Cardiorespiratory Responses to 10 Weeks of Exoskeleton-Assisted Overground Walking Training inChronic Nonambulatory Patients with Spinal Cord Injury

Exercise intensity of exoskeleton-assisted walking in patients with spinal cord injury (SCI) has been reported as moderate. However, the cardiorespiratory responses to long-term exoskeleton-assisted walking have not been sufficiently investigated. We investigated the cardiorespiratory responses to 10 weeks of exoskeleton-assisted walking training in patients with SCI. Chronic nonambulatory patients with SCI were recruited from an outpatient clinic. Walking training with an exoskeleton was conducted three times per week for 10 weeks. Oxygen consumption and heart rate (HR) were measured during a 6-min walking test at pre-, mid-, and post-training. Exercise intensity was determined according to the metabolic equivalent of tasks (METs) for SCI and HR relative to the HR reserve (%HRR). Walking efficiency was calculated as oxygen consumption divided by walking speed. The exercise intensity according to the METs (both peak and average) corresponded to moderate physical activity and did not change after training. The %HRR demonstrated a moderate (peak %HRR) and light (average %HRR) exercise intensity level, and the average %HRR significantly decreased at post-training compared with mid-training (31.6 ± 8.9% to 24.3 ± 7.3%, p = 0.013). Walking efficiency progressively improved after training. Walking with an exoskeleton for 10 weeks may affect the cardiorespiratory system in chronic patients with SCI.

Intensive Rehabilitation Program in Arterial Occlusive Disease Patients

Peripheral arterial occlusive disease (PAOD) limits walking efficiency and distance. The main disabling symptom is vasculopathy that leads to claudicatio intermittens and limits walking efficiency. Stretching techniques are effective in treatments for retractions and are used to improve flexibility of triceps surae and range of motion of the ankle. The aim of this study is to evaluate the effects of a combined walking and stretching program on walking efficiency in elderly PAOD patients. Seventy patients with PAOD stage II of the Leriche–Fontaine classification were randomly assigned into a stretching group (SG) or conditioning group (CG). Both groups participated in an eleven-day intensive rehabilitation program based on walking and strength training, while the SG performed five extra sessions of stretching. Walking autonomy was assessed through treadmill and overground tests with the recording of initial and absolute pain. A univariate ANOVA analysis was applied for the differences between the initial and final outcomes. Walking autonomy improved in both groups (p < 0.01), while only the SG improved flexibility (from −14.0 ± 8.1 to −10.3 ± 8.3 cm; p < 0.01). An intensive eleven-day rehabilitation program based on walking, strength, and stretching exercises is effective to improve the onset and the delay of pain during walking in patients with PAOD.

The Longitudinal Association of Walking Efficiency With Brain Volumes in Community-Dwelling Older Adults

Walking efficiency (WE) predicts mobility decline and is linked with higher fatigability. Fatigability is associated with cognitive decline and reduced brain volumes (BV), but the link between WE and BV is undefined. We examined associations between WE and BV in 860 participants of the BLSA (mean age 66.4(14.4) years, 54.5% women). WE was assessed during 2.5-minutes of usual-paced walking using indirect calorimetry and standardized per meter (ml/kg/m). BV measures were derived using MRI scans and an automated multi-atlas region-of-interest approach. In linear mixed models adjusted for demographics, education, BMI, intracranial volume, and cognitive status, lower baseline WE was associated with lower total, white, and gray matter, primarily in the frontal and temporal lobes (all p&lt;0.05). Longitudinally, declining WE was associated with increasing ventricular and decreasing hippocampal volumes over follow-up (all p&lt;0.01). Findings suggest rising age-related inefficiencies may reflect underlying brain atrophy and serve as a novel indicator for future interventions.

On the simple calculation of walking efficiency without kinematic information for its convenient use

Background Since walking is a daily activity not to require the maximal effort in healthy populations, a very few universal bio-parameters and/or methods have been defined to evaluate individual walking characteristics in those populations. A concept of “economy” is a potential candidate; however, walking economy highly depends on speed, so direct comparisons of economy values are difficult between studies. We investigated whether the vertical component of net walking “efficiency” (Effvert; %) is constant across speed. In that case, direct comparisons of Effvert will be possible between studies or individuals at any voluntary speed. Methods Thirty young male participants walked at eight speeds on the level or ± 5% gradients, providing vertical speeds (vvert). Differences in energy expenditure between level and uphill or downhill gradients (ΔEE) were calculated. The metabolic rate for vertical component (MRvert) was calculated by multiplying ΔEE with body mass (BM). The mechanical power output for vertical component (Pmech) was calculated by multiplying BM, gravitational acceleration, and vvert. Effvert was obtained from the ratio of Pmech to MRvert at each vvert. Delta efficiency (Delta-E; %) was also calculated from the inverse slope of the regression line representing the relationship of Pmech to MRvert. Results Upward Effvert was nearly constant at around 35% and downward Effvert ranged widely (49–80%). No significant differences were observed between upward Delta-E (35.5 ± 8.8%) and Effvert at any speeds, but not between downward Delta-E (44.9 ± 12.8%) and Effvert. Conclusions Upward ΔEE could be proportional to vvert. Upward, but not downward, Effvert should be useful not only for healthy populations but also for clinical patients to evaluate individual gait characteristics, because it requires only two metabolic measurements on the level and uphill gradients without kinematic information at any voluntary speed. Trial registration UMIN000017690 (R000020501; registered May 26th, 2015, before the first trial) and UMIN000031456 (R000035911; registered Feb. 23rd, 2018, before the first trial).

ASSOCIATION BETWEEN WALKING ENERGETICS AND FRAGMENTED PHYSICAL ACTIVITY IN MID-TO-LATE LIFE

Physical activity becomes increasingly fragmented with age, and may be an early marker of functional decline. Energy regulation has been linked with functional decline, yet whether the energy needed for walking, a common type of physical activity, is related to fragmentation of physical activity remains unknown. The study population included 493 participants aged 50-93 years from the Baltimore Longitudinal Study of Aging. Energetic measures included the energetic cost of usual-paced overground walking (ml/kg/m), the average energy expended (ml/kg/min) during a rapid-paced 400-m walk, and a cost-to-capacity ratio between the energy expended during 5-min treadmill walk (0.67 m/s, 0% grade) and the energy expended during the 400-m walk. Activity fragmentation was extracted from accelerometer data collected over ≥3 valid days and quantified via an active-to-sedentary transition probability (ASTP). Associations between the energetic measures and ASTP were assessed using multivariate linear regression models. Interactions between energetics and total daily physical activity, quantified as total log-transformed activity counts (TLAC), were also assessed. After adjusting for TLAC, demographics, body composition and comorbidity, higher cost-to-capacity ratio was associated with 3.51% greater fragmented physical activity (p=0.005). Energetics by TLAC interactions revealed that lower rapid-paced walking energy expenditure and higher cost-to-capacity ratio were only significantly associated with greater fragmentation in the most sedentary participants (p&lt;0.01 for both). Our results suggest that deterioration of walking efficiency may manifest as a more fragmented physical activity profile, especially among sedentary adults. Future longitudinal studies to understand whether declining walking efficiency predicts the onset and progression of activity fragmentation are warranted.