Introduction
For at least 150 years, scientists have studied fuel
use during various types of physical exercise.
Over this time, there has been considerable
debate relative to the importance of dietary
protein for individuals who exercise regularly.
In fact, the understanding of protein’s role in
exercise metabolism has changed dramatically
several times since the middle of the 19th
century. In the mid-1800s it was thought that
protein was the major fuel for muscle contraction
(von Liebig 1842) and, consequently, it is under-
standable that large amounts of protein were
consumed by the athletes of that time. However,
a number of studies completed later in the 19th
century and during the first part of the 20th
century (reviewed in Cathcart 1925) indicated
that protein played a much smaller role in terms
of exercise fuel (contributing less than 10% of the
energy expended during exercise). As a result,
at least in the scientific community, the belief
regarding the importance of protein in exercise
metabolism was essentially totally reversed
(going from the major contributor to virtually
no contribution). Based on these data, it was
believed that exercise did not increase one’s
need for dietary protein. It is unknown why the
observed protein contribution was considered
unimportant, but likely it was an over-reaction
to the new information which was so vastly
different from the prevailing view of the time or
perhaps simply the belief that the amount of
protein typically consumed was sufficient to
cover this small increased need. In any event, the
understanding that dietary protein needs were
unaffected by physical exercise became so domi-
nant that the vast majority of the exercise meta-
bolic work throughout the first three-quarters of
the 20th century concentrated on carbohydrate
and fat and, as a result, almost totally ignored the
role of protein (Åstrand & Rodahl 1977).
Beginning in the 1970s, first sporadically (Felig
& Wahren 1971; Poortmans 1975; Haralambie &
Berg 1976; Dohm et al. 1977; Lemon & Mullin
1980; Lemon & Nagle 1981; White & Brooks 1981;
Lemonet al. 1982), but recently more regularly
(for review, see Lemon 1997), studies began to
appear which suggested that protein intakes
in excess of sedentary recommendations may
be beneficial for those who regularly engage in
strenuous physical exercise. However, the issue
of exercise effects on protein need is extremely
complex and still there is no absolute consensus
(Lemon 1987, 1991, 1996; Butterfield 1991; Evans
1993; Millward et al. 1994; Rennie et al. 1994;
Wagenmakers & van Hall 1996). Further com-
plicating this issue is the fact that the current
dietary recommendations for protein in several
countries do not adequately address this topic
because they are based primarily on studies of
subjects who were essentially sedentary. More-
over, some recommendations have not been
kept up to date. For example, not only were the
current recommendations in the United States
published a number of years ago but, in addition,
they do not contain a single reference relating
to the possible influence of chronic exercise on