Normal Treadmill Research Articles

Electrocortical theta activity may reflect sensory prediction errors during adaptation to a gradual gait perturbation

Locomotor adaptation to abrupt and gradual perturbations are likely driven by fundamentally different neural processes. The aim of this study was to quantify brain dynamics associated with gait adaptation to a gradually introduced gait perturbation, which typically results in smaller behavioral errors relative to an abrupt perturbation. Loss of balance during standing and walking elicits transient increases in midfrontal theta oscillations that have been shown to scale with perturbation intensity. We hypothesized there would be no significant change in anterior cingulate theta power (4–7 Hz) with respect to pre-adaptation when a gait perturbation is introduced gradually because the gradual perturbation acceleration and stepping kinematic errors are small relative to an abrupt perturbation. Using mobile electroencephalography (EEG), we measured gait-related spectral changes near the anterior cingulate, posterior cingulate, sensorimotor, and posterior parietal cortices as young, neurotypical adults (n = 30) adapted their gait to an incremental split-belt treadmill perturbation. Most cortical clusters we examined (>70%) did not exhibit changes in electrocortical activity between 2–50 Hz. However, we did observe gait-related theta synchronization near the left anterior cingulate cortex during strides with the largest errors, as measured by step length asymmetry. These results suggest gradual adaptation with small gait asymmetry and perturbation magnitude may not require significant cortical resources beyond normal treadmill walking. Nevertheless, the anterior cingulate may remain actively engaged in error monitoring, transmitting sensory prediction error information via theta oscillations.

Differential effects of ankle constraints on foot placement control between normal and split belt treadmills

Mediolateral ankle moment control contributes to gait stability. Ankle moments can be constrained by walking with a shoe with a ridge underneath the sole, narrowing the mediolateral support surface. In our previous study, such ankle moment constraints resulted in an increased step width and a decrease in the degree of foot placement control, as defined by the percentage of variance in foot placement that can be explained by CoM state. However, since our previous study was performed on a split-belt treadmill and the narrow ridge could fit inside the gap between the belts, it is not evident whether these effects can be attributed to the constrained ankle moment control or to avoidance of this gap. Therefore, we investigated if the effects of ankle moment constraints are dependent on whether participants walk on a normal treadmill or a split-belt treadmill. We included fourteen healthy young adults. Walking with constrained ankle moment control resulted in a wider step width on both treadmills. Yet, the increase in step width was larger on the split-belt treadmill compared to on the normal treadmill. We only found a decreased degree of foot placement control on the split-belt treadmill, whilst the degree of foot placement control increased on the normal treadmill. We conclude that the effects of ankle moment constraints reported in our previous study were confounded by the use of a split-belt treadmill. For future research, we recommend using a normal treadmill whenever possible, because the gap in a split-belt treadmill might affect gait parameters.

Spine and lower body symmetry during treadmill walking in healthy individuals-In-vivo 3-dimensional kinematic analysis.

Although it is relevant to understand spine and lower body motions in healthy individuals for a variety of applications, such as clinical diagnosis, implant design, and the analysis of treatment outcomes, proper assessment and characterization of normative gait symmetry in healthy individuals remains unclear. The purpose of this study was to investigate the in vivo 3-dimensional (3D) spine and lower body gait symmetry kinematics during treadmill walking in healthy individuals. Sixty healthy young adults (30 males and 30 females) were evaluated during normal and fast treadmill walking using a motion capture system approach. Statistical parametric mapping and the normalized symmetry index approaches were used to determine spine, pelvis, and lower body asymmetries during treadmill walking. The spine and pelvis angular motions associated with the left and right lower limb motions, as well as the left and right lower extremity joint angles were compared for normal and fast treadmill walking. The lower lumbar left-right rotation (5.74±0.04°) and hip internal rotation (5.33±0.18°) presented the largest degrees of asymmetry during normal treadmill. Upper lumbar left-right lateral flexion (1.48±0.14°) and knee flexion (2.98±0.13°) indicated the largest asymmetries and during fast treadmill walking. Few asymmetry patterns were similar between normal and fast treadmill walking, whereas others appeared either only during normal or fast treadmill walking in this cohort of participants. These findings could provide insights into better understanding gait asymmetry in healthy individuals, and use them as reference indicators in diagnosing and evaluating abnormal gait function.

