An analysis of performance in human locomotion

Ferretti, Guido; Bringard, Aurélien; Perini, Renza

doi:10.1007/s00421-010-1482-y

Cited by 20 publications

(24 citation statements)

References 69 publications

(81 reference statements)

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“…maximal oxygen uptake ( V O )), 4,5 V O at the lactate threshold, 4,6 and the efficiency with which metabolic energy is transferred into effective power output (PO). [7][8][9][10] During relatively short competitive events (less than ~10 min) there is also an anaerobic contribution to energy expenditure, which needs to be accounted for. 3,11,12 For example, Foster et al 13 found that the relative contribution of anaerobic energy expenditure to total work done during a 3000 m time trial was 30%.…”

Section: Introductionmentioning

confidence: 99%

Factors Affecting Gross Efficiency in Cycling

et al. 2012

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There is little standardization of how to measure cycling gross efficiency (GE). Therefore, the purposes of these studies were to evaluate the effect of: i) stage duration, ii) relative exercise intensity, iii) work capacity and iv) a prior maximal incremental test on GE. Trained subjects (n=28) performed incremental tests with stage durations of 1-, 3-, and 6-min to establish the effect of stage duration and relative exercise intensity on GE. The effect of work capacity was evaluated by correlating GE with peak power output (PPO). In different subjects (n=9), GE was measured at 50% PPO with and without a prior maximal incremental test. GE was similar in 3- and 6-min stages (19.7 ± 2.8% and 19.3 ± 2.0%), but significantly higher during 1-min stages (21.1 ± 2.7%), GE increased with relative exercise intensity, up to 50% PPO or the power output corresponding to the ventilatory threshold and then remained stable. No relationship between work capacity and GE was found. Prior maximal exercise had a small effect on GE measures; GE was lower after maximal exercise. In conclusion, GE can be determined robustly so long as steady state exercise is performed and RER ≤ 1.0.

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Section: Introductionmentioning

confidence: 99%

Factors Affecting Gross Efficiency in Cycling

et al. 2012

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“…Ceteris paribus, P D is directly proportional to C x , so that dynamically favourable shapes are characterized by low C x values, as is the case for aerodynamic contemporary cars or track bicycles used for record trials (Capelli et al 1993; di Prampero 2000) (see Fig. 2.11) Since D is a force, in analogy with C, it can be expressed as mechanical work per unit of distance (Ferretti et al 2011), so that…”

Section: Energy Cost Of Locomotionmentioning

confidence: 98%

“…But walking, with respect to all other types of locomotion, is peculiar, because of the effects of pendulum-like mechanism and the ensuing transformation of potential energy into kinetic energy and vice versa. Concerning running, C was generally considered invariant in a given individual and thus independent of the running speed (di Prampero 1986;Ferretti et al 2011), possibly as a consequence of the fact that most data were obtained during treadmill running, a condition in which the running human moves with respect to the treadmill's belt, but not with respect to air (Dill 1965;di Prampero et al 1986;Hagberg and Coyle 1984;Helgerud 1994;Margaria et al 1963;McMiken and Daniels 1976;Minetti et al 2002;Padilla et al 1992, to give a few examples). Yet Pugh (1970) demonstrated that a fraction of C varies with the square of wind velocity, although this fraction was considered small.…”

