scholarly journals Mechanical energy and propulsion mechanics in roller-skiing double-poling at increasing speeds

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0255202
Author(s):  
Jørgen Danielsen ◽  
Øyvind Sandbakk ◽  
David McGhie ◽  
Gertjan Ettema
Keyword(s):  
Inverse Dynamics ◽  
Mechanical Energy ◽  
Rolling Friction ◽  
Swing Phase ◽  
Double Poling ◽  
External Power ◽  
Cross Country Skiing ◽  
Image Position ◽  
All Speeds ◽  
Body Energy

Objectives The aim of this study was to examine the effect of speed on mechanical energy fluctuations and propulsion mechanics in the double-poling (DP) technique of cross-country skiing. Methods Kinematics and dynamics were acquired while fourteen male skiers performed roller-skiing DP on a treadmill at increasing speeds (15, 21 and 27 km∙h-1). Kinetic (Ekin), potential (Epot), and total (Ebody) body mechanical energy and pole power (Ppole) were calculated. Inverse dynamics was used to calculate arm power (Parm). Trunk+leg power (PT+L) was estimated, as was the power associated with body movements perpendicular to goal-direction (E.body⊥). Results Ekin and Epot fluctuated out-of-phase throughout the cycle, at first sight indicating that pendulum-like behaviour occurs partly in DP. However, during the swing phase, the increase in Epot (body heightening) was mainly driven by positive PT+L, while the decrease in Ekin was lost to rolling friction, and during the poling phase, considerable positive Parm generation occurs. Thus, possible exchange between Ekin and Epot seem not to occur as directly and passively as in classic pendulum locomotion (walking). During the poling phase, E.body⊥fluctuated out-of-phase with Ppole, indicating a transfer of body energy to Ppole. In this way, power generated by trunk+leg mainly during the swing phase (body heightening) can be used in the poling phase as pole power. At all speeds, negative PT+L occurred during the poling phase, suggesting energy absorption of body energy not transferred to pole power. Thus, DP seem to resemble bouncing ball-like behaviour more than pendulum at faster speeds. Over the cycle, Parm contribution to Ppole (external power) was 63% at 15 km∙h-1 and 66% at 21 and 27 km∙h-1, with the remainder being PT+L contribution. Conclusions When speed increases in level DP, both power production and absorption by trunk+leg actions increase considerably. This enhanced involvement of the legs at faster speeds is likely a prerequisite for effective generation of pole power at high speeds with very short poling times. However, the relative trunk+leg power contribution did not increase at the speeds studied here.

scholarly journals Comparison of Exclusive Double Poling to Classic Techniques of Cross-country Skiing

2019 ◽  
Vol 51 (4) ◽  
pp. 760-772 ◽  
Author(s):  
THOMAS STÖGGL ◽  
OLLI OHTONEN ◽  
MASAKI TAKEDA ◽  
NAOTO MIYAMOTO ◽  
CORY SNYDER ◽  
...  
Keyword(s):  
Double Poling ◽  
Cross Country Skiing ◽  
Cross Country

scholarly journals Is There an Optimal Pole Length for Double Poling in Cross Country Skiing?

2017 ◽  
Vol 33 (3) ◽  
pp. 197-202 ◽  
Author(s):  
Franziska Onasch ◽  
Anthony Killick ◽  
Walter Herzog
Keyword(s):  
Oxygen Uptake ◽  
Body Height ◽  
Metabolic Cost ◽  
Male Athletes ◽  
Double Poling ◽  
Acute Study ◽  
Ground Contact Time ◽  
Cross Country Skiing ◽  
Cross Country ◽  
The Given

The aim of this study was to determine the effects of pole length on energy cost and kinematics in cross country double poling. Seven sub-elite male athletes were tested using pole sets of different lengths (ranging between 77% and 98% of participants’ body height). Tests were conducted on a treadmill, set to a 2% incline and an approximate racing speed. Poling forces, contact times, and oxygen uptake were measured throughout the testing. Pole length was positively correlated with ground contact time (r = .57, p < .001) and negatively correlated with poling frequency (r = −.48, p = .003). Pole length was also positively correlated with pole recovery time and propulsive impulse produced per poling cycle (r = .36, p = .031; r = .35, p = .042, respectively). Oxygen uptake and pole length were negatively correlated (r = −.51, p = .004). This acute study shows that increasing pole length for double poling in sub-elite cross country skiers under the given conditions seems to change the poling mechanics in distinct ways, resulting in a more efficient poling action by decreasing an athlete’s metabolic cost.