Intramuscular coherence during challenging walking in incomplete spinal cord injury: Reduced high-frequency coherence reflects impaired supra-spinal control

Individuals regaining reliable day-to-day walking function after incomplete spinal cord injury (iSCI) report persisting unsteadiness when confronted with walking challenges. However, quantifiable measures of walking capacity lack the sensitivity to reveal underlying impairments of supra-spinal locomotor control. This study investigates the relationship between intramuscular coherence and corticospinal dynamic balance control during a visually guided Target walking treadmill task. In thirteen individuals with iSCI and 24 controls, intramuscular coherence and cumulant densities were estimated from pairs of Tibialis anterior surface EMG recordings during normal treadmill walking and a Target walking task. The approximate center of mass was calculated from pelvis markers. Spearman rank correlations were performed to evaluate the relationship between intramuscular coherence, clinical parameters, and center of mass parameters. In controls, we found that the Target walking task results in increased high-frequency (21–44 Hz) intramuscular coherence, which negatively related to changes in the center of mass movement, whereas this modulation was largely reduced in individuals with iSCI. The impaired modulation of high-frequency intramuscular coherence during the Target walking task correlated with neurophysiological and functional readouts, such as motor-evoked potential amplitude and outdoor mobility score, as well as center of mass trajectory length. The Target walking effect, the difference between Target and Normal walking intramuscular coherence, was significantly higher in controls than in individuals with iSCI [F(1.0,35.0) = 13.042, p < 0.001]. Intramuscular coherence obtained during challenging walking in individuals with iSCI may provide information on corticospinal gait control. The relationships between biomechanics, clinical scores, and neurophysiology suggest that intramuscular coherence assessed during challenging tasks may be meaningful for understanding impaired supra-spinal control in individuals with iSCI.

Mind your step: Target walking task reveals gait disturbance in individuals with incomplete spinal cord injury

BackgroundWalking over obstacles requires precise foot placement while maintaining balance control of the center of mass (CoM) and the flexibility to adapt the gait patterns. Most individuals with incomplete spinal cord injury (iSCI) are capable of overground walking on level ground; however, gait stability and adaptation may be compromised. CoM control was investigated during a challenging target walking (TW) task in individuals with iSCI compared to healthy controls. The hypothesis was that individuals with iSCI, when challenged with TW, show a lack of gait pattern adaptability which is reflected by an impaired adaptation of CoM movement compared to healthy controls.MethodsA single-center controlled diagnostic clinical trial with thirteen participants with iSCI (0.3–24 years post injury; one subacute and twelve chronic) and twelve healthy controls was conducted where foot and pelvis kinematics were acquired during two conditions: normal treadmill walking (NW) and visually guided target walking (TW) with handrail support, during which participants stepped onto projected virtual targets synchronized with the moving treadmill surface. Approximated CoM was calculated from pelvis markers and used to calculate CoM trajectory length and mean CoM Euclidean distance TW-NW (primary outcome). Nonparametric statistics, including spearman rank correlations, were performed to evaluate the relationship between clinical parameter, outdoor mobility score, performance, and CoM parameters (secondary outcome).ResultsHealthy controls adapted to TW by decreasing anterior–posterior and vertical CoM trajectory length (p < 0.001), whereas participants with iSCI reduced CoM trajectory length only in the vertical direction (p = 0.002). Mean CoM Euclidean distance TW-NW correlated with participants’ neurological level of injury (R = 0.76, p = 0.002) and CoM trajectory length (during TW) correlated with outdoor mobility score (R = − 0.64, p = 0.026).ConclusionsThis study demonstrated that reduction of CoM movement is a common strategy to cope with TW challenge in controls, but it is impaired in individuals with iSCI. In the iSCI group, the ability to cope with gait challenges worsened the more rostral the level of injury. Thus, the TW task could be used as a gait challenge paradigm in ambulatory iSCI individuals.Trial registration Registry number/ ClinicalTrials.gov Identifier: NCT03343132, date of registration 2017/11/17.

The Accuracy and Precision of Gait Spatio-Temporal Parameters Extracted from an Instrumented Sock during Treadmill and Overground Walking in Healthy Subjects and Patients with a Foot Impairment Secondary to Psoriatic Arthritis.

