Torso Stabilization Reduces the Metabolic Cost of Producing Cycling Power

2005 ◽  
Vol 30 (4) ◽  
pp. 433-441 ◽  
Author(s):  
John McDaniel ◽  
Andrew Subudhi ◽  
James C. Martin
Keyword(s):  
Ventilatory Threshold ◽  
Muscle Metabolism ◽  
Control Unit ◽  
Metabolic Cost ◽  
Cycle Ergometer ◽  
Whole Body ◽  
Strongly Correlated ◽  
Wide Range ◽  
Static Contraction ◽  
Power Outputs

Many researchers have used cycling exercise to evaluate muscle metabolism. Inherent in such studies is an assumption that changes in whole-body respiration are due solely to respiration at the working muscle. Some researchers, however, have speculated that the metabolic cost of torso stabilization may contribute to the metabolic cost of cycling. Therefore, our primary purpose was to determine whether a torso stabilization device would reduce the metabolic cost of producing cycling power. Our secondary purpose was to determine the validity of the ergometer used in this study. Nine male cyclists cycled on a Velotron cycle ergometer at mechanical power outputs intended to elicit 50, 75, and 100% of their ventilatory threshold at 40, 60, and 80 rpm, with and without torso stabilization. Power was controlled by the Velotron in iso-power mode and measured with an SRM powermeter. We determined metabolic cost by indirect calorimetery and recorded power output. Torso stabilization significantly reduced metabolic cost of producing submaximal power (1%), and reduction tended to be greatest at the lower pedaling rates where pedaling force was greatest (1.6% at 40 rpm, 1.2% at 60 rpm, 0.2% at 80 rpm). Power, measured with the SRM powermeter, was strongly correlated with that specified to the Velotron ergometer control unit (R2 > 0.99). We conclude that muscular contractions associated with torso stabilization elicit significant metabolic costs, which tend to be greatest at low pedaling rates. Researchers who intend to make precise inferences regarding metabolism in the working muscles of the legs may wish to provide torso stabilization as a means of reducing variability, particularly when comparing metabolic data across a wide range of pedaling rates. Key words: efficiency, economy, metabolism, static contraction, work

A computer simulation of free-range exercise in the laboratory

1999 ◽  
Vol 87 (4) ◽  
pp. 1386-1391 ◽  
Author(s):  
E. Terblanche ◽  
J. A. Wessels ◽  
R. I. Stewart ◽  
J. H. Koeslag
Keyword(s):  
Computer Simulation ◽  
Aerodynamic Drag ◽  
Cycle Ergometer ◽  
Input Stimulus ◽  
Laboratory Exercise ◽  
Free Range ◽  
Drag Forces ◽  
Wide Range ◽  
Power Outputs ◽  
Fundamental Requirement

We present a technique for simulating dynamic field (free-range) exercise, using a novel computer-controlled cycle ergometer. This modified cycle ergometer takes into account the effect of friction and aerodynamic drag forces on a 70-kg cyclist in a racing position. It also affords the ability to select different gear ratios. We have used this technique to simulate a known competition cycle route in Cape Town, South Africa. In an attempt to analyze the input stimulus, in this case the generated power output of each cyclist, eight subjects cycled for 40 min at a self-selected, comfortable pace on the first part of the simulated route. Our results indicate that this exercise input excites the musculocardiorespiratory system over a wide range of power outputs, both in terms of amplitude and frequency. This stimulus profile thereby complies with the fundamental requirement for nonlinear (physiological) systems analysis and identification. Through a computer simulation, we have devised a laboratory exercise protocol that not only is physiologically real but also overcomes the artificiality of most traditional laboratory exercise protocols.

scholarly journals Soft tissue deformations explain most of the mechanical work variations of human walking

2021 ◽  
Author(s):  
Tim J. van der Zee ◽  
Arthur D. Kuo
Keyword(s):  
Soft Tissue ◽  
Soft Tissues ◽  
Metabolic Cost ◽  
Step Length ◽  
Mechanical Work ◽  
Metabolic Energy ◽  
Whole Body ◽  
Negative Work ◽  
Work Distribution ◽  
Wide Range