Time-To-Contact Analysis of Gait Stability in the Swing Phase of Walking in People With Multiple Sclerosis

Motor Control ◽  
2015 ◽  
Vol 19 (4) ◽  
pp. 289-311 ◽  
Author(s):  
Jebb G. Remelius ◽  
Richard E.A. van Emmerik
Keyword(s):  
Multiple Sclerosis ◽  
Center Of Mass ◽  
Swing Phase ◽  
The Body ◽  
Head Movements ◽  
Gait Stability ◽  
Time To Contact ◽  
Prospective Control ◽  
Body Center ◽  
All Speeds

This study investigated timing and coordination during the swing phase of swing leg, body center of mass (CoM) and head during walking people with multiple sclerosis (MS; n = 19) and controls (n = 19). The MS group showed differences in swing phase timing at all speeds. At imposed but not preferred speeds, the MS group had less time to prepare for entry into the unstable equilibrium, as the CoM entered this phase of swing earlier. Time-to-contact coupling, quantifying the coordination between the CoM and the swing foot, was not different between groups. The projection of head motion on the ground occurred earlier after toeoff and was positioned closer to the body in the MS group, illustrating increased reliance on visual exproprioception in which vision of the body in relation to the surface of support is established. Finally, prospective control, linking head movements to the swing foot time-to-contact and next step landing area, was impaired in the MS group at higher gait speeds.

scholarly journals Energy storage and release of prosthetic feet Part 1: Biomechanical analysis related to user benefits

1997 ◽  
Vol 21 (1) ◽  
pp. 17-27 ◽  
Author(s):  
K. Postema ◽  
H. J. Hermens ◽  
J. De Vries ◽  
H. F.J.M. Koopman ◽  
W. H. Eisma
Keyword(s):  
Energy Storage ◽  
Gait Analysis ◽  
Inverse Dynamics ◽  
Mechanical Energy ◽  
Randomised Trial ◽  
Metabolic Energy ◽  
Biomechanical Analysis ◽  
Double Blind ◽  
Measuring Device ◽  
Prosthetic Feet

The energy storing and releasing behaviour of 2 energy storing feet (ESF) and 2 conventional prosthetic feet (CF) were compared (ESF: Otto Bock Dynamic Pro and Hanger Quantum; CF: Otto Bock Multi Axial and Otto Bock Lager). Ten trans-tibial amputees were selected. The study was designed as a double-blind, randomised trial. For gait analysis a VICON motion analysis system was used with 2 AMTI force platforms. A special measuring device was used for measuring energy storage and release of the foot during a simulated step. The impulses of the anteroposterior component of the ground force showed small, statistically non-significant differences (deceleration phase: 22.7–23.4 Ns; acceleration phase: 17.0–18.4 Ns). The power storage and release phases as well as the net results also showed small differences (maximum difference in net result is 0.03 J kg−1). It was estimated that these differences lead to a maximum saving of 3% of metabolic energy during walking. It was considered unlikely that the subjects would notice this difference. It was concluded that during walking differences in mechanical energy expenditure of this magnitude are probably not of clinical relevance. Ankle power, as an indicator for energy storage and release gave different results to the energy storage and release as measured with the special test device, especially during landing response. In the biomechanical model (based on inverse dynamics) used in the gait analysis the deformation of the material is not taken into consideration and hence this method of gait analysis is probably not suitable for calculation of shock absorption.

