Oxygen uptake efficiency slope in community-dwelling ambulant stroke survivors during walking and stair climbing: a cross-sectional study.

BACKGROUND: Oxygen uptake efficiency slope during submaximal tests has been proposed as a more appropriate measure of aerobic capacity after suffering a stroke, since some individuals cannot tolerate maximal exercise testing. However, it has not yet been investigated whether the oxygen uptake efficiency slope is able to differentiate between healthy individuals and those who have suffered a stroke. OBJECTIVES: To compare the oxygen uptake efficiency slope during walking and stair climbing between stroke survivors and age- and sex-matched healthy controls. METHODS: This is a cross-sectional study in which 18 individuals who had suffered a stroke (stroke survivors) and 18 healthy controls matched for sex and age were included. Oxygen consumption and minute ventilation were collected breath-by-breath during walking (6-min Walk Test) and stair climbing. The oxygen uptake efficiency slope was estimated by the slope of the line obtained through linear regression. RESULTS: The stroke survivors had a lower oxygen uptake efficiency slope during the 6-min Walk Test than the healthy controls (MD 498, 95% CI 122 to 873, p = .01). The between-group difference for the Stair Test was smaller and not statistically significant (MD 349, 95%CI -73 to 772, p = .10). CONCLUSIONS: Stroke survivors had lower oxygen uptake efficiency slope during the performance of the 6-min Walk Test when compared to sex- and age-matched healthy controls. This suggests that stroke survivors have worse cardiopulmonary capacity.

Oxygen pulse best predicts energy expenditure during stair ascent and descent in individuals with chronic stroke.

BACKGROUND: To determine whether minute ventilation-to-carbon dioxide production (VE/VCO2), oxygen pulse (VO2/HR), and rate pressure product (RPP: VO2 * HR/1000) can explain energy expenditure during stair ascent/descent and whether energy expenditure during stair ascent/descent can discriminate between walking abilities in individuals with chronic stroke. MATERIALS AND METHODS: Regression analysis of cross-sectional data from 50 individuals between 1 and 4 years post-stroke was carried out to investigate the prediction of energy expenditure during stair ascent/descent. In addition, discriminant analysis was carried out to investigate the discrimination between walking abilities for energy expenditure: community (walking speed ≥ 0.8 m/s) and non-community (walking speed < 0.8 m/s) walkers. RESULTS: Oxygen pulse and rate pressure product were retained in the model. Oxygen pulse alone explained 70% of the variance in energy expenditure during stair ascent/descent. By adding rate pressure product, 79% of the variance was explained. Energy expenditure was able to discriminate the community from the non-community walkers, with a cutoff value of 13.8 ml∙kg-1∙min-1 and correctly classified 62% of the non-community and 78% of the community walkers. CONCLUSION: Oxygen pulse and rate pressure product significantly predicted energy expenditure during stair ascent/descent in individuals with chronic stroke. Energy expenditure during stair ascent/descent discriminated community from non-community walkers.

Influence and benefits of foot orthoses on kinematics, kinetics and muscle activation during step descent task.

BACKGROUND: Medial wedged foot orthoses are frequently prescribed to reduce retropatellar stress in patients with patellofemoral pain (PFP) by controlling calcaneal eversion and internal rotation of the tibia. During activities of daily living, the highest patella loads occur during stair descent, but the effect of foot orthoses during stair descent remains unclear. RESEARCH QUESTION: The purpose of this study was to compare the kinematics, kinetics and muscle activation during a step descent task in healthy volunteers using three designs of foot orthoses (insoles). METHODS: Sixteen healthy subjects with a mean age of 25.7 years, BMI of 23.3, and +5 Foot Posture Index were recruited. Subjects performed a step down task from 20 cm using a 5o rearfoot medial wedge (R), a 5o rearfoot and forefoot medial wedge (R/F), and a control flat insole (C). RESULTS: Significant improvements in control were seen in the R and R/F insoles over the C insole in the foot and at the ankle and hip kinematics. The R and R/F insoles increased the knee adduction moments, but reduced knee internal rotation moment compared to the C insole. Abductor hallucis (AH) activity was reduced with both insoles, whereas tibialis anterior (TA) activity was reduced with the R insole only. SIGNIFICANCE: Foot orthoses can change joint mechanics in the foot and lower limbs providing greater stability and less work done by AH and TA muscles. This data supports the use of foot orthoses to provide functional benefits during step descent, which may benefit patients with PFP.

