December 2022 in Aalborg University in Denmark. Participants were community-dwelling adults 65 years or older and were able to walk without a walking aid. Participants were randomized to either PBT (intervention group) or treadmill walking (control group). Data analyses were based on the intention-to-treat principle. Interventions: Participants who were randomized to the intervention group underwent four 20-minute sessions of PBT, including 40 slip, trip, or mixed slip and trip perturbations. Participants who were randomized to the control group performed four 20-minute sessions of treadmill walking at their preferred speed. The 3 initial training sessions were completed within the first week, whereas the fourth session was performed after 6 months. Main Outcomes and Measures: Primary outcome was the daily-life fall rates that were collected from fall calendars for the 12 months after the third training session. Secondary outcomes were the proportion of participants with at least 1 fall and recurrent falls, time to first fall, fall-related fractures, fall-related injuries, fall-related health care contacts, and daily-life slip and trip falls. Results: A total of 140 highly functioning, community-dwelling older adults (mean [SD] age, 72 [5] years; 79 females [56%]), 57 (41%) of whom had a fall in the past 12 months, were included in this trial. Perturbation training had no significant effect on daily-life fall rate (incidence rate ratio [IRR]: 0.78; 95% CI, 0.48-1.27) or other fall-related metrics. However, there was a significant reduction in laboratory fall rates at the posttraining assessment (IRR, 0.20; 95% CI, 0.10-0.41), 6-month follow-up (IRR, 0.47; 95% CI, 0.26-0.86), and 12-month follow-up (IRR, 0.37; 95% CI, 0.19-0.72). Conclusions and Relevance: Results of this trial showed that participants who received an 80-minute PBT intervention experienced a statistically nonsignificant 22% reduction in daily-life fall rates. There was no significant effect on other daily-life fall-related metrics; however, a statistically significant decrease in falls was found in the laboratory setting. Trial Registration: ClinicalTrials.gov Identifier: NCT04733222.

Effects of treadmill slip and trip perturbation-based balance training on falls in community-dwelling older adults (STABILITY): study protocol for a randomised controlled trial.

INTRODUCTION: Falls among older adults are most frequently caused by slips and trips and can have devastating consequences. Perturbation-based balance training (PBT) have recently shown promising fall preventive effects after even small training dosages. However, the fall preventive effects of PBT delivered on a treadmill are still unknown. Therefore, this parallel-group randomised controlled trial aims to quantify the effects of a four-session treadmill-PBT training intervention on falls compared with treadmill walking among community-dwelling older adults aged 65 years or more. METHODS AND ANALYSIS: 140 community-dwelling older adults will be recruited and randomised into either the treadmill-PBT or the treadmill walking group. Each group will undergo three initial training sessions within a week and an additional 'booster' session after 26 weeks. Participants in the treadmill-PBT group will receive 40 slip and/or trip perturbations induced by accurately timed treadmill belt accelerations at each training session. The primary outcome of interest is daily life fall rates collected using fall calendars for a follow-up period of 52 weeks. Secondary outcomes include physical, cognitive and social-psychological fall-related risk factors and will be collected at the pre-training and post-training test and the 26-week and 52-week follow-up tests. All outcomes will be analysed using the intention-to-treat approach by an external statistician. A Poisson's regressions with bootstrapping, to account for overdispersion, will be used to compare group differences in fall rates. ETHICS AND DISSEMINATION: The study protocol has been approved by the North Denmark Region Committee on Health Research Ethics (N-20200089). The results will be disseminated in peer-reviewed journals and at international conferences. TRIAL REGISTRATION NUMBER: NCT04733222.

Effect of Modulated TENS on Corticospinal Excitability in Healthy Subjects.

Conventional transcutaneous electrical nerve stimulation (TENS) has been reported to effectively alleviate chronic pain, including phantom limb pain (PLP). Recently, literature has focused on modulated TENS patterns, such as pulse width modulation (PWM) and burst modulation (BM), as alternatives to conventional, non-modulated (NM) sensory neurostimulation to increase the efficiency of rehabilitation. However, there is still limited knowledge of how these modulated TENS patterns affect corticospinal (CS) and motor cortex activity. Therefore, our aim was to first investigate the effect of modulated TENS patterns on CS activity and corticomotor map in healthy subjects. Motor evoked potentials (MEP) elicited by transcranial magnetic stimulation (TMS) were recorded from three muscles before and after the application of TENS interventions. Four different TENS patterns (PWM, BM, NM 40 Hz, and NM 100 Hz) were applied. The results revealed significant facilitation of CS excitability following the PWM intervention. We also found an increase in the volume of the motor cortical map following the application of the PWM and NM (40 Hz). Although PLP alleviation has been reported to be associated with an enhancement of corticospinal excitability, the efficiency of the PWM intervention to induce pain alleviation should be validated in a future clinical study in amputees with PLP.