Humans perform mechanical work during walking, some by leg joints actuated by muscles, and some by passive, dissipative soft tissues. Dissipative losses must be restored by active muscle work, potentially in amounts sufficient to cost substantial metabolic energy. The most dissipative, and therefore costly, walking conditions might be predictable from the pendulum-like dynamics of the legs. If this behavior is systematic, it may also predict the work distribution between active joints and passive soft tissues. We therefore tested whether the overall negative work of walking, and the fraction due to soft tissue dissipation, are both predictable by a simple dynamic walking model across a wide range of conditions. The model predicts whole-body negative work from the leading leg's impact with ground (termed the Collision), to increase with the squared product of walking speed and step length. We experimentally tested this in humans (N=9) walking in 26 different combinations of speed (0.7 – 2.0 m·s−1) and step length (0.5 – 1.1 m), with recorded motions and ground reaction forces. Whole-body negative Collision work increased as predicted (R2=0.73), with a consistent fraction of about 63% (R2=0.88) due to soft tissues. Soft tissue dissipation consistently accounted for about 56% of the variation in total whole-body negative work, across a wide range of speed and step length combinations. During typical walking, active work to restore dissipative losses could account for 31% of the net metabolic cost. Soft tissue dissipation, not included in most biomechanical studies, explains most of the variation in negative work of walking, and could account for a substantial fraction of the metabolic cost.

scholarly journals Somatotype Variables Related to Muscle Torque and Power in Judoists

2011 ◽  
Vol 30 (1) ◽  
pp. 21-28 ◽  
Author(s):  
Joanna Lewandowska ◽  
Krzysztof Buśko ◽  
Anna Pastuszak ◽  
Katarzyna Boguszewska
Keyword(s):  
Power Output ◽  
Body Height ◽  
Correlation Coefficients ◽  
Cycle Ergometer ◽  
Strongly Correlated ◽  
Muscle Torque ◽  
Ergometer Exercise ◽  
Muscle Groups ◽  
Power Outputs ◽  
Static Conditions

Somatotype Variables Related to Muscle Torque and Power in Judoists The purpose of this study was to examine the relationship between somatotype, muscle torque and power output in judoists. Thirteen judoists (age 18.4±3.1 years, body height 178.6±8.2 cm, body mass 82.3±15.9 kg) volunteered to participate in this study. Somatotype was determined using the Heath-Carter method. Maximal muscle torques of elbow, shoulder, knee, hip and trunk flexors as well as extensors were measured under static conditions. Power outputs were measured in 5 maximal cycle ergometer exercise bouts, 10 s each, at increasing external loads equal to 2.5, 5.0, 7.5, 10.0 and 12.5% of body weight. The Pearson's correlation coefficients were calculated between all parameters. The mean somatotype of judoists was: 3.5-5.9-1.8 (values for endomorphy, mesomorphy and ectomorphy, respectively). The values (mean±SD) of sum of muscle torque of ten muscle groups (TOTAL) was 3702.2±862.9 N × m. The power output ranged from 393.2±79.4 to 1077.2±275.4 W. The values of sum of muscle torque of right and left upper extremities (SUE), sum of muscle torque of right and left lower extremities (SLE), sum of muscle torque of the trunk (ST) and TOTAL were significantly correlated with the mesomorphic component (0.68, 0.80, 0.71 and 0.78, respectively). The ectomorphic component correlated significantly with values of SUE, SLE, ST and TOTAL (-0.69, -0.81, -0.71 and -0.79, respectively). Power output was also strongly correlated with both mesomorphy (positively) and ectomorphy (negatively). The results indicated that the values of mesomorphic and ectomorphic somatotype components influence muscle torque and power output, thus body build could be an important factor affecting results in judo.

