Misuse of “Power” and other mechanical terms in sport
and exercise science research
WINTER, Edward M., ABT, Grant, BROOKES, F.B. Carl, CHALLIS, John H.,
FOWLER, Neil E., KNUDSON, Duane V., KNUTTGEN, Howard G.,
KRAEMER, William J., LANE, Andrew M., MECHELEN, Willem van,
MORTON, R. Hugh, NEWTON, Robert U., WILLIAMS, Clyde and YEADON,
M. R.
Available from Sheffield Hallam University Research Archive (SHURA) at:
http://shura.shu.ac.uk/13594/
This document is the author deposited version. You are advised to consult the
publisher's version if you wish to cite from it.
Published version
WINTER, Edward M., ABT, Grant, BROOKES, F.B. Carl, CHALLIS, John H.,
FOWLER, Neil E., KNUDSON, Duane V., KNUTTGEN, Howard G., KRAEMER,
William J., LANE, Andrew M., MECHELEN, Willem van, MORTON, R. Hugh,
NEWTON, Robert U., WILLIAMS, Clyde and YEADON, M. R. (2016). Misuse of
“Power” and other mechanical terms in sport and exercise science research. Journal
of Strength and Conditioning Research, 30 (1), 292-300.
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See http://shura.shu.ac.uk/information.html
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Misuse of "Power" and other mechanical terms in Sport and Exercise Science Research
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Abstract
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In spite of the Système International d’Unitès (SI) that was published in 1960, there
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continues to be widespread misuse of the terms and nomenclature of mechanics in
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descriptions of exercise performance. Misuse applies principally to failure to
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distinguish between mass and weight, velocity and speed, and especially the terms
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"work" and "power." These terms are incorrectly applied across the spectrum from
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high-intensity short-duration to long-duration endurance exercise. This review
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identifies these misapplications and proposes solutions. Solutions include adoption of
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the term "intensity" in descriptions and categorisations of challenge imposed on an
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individual as they perform exercise, followed by correct use of SI terms and units
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appropriate to the specific kind of exercise performed. Such adoption must occur by
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authors and reviewers of sport and exercise research reports to satisfy the principles
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and practices of science and for the field to advance.
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1. INTRODUCTION
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The French philosopher and Nobel Laureate André Gide (1869-1951) is reputed to
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have begun talks he gave with the following extract from his 1950 publication
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Autumn Leaves:
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Everything's already been said, but since nobody was listening, we
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have to start again.
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Sport and exercise science is the scientific study of factors that influence the ability to
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perform exercise (also known, according to circumstances, as physical activity) as
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well as the resulting adaptations. This study is directed principally at humans but it is
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also applicable to equine, canine, avian, and other animal contexts. Importantly,
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terms and nomenclature used to describe exercise should abide by the Système
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International d'Unités (SI) i.e. be simple, precise, and accurate. The SI system
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comprises seven base units, prefixes and derived units (Table 1). This enables
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scientists from different disciplines to communicate effectively (24) and germane here,
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to advance sport and exercise science. With Institutional ethics approval, the purpose
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of this review is to highlight principally how "power", but also other SI mechanical
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variables, are misused in many exercise science research reports and then indicate
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correct use of terms and nomenclature that best describe and evaluate exercise
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performance. The review will define exercise and then proceed to examine misuse of
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mass and weight, work, velocity, power, and efficiency. For all physical activities
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Newton's Second Law will be demonstrated as the fundamental mechanical
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relationship used to document the causes of performance. A case will be made to
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abandon the phrase "critical power" and adopt instead "critical intensity" for the
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otherwise laudable concept of tolerance to exercise. Finally, a recommendation will
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be made to ensure that if sport and exercise science research is to be recognised as an
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established and credible area of application of science and so advance, terms and
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nomenclature to describe the performance of exercise must abide by principles of
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mechanics laid down by Newton and in turn, use the SI.
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2. EXERCISE
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For military, occupational, and within the last two hundred years or so, sport-, leisure-
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related, health and quality-of-life reasons, the need to quantify either total exercise
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accomplished or the effectiveness with which exercise is performed has been a
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principal focus. This focus continues.
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The World Health Organisation defines exercise as:
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A subcategory of physical activity that is planned, structured,
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repetitive, and purposeful in the sense that the improvement or
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maintenance of one or more components of physical fitness is the
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objective. (http://www.who.int/dietphysicalactivity/pa/en/).
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Exercise can also be defined as:
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A potential disruption to homeostasis by muscle activity that is
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either exclusively or in combination, concentric, isometric or
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eccentric.
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(33).
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Only one of these definitions (33) acknowledges that either deliberately or out of
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necessity, gross external movement is not always a primary outcome. Where
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accelerated movement does occur, the activities are dynamic. Where it does not, the
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activities are static. Examples of the latter are the primarily isometric muscle actions
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in balance, a yoga pose, or in gymnastics, strength poses such as the crucifix on rings.
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In some sports such as gymnastics, and weight-lifting, movement after completion of
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dismount or lift is undesirable and is penalised by the judges or referees. In others
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such as archery and shooting, stillness is crucial for performance (34). Even in
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dynamic sports such as luge, skeleton bobsled and swimming, the ability to hold
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streamlined positions of the body is decisive
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(http://www.geomagic.com/en/community/case-studies/british-team-uses-geomagic-
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3d-reverse-engineering-to-streamline-/, 9). Similarly, in sailing, the ability to
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maintain high-force, isometric muscle activity for prolonged durations is crucial. In
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scrums in Rugby Union, 16 players can be primarily exercising isometrically for 10 s
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or so with maximal effort, yet minimal external movement occurs. Even in dynamic
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activities such as running and swimming, stabiliser and fixator muscles act either
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actually or quasi isometrically. Moreover, many activities of daily living require little
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or no movement (e.g. maintenance of posture, supporting objects in domestic tasks,
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screwing the tops on jars until tight and maintaining yoga poses).
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While the ability of muscle to exert force in a discrete task is important, the ability
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repeatedly to exert force (i.e. sustain exercise in endurance activities), is equally
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important. Effective endurance performance requires an ability to delay the onset of
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fatigue - taken here to be "any reduction in force-generating capacity (measured as
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maximum voluntary muscle action), regardless of the task performed" (5).
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3. QUANTIFYING THE ABILITY TO PERFORM EXERCISE
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Precise quantification of exercise is an integral part of research to improve our
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knowledge and understanding of factors that influence the ability to perform exercise.
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However, there is a key confounding factor that traps the unwary: human and other
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animal bodies are not simple, rigid systems. They are complex, multi-segment
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systems and muscular performance does not always result in movement. Even where
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movement does occur and in spite of concerns expressed by many (1, 17, 18, 24, 27,
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30, 33), exercise science researchers frequently misapply classical mechanics
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presented by Newton in 1687 in his three-volume Philosophæ Naturalis Principia
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Mathematica (Mathematical Principles of Natural Philosophy). Misapplications are
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most common for the mechanical variables “work”, “velocity”, “power” and
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