Glossary

A | B | C | D | E | F | G | H | I | J | K | L

M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

Gluconeogenesis
The production of glucose or glycogen in the liver from precursors, such as glycerol from triglycerides or from amino acids. Gluconeogenesis is important in maintaining glucose levels in endurance events when glycogen stores have been depleted.

Glucose
A monosaccharide, the primary circulating sugar in the blood and the major energy source of the body. The brain requires a constant level of glucose. Without insulin, as is the case with diabetics, glucose cannot be metabolized. Glucose levels elevate in diabetes and alternate fuels are used for life function for a limited amount of time.

Glucose-Alanine Cycle or Alanine-Glucose Cycle
As exercise intensity increases there is an increase release of alanine from the active muscle. Alanine is thought to be indirectly involved in the energy requirements of exercise. Alanine is synthesized from pyruvate with nitrogen in part coming from another amino acid leucine. Alanine is transported to the liver where it loses the nitrogen and is converted back to glucose. After four hours of light exercise glucose from alanine can account for almost half of the glucose released from the liver.

Glycemic Index ranks foods based on the their immediate effect on blood glucose or blood sugar levels after ingestion. A low glycemic index food causes a smaller rise in blood sugar. A high glycemic index food causes a quick elevation of blood sugar levels and a higher insulin response.

Glycogen
The storage form of carbohydrate located in the liver and skeletal muscle. Depletion leads to fatigue, alternate fuels (fats and proteins) and gluconeogenesis. Restoring glycogen with proper nutrition is important for the recovery of athletes after intense training or competition.

Glycogenolysis
The breakdown of glycogen to produce glucose that is important at the beginning of an exercise session.

Glycolysis
One of the energy pathways that catabolizes glucose. The process occurs in cellular cytoplasm and can occur without the presence of oxygen (anaerobic glycolysis) which yields lactic acid instead of pyruvate. When oxygen is available, lactic acid is converted back to pyruvate during recovery. If oxygen is available pyruvate is formed without lactic acid.

Graded Exercise Test (GXT)
A GXT is used to diagnose cardiovascular disease or to assess the functional capacity or physical fitness of a person. Commonly the test involves continuous exercise on a treadmill or bicycle with standardized increases in difficulty. EKG, blood pressure, heart rate, and sometimes, direct measurement of oxygen consumption are performed with the test. The diagnostic test focuses on the EKG while a functional test focuses on the duration of the test which is directly related to the maximal oxygen consumption. Tests are maximal or submaximal. Sometimes maximal oxygen consumption is estimated because the standardized protocol of the test can predict maximal oxygen consumption from the amount of time and intensity that is endured during the test. The test can be ended if cardiac symptoms occur. A positive GXT indicates the presence of cardiovascular disease. A negative GXT indicates that cardiovascular disease is unlikely at the time of the test. False negatives and false positives are possible.

Gram
A scientific measurement of mass. There are about 454 grams in 1 pound.

Gravity
The attraction force of two objects that is directly proportional to their masses and indirectly proportional to the squared distance between the two objects. On earth this force causes bodies to fall to the ground, if they are not supported by musculoskeletal activity.

Ground Reaction Force
The resultant force of a supporting surface that is equal and opposite to the force that is applied to the surface.

©Copyright 1999-2007 Apriori, Inc. All Rights Reserved.

All products mentioned are trademarks or registered trademarks of their respective owners.