Association between increase in vertical ground reaction force loading rate and pain level in women with patellofemoral pain after a patellofemoral joint loading protocol.

BACKGROUND: The etiology of patellofemoral pain (PFP) is thought to be the result of increased patellofemoral joint (PFJ) load and aberrant lower extremity mechanics, including altered vertical ground reaction forces (VGRF). However, few studies have investigated the association between an increase in pain and VGRF loading rates in the context of PFP. Thus, this study aimed to investigate the immediate effects of PFJ loading on pain and VGRF loading rate, and to see if there is a link between modification of both pain and VGRF loading rate during stair negotiation. METHODS: Thirty-four women with PFP underwent VGRF analysis during stair negotiation under two conditions: with (condition 2) and without (condition 1) being previously submitted to a PFJ loading protocol in order to or not to exacerbate their knee pain, respectively. RESULTS: The VGRF loading rates were significantly higher in condition 2 (Mean ± standard deviation (SD)=4.0±0.6N/s) compared to condition 1 (Mean±SD=3.6±0.5N/s) during stair ascent and during stair descent (Mean±SD: condition 1=6.3±1.1N/s; condition 2=7.0±1.4N/s). In addition, VGRF loading rates were higher during stair descent compared to stair ascent in both conditions. There were significant correlations between the increase in pain and VGRF loading rate during both tasks. CONCLUSION: There seemed to be an important relation between the increase in pain and VGRF loading rates in women with PFP. Based on these findings, interventions aimed at reducing VGRF loading rates are important in the context of PFP.

Should we consider steps with variable height for a safer stair negotiation in older adults?

BACKGROUND: Effects of exercise on foot clearances are important. In older adults variations in foot clearances during walking may lead to a fall, but there is a lack of information concerning stair negotiation in older adults. Whether a condition of post exercise changes foot clearances between steps of a staircase in older adults still unknown. OBJECTIVE: To determine differences in clearances when older adults negotiate different steps of a staircase before and after a session of aerobic exercise. METHODS: Kinematics data from 30 older adults were acquired and the toe and heel clearances were determined for each step. Clearances were compared between the steps. RESULTS: Smaller clearances were found at the highest step during ascending and descending, which was not changed by exercise. Smaller clearances suggest higher risk of tripping at the top of the staircase, regardless of exercise. CONCLUSION: A smaller step at the top of a short flight of stairs could reduce chances of tripping in older adults. It suggests that steps with variable height could make stair negotiation safer in older adults. This hypothesis should be tested in further studies.

Proximal mechanics during stair ascent are more discriminate of females with patellofemoral pain than distal mechanics.

BACKGROUND: Several hypotheses have been proposed to explain the pathomechanisms underlying patellofemoral pain (PFP). Concurrent evaluation of lower limb mechanics in the same PFP population is needed to determine which may be more important to target during rehabilitation. This study aimed to investigate possible differences in rearfoot eversion, hip adduction, and knee flexion during stair ascent; the relationship between these variables; and the discriminatory capability of each in identifying females with PFP. METHOD: Thirty-six females with PFP and 31 asymptomatic controls underwent three-dimensional kinematic analyses during stair ascent. Between-group comparisons were made for peak rearfoot eversion, hip adduction, and knee flexion. Pearson's correlation coefficients were calculated to evaluate relationships among these parameters. Receiver operating characteristic curves were applied to identify the discriminatory capability of each. FINDINGS: Females with PFP ascended stairs with reduced peak knee flexion, greater peak hip adduction and peak rearfoot eversion. Peak hip adduction (>10.6°; sensitivity=67%, specificity=77%) discriminated females with PFP more effectively than rearfoot eversion (>5.0°; sensitivity=58%, specificity=67%). Reduced peak hip adduction was found to be associated with reduced peak knee flexion (r=0.54, p=0.002) in females with PFP. INTERPRETATION: These findings indicate that proximal, local, and distal kinematics should be considered in PFP management, but proximally targeted interventions may be most important. The relationship of reduced knee flexion with reduced hip adduction also indicates a possible compensatory strategy to reduce patellofemoral joint stress, and this may need to be addressed during rehabilitation.

