Sports Nutrition - HECO 336....
Adequate energy is the basis for
all sport whether it be endurance, strength or a combination. Energy
is the capacity to do work. The human body has chemical, electrical,
radiant and mechanical energy systems. In the human body we can measure
energy in terms of heat using a kcalorie. One kcalorie is equal to
the energy needed to raise the temperature of 1 kg water 1° C.
1 kcal. is equivalent to:
3,086 foot-pounds
427 KGM
4.2 Kj
200 ml O2
PHOSPHAGEN SYSTEM
The phosphagen system supplies ATP
to the muscle cell for immediate energy. All other systems work to
support this, however their rate of ATP production is much slower, thus
explosive bursts of strength or speed deplete ATP within 30 seconds.
ATP however is backed up by creatine phosphate [creatine-P or sometimes
called phosphocreatine (PC)]. Creatine is synthesized in the liver
from the amino acid glycine and then transported to the muscle cell's mitochondria
where it combines with free phosphate. Creatine-P's function is to
rapidly dephosphorylate and give the free PO4 to ADP for resynthesis of
ATP. However, PC's content is also limited in the cell so the combined
available energy from these two products may last for around two minutes.
Sports which rely most heavily on this energy system include: power lifting,
shot put, discus, high jump, the "slam dunk" and golf.
GLYCOLYSIS-LACTIC ACID SYSTEM
Glycolysis is the breakdown of glucose
to pyruvate and when continued in an anaerobic mode pyruvate is converted
to lactic acid. Glycolysis is the primary energy system used for
power and strength. The duration of this system is limited due to
the accumulation of lactate which increases the acidity of the cell (lowering
the pH). The burning sensation felt in muscle undergoing high levels
of glycolysis is from both anoxia (lack of oxygen) and acidity. The
result is muscle fatigue and the inability of the athlete to continue to
perform. Sports which rely most heavily on this energy system include:
track events under one mile, baseball, football, tennis and rowing.
See the carbohydrate unit
for an in-depth look at energy pathways and the use of carbohydrate fuels
AEROBIC SYSTEM
The aerobic system is like
the EnergizerTM Bunny
- it just keeps going and going and going ......... . This
system is a multi -fuel engine, at rest it relies on fatty acids and glucose
as its' primary fuel sources. However, during prolonged endurance
activity, this system may also utilize amino acids when carbohydrate reserves
become low. All substrates are converted to acetyl CoA before they
enter the aerobic system - the Tricarboxylic Acid Cycle (TCA Cycle).
The high energy products of the TCA cycle enter the Electron Transport
System (ETS) where their trapped energy is used to resynthesize ATP.
Sports which rely most heavily on this energy system include: marathon,
thriathlete, cross country skiing, track events longer than one mile, soccer,
field and ice hockey, lacrosse and basketball.
One benefit of training is that it improves both the level of intensity and length of time an athlete can perform a particular activity. The end result is an increase in speed, power and endurance. Some specific effects of training are listed below.
1. increase in VO2 max and increase
in % VO2 at which you can perform.
2. increase in oxidative enzymes
(for aerobic training).
3. increase in glycolytic enzymes
(for speed/power training).
4. increase in glycogen storage
capacity especially if CHO consumption follows glycogen depletion.
5. increase in blood volume.
6. increase in cardiac output (aerobic
training).
7. myofibril hypertrophy (hyperplasia?
with heavy anaerobic training).
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Cardiovascular |
Copyright © 2000 Department of Human Ecology [HECO] , The University
of Tennessee at Chattanooga. All rights reserved.
The University of Tennessee at Chattanooga is an equal employment opportunity/affirmative
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Please send your questions, comments, and suggestions to: Holly-Dieken@utc.edu
Last Modified: Jul 18, 2000