Active Voice: Precisely, What Do We Mean— Force, Work & Power?

By Howard G. Knuttgen, Ph.D., FACSM

Having participated in ACSM’s 2015 annual meeting in San Diego, I was highly impressed with the quality of the science being reported. At the same time, however, I was greatly disappointed with the frequent inappropriate use of the term “work.” While “work” in everyday language can refer to anything from a vocation to a composition of music, for science and medicine it is defined in the international system of measurement as, “the product of a force component by the magnitude of displacement (distance)” and quantified in joules (J). A quantity of work can be performed over any period of time and, if quantified in terms of a unit of time, it must be reported as “power” for which the international system unit is the watt (W). 

Having lived and worked in the Scandinavian countries for over three years where research into exercise has been carried out vigorously for almost 100 years, I believe that I can trace the problem of the inappropriate use of the term “work” to the fact that there is no equivalent term in any of the Scandinavian languages for “exercise”. Investigators from these countries employ a term for muscular activity that is the same one used in these languages for any vocation (Norwegian – arbeid, Swedish – arbete, and Danish – arbejde). It is, therefore, not surprising that the Scandinavian investigators such as Erling Asmussen, P.-O. Åstrand, Bengt Saltin, and Björn Ekblom have used the term “work” instead of “exercise” when publishing in English. However, it is incorrect. 

Further support to my objection regarding what I heard at ACSM’s annual meeting is my observation that, in every instance where the presenter inappropriately identified the physical activity as “work” he/she then quantified the performance in watts, the international unit for Power. If an investigator does, indeed, wish to present the total work involved in a physical activity, the international unit must be the joule (J) which is independent of time. Work performed per unit of time is Power, the measure of the exercise intensity. 

Editorial Note: While serving as editor-in-chief of MSS, Dr. Knuttgen first addressed this topic in an editorial statement. The statement may be accessed by members through the ACSM website. Go to “My Journals” and locate the article “Force, Work, Power, and Exercise”, in the fall 1978 issue. A reminder about this also is presented in ACSM’s online Call for Abstracts each year, as follows: To ensure consistency and clarity, it is directed that authors use the terms as defined by MSSE “Information for Authors,” while utilizing the units of measurement of the Systeme International de’Unite (SI)Additional guidance on terminology and units of measurement for describing exercise and sports performance, as compiled by the Sub-committee on Publications in the Sports Sciences, IOC (International Olympic Committee) Medical Commission, is available online (at the source, see pages xiii-xiv).

Viewpoints presented on the ACSM blog reflect opinions of the authors and do not necessarily reflect positions or policies of ACSM. 

Howard G. (Skip) Knuttgen, Ph.D., FACSM, is senior lecturer in physical medicine and rehabilitation at the Harvard University Medical School in Boston, Massachusetts. His research expertise is in skeletal muscle physiology and the related implications for human physical performance and clinical care in sports medicine. He completed his doctoral degree at the Ohio State University in 1959 and was a Fulbright Scholar in Human Physiology at the University of Copenhagen, 1959-1961. 

Skip has a stellar record of leadership in ACSM, serving as ACSM’s 17th president during an important transformational period for our association. He was editor-in-chief of ACSM’s flagship journal, Medicine and Science in Sports (formerly MSS, now Medicine & Science in Sports & Exercise® or MSSE), from 1974-79. In 1983, Dr. Knuttgen, was responsible for spearheading ACSM’s International Scholars Program, which since has fostered collaborations between young clinicians and scientists from other countries with ACSM members in the United States. 

The ACSM blog is pleased to present this commentary by Dr. Knuttgen, relating to his impressions and recommendations regarding the importance of precision in scientific communication.

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