Propulsive Forces Applied to the Body's Center of Mass Affect Metabolic Energetics Poststroke

OBJECTIVE

To investigate the effect of timing and magnitude of horizontally directed propulsive forces to the center of mass (COM) on the metabolic cost of walking (COW) for individuals poststroke.

DESIGN

Repeated-measures, within-subject design.

SETTING

Research laboratory.

PARTICIPANTS

A total of 9 individuals with chronic hemiparesis poststroke and 7 unimpaired similarly aged controls (N=16).

INTERVENTION

Individuals walked on a treadmill in 2 separate studies. First, we compared the metabolic COW with an anterior force applied to the COM that (1) coincided with paretic propulsion or (2) was applied throughout the gait cycle. Next, we compared the metabolic COW with anterior (assistive) or posterior (resistive) forces applied during paretic propulsion.

MAIN OUTCOME MEASURE

Metabolic COW.

RESULTS

The COW was significantly greater in the Stroke group. Anterior (propulsive) assistance reduced the COW differently based on group. The Stroke group exhibited a 12% reduction in COW when assistance was provided only during paretic propulsion, but not when assistance was provided throughout the gait cycle. In contrast, the Control group demonstrated reduced COW during both anterior assistance conditions. In addition, we observed that resistance during paretic propulsion (simulated hemiparesis for Control group) significantly increased the COW.

CONCLUSIONS

Systematically manipulating propulsive forces at the body's COM had a profound influence on metabolic cost. The timing of propulsive forces to the COM is important and needs to coincide with paretic terminal stance. Additional internally or externally generated propulsive forces applied to the body's COM poststroke may produce a lower metabolic COW.

Carbohydrate and fat oxidation in persons with lower limb amputation during walking with different speeds

BACKGROUND

Studies suggest that the energy expenditure of healthy persons (control) during walking with the preferred walking speed in steady-state conditions is dominated by fat oxidation. Conversely, carbohydrate and fat oxidation during walking is little investigated in transfemoral amputees.

OBJECTIVES

To investigate carbohydrate and fat oxidation, energy cost of walking, and percent utilization of maximal aerobic capacity [Formula: see text]during walking.

STUDY DESIGN

Eight transfemoral amputees and controls walked with their preferred walking speed and speeds 12.5% and 25% slower and faster than their preferred walking speed.

METHODS

Energy expenditure and fuel utilization were measured using a portable metabolic analyzer. Metabolic values are means ± standard deviation.

RESULTS

For transfemoral amputees (37.0 ± 10.9 years) and controls (39.0 ± 12.3 years), fat utilization at the preferred walking speed was 44.8% ± 7.2% and 45.0% ± 7.2% of the total energy expenditure, respectively. The preferred walking speed of the transfemoral amputees and controls was close to a metabolic cross-over speed, which is the speed where carbohydrate utilization increases steeply and fat utilization decreases. When walking fast, at 90 m min^-1 (preferred walking speed plus 25%), transfemoral amputees utilized 70.7% ± 5.6% of their [Formula: see text], while the controls utilized 30.9% ± 4.5% ( p < 0.001) at the matching speed (control preferred walking speed). At 90 m min^-1, carbohydrate utilization was 78% ± 4.7% and 55.2% ± 7.2% of the total energy expenditure for the transfemoral amputees and controls, respectively ( p < 0.01). Compared to the control, energy cost of walking was higher for the transfemoral amputees at all speeds (all comparisons; p < 0.001).

CONCLUSION

At the preferred walking speed, carbohydrate, not fat, dominates energy expenditure of both transfemoral amputees and controls. For the transfemoral amputees, consequences of fast walking are very high [Formula: see text] utilization and rate of carbohydrate oxidation. Clinical relevance Research on the relationships between physical effort and fuel partitioning during ambulation could provide important insights for exercise-rehabilitation programs for lower limb amputees (LLA). Regular endurance exercise will improve maximal aerobic capacity and enable LLA to walk faster and at the same time expend less energy and improve fat utilization.