The objectives of this study were to assess the accuracy and precision of a system combining an IMU-instrumented sock and a validated algorithm for the estimation of the spatio-temporal parameters of gait. A total of 25 healthy participants (HP) and 21 patients with foot impairments secondary to psoriatic arthritis (PsA) performed treadmill walking at three different speeds and overground walking at a comfortable speed. HP performed the assessment over two sessions. The proposed system’s estimations of cadence (CAD), gait cycle duration (GCD), gait speed (GS), and stride length (SL) obtained for treadmill walking were validated versus those estimated with a motion capture system. The system was also compared with a well-established multi-IMU-based system for treadmill and overground walking. The results showed a good agreement between the motion capture system and the IMU-instrumented sock in estimating the spatio-temporal parameters during the treadmill walking at normal and fast speeds for both HP and PsA participants. The accuracy of GS and SL obtained from the IMU-instrumented sock was better compared to the established multi-IMU-based system in both groups. The precision (inter-session reliability) of the gait parameter estimations obtained from the IMU-instrumented sock was good to excellent for overground walking and treadmill walking at fast speeds, but moderate-to-good for slow and normal treadmill walking. The proposed IMU-instrumented sock offers a novel form factor addressing the wearability issues of IMUs and could potentially be used to measure spatio-temporal parameters under clinical conditions and free-living conditions.

Contributions of spatial and temporal control of step length symmetry in the transfer of locomotor adaptation from a motorized to a non-motorized split-belt treadmill.

Walking requires control of where and when to step for stable interlimb coordination. Motorized split-belt treadmills which constrain each leg to move at different speeds lead to adaptive changes to limb coordination that result in after-effects (e.g. gait asymmetry) on return to normal treadmill walking. These after-effects indicate an underlying neural adaptation. Here, we assessed the transfer of motorized split-belt treadmill adaptations with a custom non-motorized split-belt treadmill where each belt can be self-propelled at different speeds. Transfer was indicated by the presence of after-effects in step length, foot placement and step timing differences. Ten healthy participants adapted on a motorized split-belt treadmill (2 : 1 speed ratio) and were then assessed for after-effects during subsequent non-motorized treadmill and motorized tied-belt treadmill walking. We found that after-effects in step length difference during transfer to non-motorized split-belt walking were primarily associated with step time differences. Conversely, residual after-effects during motorized tied-belt walking following transfer were associated with foot placement differences. Our data demonstrate decoupling of adapted spatial and temporal locomotor control during transfer to a novel context, suggesting that foot placement and step timing control can be independently modulated during walking.

Effects of an Exercise Therapy Targeting Knee Kinetics on Pain, Function, and Gait Kinetics in Patients With Knee Osteoarthritis: A Randomized Clinical Trial.

In this study, the effects of an exercise therapy comprising yoga exercises and medial-thrust gait (YogaMT) on lower-extremity kinetics, pain, and function in patients with medial knee osteoarthritis were investigated. Fifty-nine patients were randomly allocated to three treatment groups: (a)the YogaMT group practiced yoga exercises and medial thrust gait, (b)the knee-strengthening group performed quadriceps- and hamstring-strengthening exercises, and (c)the treadmill walking group practiced normal treadmill walking in 12 supervised sessions. The adduction and flexion moments of the hip, knee, and ankle; pain intensity; and 2-min walking test were assessed before and after treatment and at 1-month follow-up. The YogaMT group experienced a significant reduction in knee adduction moment. All groups showed significant improvement in pain and function. The YogaMT may reduce medial knee load in patients with knee osteoarthritis in the short term. A larger clinical trial is required to investigate the long-term outcomes of this intervention.

Bifurcation Stenting Using Bioresorbable Vascular Scaffold in an Adult Male With Radiation-Induced Coronary Artery Disease and Hodgkin Lymphoma: A Case Report

