scholarly journals To slide or stride: when should Adélie penguins (Pygoscelis adeliae) toboggan?

1991 ◽  
Vol 69 (1) ◽  
pp. 221-225 ◽  
Author(s):  
Rory P. Wilson ◽  
Boris Culik ◽  
Dieter Adelung ◽  
N. Ruben Coria ◽  
Hugo J. Spairani
Keyword(s):  
Energy Expenditure ◽  
Stride Length ◽  
Stride Frequency ◽  
Pygoscelis Adeliae ◽  
Additional Energy ◽  
High Incidence ◽  
The Coefficient Of Friction ◽  
Almost All ◽  
Leg Movements ◽  
Adélie Penguins

We noted whether Adélie penguins (Pygoscelis adeliae), when travelling over snow, walked or tobogganed according to gradient, snow friction, or snow penetrability. Both walking and tobogganing penguins reduced stride length and stride frequency, and thus speed, with increasing uphill gradient although tobogganing birds travelled faster and with fewer leg movements. The incidence of tobogganing increased with decreasing friction between penguin and snow. The percentage of penguins tobogganing was also highly positively correlated with increasing snow penetrability. Penguins walking on soft snow must expend additional energy to pull their feet through the snow, whereas tobogganing birds do not sink. It is to be expected that Adélie penguins would utilize the most energetically favourable form of travel which, under almost all conditions, appeared to be tobogganing. Although tobogganing appears to be energetically more efficient than walking, rubbing the feathers over snow increases the coefficient of friction in unpreeened plumage. We propose that a high incidence of tobogganing necessitates increased feather care and that the decision whether to walk or toboggan probably represents a balance between immediate energy expenditure and subsequent energy and time expended maintaining plumage condition.

scholarly journals Energetics of vertical kilometer foot races; is steeper cheaper?

2016 ◽  
Vol 120 (3) ◽  
pp. 370-375 ◽  
Author(s):  
Nicola Giovanelli ◽  
Amanda Louise Ryan Ortiz ◽  
Keely Henninger ◽  
Rodger Kram
Keyword(s):  
Energy Expenditure ◽  
Video Analysis ◽  
Vertical Velocity ◽  
Stride Length ◽  
Duty Factor ◽  
Stride Frequency ◽  
Ground Contact ◽  
Metabolic Rates ◽  
Metabolic Costs

Vertical kilometer foot races consist of a 1,000-m elevation gain in <5,000 m of overall distance, and the inclines of the fastest courses are ∼30°. Previous uphill locomotion studies have focused on much shallower angles. We aimed to quantify the metabolic costs of walking and running on very steep angles and to biomechanically distinguish walking from running. Fifteen runners (10 male, 5 female, 32.9 ± 7.5 yr, 1.75 ± 0.09 m, 64.3 ± 9.1 kg) walked and ran for 5 min at seven different angles (9.4, 15.8, 20.4, 24.8, 30.0, 35.0, and 39.2°) all at a fixed vertical velocity (0.35 m/s). We measured the metabolic rates and calculated the vertical costs of walking (Cwvert) and running (Crvert). Using video analysis, we determined stride frequency, stride length, and duty factor (fraction of stride that each foot is in ground contact). At all angles other than 9.4°, Cwvert was cheaper than Crvert (average −8.45 ± 1.05%; P < 0.001). Further, broad minima for both Cwvert and Crvert existed between 20.4 and 35.0° (average Cwvert 44.17 ± 0.41 J·kg−1·m−1 and average Crvert 48.46 ± 0.35 J·kg−1·m−1). At all angles and speeds tested, both walking and running involved having at least one foot on the ground at all times. However, in walking, stride frequency and stride length were ∼28% slower and longer, respectively, than in running. In conclusion, we found that there is a range of angles for which energy expenditure is minimized. At the vertical velocity tested, on inclines steeper than 15.8°, athletes can reduce their energy expenditure by walking rather than running.