Time to exhaustion during cycling is not well predicted by critical power calculations

2020 ◽  
Vol 45 (7) ◽  
pp. 753-760 ◽  
Author(s):  
Jesus G. Pallarés ◽  
Jose R. Lillo-Bevia ◽  
Ricardo Morán-Navarro ◽  
Victor Cerezuela-Espejo ◽  
Ricardo Mora-Rodriguez
Keyword(s):  
Oxygen Consumption ◽  
Power Output ◽  
Critical Power ◽  
Maximal Oxygen Consumption ◽  
Cycle Ergometer ◽  
Time To Exhaustion ◽  
Wingate Anaerobic Test ◽  
Wide Range ◽  
Power Outputs ◽  
Anaerobic Test

Three to 5 cycling tests to exhaustion allow prediction of time to exhaustion (TTE) at power output based on calculation of critical power (CP). We aimed to determine the accuracy of CP predictions of TTE at power outputs habitually endured by cyclists. Fourteen endurance-trained male cyclists underwent 4 randomized cycle-ergometer TTE tests at power outputs eliciting (i) mean Wingate anaerobic test (WAnTmean), (ii) maximal oxygen consumption, (iii) respiratory compensation threshold (VT2), and (iv) maximal lactate steady state (MLSS). Tests were conducted in duplicate with coefficient of variation of 5%–9%. Power outputs were 710 ± 63 W for WAnTmean, 366 ± 26 W for maximal oxygen consumption, 302 ± 31 W for VT2 and 247 ± 20 W for MLSS. Corresponding TTE were 00:29 ± 00:06, 03:23 ± 00:45, 11:29 ± 05:07, and 76:05 ± 13:53 min:s, respectively. Power output associated with CP was only 2% lower than MLSS (242 ± 19 vs. 247 ± 20 W; P < 0.001). The CP predictions overestimated TTE at WAnTmean (00:24 ± 00:10 mm:ss) and MLSS (04:41 ± 11:47 min:s), underestimated TTE at VT2 (–04:18 ± 03:20 mm:ss; P < 0.05), and correctly predicted TTE at maximal oxygen consumption. In summary, CP accurately predicts MLSS power output and TTE at maximal oxygen consumption. However, it should not be used to estimate time to exhaustion in trained cyclists at higher or lower power outputs (e.g., sprints and 40-km time trials). Novelty CP calculation enables to predict TTE at any cycling power output. We tested those predictions against measured TTE in a wide range of cycling power outputs. CP appropriately predicted TTE at maximal oxygen consumption intensity but err at higher and lower cycling power outputs.

A Novel Approach for Lactate Threshold Assessment Based on Rating of Perceived Exertion

2013 ◽  
Vol 8 (3) ◽  
pp. 263-270 ◽  
Author(s):  
Nicolas Fabre ◽  
Laurent Mourot ◽  
Livio Zerbini ◽  
Barbara Pellegrini ◽  
Lorenzo Bortolan ◽  
...  
Keyword(s):  
Lactate Threshold ◽  
Perceived Exertion ◽  
Ventilatory Threshold ◽  
Lactate Concentration ◽  
Cycle Ergometer ◽  
Rating Of Perceived Exertion ◽  
Strongly Correlated ◽  
Incremental Test ◽  
Distance Method ◽  
Novel Approach

This study tested the hypothesis that the DMAX (for maximal distance) method could be applied to ratings of perceived exertion (RPE), to propose a novel method for individual detection of the lactate threshold (LT) using RPE alone during an incremental test to exhaustion. Twenty-one participants performed an incremental test on a cycle ergometer. At the end of each stage, lactate concentration was measured and the participants estimated RPE using the Borg CR100 scale. The intensity corresponding to the fixed lactate values of 2 or 4 mmol · L−1(2mM and 4mM), the ventilatory threshold (VT), the respiratory-compensation point (RCP), and the instant of equality of pulmonary gas exchange (RER=1.00) were determined. Lactate (DMAX La) and RPE (DMAX RPE) thresholds were determined using the DMAX method. Oxygen uptake (VO2), heart rate, and power output measured at DMAX RPE and at DMAX La were not statistically different. Bland-Altman plots showed small bias and good agreements when DMAX RPE was compared with the DMAX La and RER=1.00 methods (bias = −0.05% and −2% of VO2max, respectively). Conversely, VO2 from the DMAX RPE method was lower than VO2 at 4 mM and at RCP and was higher than VO2 at 2 mM and at VT. VO2 at DMAX RPE was strongly correlated with VO2 at DMAX La (r = .97), at RER=1.00 (r = .97), at 2 mM (r = .85), at 4 mM (r = .93), at VT (r = .95), and at RCP (r = .95). The combination of the DMAX method with the RPE responses permitted precise and individualized estimates of LT using the DMAX method.