Relationship between oxygen cost of walking and level of walking disability after stroke: An experimental study

BACKGROUND AND PURPOSE

Since physical inactivity is the major risk factor for recurrent stroke, it is important to understand how level of disability impacts oxygen uptake by people after stroke. This study investigated the nature of the relationship between level of disability and oxygen cost in people with chronic stroke.

METHODS

Level of walking disability was measured as comfortable walking speed using the 10-m Walk Test reported in m/s with 55 ambulatory people 2 years after stroke. Oxygen cost was measured during 3 walking tasks: overground walking at comfortable speed, overground walking at fast speed, and stair walking at comfortable speed. Oxygen cost was calculated from oxygen uptake divided by distance covered during walking and reported in ml∙kg^-1 ∙m^-1 .

RESULTS

The relationship between level of walking disability and oxygen cost was curvilinear for all 3 walking tasks. One quadratic model accounted for 81% (95% CI [74, 88]) of the variance in oxygen cost during the 3 walking tasks: [Formula: see text] DISCUSSION: The oxygen cost of walking was related the level of walking disability in people with chronic stroke, such that the more disabled the individual, the higher the oxygen cost of walking; with oxygen cost rising sharply as disability became severe. An equation that relates oxygen cost during different walking tasks according to the level of walking disability allows clinicians to determine oxygen cost indirectly without the difficulty of measuring oxygen uptake directly.

The influence of cognitive load on metabolic cost of transport during overground walking in healthy, young adults

PURPOSE

Our aim was to examine whether cognitive processing during walking increases the metabolic cost of transport in healthy young adults.

METHODS

Twenty healthy, young adults completed five conditions: (1) walking at a self-selected speed (spontaneous single-task), (2) seated resting (baseline), (3) performing cognitive task while seated (cognitive single-task), (4) walking while simultaneously performing the cognitive task (dual-task), and (5) single-task walking at a speed that matched the participant's dual-task gait speed (matched single-task). Rate of oxygen consumption (V̇O₂) was recorded during all conditions. Gait speed and cost of walking (Cw; oxygen consumed per distance traveled) were recorded during all walking conditions. Reaction time and accuracy of responses in the cognitive task were recorded during all cognitive task conditions. Data from the fifth minute of each 5-min condition were analyzed.

RESULTS

There was no difference in V̇O₂ between the dual-task and matched single-task walking conditions. V̇O₂ in the seated cognitive condition was significantly smaller than both walking conditions, but was not significantly different than zero. Cw was significantly greater during the matched single-task walking condition than during the dual-task walking condition. However, the difference in Cw was so small that it is unlikely to be clinically significant (0.008 mLO₂/kg/m, 95% CI 0.002-0.014).

CONCLUSIONS

Cognitive processing while walking may not increase energy demands of walking in healthy young adults. Maintaining non-preferred gait speed (matched speed) overground continuously for 5 min may require attentional resources, and thereby increase metabolic costs relative to walking at habitual speed.

How strongly is aerobic capacity correlated with walking speed and distance after stroke? Systematic review and meta-analysis

BACKGROUND

Restoration of walking capacity, as reflected by walking speed and walking distance, is a primary goal after stroke. Peak aerobic capacity (peak oxygen consumption [V̇o₂peak]) is suggested to be correlated with walking capacity after stroke. Although the strength of this correlation is unclear, physical therapy programs often target walking capacity by means of aerobic training.

PURPOSE

The purpose of this systematic review was to summarize the available evidence on the correlation between V̇o₂peak and walking capacity.

DATA SOURCES

The databases MEDLINE, CINAHL, EMBASE, Cochrane Library, and SPORTDiscus were searched up to May 2014.

STUDY SELECTION

Cross-sectional studies reporting correlation coefficients between V̇o₂peak and walking capacity in stroke were included, along with longitudinal studies reporting these correlation coefficients at baseline.

