NUTRITION IN SPORT

134 nutrition and exercise

protein requirements after 1977 (US Food and

Nutrition Board 1989). As a great many studies

have examined the question of exercise effects on

dietary protein needs since then, the rationale for

this strategy is unclear. Interestingly, over this

entire time period (in fact, going as far back as

there are records), regardless of the scientific

opinion, many athletes, especially those

involved in heavy resistance (strength/power)

activities, have consumed routinely vast

amounts (300–775% of the recommended daily

allowance (RDA)) of dietary protein (Steen 1991;

Kleineret al. 1994).

With this background in mind, this chapter

reviews some of the more recent experimental

results, outlines several methodological concerns

that may compromise some of the experimen-

tal data, examines the limited information on

whether supplemental protein can enhance

exercise performance, and considers a variety of

potential underlying mechanisms responsible, in

an attempt to understand how physical exercise

affects dietary protein needs.

Protein metabolism simplified

A brief outline of how the body metabolizes

protein is shown in Fig. 10.2. Although the free

amino acid pool(s) contain(s) only a very small

percentage of the body’s amino acids (the vast

majority are in tissue protein), the important role

of the body’s free amino acid pool(s) (through

Fig. 10.1Athletes in both strength and endurance

events have a greater dietary protein requirement than

sedentary individuals. (a) Photo © Allsport / J.

Jacobsohn. (b) Photo © Allsport / G.M. Prior.

(a)

(b)