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  Last updated: 10/10/2020


absolute work - The actual number of Calories expended in accomplishing a task. It is the same for all individuals and is not affected by the level of conditioning.

adenosine diphosphate - A chemical compound, transformed into ATP (see below) as food energy is incorporated into the cell by the addition of a phosphate group (and which is also reformed as cellular energy is released by the breakdown of ATP); an intermediate in the cellular energy production pathway.

adenosine triphosphate - An organic molecule which stores energy in the cell. It is the last step in the transfer of food energy into the physical work of the muscle.

aerobic metabolism - Cellular activity or energy release that requires oxygen.

air speed - the velocity of the bike through the air. It is the speed used to calculate the energy needs at any speed.

amino acid - A molecule formed from the hydrolysis (digestion) of protein.

anaerobic metabolism - Cellular activity or energy release that is oxygen independent. Much less efficient than aerobic metabolism in terms of the amount of food energy transformed into cellular energy.

anaerobic threshold (AT) (see also lactate threshold) - The level of effort (usually expressed as a percentage of VO2 max.) where lactic acid levels begin to rise (more lactate is produced than can be metabolized).

anemia - A low red blood cell count.

anecdote (anecdotal) - a personal story or understanding of a product or situation.

antioxidant - a molecule that can neutralize free radicals before they interact with living tissue.

arterio-venous (A-V) O2 difference - The difference in oxygen concentration in the blood being delivered to an organ (usually muscle), the arterial concentration, and the blood leaving, the venous concentration. Generally expressed as a volume per minute.

basal metabolic rate (BMR) - The energy needs of an individual at rest. Also referred to by some as the Resting Energy Expenditure (REE)

Beets - a vegetable high in nitrates, a proven performance enhancer.

beta-alanine - a performance enhancing supplement; beta-alanine is a nonessential amino acid thought to be a precursor to carnosine in muscle tissue.

blood doping - Red blood cell reinfusion to improve athletic performance.

blood volume - The total volume of liquid - both red blood cells and plasma - within the circulatory system. Approximately 5 liters with 40% red blood cells and 60% plasma.

bonk - A descriptive term identifying the point at which liver and muscle glycogen are depleted and energy production is dependent on fatty acid metabolism. the bonk usually develops 1 to 2 hours into a ride and is a particular problem if "on the bike" carbohydrate supplements are not used to extend internal muscle glycogen stores. It's onset can be delayed by eating carbohydrates. Also known as the "knock" in England or "hitting the wall" in running.


Caffeine - a legal stimulant that is used to reduce fatigue and as an endurance aid for some activities.

Caloric replacement - The number of Calories that must be eaten to replace those expended in carrying a defined activity.

calorie - A measurement unit for energy. A scientific unit. The energy required to raise the temperature of 1 gram of water 1 degree Centigrade.

Calorie (note the capital C)- A unit of energy equal to 1000 calories (a commonly used scientific term, note the small case c). This is the unit used when referring to the energy content of foods as well as to the production and utilization of energy in living organisms.

carbohydrate - An organic compound which contains carbon, hydrogen, and oxygen. It is a source of energy for the cell yielding 4.1 Calories per gram.

carbohydrate loading - changing the composition of the diet to maximize internal carbohydrate (glycogen) stores.

cardiac drift - the gradual increase in heart rate that occurs during prolonged exercise bouts being performed at a constant intensity.

cardiac output - The volume of blood pumped by the heart in liters/minute. It is a product of the heart rate and the stroke volume (blood pumped per beat).

cardiac stress testing - Specialized studies to uncover asymptomatic coronary artery disease.

carnitine - a performance enhancing supplement; found mainly in meats (a non-vegetarian diet contains 100-300 mg per day), but also synthesized in the kidney and liver from lysine and methionine.

carnosine - buffers hydrogen ions, making muscle tissue less acidic, delaying the onset of fatigue in anaerobic metabolism.

century ride - Usually a bicycle ride of 100 miles. There are also metric centuries of 100 kilometers.

chyme - The semi fluid mass of partly digested food emptied from the stomach into the duodenum.

citrulline - an amino acid produced as a byproduct of the enzymatic production of nitric oxide from the arginine. A potential prophyllactic for development of delayed onset muscle pain.

complex carbohydrate - An molecule composed of at least two simple (single) carbohydrate molecules.

concentric muscle contraction - The length of the muscle is shortened as it overcomes resistance.