DATA EXTRACTION

The methodological quality of the studies was assessed using a checklist of 27 items for observational research. Information on study design, stroke severity and recovery, and assessments and outcome of V̇o₂peak and walking capacity, as well as the reported correlation coefficients, were extracted.

DATA SYNTHESIS

Thirteen studies involving 454 participants were included. Meta-analyses showed combined correlation coefficients (rɱ) for V̇o₂peak and walking speed and for V̇o₂peak and walking distance of .42 (95% credibility interval=.31, .54) and .52 (95% credibility interval=.42, .62), respectively.

LIMITATIONS

The studies included in the present review had small sample sizes and low methodological quality. Clinical and methodological diversity challenged the comparability of the included studies, despite statistical homogeneity. Relevant data of 3 studies could not be retrieved.

CONCLUSIONS

The strength of the correlation of V̇o₂peak with walking speed was low and moderate for V̇o₂peak and walking distance, respectively, indicating that other factors, besides V̇o₂peak, determine walking capacity after stroke.

High metabolic cost and low energy expenditure for typical motor activities among individuals in the chronic phase after stroke

BACKGROUND AND PURPOSE

Energy variables, such as metabolic cost (MC) and energy expenditure (EE), are important characteristics of motor activities that can influence daily activity and have implications for health. In individuals poststroke, these variables have previously been described only for walking. Our goal was to characterize the MC and EE of typical motor activities among individuals in the chronic phase poststroke and compare them with those of able-bodied individuals.

METHODS

Eleven individuals with poststroke and 8 able-bodied individuals participated in this study. Four activities were tested: sit-to-walk-to-sit, walking over an obstacle course, walking at a comfortable speed, and reaching for an object while in a standing position. Each activity was performed repeatedly for 8 minutes, while oxygen consumption was recorded. The MC of the activities was calculated by dividing the mean oxygen consumption by walking speed or the number of repetitions. The EE was represented by metabolic equivalents.

RESULTS

There was a significant interaction effect of group and activity on MC and EE (P = 0.001 and P = 0.007, respectively). In the participants poststroke, the MC of mobility activities ranged from 0.24 (0.06) to 0.3 (0.06) mL/kg/m, and the MC of the standing activity was 0.1 (0.03) mL/kg/repetition. The MC was higher for the participants poststroke than for the able-bodied participants (P < 0.001). The EE of the participants poststroke ranged from 1.96 (0.4) to 3.83 (0.6) metabolic equivalents and was lower compared with the able-bodied participants (P = 0.001).

DISCUSSION AND CONCLUSIONS

Individuals poststroke have high MC and low EE across various motor activities. These findings suggest that rehabilitation programs need to specifically address the energetic domain.Video Abstract available. See Video (Supplemental Digital Content 1, http://links.lww.com/JNPT/A75) for more insights from the authors.

Is There Evidence That Active Videogames Increase Energy Expenditure and Exercise Intensity for People Poststroke and with Cerebral Palsy?

This article asked and answered the question of whether there was evidence to support the use of videogames for promotion of wellness and fitness for people poststroke and those with cerebral palsy (CP). A literature search of PubMed, CINAHL, and PEDro using a population, intervention, and outcome (PIO) approach and the key words "stroke (or CP) AND video games (and synonyms) AND energy expenditure (EE) (and synonyms)" was conducted. It yielded two relevant references for people poststroke and five references for people with CP. The literature extraction and synthesis by the categories of the PIO indicated that most studies used only the population of interest, except two that compared the EE with that of healthy controls. The main finding is that both people poststroke (moderate severity) and people with CP (mild severity) can achieve moderate EE playing Wii(™) (Nintendo, Kyoto, Japan), PlayStation(®) (Sony, Tokyo, Japan), and Kinect(™) (Microsoft, Redmond, WA) games. Adults with CP of mild severity played the videogames at vigorous levels, whereas those with severe CP played them at low levels. There appears to be an interaction between development and severity that influences the exercise intensity measured by EE. The findings suggests that videogames are a gateway for wellness promotion.

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.