Age- and sex-related bone uptake of Tc-99m-HDP measured by whole-body bone scanning

2000 ◽  
Vol 39 (05) ◽  
pp. 127-132 ◽  
Author(s):  
Nicole Sieweke ◽  
K. H. Bohuslavizki ◽  
W. U. Kampen ◽  
M. Zuhayra ◽  
M. Clausen ◽  
...  
Keyword(s):  
Whole Body ◽  
Bone Lesions ◽  
Men And Women ◽  
Bone Uptake ◽  
Normal Bone ◽  
Age Related ◽  
Number Of Patients ◽  
Wide Range ◽  
Bone Scans ◽  
Body Bone

Summary Aim of this study was to validate a recently introduced new and easy-to-perform method for quantifying bone uptake of Tc-99m-labelled diphosphonate in a routine clinical setting and to establish a normal data base for bone uptake depending on age and gender. Methods: In 49 women (14-79 years) and 47 men (6-89 years) with normal bone scans as well as in 49 women (33-81 years) and 37 men (27-88 years) with metastatic bone disease whole-body bone scans were acquired at 3 min and 3-4 hours p.i. to calculate bone uptake after correction for both urinary excretion and soft tissue retention. Results: Bone uptake values of various age-related subgroups showed no significant differences between men and women (p >0.05 ). Furthermore, no differences could be proven between age-matched subgroups of normals and patients with less than 10 metastatic bone lesions, while patients with wide-spread bone metastases revealed significantly increased uptake values. In both men and women highest bone uptake was obtained (p <0.05 ) in subjects younger than 20 years with active epiphyseal growth plates. In men, bone uptake slowly decreased with age up to 60 years and then showed a tendency towards increasing uptake values. In women, the mean uptake reached a minimun in the decade 20-29 years and then slowly increased with a positive linear correlation of age and uptake in subjects older than 55 years (r = 0.57). Conclusion: Since the results proposed in this study are in good agreement with data from literature, the new method used for quantification could be validated in a large number of patients. Furthermore, age- and sexrelated normal bone uptake values of Tc-99m-HDP covering a wide range of age could be presented for this method as a basis for further studies on bone uptake.

scholarly journals Using a simple rope-pulley system that mechanically couples the arms, legs, and treadmill reduces the metabolic cost of walking

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Daisey Vega ◽  
Christopher J. Arellano
Keyword(s):  
Metabolic Cost ◽  
Metabolic Energy ◽  
Metabolic Effects ◽  
Whole Body ◽  
Walking Ability ◽  
Arm Swing ◽  
Pulley System ◽  
Young Subjects ◽  
Walking Recovery ◽  
Set Up

Abstract Background Emphasizing the active use of the arms and coordinating them with the stepping motion of the legs may promote walking recovery in patients with impaired lower limb function. Yet, most approaches use seated devices to allow coupled arm and leg movements. To provide an option during treadmill walking, we designed a rope-pulley system that physically links the arms and legs. This arm-leg pulley system was grounded to the floor and made of commercially available slotted square tubing, solid strut channels, and low-friction pulleys that allowed us to use a rope to connect the subject’s wrist to the ipsilateral foot. This set-up was based on our idea that during walking the arm could generate an assistive force during arm swing retraction and, therefore, aid in leg swing. Methods To test this idea, we compared the mechanical, muscular, and metabolic effects between normal walking and walking with the arm-leg pulley system. We measured rope and ground reaction forces, electromyographic signals of key arm and leg muscles, and rates of metabolic energy consumption while healthy, young subjects walked at 1.25 m/s on a dual-belt instrumented treadmill (n = 8). Results With our arm-leg pulley system, we found that an assistive force could be generated, reaching peak values of 7% body weight on average. Contrary to our expectation, the force mainly coincided with the propulsive phase of walking and not leg swing. Our findings suggest that subjects actively used their arms to harness the energy from the moving treadmill belt, which helped to propel the whole body via the arm-leg rope linkage. This effectively decreased the muscular and mechanical demands placed on the legs, reducing the propulsive impulse by 43% (p < 0.001), which led to a 17% net reduction in the metabolic power required for walking (p = 0.001). Conclusions These findings provide the biomechanical and energetic basis for how we might reimagine the use of the arms in gait rehabilitation, opening the opportunity to explore if such a method could help patients regain their walking ability. Trial registration: Study registered on 09/29/2018 in ClinicalTrials.gov (ID—NCT03689647).