La ventilación no invasiva mejora los resultados en las pruebas de ejercicio en pacientes con enfermedad pulmonar obstructiva crónica / Non-invasive ventilation improves the outcome of exercise in COPD patients

Existen pocos estudios sobre el efecto de la Ventilación de doble nivel de presión positiva (VNI) sobre el ejercicio en pacientes con EPOC. El objetivo fue evaluar el impacto de la VNI en la respuesta a ejercicios máximos ysubmáximos en pruebas de campo en pacientes con EPOC. Fueron incluidos pacientes con EPOC (definición GOLD). Se les realizó una prueba de 6 minutos (según normativas de ATS), de escalera (Girish et al., Chest 2001) y ShuttleTest (Singh et al., Thorax 1992) con medición de escala de Borg de miembros inferiores y disnea, saturación arterial y frecuencia cardíaca. A través de una máscara nasal, se adaptó VNI con promedio 15 cmH2O de IPAP y 4 cmH2O de EPAP, y luego se realizaronlas mismas pruebas de ejercicio. Fueron evaluados 11 pacientes con EPOC: mediana edad: 61 años (IC25-75%, 58-75), sexo masculino 72%, FVC: 65% (IC25-75%, 60,1-70); FEV1: 37,4(IC25-75%, 33,97-42,5); FEV1/FVC: 46 (IC25-75%, 42,5-52,5); PaO2:68 mmHg (IC25-75%,63-75,3); PaCO2:40mmHg (IC25-75%,39-41).En la prueba de 6 minutos, se observó que la VNI aumentaba la distancia caminada en 61.78 % (p=0.001) la distancia caminada y la carga (kg.m) en 16,55% (p=0.002). No había cambios significativos en los síntomas (fatiga y disnea) por escala de Borg. En la prueba de escalera, se observó que la VNI incrementaba la velocidad de ascensoen 11,81% (p=0.05), sin cambios significativos en los síntomas o la altura ascendida. En el shuttle test, se observó que la VNI aumenta la distancia caminada en 30.6% (p=0.001), sin cambio significativos en los síntomas.En conclusión, se observó una significativa mejoría en las distancias caminadas y mayor velocidad de ascenso en la de escalera. Es la primera comunicación del efecto de la VNIsobre pruebas de escalera en pacientes con EPOC.

There are few exercise studies about the effect of bi-level non-invasive ventilation (NIV) on the exercise in COPD patients. The objective of the study was to evaluate the impact of NIV on the results of submaximal and maximal field exercise tests in COPD patients. The COPD patients were selected according to the GOLD definition. The study tests included: the six minute walking test (ATS guidelines), stair climbing test (Girish et al., Chest 2001) and shuttle test (Singh et al., Thorax 1992) which were measured with the Borg scale for legs and dyspnea, arterial saturation and heart rate. With a nasal mask, the NIV was adapted with pressure support ventilation through 15 cm H2O of IPAP and 4 cm H2O of EPAP. Then, the same exercise tests were performed. Eleven COPD patients were evaluated: age (median) 61 years (IC25-75%, 58-75), male sex 72%, FVC: 65% (IC25-75%, 60.1-70); FEV1: 37.4(IC25-75%, 33.97-42.5); FEV1/FVC: 46 (IC25-75%, 42.5-52.5); PaO2: 68 mmHg (IC25-75%,63-75.3); PaCO2: 40mmHg(IC25-75%, 39-41). The NIV increased the walked distance by 61.78% (p=0.001) and load (kg.m) by 16.55%(p=0.002) in the six minute walking test. There was no significant difference in the symptoms (dyspnea and fatigue) in the Borg scale. The NIV increased the ascent velocity by 11.81% (p=0.05) in the stair climbing test. No significant changes in symptoms and ascended height were observed. The NIV increased the walked distance by 30.6% (p=0.001), without significant changes in symptoms. As conclusion, distance increased significantly with NIV in the six minute walking test and shuttle test. A higher velocity was observed in the stair climbing test. This study was the first experience of NIV on the stair climbing test in COPD patients.