Concini test - A method of measuring your AT (and LT).

concentration - The amount of a substance in a defined volume of liquid.

cramp, stomach - An increase in small and large intestinal activity.

cramp, muscle - An intense, active contraction of the muscle cells.

creatine phosphokinase (CPK) - An enzyme found in muscle cells (heart, skeletal, smooth muscle).

cross training - Using an alternative sports activity to maintain cardiovascular fitness while taking a physical and psychological training break.

diary - A written record of your training program.

deconditioning - The loss of physical ability that occurs with a decrease in activity.

dilutional hyponatremia - a low blood sodium level from drinking excessive electrolyte free fluids.

disaccharide - A carbohydrate composed of two simple carbohydrate molecules.

diuretic - Any compound which promotes water excretion by the kidneys. Generally a medication although naturally occurring chemicals such as caffeine have a diuretic effect as well.

DOMS (delayed onset muscle pain) - muscle soreness (or stiffness) that occurs 8 to 24 hours after exercise, peaking at 48 to 72 hours.

doping - the use of a substance (as an anabolic steroid or erythropoietin) or technique (as blood doping) to illegally improve athletic performance. See also mechanical doping.

double blinded - comparing two groups (neither of which knows which agent they are receiving) in carefully monitored or "controlled" studies - one group being given an active ingredient being investigated and the other group given an inactive or sham agent.

drafting - Following another rider closely to decrease the energy requirements for a ride.

eccentric muscle contraction - the muscle works actively (actively lengthens) to slow its lengthening against a force .

efficiency - The ratio of energy expended (work performed, generally in Calories) to energy required (Calories eaten in the case of human efficiency).

energy - Having the ability to perform work. The presence of energy is revealed only when a change takes place. Potential energy is stored energy. Kinetic energy is the energy of motion.

ergogenic - When used to describe dietary changes or supplements, indicating the ability to increase maximal physical performance.

erythropoietin (EPO) - a hormone, produced by the kidney, which stimulates the bone marrow to produce red blood cells.

essential - Necessary. In the context of nutrition, this refers to the basic food elements (fats and amino acids) which cannot be synthesized by the body. These substances are necessary for cellular metabolism and viability and are therefore an essential part of the daily diet.

exhaustion - The point at which the athlete cannot maintain a high level of physical activity in spite of an adequate blood glucose supply. It is related to a change in the muscle itself.

fartlick - a modification of interval training, using alternate periods of slow and fast riding to improve aerobic capacity. From Swedish meaning "speed play".

fat - The component of food and tissue, made up of mainly of the organic compounds triglycerides and cholesterol, containing 9.1 Calories per gram.

fatigue - The point at which the muscle cells are no longer working efficiently. It can be due to depletion of the body's glucose stores, reversible with oral glucose supplements (the bonk). But also glucose independent, related to changes in the muscle cell itself

fatty acid (FA) - One of the molecules making up a triglyceride, the basic molecule in fat cells. The intermediary in the metabolism of fat to provide energy.

fluid deficit - The difference between the body's ideal water content and actual water content (usually after exercise).

force - That ability of energy that can change the state of rest or motion in matter.

free radical - A molecule with an unpaired electron, a normal by product of all biologic systems (exercising or not), that is unstable and can produce cellular damage.

fructose - Fruit sugar. A hexose. It can be used by the cell as a carbohydrate energy source in the absence of insulin.

gear inches - Expression of the ratio of the number of revolutions of the drive wheel for every complete revolution of the crank arm. Calculated by dividing the number of teeth on the rear cog into the number of teeth on the front chain ring and then multiplying by the diameter of the rear wheel (usually 27").

Ginger - for post exercise muscle pain.

gluconeogenesis - The production of glucose, a carbohydrate, from either fat or protein.

glucose - The monosaccharide (single sugar molecule) that is the single most important carbohydrate in cellular energy metabolism.

glycemic index (GI) A quantifiable measure that reflects how quickly an ingested carbohydrate will trigger a rise in the circulating blood glucose level.

glycerol - a chemical compound which forms the backbone of the triglyceride molecule (glycerol plus 3 fatty acids), the storage form of lipids in fat cells. A clear, syrupy, and extremely sweet substance, glycerol has a water retaining effect when taken orally.

glycogen - The complex carbohydrate molecule used to store carbohydrates in the liver and muscle cells. When carbohydrate energy is needed, glycogen is converted into glucose for use by the muscle cells.

ground speed - the velocity of the bike relative to the ground. It is the speed you read on your cycling computer.