Maintenance of nest quality in Adélie penguins Pygoscelis adeliae: an additional benefit to life in the center

Polar Biology ◽  
2021 ◽  
Author(s):  
Virginia Morandini ◽  
Katie M. Dugger ◽  
Amélie Lescroël ◽  
Annie E. Schmidt ◽  
Grant Ballard
Keyword(s):  
Additional Benefit ◽  
Pygoscelis Adeliae ◽  
Nest Quality ◽  
Adélie Penguins

scholarly journals Functional Electrical Stimulation Changes Dynamic Resources in Children With Spastic Cerebral Palsy

2006 ◽  
Vol 86 (7) ◽  
pp. 987-1000 ◽  
Author(s):  
Chia-Ling Ho ◽  
Kenneth G Holt ◽  
Elliot Saltzman ◽  
Robert C Wagenaar
Keyword(s):  
Cerebral Palsy ◽  
Electrical Stimulation ◽  
Functional Electrical Stimulation ◽  
Stride Length ◽  
The Body ◽  
Stride Frequency ◽  
Spastic Cerebral Palsy ◽  
Significant Difference ◽  
Muscle Complex ◽  
Spring System

Abstract Background and Purpose. Children with cerebral palsy (CP) often are faced with difficulty in walking. The purpose of this experiment was to determine the effects of functional electrical stimulation (FES) applied to the gastrocnemius-soleus muscle complex on the ability to produce appropriately timed force and reduce stiffness (elastic property of the body) and on stride length and stride frequency during walking. Subjects and Methods. Thirteen children with spastic CP (including 4 children who were dropped from the study due to their inability to cooperate) and 6 children who were developing typically participated in the study. A crossover study design was implemented. The children with spastic CP were randomly assigned to either a group that received FES for 15 trials followed by no FES for 15 trials or a group that received no FES for 15 trials followed by FES for 15 trials. The children who were having typical development walked without FES. Kinematic data were collected for the children with CP in each walking condition and for the children who were developing typically. Impulse (force-producing ability) and stiffness were estimated from an escapement-driven pendulum and spring system model of human walking. Stride length and stride frequency also were measured. To compare between walking conditions and between the children with CP and the children who were developing typically, dimensional analysis and speed normalization procedures were used. Results. Nonparametric statistics showed that there was no significant difference between the children with CP in the no-FES condition and the children who were developing typically on speed-normalized dimensionless impulse. In contrast, the children with CP in the FES condition had a significantly higher median value than the children who were developing typically. The FES significantly increased speed-normalized dimensionless impulse from 10.02 to 16.32 when comparing walking conditions for the children with CP. No significant differences were found between walking conditions for stiffness, stride length, and stride frequency. Discussion and Conclusion. The results suggest that FES is effective in increasing impulse during walking but not in decreasing stiffness. The effect on increasing impulse does not result in more typical spatiotemporal gait parameters. [Ho CL, Holt KG, Saltzman E, Wagenaar RC. Functional electrical stimulation changes dynamic resources in children with spastic cerebral palsy. Phys Ther. 2006;86:987–1000.]

scholarly journals Methods of determination of frictional resistances in sheet metal forming of car body sheets

2018 ◽  
Vol 19 (6) ◽  
pp. 756-760
Author(s):  
Tomasz Trzepieciński ◽  
Irena Nowotyńska
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Complex Function ◽  
Forming Process ◽  
The Coefficient Of Friction ◽  
Displacement Speed ◽  
Almost All ◽  
Lubrication Conditions

The friction phenomenon existed in almost all plastic working processes, in particular sheet metal forming, is a complex function of the material's properties, parameters of the forming process, surface topography of the sheet and tools, and lubrication conditions. During the stamping of the drawpieces there are zones differentiated in terms of stress and strain state, displacement speed and friction conditions. This article describes the methods for determining the value of the coefficient of friction in selected areas of sheet metal and presents the drawbacks and limitations of these methods.

scholarly journals Supervised Exercise Training Improves 6 min Walking Distance and Modifies Gait Pattern during Pain-Free Walking Condition in Patients with Symptomatic Lower Extremity Peripheral Artery Disease

Sensors ◽  
2021 ◽  
Vol 21 (23) ◽  
pp. 7989
Author(s):  
Stefano Lanzi ◽  
Joël Boichat ◽  
Luca Calanca ◽  
Lucia Mazzolai ◽  
Davide Malatesta
Keyword(s):  
Stride Length ◽  
Gait Pattern ◽  
Walking Distance ◽  
Stride Frequency ◽  
Walk Test ◽  
Relative Duration ◽  
Foot Kinematics ◽  
Supervised Exercise ◽  
Artery Disease ◽  
Kinematics Parameters