INTRODUCTION: Radiation-induced coronary artery disease is associated with absolute risk between 0.1% and 0.5% per year after mediastinal radiotherapy of Hodgkin disease. Risk increases with time and becomes statistically significant after 10 years. This often involves the left anterior descending (LAD) and right coronary arteries with proximal arterial narrowing involving the coronary ostia. This is the first documented case of radiation-induced coronary artery disease in a 25-year-old Filipino man diagnosed with nodular sclerosing-type Hodgkin lymphoma stage IIA treated with percutaneous revascularization using bioresorbable vascular scaffolds in a bifurcation type of lesion admitted at St Luke’s Medical Center for chest pain. Patient reported progressive worsening of exertional angina 16 months after chemotherapy and external beam radiation therapy in the neck and mediastinum. Treadmill exercise test revealed inducible ischemia in the inferior leads at stage 3, 7 metabolic equivalents. Coronary angiogram showed severe stenosis involving the midsegment of the proximal LAD artery and the ostial-to-proximal segment of the first diagonal branch, a bifurcation lesion, Medina 1,1,1. A percutaneous coronary intervention was successfully done using two bioresorbable vascular scaffolds via T-and-protrude bifurcation stenting technique and achieves a brisk TIMI (Thrombolysis In Myocardial Infarction) 3 flow. Follow-up after 6 months showed a normal treadmill exercise test. However, patient still complains of occasional chest pain and epigastric discomfort. Coronary angiogram was repeated demonstrating an 80% stenosis in the proximal LAD without evidence of in-stent stenosis. This was confirmed by optical coherence tomography with adequate stent apposition to the intima with a note of a large chronic red thrombus proximal to the previously deployed stent; thus, percutaneous coronary intervention using drug-eluting stent was performed. KEYWORDS: radiation-induced coronary artery disease, Hodgkin lymphoma, bifurcation stenting, bioresorbable vascular scaffold, optical coherence tomography

The Effects Of Acute Antigravity Treadmill Exercise On Inflammatory Markers In Elite Athletes

PURPOSE: The aim of this study was to compare the responses of interleukin-8 (IL-8), tumor necrosis factor-α (TNF-α) and C reactive protein (CRP) to antigravity treadmill exercise and normal treadmill exercise in male football players. METHODS: Eleven male football players aged between 18- 22 years, with at least 2 years of football history and regularly trained were included in the study. VO2max values of the athletes were calculated with 20 Meter Shuttle Test. The participants were randomly allocated to two groups. Half of the participants were exercised on the antigravity treadmill and half of them were exercised on the normal treadmill for 45 minutes on % 70 of VO2max values. After a week participants were exercised vice versa. IL-8, TNF-α and CRP levels were analyzed before, immediately after, 30 minutes and 2 hours after the exercises. RESULTS: CRP levels did not change with time in the antigravity and normal treadmill exercise and it was not different between the both groups (P > 0.05). TNF-α levels were lower 30 minutes after the exercise than the immediately after the exercise in the normal treadmill exercise (P < 0.05). However, it did not change with time in the antigravity treadmill exercise and was not different between the both groups (P > 0.05). IL-8 levels were higher 2 hours after the exercise than the before and immediately after the exercise in the antigravity treadmill exercise (P < 0.05). However, it did not change with time in the normal treadmill exercise and was not different between the both groups (P > 0.05). CONCLUSIONS: Antigravity treadmill exercise differently affects inflammatory processes than the normal treadmill exercise.

Stable Body Temperature in Trained Runners Despite Localized Heating within Alter GTM Treadmill

Lower body positive pressure treadmills (LBPPT) are beneficial for rehabilitation and exercise training. Running on a LBPP treadmill (AlterGTM) involves sealing the lower half of the body in a high air pressure flexible sealed chamber to simulate exercise at lower body weight. The effects of the sealed chamber on treadmill and tympanic temperature during exercise have yet to be investigated. The purpose of the study was to measure treadmill and tympanic temperatures while participants were running on a normal treadmill and compare temperatures to running on a LBPP treadmill. Fifteen well-trained runners completed three running trials on a LBPP treadmill at 60, 75, and 85% of body weight (BW). A 100% BW trial was run on a normal treadmill. Participants ran at three steady state speeds (2.9, 3.4, and 3.8 m·s-1) for four minutes each. Room air, tympanic, and LBPPT chamber temperatures (°C) were recorded. The main finding was that treadmill temperature was significantly greater among the three BW conditions on the LBPPT compared to normal treadmill (average of all LBPPT, 30.7 ± 2.3°C, normal treadmill, 22.5 ± 2.1°C). Tympanic temperatures were not different between all BW conditions. Runners may use LBPPT for rehabilitation or low-impact training yet should be aware of the increase in LBPP chamber temperature.

Is Heart Rate Recovery Really Associated with Severity of Coronary Artery Disease in Patients with Normal Exercise Treadmill Test?

