External work in level walking

Gersten, Jerome W.; Orr, William; Sexton, A. W.; Okin, D.

doi:10.1152/jappl.1969.26.3.286

Cited by 17 publications

(5 citation statements)

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“…In the 1960s, some authors attempted to measure the external mechanical work produced by walking by using portable accelerometers (Cavagna et al 1963, Gersten et al 1969. This method has permitted the evaluation of the energy output of the body and an understanding of the mechanisms of gait.…”

Section: Discussionmentioning

confidence: 99%

Can accelerometry accurately predict the energy cost of uphill/downhill walking?

2001

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To evaluate whether an activity monitor based on body acceleration measurement can accurately assess the energy cost of the human locomotion, 12 subjects walked a combination of three different speeds (preferred speed +/- 1 km/h) and seven slopes (-15 to +15% by steps of 5%) on a treadmill. Body accelerations were recorded using a triaxial accelerometer attached to the low back. The mean of the integral of the vector magnitude (norm) of the accelerations (mIAN) was calculated. VO2 was measured using continuous indirect calorimetry. When the results were separately analysed for each incline, mIAN was correlated to VO2 (average r = 0.87, p<0.001, n = 36). VO2 was not significantly correlated to mIAN when data were globally analysed (n = 252). Large relative errors occurred when predicted VO2 (estimated from data of level walking) was compared with measured VO2 for different inclines (-53% at +15% incline, to +55% at -15% incline). It is concluded that without an external measurement of the slope, the standard method of analysis of body accelerations cannot accurately predict the energy cost of uphill or downhill walking.

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Section: Discussionmentioning

confidence: 99%

Can accelerometry accurately predict the energy cost of uphill/downhill walking?

2001

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“…Another significant error can be seen when assessing the technique used by certain researchers (12) who have attached a marker or accelerometer near the anatomic center of gravity.…”

Section: Discussionmentioning

confidence: 99%

“…Also, the force plate does not record any measure of segment rotational kinetic energy. In 1969 Gersten and colleagues(12) utilized a triaxial…”

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confidence: 99%

A new definition of mechanical work done in human movement

Winter¹

1979

Journal of Applied Physiology

201

119

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The definition of efficiency of human movement has often been unable to cope with activities such as level gait because the numerator of the efficiency equation includes only external work done by the body on an external load. The major purpose of this paper is to propose a definition that not only accounts for any external work but also the internal work done by the limbs themselves. The internal work involves a new biomechanical analysis that takes into account all potential and kinetic energy components, all exchanges of energy within and between segments, and both positive and negative work done by the muscles. This analysis was applied to a study of over-ground level gait on eight subjects walking at different walking speeds. The internal work/stride as calculated from the sum of segment energies was compared with the same calculation on the body's center of mass energy. The latter was found to be in error (low) by 16.2% and could be low by as much as 40%. The average internal work per body mass per distance walked was 1.09 J/kg.m.

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“…They evaluated stride length (70,72), joint forces and moments (9,13,38), joint ranges of motion (50), path of the center of pressure on the foot (32,77), mechanical power (47,79), external work (28), timing of gait events (77), braking impulse (54), and the effects of speed on mechanics (64).…”

Section: Introductionmentioning

confidence: 99%