Influence of Pedaling Rate on Muscle Mechanical Energy in Low Power Recumbent Pedaling Using Forward Dynamic Simulations

2007 ◽  
Author(s):  
Nils A. Hakansson ◽  
Maury L. Hull
Keyword(s):  
Low Power ◽  
Dynamic Model ◽  
Inverse Dynamics ◽  
Muscle Power ◽  
Mechanical Energy ◽  
Triceps Surae ◽  
Knee Extensors ◽  
Individual Muscle ◽  
The Individual ◽  
Pedaling Rate

An understanding of the muscle power contributions to the crank and limb segments in recumbent pedaling would be useful in the development of rehabilitative pedaling exercises. The objectives of this work were to (i) develop a forward dynamic model to simulate low-power pedaling in the recumbent position, (ii) use the model to quantify the power contributions of the muscles to driving the crank and limb segments, and (iii) determine whether there were differences in the muscle power contributions required to simulate recumbent pedaling at three different pedaling rates. A forward dynamic model was used to determine the individual muscle excitation amplitude and timing to drive simulations that best replicated experimental kinematics and kinetics of recumbent pedaling. The segment kinematics, pedal reaction forces, and electromyograms (EMG) of 10 muscles of the right leg were recorded from 16 subjects as they pedaled a recumbent ergometer at 40, 50, and 60 rpm and a constant 50 W workrate. Intersegmental joint moments were computed using inverse dynamics and the muscle excitation onset and offset timing were determined from the EMG data. All quantities were averaged across ten cycles for each subject and averaged across subjects. The model-generated kinematic and kinetic quantities tracked almost always within 1 SD of the experimental data for all three pedaling rates. The uniarticular hip and knee extensors generated 65 percent of the total mechanical work in recumbent pedaling. The triceps surae muscles transferred power from the limb segments to the crank and the bi-articular muscles that crossed the hip and knee delivered power to the crank during the leg transitions between flexion and extension. The functions of the individual muscles did not change with pedaling rate, but the mechanical energy generated by the knee extensors and hip flexors decreased as pedaling rate increased. By varying the pedaling rate, it is possible to manipulate the individual muscle power contributions to the crank and limb segments in recumbent pedaling and thereby design rehabilitative pedaling exercises to meet specific objectives.

Kinematic, kinetic and electromyographic adaptation to speed and resistance in double poling cross country skiing

2012 ◽  
Vol 113 (6) ◽  
pp. 1385-1394 ◽  
Author(s):  
Johnny Nilsson ◽  
Fredrik Tinmark ◽  
Kjartan Halvorsen ◽  
Anton Arndt
Keyword(s):  
Double Poling ◽  
Cross Country Skiing ◽  
Cross Country

scholarly journals Mechanical Energy and Propulsion in Ergometer Double Poling by Cross-country Skiers

2015 ◽  
Vol 47 (12) ◽  
pp. 2586-2594 ◽  
Author(s):  
JØRGEN DANIELSEN ◽  
ØYVIND SANDBAKK ◽  
HANS-CHRISTER HOLMBERG ◽  
GERTJAN ETTEMA
Keyword(s):  
Mechanical Energy ◽  
Double Poling ◽  
Cross Country

scholarly journals Recent Advances in Self-Powered Electrochemical Systems

Research ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Linglin Zhou ◽  
Di Liu ◽  
Li Liu ◽  
Lixia He ◽  
Xia Cao ◽  
...  
Keyword(s):  
Mechanical Energy ◽  
Power Source ◽  
Triboelectric Nanogenerator ◽  
Application Domain ◽  
Important Research ◽  
Electrochemical System ◽  
Electrochemical Systems ◽  
External Power Source ◽  
External Power ◽  
Self Powered

Electrochemistry, one of the most important research and production technology, has been widely applicated in various fields. However, the requirement of external power source is a major challenge to its development. To solve this issue, developing self-powered electrochemical system (SPES) that can work by collecting energy from the environment is highly desired. The invention of triboelectric nanogenerator (TENG), which can transform mechanical energy into electricity, is a promising approach to build SPES by integrating with electrochemistry. In this view, the latest representative achievements of SPES based on TENG are comprehensively reviewed. By harvesting various mechanical energy, five SPESs are built, including electrochemical pollutants treatment, electrochemical synthesis, electrochemical sensor, electrochromic reaction, and anticorrosion system, according to the application domain. Additionally, the perspective for promoting the development of SPES is discussed.

Arm, Trunk and Leg Contributions to Double Poling Performance in Cross-Country Skiing

2004 ◽  
Vol 36 (Supplement) ◽  
pp. S14
Author(s):  
Gerald A. Smith ◽  
Johnny Nilsson ◽  
Bent Kvamme ◽  
Jarle Ure ◽  
Frank Ingjer
Keyword(s):  
Double Poling ◽  
Cross Country Skiing ◽  
Cross Country
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