Background and Objectives: Rapid diagnosis and treatment of cardiovascular diseases is really helpful in reducing further complications. There are different modalities for this goal but each has benefits and limitations. Exercise Treadmill Test (ETT) is a non-invasive, cheap and accessible test. Coronary CT Angiography (CTA) is recently considered as an applied modality for assessing severity of Coronary Artery Disease (CAD). In this study we aimed to investigate possible association between Heart Rate Recovery (HRR) in ETT and severity of CAD in CTA.

P1497Reversible exercise-induced left ventricular dysfunction in symptomatic patients with previous Takotsubo syndrome - Insights from exercise echocardiography

Abstract Introduction Takotsubo syndrome (TTS) is an acute heart failure syndrome usually associated with rapid and spontaneous recovery of left ventricular (LV) function. However, approximately 10% of patients have persistent symptoms and seek further medical advice. Purpose To determine the cardiovascular haemodynamic and LV contractile response to exercise in these TTS survivors with ongoing symptoms. Methods This was a case-control study of 20 symptomatic patients with previous TTS referred for treadmill exercise echocardiography (EE), and 20 age-, sex- and ethnicity-matched control subjects with normal treadmill EE. Among the TTS group, EE was performed at a median of 8 months (mean 17±21 months) following the index event. Demographic characteristics, resting and EE data were collected. LV ejection fraction (EF) was measured at rest and peak stress. Global longitudinal and circumferential strain (GLS, GCS) were measured at rest. Results All 20 TTS patients were Caucasian postmenopausal females (mean age 63.5±6.6 years). There were no significant differences in body mass index (BMI), resting heart rate (HR) and the prevalence of cardiovascular risk factors compared to controls. Resting systolic and diastolic blood pressure (SBP, DBP) were higher in TTS patients (144±17 mmHg versus 128±18 mmHg, and 81±10 mmHg versus 74±9 mmHg, respectively). A comparative analysis of the resting and stress echo data is given in Table 1. The stress echo data showed similar exercise time and peak HR, but higher peak SBP in TTS patients. TTS patients had blunted contractile response to exercise with lower peak LVEF, ΔLVEF (exercise minus resting EF) and peak wall motion score index (WMSI) compared to controls. Among the 20 TTS patients, 12 had exercise-induced wall motion abnormalities: 6 involved the apical segments and 6 developed global dysfunction. In these 12 patients, the mean ΔLVEF was reduced (4%). In the other 8 patients, the ΔLVEF was 16% and pooled the TTS cohort had blunted contractile response with exercise compared to controls (ΔLVEF 8% vs. 19% in the control group, p=0.001). Table 1 Conclusions Our study shows that symptomatic patients with previous TTS have a blunted contractile response to exercise manifest as reversible apical or global LV dysfunction. These findings might indicate the need for treatment. Further systematic investigation of the therapeutic and prognostic implications of this reversible exercise-induced myocardial dysfunction is needed.

Prevalence of complete and incomplete right bundle branch block in young athletes: A local study

Sparse data exists to characterize the disease prevalence in athletic patients with complete and incomplete right bundle branch block: (CRBBB) and (IRBBB) respectively. We sought to determine this prevalence in a local sport medical centre. We analysed ECG of athletes on-going a routine and mandatory medical examination in our local sport medical centre. All participants had 2 months of regular activity for at least 4 hours a week (h/w) prior to inclusion. Median follow-up period was 18 months. Five hundred and forty-eight athletes were enrolled in the study. History, physical examination and a 12 lead standard ECG was performed for all the participants. Demographic and baseline information for the study participants are exposed in Table 1. BBBD pattern was found in 77 (14%) participants, only one had CRBBB. IRBBB prevalence was 13.86% and CRBBB 0.1%. The athlete with CRBBB had not associated electrocardiographic anomalies suggesting Brugada syndrome or arrythmogenic right ventricle cardiomyopathy. He had a normal Treadmill stress test. His echocardiogram showed mild right ventricle dilatation and was allowed to continue his activity. No events were noticed in this population subset. RBBB is not rare in athlete's community. IRBBB is more common and considered benign. CRBBB is more rare and needs further work-up.

