Changes in metabolic cost of transport following locomotor training poststroke.

BACKGROUND: The energy cost of transport is higher for persons with stroke compared with neurologically intact subjects, and this has a negative impact on ambulatory activity and function. Whether the high energy cost of walking after stroke is influenced by gait training interventions is generally not considered. OBJECTIVE: To examine changes in the energy cost of transport with a gait training intervention after stroke and to identify whether energy cost changes independent of changes in walking speed. METHODS: Persons with chronic (≯6 months) stroke participated in an intervention combining fast walking and functional electrical stimulation of the ankle dorsi-and plantarflexor muscles. Oxygen consumption, walking speed, and endurance were measured pre and post training. Energy and caloric cost of transport were calculated at self-selected and absolute speeds at each time point. RESULTS: Eleven subjects (age 61.8 ± 8 years) participated. Self-selected and fastest walking speed and 6-minute walk test distance improved after the intervention (F = 67.5, P < .001; F = 40.9, P < .001; F = 20.2, P = .001, respectively). Energy and caloric cost of transport at self-selected speed improved (F = 8.63, P = .015, and F = 7.87, P = .019, respectively) but did not change at an absolute speed pre-to postintervention. CONCLUSIONS: Energy and caloric cost of transport at self-selected walking speeds improved pre to post training but were unaffected at an absolute walking speed, suggesting that the improved energy cost of transport was through improvements in the subject's self-selected walking speed. These results illustrate that improvements in walking speed following an intervention are an important mechanism by which the energy cost of transport can be reduced post stroke.

Influence of speed on walking economy poststroke.

BACKGROUND AND OBJECTIVE: Walking speed influences energy cost in healthy adults, but its influence when walking is impaired due to stroke is not clear. This study investigated the effect of manipulating walking speed on the energy economy of walking poststroke. METHODS: Sixteen persons with chronic stroke underwent a clinical examination, including several lower extremity impairment measures. consumption (VO(2)) was measured as they walked at their self-selected speed (Free), 20% slower (Slow), their fastest possible speed (Fastest), and 2 speeds between Free and Fastest speeds. VO(2) was normalized to body mass and speed, resulting in energy cost per meter walked (CW). RESULTS: A main effect for speed was observed (P = .00001), with faster than self-selected speeds showing greater relative economy as a whole. However, for 5 subjects with the fastest walking speeds (>1.2 m/s), there was a trend toward decreasing relative economy at speeds higher than self-selected speed (P = .18). There was a negative correlation between improvement in CW at the most economical speed and (a) Free speed (r = -.857; P < .0001) and (b) lower extremity Fugl-Meyer scores (r = -.653; P = .006). CONCLUSIONS: For those poststroke whose fastest walking speed after stroke is below 1.2 m/s, walking economy improves when speed is increased above the self-selected walking speed. The results suggest that for persons poststroke with very slow self-selected walking speeds, improvements in walking speed could be accompanied by improvements in walking economy if faster walking speeds can be attained through intervention.

Ultrasound assessment of popliteal vein compliance during a short deflation protocol.

The purpose of the present study was to determine whether ultrasound is a useful tool to measure the venous characteristics of the lower extremity during a standard venous collecting cuff deflation protocol. To accomplish this, lower extremity pressure-cross-sectional area (CSA) and pressure-volume relationships were measured in eight (25 +/- 1 yr) supine subjects. Popliteal vein CSA was assessed by using high-resolution ultrasound, while calf volume changes were simultaneously assessed by using venous occlusion plethysmography (VOP). Pressure-CSA and pressure-volume relationships were assessed at baseline, during the cold pressor (CP) test, and following sublingual nitroglycerin (NTG) administration. Relationships were modeled with a quadratic regression equation, and beta(1) and beta(2) were used as indexes of venous compliance. Popliteal vein regression parameters beta(1) (8.485 +/- 2.616 vs. 7.638 +/- 2.664, baseline vs. CP; 8.485 +/- 2.616 vs. 7.734 +/- 3.076, baseline vs. NTG; both P > 0.05) and beta(2) (-0.0841 +/- 0.0241 vs. -0.0793 +/- 0.0242, baseline vs. CP; -0.0841 +/- 0.0241 vs. -0.0771 +/- 0.0280, baseline vs. NTG; both P > 0.05) were not affected by CP or NTG. Similarly, calf regression parameters beta(1) and beta(2), obtained with VOP, were not altered during either trial. Intraclass correlations for venous compliance assessed with ultrasound and VOP were 0.92 and 0.97, respectively, indicating acceptable reproducibility. These data suggest that ultrasound is a functional and reproducible tool to assess the venous characteristics of the lower extremity, in addition to VOP. Additionally, popliteal vein and calf compliance were not affected by the CP test or NTG.