Search results for "Energetic cost"
showing 8 items of 8 documents
Let the machine do the work: learning to reduce the energetic cost of walking on a split‐belt treadmill
2019
In everyday tasks such as walking and running, we often exploit the work performed by external sources to reduce effort. Recent research has focused on designing assistive devices capable of performing mechanical work to reduce the work performed by muscles and improve walking function. The success of these devices relies on the user learning to take advantage of this external assistance. Although adaptation is central to this process, the study of adaptation is often done using approaches that seem to have little in common with the use of external assistance. We show in 16 young, healthy participants that a common approach for studying adaptation, split-belt treadmill walking, can be under…
The basal energy expenditure of female athletes vs. sedentary women as related to their family history of type 2 diabetes
2001
The purpose of this study was to investigate the basal metabolic rate (BMR) in 16 professional sportswomen (soccer players) versus 15 sedentary women, as related to the presence (FH+) or absence (FH-) of a family history of type 2 diabetes. The sportswomen, in toto, had a significantly higher BMR than expected from predictive equations (+14.92%). However, the difference was limited only to FH- sportswomen (+18.66%, p<0.0005). FH- sportswomen showed a significantly higher measured BMR than FH+ sportswomen (p<0.005), and FH+ (p=0.058) and than FH- (p<0.05) sedentary women. There were no other significant differences relative to physical, metabolic and plasmatic data between the groups. The sp…
Influence of ultra-long-term fatigue on the oxygen cost of two types of locomotion.
2000
The aim of this study was to examine the effects of fatigue induced by a 65-km ultramarathon on the oxygen cost of running (Cr) and cycling (Ccycl). The day before and immediately after the race, a group of nine well-trained male subjects performed two sub-maximal 4-min exercise bouts: one cycling at a power corresponding to 1.5 W · kg−1 body mass on an electromagnetically braked ergometer, and one running at 11 km · h−1 on a flat asphalt roadway. Before oxygen cost determinations, the subjects performed 12 “ankle” jumps at a given frequency that was fixed by an electronic metronome (2.5 Hz). From the non-fatigued to the fatigued condition, there was a significant increase in minute ventila…
Mechanical step variability during treadmill running.
1995
The present study was designed to study intra-individual step variability measured both on vertical displacement of the body (delta Z) and on step time (delta t) parameters by means of a kinematic arm and during treadmill running. A group of 17 subjects ran successively at 60%, 80%, 100% and 140% of their maximal aerobic velocity (Vamax). The total number of steps analysed was 6116. The absolute delta Z step variability (sigma delta Z) ranged between 5 mm and 21 mm while the absolute delta t variability (sigma delta t) ranged between 6 ms and 40 ms. Step variabilities were due to step asymmetry (from 38.5% to 48.5% of the step variability) and to stride variability. For submaximal velocitie…
Differences in contractile behaviour between the soleus and medial gastrocnemius muscles during human walking
2012
The functional roles of individual lower limb muscles during human walking may differ depending on walking speed or duration. In this study, 11 volunteers walked on a treadmill for 60 min at speeds corresponding to both optimal and 20% above optimal energetic cost of transport whilst oxygen consumption and medial gastrocnemius (MG) and soleus fascicle lengths were measured. Although energetic cost of transport was ∼12% higher at the faster speed, it remained constant over 60 min at both speeds, suggesting that humans can walk for prolonged periods at a range of speeds without compromising energetic efficiency. The fascicles of both muscles exhibited rather ‘isometric’ behaviour during the e…
Fractal analyses reveal independent complexity and predictability of gait
2017
Locomotion is a natural task that has been assessed since decades and used as a proxy to highlight impairments of various origins. Most studies adopted classical linear analyses of spatio-temporal gait parameters. Here, we use more advanced, yet not less practical, non-linear techniques to analyse gait time series of healthy subjects. We aimed at finding more sensitive indexes related to spatio-temporal gait parameters than those previously used, with the hope to better identify abnormal locomotion. We analysed large-scale stride interval time series and mean step width in 34 participants while altering walking direction (forward vs. backward walking) and with or without galvanic vestibular…
The fouling phenomenon in membrane bioreactors: assessment of different strategies for energy saving
2012
Membrane fouling represents one of the major limiting issue for membrane bioreactor (MBR) in the wastewater treatment field. Membrane fouling and high aeration requirement (for inducing shear stress to limit fouling) in MBR systems make the operation of such systems economically demanding due to high energetic costs. Despite several studies on MBR fouling have been performed a comprehensive knowledge on how to reduce membrane fouling and consequently energy saving is still lacking and controversial. The aim of this study is to gain insights on the optimization of the operating conditions in an MBR system. In particular, the influence of the aeration intensity and the durations of filtration…
Survival analysis of three clones of Brachionus plicatilis (Rotifera)
1994
Age-specific survival schedules of females from three genetically different clones of Brachionus plicatilis were analyzed at several environmental conditions in the laboratory.