scholarly journals Partitional calorimetry

2019 ◽  
Vol 126 (2) ◽  
pp. 267-277 ◽  
Author(s):  
Matthew N. Cramer ◽  
Ollie Jay
Keyword(s):  
Heat Balance ◽  
Estimation Error ◽  
Fluid Replacement ◽  
Whole Body ◽  
Exposure Limits ◽  
Experimental Conditions ◽  
Direct Calorimetry ◽  
Fundamental Properties ◽  
Wide Range ◽  
Partitional Calorimetry

For thermal physiologists, calorimetry is an important methodological tool to assess human heat balance during heat or cold exposures. A whole body direct calorimeter remains the gold standard instrument for assessing human heat balance; however, this equipment is rarely available to most researchers. A more widely accessible substitute is partitional calorimetry, a method by which all components of the conceptual heat balance equation—metabolic heat production, conduction, radiation, convection, and evaporation—are calculated separately based on fundamental properties of energy exchange. Since partitional calorimetry requires relatively inexpensive equipment (vs. direct calorimetry) and can be used over a wider range of experimental conditions (i.e., different physical activities, laboratory or field settings, clothed or seminude), it allows investigators to address a wide range of problems such as predicting human responses to thermal stress, developing climatic exposure limits and fluid replacement guidelines, estimating clothing properties, evaluating cooling/warming interventions, and identifying potential thermoregulatory dysfunction in unique populations. In this Cores of Reproducibility in Physiology (CORP) review, we summarize the fundamental principles underlying the use of partitional calorimetry, present the various methodological and arithmetic requirements, and provide typical examples of its use. Strategies to minimize estimation error of specific heat balance components, as well as the limitations of the method, are also discussed. The goal of this CORP paper is to present a standardized methodology and thus improve the accuracy and reproducibility of research employing partitional calorimetry.

Composition and Mechanics of Routine Swimming of Rainbow Trout, Oncorhynchus mykiss

1991 ◽  
Vol 48 (4) ◽  
pp. 583-590 ◽  
Author(s):  
Paul W. Webb
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Correction Factor ◽  
Swimming Speed ◽  
Angular Acceleration ◽  
Force Balance ◽  
Whole Body ◽  
Strongly Correlated ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Tail Beat

Routine swimming encompasses all volitional motions of fish. It is usually assumed to be quasi-steady, i.e. routine swimming is mechanically equivalent to steady swimming. Routine swimming of rainbow trout, Oncorhynchus mykiss, was dominated by unsteady motions of linear and centripetal (angular) acceleration. Constant-speed swimming was rare. Mean speeds and acceleration rates were small. Tail-beat frequencies were nevertheless strongly correlated with mean swimming speed, but increased more rapidly with increasing speed in routine swimming than in steady swimming. Tail-beat amplitudes and propulsive wavelengths were similar to values seen in steady swimming. The composition of routine swimming and analysis of the force balance showed that routine swimming was not quasi-steady. Therefore, forces and rates of working should be estimated from a complete description of whole-body deformation. This is impractical. Drag dominated resistance in routine swimming, such that average thrust (= resistance) may be computed from mean speed and/or averaged kinematic variables for the trailing edge with a correction factor of approximately 3. Analysis of routine swimming may permit comparisons among a wider range of vertebrates than possible with commonly used methods.

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