PMID- 6789029
OWN - NLM
STAT- MEDLINE
DCOM- 19810915
LR  - 20141120
IS  - 0195-9131 (Print)
IS  - 0195-9131 (Linking)
VI  - 13
IP  - 3
DP  - 1981
TI  - Effects of exercise on protein and amino acid metabolism.
PG  - 141-9
AB  - At rest, especially during starvation, protein (via hepatic gluconeogenesis 
      and/or direct oxidation) contributes significantly to the body's total metabolic 
      requirement. During exercise, carbohydrate (CHO) and free fatty acids (FFA) are 
      generally regarded as the major energy sources. Although protein has the 
      capability, it has seldom been considered as an important exercise energy source 
      based largely on 24-h urinary nitrogen (N) excretion values. Contrary to 
      classical belief, recent determinations of N in sweat suggest that total N 
      excretion is in fact increased with exercise. This should not be surprising when 
      one considers that prolonged exercise substrate shifts and hormonal changes are 
      in many ways analogous to the situation that occurs during starvation. In 
      addition, in vitro experiments have demonstrated that skeletal muscle, as well as 
      liver, has the capacity to oxidize a number of amino acids. This information, 
      together with the in vivo exercise observations of an increased alanine output 
      from skeletal muscle and an increased 14CO2 evolution following [14C] leucine 
      injection or ingestion, indicates that some amino acids contribute to exercise 
      energy needs. Although a number of mechanisms have been suggested, the current 
      evidence strongly suggests that the branched-chain amino acids (glucose-alanine 
      cycle) are the most important. In conclusion, it appears that the earlier studies 
      which indicated that protein/amino acid utilization did not increase during 
      exercise may have been premature. Although clearly not as important as either CHO 
      or FFA, recent investigations employing both humans and laboratory animals 
      suggest that protein/amino acids, under some conditions, may contribute 
      significantly to total exercise calories.
FAU - Lemon, P W
AU  - Lemon PW
FAU - Nagle, F J
AU  - Nagle FJ
LA  - eng
PT  - Journal Article
PL  - United States
TA  - Med Sci Sports Exerc
JT  - Medicine and science in sports and exercise
JID - 8005433
RN  - 0 (Amino Acids)
RN  - 0 (Blood Glucose)
RN  - 0 (Fatty Acids, Nonesterified)
RN  - 0 (Proteins)
RN  - 142M471B3J (Carbon Dioxide)
RN  - 8W8T17847W (Urea)
SB  - IM
MH  - Amino Acids/*metabolism
MH  - Animals
MH  - Blood Glucose/metabolism
MH  - Carbohydrate Metabolism
MH  - Carbon Dioxide/metabolism
MH  - Energy Metabolism
MH  - Fatty Acids, Nonesterified/metabolism
MH  - Humans
MH  - In Vitro Techniques
MH  - Liver/metabolism
MH  - Muscles/metabolism
MH  - *Physical Exertion
MH  - Proteins/*metabolism
MH  - Rats
MH  - Starvation/metabolism
MH  - Sweat
MH  - Urea/metabolism/urine
OID - NASA: 81244127
EDAT- 1981/01/01 00:00
MHDA- 1981/01/01 00:01
CRDT- 1981/01/01 00:00
PHST- 1981/01/01 00:00 [pubmed]
PHST- 1981/01/01 00:01 [medline]
PHST- 1981/01/01 00:00 [entrez]
PST - ppublish
SO  - Med Sci Sports Exerc. 1981;13(3):141-9.