High Intensity Training (HIT) - Another name for interval training..

hitting the wall - A descriptive term identifying that point at which both liver and muscle glycogen have been depleted and maximum energy output cannot be maintained. It can be delayed by eating carbohydrates while exercising, but cannot be reversed once it occurs.

hyperthermia - An increase in your core body temperature.

hyponatremia - An abnormally low concentration of sodium in body fluids.

hypothermia - A decrease in your core body temperature.

insomnia - The inability to fall asleep, or awakening without a full night's sleep (based on personal history and past patterns).

international units - see SI

intervals - Repeated periods of intense physical activity (the exercise interval) alternating with periods of recovery (the relaxation interval). The most effective way to increase your VO2max and thus peak performance.

isometric muscle contraction - the length of the muscle remains constant as force (weight) is applied.

joule - A scientific unit of energy. See the conversion table in Appendix B for the equivalent in calories and Calories.

lactate threshold (LT)- The % of VO2max. at which the cardiovascular system can no longer provide adequate oxygen for exercising muscle cells and lactic acid starts to accumulate in muscle cells and subsequently in the blood as well.

lactic acid - An acidic by-products of anaerobic metabolism. It is unlikely to be the culprit for "the burn" or have a negative effect on muscle functioning, but rather provides an alternative carbohydrate fuel source which may help spare glycogen in the exercising muscle.

Lyme disease - a bacterial infection (Borellia burgdorfer) which is spread by the deer tick. The initial infection mimics the flu, but long term it can cause a debilitating arthritis.

maximal oxygen consumption (VO2max) - The maximum amount (usually expressed as a volume, liter) of oxygen that an individual can consume in a defined period of time (usually 1 minute). It may be expressed per kilogram of body weight (ml/kg/min). It reflects the upper limit of aerobic metabolism and limited by the amount of oxygen that can be delivered into the working muscle cells. Basically a product of the maximal cardiac output and maximal arterial-venous oxygen difference at the capillary-cell interface.

maximum heart rate (MHR) - The maximum attainable heart rate for an individual. It decreases with age and can be estimated using the formula: MHR = 220 - age in years.

mechanical doping - using technology to gain an unfair advantage in an athletic event. Also known as technologic fraud.

metabolism - The biochemical cellular functions involved in maintaining viability, usually synonymous with energy production.

minerals - Inorganic elements that are essential constituents of all cells.

mitochondria - The organelle of the cell where glucose, fat, or protein are oxidized to release energy for cell activities.

monosaccharide - A carbohydrate consisting of a single molecule.

muscle, skeletal - The contractile cells which make up over 1/2 of the body weight of a lean individual. Muscle cells contain two proteins - actin and myosin - which chemically interact to shorten the muscle fiber when stimulated by nerve impulses.

muscle cramp - see cramp, muscle

Nitrates - a proven performance enhancer. Found in many vegetables (beets are the most commonly suggested).

nitrogen balance - A measure of protein metabolism

osmotic activity - Relating to the concentration (number of molecules in a given volume) of a solution.

overreaching - The fatigue we feel at the end of a particularly hard week of riding. It is really just an extension of post ride fatigue, and is, with recovery, part of the normal training cycle.

overtraining - The debilitating and often long term (lasting weeks to months) fatigue which limits rather than stimulates improvement in performance.

oxidation - The process of using oxygen in a chemical reaction to release energy.

oxygen consumption (or VO2) - The total volume of oxygen utilized during a specified period of time to meet cellular energy needs.

oxygen debt - The volume of oxygen required to metabolize and remove lactic acid and other metabolic products accumulated during a period of anaerobic muscle cell metabolism.

paceline - Several cyclists drafting (following closely) one another in a line to minimize energy needs and improve the performance of the group.

pacing - A training and competition strategy for extreme efforts of greater than 30 seconds duration The athlete holds back just enough that his perceived effort limit is not reached until he is at the finish line.

perceived effort - A philosophy of training and riding based on how you feel rather than objective measures such as heart rate.

periodization - A segmented program (generally blocks of training developed within a specified number of training season periods) with individual blocks oriented towards specific goals. For example an early season block is generally allocated to aerobic training. Many pros use the periodization approach to facilitate multiple peaks during a single season of competition.