Short-interval intracortical inhibition and facilitation targeting upper and lower limb muscles.

Transcranial magnetic stimulation (TMS) can be used to study excitability of corticospinal neurons in human motor cortex. It is currently not fully elucidated if corticospinal neurons in the hand vs. leg representation show the same or different regulation of their excitability by GABAAergic and glutamatergic interneuronal circuitry. Using a paired-pulse TMS protocol we tested short-interval intracortical inhibition (SICI) and short-interval intracortical facilitation (SICF) in 18 healthy participants. Motor evoked potentials were evoked in one hand (abductor digiti minimi) and one leg muscle (tibialis anterior), with systematic variation of the intensities of the first (S1) and second (S2) pulse between 60 and 140% resting motor threshold (RMT) in 10% steps, at two interstimulus intervals of 1.5 and 2.1 ms. For the hand and leg motor representations and for both interstimulus intervals, SICI occurred if the intensities of S1 < RMT and S2 > RMT, while SICF predominated if S1 = S2 ≤ RMT, or S1 > RMT and S2 < RMT. Findings confirm and extend previous evidence that the regulation of excitability of corticospinal neurons of the hand versus leg representation in human primary cortex through GABAAergic and glutamatergic interneuronal circuits is highly similar, and that corticospinal neurons of both representations are activated by TMS transsynaptically in largely identical ways.

Decrease in force steadiness with aging is associated with increased power of the common but not independent input to motor neurons.

Declines in motor function with advancing age have been attributed to changes occurring at all levels of the neuromuscular system. However, the impact of aging on the control of muscle force by spinal motor neurons is not yet understood. In this study on 20 individuals aged between 24 and 75 yr (13 men, 7 women), we investigated the common synaptic input to motor neurons of the tibialis anterior muscle and its impact on force control. Motor unit discharge times were identified from high-density surface EMG recordings during isometric contractions at forces of 20% of maximal voluntary effort. Coherence analysis between motor unit spike trains was used to characterize the input to motor neurons. The decrease in force steadiness with age ( R2 = 0.6, P < 0.01) was associated with an increase in the amplitude of low-frequency oscillations of functional common synaptic input to motor neurons ( R2 = 0.59; P < 0.01). The relative proportion of common input to independent noise at low frequencies increased with variability (power) in common synaptic input. Moreover, variability in interspike interval did not change and strength of the common input in the gamma band decreased with age ( R2 = 0.22; P < 0.01). The findings indicate that age-related reduction in the accuracy of force control is associated with increased common fluctuations to motor neurons at low frequencies and not with an increase in independent synaptic input. NEW & NOTEWORTHY The influence of aging on the role of spinal motor neurons in accurate force control is not yet understood. We demonstrate that aging is associated with increased oscillations in common input to motor neurons at low frequencies and with a decrease in the relative strength of gamma oscillations. These results demonstrate that the synaptic inputs to motor neurons change across the life span and contribute to a decline in force control.

Efficient neuroplasticity induction in chronic stroke patients by an associative brain-computer interface.

Brain-computer interfaces (BCIs) have the potential to improve functionality in chronic stoke patients when applied over a large number of sessions. Here we evaluated the effect and the underlying mechanisms of three BCI training sessions in a double-blind sham-controlled design. The applied BCI is based on Hebbian principles of associativity that hypothesize that neural assemblies activated in a correlated manner will strengthen synaptic connections. Twenty-two chronic stroke patients were divided into two training groups. Movement-related cortical potentials (MRCPs) were detected by electroencephalography during repetitions of foot dorsiflexion. Detection triggered a single electrical stimulation of the common peroneal nerve timed so that the resulting afferent volley arrived at the peak negative phase of the MRCP (BCIassociative group) or randomly (BCInonassociative group). Fugl-Meyer motor assessment (FM), 10-m walking speed, foot and hand tapping frequency, diffusion tensor imaging (DTI) data, and the excitability of the corticospinal tract to the target muscle [tibialis anterior (TA)] were quantified. The TA motor evoked potential (MEP) increased significantly after the BCIassociative intervention, but not for the BCInonassociative group. FM scores (0.8 ± 0.46 point difference, P = 0.01), foot (but not finger) tapping frequency, and 10-m walking speed improved significantly for the BCIassociative group, indicating clinically relevant improvements. Corticospinal tract integrity on DTI did not correlate with clinical or physiological changes. For the BCI as applied here, the precise coupling between the brain command and the afferent signal was imperative for the behavioral, clinical, and neurophysiological changes reported. This association may become the driving principle for the design of BCI rehabilitation in the future. Indeed, no available BCIs can match this degree of functional improvement with such a short intervention.