This study aimed to investigate the effects of supervised exercise training (SET) on spatiotemporal gait and foot kinematics parameters in patients with symptomatic lower extremity peripheral artery disease (PAD) during a 6 min walk test. Symptomatic patients with chronic PAD (Fontaine stage II) following a 3 month SET program were included. Prior to and following SET, a 6 min walk test was performed to assess the 6 min walking distance (6MWD) of each patient. During this test, spatiotemporal gait and foot kinematics parameters were assessed during pain-free and painful walking conditions. Twenty-nine patients with PAD (65.4 ± 9.9 years.) were included. The 6MWD was significantly increased following SET (+10%; p ≤ 0.001). The walking speed (+8%) and stride frequency (+5%) were significantly increased after SET (p ≤ 0.026). The stride length was only significantly increased during the pain-free walking condition (+4%, p = 0.001), whereas no significant differences were observed during the condition of painful walking. Similarly, following SET, the relative duration of the loading response increased (+12%), the relative duration of the foot-flat phase decreased (−3%), and the toe-off pitch angle significantly increased (+3%) during the pain-free walking condition alone (p ≤ 0.05). A significant positive correlation was found between changes in the stride length (r = 0.497, p = 0.007) and stride frequency (r = 0.786, p ≤ 0.001) during pain-free walking condition and changes in the 6MWD. A significant negative correlation was found between changes in the foot-flat phase during pain-free walking condition and changes in the 6MWD (r = −0.567, p = 0.002). SET was found to modify the gait pattern of patients with symptomatic PAD, and many of these changes were found to occur during pain-free walking. The improvement in individuals’ functional 6 min walk test was related to changes in their gait pattern.

Guidelines for people approaching breeding groups of Adélie penguins (Pygoscelis adeliae)

Polar Record ◽  
1998 ◽  
Vol 34 (191) ◽  
pp. 287-292 ◽  
Author(s):  
Melissa Giese
Keyword(s):  
Heart Rate ◽  
Natural Disturbances ◽  
Measurable Effect ◽  
Pygoscelis Adeliae ◽  
Heart Rates ◽  
Incubation Behaviour ◽  
Breeding Groups ◽  
Least Disturbance ◽  
South Polar ◽  
Adélie Penguins

AbstractIncreases in the number of people travelling to Antarctica has led to more frequent interactions between people and Antarctic wildlife, yet the effects of visitation on the animals has received limited scientific assessment. This study conducted experiments to measure the responses of incubating Adélie penguins (Pygoscelis adeliae) to controlled human approaches to determine which approach distances and approach styles caused the least disturbance to the birds. Three minimum approach distances were tested: 30, 15, and 5 m. Approaching penguins to 30 m had no measurable effect on either their behaviour or heart rate, while approaching as close as 15 m significantly elevated their heart rates above resting, undisturbed levels even though there was no behavioural indication of this response. Approaching penguins to 5 m significantly interrupted the penguins' incubation behaviour, with the potential to cause egg-cooling. Approaches to 5 m elevated heart rates above those measured when birds were undisturbed, approached to either 15 or 30 m, or exposed to ‘natural’ disturbances (that is, other penguins or south polar skuas, Catheracta maccormicki). The study also identified certain Adelie penguin behaviours that may be indicative of disturbance in response to human visitation. People visiting breeding penguins could learn to identify these behaviours, so they can monitor and modify any effects of their visit.

On Poverty and Inequality in Latin America

1996 ◽  
Vol 38 (2-3) ◽  
pp. 15-37 ◽  
Author(s):  
Gert Rosenthal
Keyword(s):  
Latin America ◽  
Financial Stability ◽  
Absolute Poverty ◽  
Export Sector ◽  
Positive Side ◽  
Poverty And Inequality ◽  
Standards Of Living ◽  
The Social ◽  
High Incidence ◽  
Almost All

It is by now conventional wisdom to say that, while the countries of Latin America have improved their economic performance over the past few years, the majority of their populations have suffered a reversal in their standards of living compared to, let us say, 1980. After the protracted recession and acute macroeconomic disequilibria which was experienced by almost all the countries during the first half of the 1980s, many are staging a recovery in the 1990s. On the positive side, some of the indicators most frequently cited include the resumption of growth (albeit at moderate rates), greater financial stability, an increasingly diversified export sector, and political democratization. On the negative side, one finds inevitable mention of the following: inequitable distribution of income, a high incidence of absolute poverty, and the social tensions that tend to accompany them.

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