Stable Detection of Movement Intent From Peripheral Nerves: Chronic Study in Dogs

Peripheral nerves provide access to highly processed and segregated neural command signals from the brain that control skeletal muscles. Detecting these signals could provide lifelike, intuitive control of high-degree-of-freedom prosthetic limbs. However, detection of individual fascicle neural activity within a nerve has not yet been accomplished without compromising the nerve. The purpose of this study was to detect fascicular-level neural activity in freely moving animals with nonpenetrating nerve cuff electrodes. Three dogs were implanted with 16-contact flat interface nerve electrodes (FINEs) on the sciatic nerve with total duration of the implant ranging from four to nine months with functional recordings lasting 2.2–7.5 months. The recorded neural activity during normal treadmill walking was used to localize fascicular sources within the nerve and their recovered activity was compared with the ankle movements using binary classification against gait phase. The signal-to-noise ratio (SNR) of the neural signals obtained from the FINE was between 3.65 and 7.59 dB. Postmortem analysis showed that the focal points of the recovered fascicular activity were located within 0.75 $\pm$ 0.38 mm from the nearest major fascicles. The two movement intents recovered from each fascicle matched the actual observed ankle movements with overall accuracy of 70%–80% and false crosstalk rate of < 10%. The significant outcome of this study is detecting multiple voluntary fascicular activities with consistent accuracy over time from freely moving animals. It demonstrates the potential of using the FINE in the designs of intuitively controlled advanced prostheses and ultimately improving patient’s quality of life.

Metabolic Cost and Fuel Utilization of Normal and Lower Body Positive Pressure Treadmill Running

Lower body positive pressure (LBPP) treadmill walking and running are being used more frequently in clinical and athletic settings. Accurate exercise intensity and knowledge of fuel utilization is a needed for proper exercise prescription especially for obese patients that may benefit from LBPP exercise. It is unclear if current ACSM metabolic equations are suitable for LBPP running. There are currently no accepted calculations to estimate caloric cost or exercise intensity for LBPP running. PURPOSE: To measure oxygen uptake and caloric expenditure of treadmill running at normal body weight and LBPP. METHODS: Thirteen physically active non-obese participants completed four bouts of running exercise in a counterbalanced manner: (a) running on a normal (100% body weight, BW) treadmill (TM) and (b) running on a LBPP treadmill at 40, 60, and 85% of BW for 4 min intervals. Oxygen consumption was measured using open flow indirect calorimetry (Medgraphics Ultima) and last minute averages were defined as steady state. RESULTS: Volunteers’ average (±SD) absolute VO2 at a treadmill speed of 3.13 m·s-1 was 1528.38±308.38,1762.00±341.57, 2037.07±337.47, and 2453.23±406.49 ml·min-1 for 40, 60, 85, and 100% body weight. Respiratory exchange ratio (RER) at a treadmill speed of 3.13 m·s-1 was 0.91±0.05, 0.93±0.08, 0.98±0.05, and 1.02±0.07 for all four weighted conditions (40, 60, 85, and 100% BW, respectively). Average caloric expenditure was 7.55±1.51, 8.74±1.74, 9.51±1.72, and 12.43±2.01 kcal·min-1 for 40, 60, 85, and 100% BW, respectively. CONCLUSION: As expected, treadmill running in LBPP resulted in significantly lower oxygen consumption and caloric expenditure at all three reduced weight conditions compared to 100% BW. One-way repeated measures ANOVAs indicated statistically significant differences in VO2 across all four BW conditions F(3,36) = 64.636, p < 0.05, partial η2 = 0.843, and in caloric expenditure F(3,36) = 81.460, p < 0.05, partial η2 = 0.872. The percent difference in VO2 from TM and LBPP conditions (85, 60, and 40% of BW) was only ~15, 30, and 40%. We conclude that metabolic cost of LBPP running is significantly less than normal treadmill running, yet the decrease in VO2 and caloric expenditure is not as great as predicted by the change in body mass.

Cardiovascular Response of Running on a Normal and Lower Body Positive Pressure Treadmill

Cardiovascular Response of Running on a Normal and Lower Body Positive Pressure Treadmill

Gait speed influences aftereffect size following locomotor adaptation, but only in certain environments.

