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Bonk has long been a colloquial term, slightly jocular in its connotation, meaning sexual intercourse, but has recently become more commonly used as a jargon term by endurance athletes, primarily cyclists and long-distance runners, to describe a condition when the athlete suddenly loses energy and fatigue sets in, usually caused when glycogen stores in the liver and muscles are depleted, resulting in a major performance drop. Wikipedia does not have an article with this exact name. ... Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 150 languages. ... It has been suggested that Duration of sexual intercourse be merged into this article or section. ... A cyclist is a person who engages in cycling whether as a sport or rides a bicycle for recreation or transportation. ... Electron micrograph of a section of a liver cell showing glycogen deposits as accumulations of electron dense particles (arrows). ... The liver is an organ present in vertebrates and some other animals. ... A top-down view of skeletal muscle Muscle (from Latin musculus little mouse [1]) is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. ...

In fact, the term "bonk" for cycling fatigue is much older than many realise. A recent DVD issued by the British Transport Films Collection contains several old films, one of which entitled "Cyclists Special", a colour film produced in 1955, tells the story of a party of cyclists touring the English countryside. At one point they stop for refreshments and the film's commentator states that if they didn't rest and eat they would get "the bonk". So it was obviously in common parlance amongst cyclists over half a century ago and of greater age than the sexual connotation more familiarly known today. Source: "See Britain by Train", British Transport Films Collection 2005, Volume Two, Disc One, Track Three.

The term can be used both as a noun ("hitting the bonk") and a verb ("to bonk halfway through the race"). This condition is also known to long-distance (marathon) runners, who usually refer to it as "hitting the wall". It is also referred to as the "green grass" as pupil dilation causes vivid hues to appear. Such fatigue can become seriously debilitating; for example in cycling, due to the support provided by the bicycle, exhaustion can reach the point where the cyclist is unable to stand. Modern-day marathon runners Runners in ancient Greece. ...

Whenever athletes are engaged in exercise over a long period of time, their bodies produce energy via two mechanisms:

• via fat metabolism and
• via breakdown of glycogen into glucose, followed by glycolysis.

How much energy comes from either source depends on the intensity of the exercise. During intense exercise which approaches one's VO₂ max, most of the energy required comes from glycogen. Glucose (Glc), a monosaccharide (or simple sugar), is the most important carbohydrate in biology. ... Glycolysis is a metabolic pathway by which a 6-carbon glucose (Glc) molecule is oxidized to two molecules of pyruvic acid (Pyr). ... VO2 max is the maximum capacity to transport and utilize oxygen during incremental exercise. ...

The average human body usually stores enough glycogen to generate 1500 to 2000 kcal of energy. Intense cycling or running can easily consume 600-800 or more kcal per hour. Unless glycogen stores are replenished during exercise, after 2 hours of continuous cycling or 15 to 20 miles (24 to 32 km) of running, glycogen stores will be depleted. Symptoms of depletion include general weakness, fatigue, and manifestations of hypoglycemia, such as dizziness and even hallucinations. Symptoms will not be relieved by short periods of rest. This condition is potentially dangerous and should be avoided. A calorie is a unit of measurement for energy. ... Hypoglycemia (hypoglycæmia in the UK) is a medical term referring to a pathologic state produced by a lower than normal level of sugar (glucose) in the blood. ... A hallucination is a sensory perception experienced in the absence of an external stimulus, as distinct from an illusion, which is a misperception of an external stimulus. ...

There are several approaches to prevent glycogen depletion:

1. Carbohydrate loading is used to ensure that the initial glycogen levels are maximized, thus prolonging the exercise. This technique amounts to increasing complex carbohydrate intake during the last few days before the event.
2. Consuming food or drinks containing carbohydrates during the exercise. This is an absolute must for very long distances; it's estimated that Tour de France competitors receive up to 50% of their daily caloric intake from on-the-bike supplements.
3. Lowering the intensity of the exercise to the so-called 'fat loss' level (heart rate of 130 bpm for a 30-year-old athlete) will lower both the energy requirements per unit of distance and the fraction of the energy that comes from glycogen.

In sports, carbohydrate loading, also known as carbo-loading, is a strategy employed by endurance athletes such as marathon runners to maximize the storage of glycogen in the muscles. ... The Tour de France is the worlds best-known cycling race, a 22 day long, 20 stage road race that covers over 4000km. ... Beats per minute (bpm) is a unit typically used as either a measure of tempo in music, or a measure of ones heart rate. ...

Bonk training

"Bonk training" is an exercise program designed for weight loss. It suggests the following strategy on an empty stomach the first thing in the morning, when glycogen store levels are low: consume coffee or caffeine equivalent to 2 or 3 cups of coffee, run or cycle at a casual pace (60% of max heart rate) for 20-90 minutes, have a normal breakfast right after exercising. Proponents claim this will force the body to "bonk" shortly into the exercise, and subsequently burn more fat to generate the energy. It is not clear how medically sound this idea is; exerting too much energy and "bonking hard," or experiencing severe hypoglycemia can be dangerous.Bonk Training Heart rate is a term used to describe the frequency of the cardiac cycle. ... Hypoglycemia (hypoglycæmia in the UK) is a medical term referring to a pathologic state produced by a lower than normal level of sugar (glucose) in the blood. ...

See also

• Fatigue (medical)