pedal cadence - The revolutions per minute of your pedals and cranks.

placebo - An inactive compound.

plasma volume - The volume of fluid within the circulatory system. Approximately 60% of the blood volume.

polarized training - Focusing training time (mileage) on Zones 1 and 3, avoiding Zone 2. The strategy of alternating between easy and very hard effort (avoiding the middle).

polymer - A molecular compound made up of a chain of similar units. In the context of this text it refers to a chain of simple glucose molecules.

post ride fatigue - A normal response to several hours of vigorous exercise which indicates you are pushing your training limits.

power - The rate at which work is done. Force times Distance (work) divided by Time or (F x D)/T. Power can be expressed in watts. If an 80-kg bicycle and rider are raised 3 meters in 1 minute, power expended is 240 kg-meters per minute (kgm/min).

protein - The building block of cells and animal tissues. Also available as a second line energy source after carbohydrates and fats. Made up of subunits called amino acids. Contain 4.1 Calories per gram of weight.

pulmonary - related to the lungs or breathing.

Q factor - This is the measurement between the pedal mounting surfaces (outside surface) on the crankarms (and indirectly the distance between the midline of each foot - which translates all the way up to the knees and hips.)

recovery, post ride - as you get off the bike at the end of your ride, attention to hydration, glycogen store replacement, and assessment of the level of fatigue will play a role in preparation for the next time on the bike, especially for competitive and multiday riders.

RED-S - Relative Energy Deficiency in Sport. A fatigue syndrome that can develop when a rider's nutrition is adequate to replace the Calories consumed by their physical training program.

relative work rate - The percentage of a person's VO2max required to accomplish a task. Even though the absolute work is the same for all riders, the relative work rate can vary from individual to individual, depending on the level of conditioning.


resting heart rate - The heart rate (in beats per minute) at rest, generally taken on awakening in the morning. Considered a good reflection of the state of cardiovascular conditioning.

saddle sore - An area of irritation or actual infection in the area that contacts the saddle (or in the groin area)

second wind - The phenomenon of a perceived easing of effort after a period of anaerobic metabolism. It is thought to be related to a shift in energy metabolism toward utilization of lactate as a fuel.

SI units (international units) - The international system of units (as opposed to the English system) based on the metric system. In the US nutritional literature, the English system remains the most widely used.

spinning - Keeping your pedal cadence high with a low load per revolutions on you legs/knees. Generally on the flats or while on a trainer.

spin classes - A group approach to stationary cycling. The most realistic alternative to "on the road" training.

stationary cycling - Using rollers or a stationary bike to allow training in the dark winter months or during bad weather.

stroke volume - Amount of blood pumped per heart beat

trace element - Any mineral that is only present in the body in minute concentrations.

traveler's diarrhea - a change in bowel habits experienced during travel outside one's home country. Rates of between 20% to 50% have been reported.

triathlon - An event with three separate athletic components, usually swimming, cycling, and running (in that order).

triglyceride - The basic molecule of fat (adipose) tissue. Triglycerides contain 9.3 Calories per gram.

urea - The final byproduct of protein metabolism in man.

VO2 max (see also Maximal Oxygen Consumption) - The maximum amount of oxygen that an individual can utilize in a set period of time (generally expressed as a volume i.e. liters per min). It can also be normalized per kilogram of body weight (i.e. ml per kg BW per min). It is a measurement of the upper limit of aerobic muscle cell metabolism and is dependent on both the maximal cardiac output and the maximal arterial-venous oxygen difference at the muscle or tissue level.

volume of exercise - the total time spent exercising in any particular time interval (usually week or month).

watt - a measure of power (work done during a specified unit of time). 1 watt = 0.73756 ft-lbs/sec, 0.01433 Calories/min, 0.0013 horsepower, or 6.12 kg-meter/minute.

weight control - The use of both eating and exercise strategies to maintain optimal body mass.

weight training - The use of resistance exercises (usually weights) to maintain or increase muscle mass and tone.

work - The application of force over a distance (without any limitation as to the time involved). For example, moving 80 kg over a vertical distance of 2 meters equals 160 kg-meters (kgm) of work. The same amount of work is required to accomplish this task in 1 minute or 5 minutes.

ZONE diet plan - A diet with a relatively high fat diet (40% carbohydrates, 30% protein, 30% fat vs the usual athlete's diet of 60/15/25) purported to increase athletic performance and promote weight loss.

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