Movements learned in one set of conditions may not generalize to other conditions. For example, practicing walking on a split-belt treadmill subsequently changes coordination between the legs during normal ("tied-belt") treadmill walking; however, there is limited generalization of these aftereffects to natural walking over the ground. We hypothesized that generalization of split-belt treadmill adaptation to over-ground walking would be improved by maintaining consistency in other task variables, specifically gait speed. This hypothesis was based on our previous finding that treadmill aftereffect size was sensitive to gait speed: Aftereffects were largest when tested on tied-belts running at the same speed as the slower belt during split-belt adaptation. In the present study, healthy adults were assigned to a "slow" or "fast" over-ground walking group. Both groups adapted to split-belts (0.7:1.4m/s), and treadmill aftereffects were tested on tied-belts at the slow (0.7m/s) and fast (1.4m/s) speeds. All participants were subsequently transferred to the over-ground environment. The slow and fast groups walked over-ground at 0.7 and 1.4m/s, respectively. As in previous work, we found that the size of aftereffects during treadmill walking was speed-dependent, with larger aftereffects occurring at 0.7m/s compared with 1.4m/s. However, over-ground walking aftereffects were less sensitive to changes in gait speed. We also found that aftereffects in spatial coordination generalized more to over-ground walking than aftereffects in temporal coordination across all speeds of walking. This suggests that different factors influence aftereffect size in different walking environments and for different measures of coordination.

Increased T-wave alternans is associated with subclinical myocardial structural and functional abnormalities in patients with type 2 diabetes

BackgroundIncreased T wave alternans (TWA) represents ventricular depolarization heterogeneity and is a non-invasive marker of sudden cardiac death. This study sought to determine whether myocardial structural alteration and dysfunction in patients with type 2 diabetes mellitus (T2DM) is associated with an increased TWA. MethodsWe recruited 108 T2DM patients (59.2±9.7 years and 52% male) without prior history of cardiovascular disease and normal treadmill stress testing. TWA was analyzed during treadmill testing in all standard precordial leads by time-domain method. Transthoracic echocardiography was performed to measure myocardial structural alteration by calibrated integrated backscatter (IBS), left ventricular (LV) systolic function by conventional method, and speckle tracking-derived global longitudinal strain (GLS), and LV diastolic function. ResultsA total of 29 (26.9%) patients had a high TWA of ≥47mV (defined by ≥75 percentile of the study population). Patients with and without elevated TWA had a similar LV dimension and ejection fraction. Nonetheless, patients with high TWA had a higher calibrated IBS (−15.8±4.0dB vs. −17.9±5.3dB, p=0.04), more impaired GLS (−18.4±2.0% vs. −19.3±1.4%, p=0.02), and a higher prevalence of diastolic dysfunction (60 vs. 33%, p=0.02). Multivariable analysis demonstrated that high TWA was independently associated with calibrated IBS, GLS, and LV diastolic dysfunction grading. ConclusionsOur results demonstrated that calibrated IBS, GLS, and LV diastolic dysfunction are independent predictors for high TWA in T2DM patients. These findings suggest that subclinical myocardial structural and functional abnormalities may contribute to high TWA in T2DM patients.

Surface effects on in-shoe plantar pressure and tibial impact during running

PurposeThis study aims to explore the effects of running on different surfaces on the characteristics of in-shoe plantar pressure and tibial acceleration. MethodsThirteen male recreational runners were required to run at 12 km/h velocity on concrete, synthetic track, natural grass, a normal treadmill, and a treadmill equipped with an ethylene vinyl acetate (EVA) cushioning underlay (treadmill_EVA), respectively. An in-shoe plantar pressure system and an accelerometer attached to the tibial tuberosity were used to record and analyze the characteristics of plantar pressure and tibial impact during running. ResultsThe results showed that there were no significant differences in the 1st and 2nd peak plantar pressures (time of occurrence), pressure–time integral, and peak pressure distribution for the concrete, synthetic, grass, and normal treadmill surfaces. No significant differences in peak positive acceleration were observed among the five tested surface conditions. Compared to the concrete surface, however, running on treadmill_EVA showed a significant decrease in the 1st peak plantar pressure and the pressure–time integral for the impact phase (p < 0.05). These can be further ascribed to a reduced peak pressure observed at heel region (p < 0.05). ConclusionThere may not be an inevitable relationship between the surface and the lower-limb impact in runners. It is, however, still noteworthy that the effects of different treadmill surfaces should be considered in the interpretation of plantar pressure performance and translation of such results to overground running.