Section: Energy Cost Of Locomotionmentioning

confidence: 99%

Aerobic Metabolism and the Steady-State Concept

Ferretti

2015

Energetics of Muscular Exercise

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This chapter contains an analysis of the steady-state concept, as it is applied during light exercise. In this case, oxygen consumption increases upon exercise onset to attain a steady level, which can be maintained for a long period of time. The steady-state oxygen consumption is proportional to the exerted mechanical power. Under these circumstances, there is neither accumulation of lactate in blood nor changes in muscle phosphocreatine concentration: aerobic metabolism sustains the entire energy requirement of the exercising body. Once the steady state has been attained, the flow of oxygen is the same at all levels along the respiratory system. The quantitative relations determining the flow of oxygen across the alveoli and in blood are discussed. Special attention is given to the effects of ventilation-perfusion inequality and to the diffusion-perfusion interaction equations. The cardiovascular responses at exercise steady state are analysed in the context of the equilibrium between systemic oxygen delivery and systemic oxygen return. The relationship between oxygen consumption and power is discussed, along with the distinction between external and internal work during cycling. The concepts of mechanical efficiency of exercise and energy cost of locomotion are analysed. Concerning the latter, the distinction between aerodynamic work and frictional work is introduced. The roles of the cross-sectional surface area on the frontal plane and of air density in aerodynamic work are discussed. To end with, an equation linking ventilation, circulation and metabolism at exercise in a tight manner is developed, around the notion that the homeostasis of the respiratory system at exercise is maintained around given values of the constant oxygen return. This equation tells that, as long as we are during steady-state exercise in normoxia, any increase in the exercise metabolic rate requires an increase in ventilation that is proportional to that in oxygen consumption only if the pulmonary respiratory quotient stays invariant does not change, and an increase in cardiac output that is not proportional to the corresponding increase in oxygen consumption. At intense exercise, when lactate accumulation also occurs and hyperventilation superimposes, a new steady state would be attained only at P A CO 2 values lower than 40 mmHg: the homeostasis of the respiratory system would be modified. This new steady state, however, is never attained in fact, for reasons that are discussed in Chap. 3.

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“…P max is defined as the apex of the P ext -cadence relationship at a specific performance level and C opt is defined as the specific value at which P max occurs (Dorel et al 2005(Dorel et al , 2010Emanuele and Denoth 2011;Hintzy et al 1999;Martin et al 1997). It is clear that the longer the given race distance, the lower the sustainable P max , respectively, the sustainable performance level will be (di Prampero 2003;Ferretti et al 2011). Thus, P max in a short-term sprint cycling performance is by a multiple greater than P max in an endurance cycling performance.…”

Section: Introductionmentioning

confidence: 99%

Influence of road incline and body position on power–cadence relationship in endurance cycling

Emanuele

Denoth

2011

Eur J Appl Physiol

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In race cycling, the external power-cadence relationship at the performance level, that is sustainable for the given race distance, plays a key role. The two variables of interest from this relationship are the maximal external power output (P (max)) and the corresponding optimal cadence (C (opt)). Experimental studies and field observations of cyclists have revealed that when cycling uphill is compared to cycling on level ground, the freely chosen cadence is lower and a more upright body position seems to be advantageous. To date, no study has addressed whether P (max) or C (opt) is influenced by road incline or body position. Thus, the main aim of this study was to examine the effect of road incline (0 vs. 7%) and racing position (upright posture vs. dropped posture) on P (max) and C (opt). Eighteen experienced cyclists participated in this study. Experiment I tested the hypothesis that road incline influenced P (max) and C (opt) at the second ventilatory threshold ([Formula: see text] and [Formula: see text]). Experiment II tested the hypothesis that the racing position influenced [Formula: see text], but not [Formula: see text]. The results of experiment I showed that [Formula: see text] and [Formula: see text] were significantly lower when cycling uphill compared to cycling on level ground (P < 0.01). Experiment II revealed that [Formula: see text] was significantly greater for the upright posture than for the dropped posture (P < 0.01) and that the racing position did not affect [Formula: see text]. The main conclusions of this study were that when cycling uphill, it is reasonable to choose (1) a lower cadence and (2) a more upright body position.

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An analysis of performance in human locomotion

Cited by 20 publications

References 69 publications

Factors Affecting Gross Efficiency in Cycling

Factors Affecting Gross Efficiency in Cycling

Aerobic Metabolism and the Steady-State Concept

Influence of road incline and body position on power–cadence relationship in endurance cycling

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