Causes of Cramping, RoadBikeRider article






RBR Premium Member Tom D. recently e-mailed us an excellent set of questions on cramping based on his own ongoing issues with cramps. His experience and the myriad issues surrounding the prevention and treatment of cramps (along with the fact that it's a topic I've researched and written about extensively, and that continues to be of interest) led me to write a 2-part series of articles in response. Part 1 discusses Tom's problems, which are common to many roadies, and what scientists know about cramps. Part 2, next week, will discuss the role of supplements and other ways of preventing cramps.

Tom's Troubles With Cramps

Tom wrote:

When I started riding, I never had any sort of cramping issue regardless of the mileage or the temperature/humidity. After three years of riding I purchased a new bicycle and had a custom fit performed. The seat was changed from a 143 mm to a 155 mm wide saddle and the seat height was raised some 1.5 inches. About two months after that my adductors started cramping [adductors are the thigh muscles on the interior portion of the thigh]. I had a second fitting done four years ago by another shop. The fitter came up with the same saddle width of 155, but lowered the seat 1/2 inch. The cramping continues.

I hydrate a lot on all rides. When I feel the "flutter" of adductor cramps coming on during a ride (normally, it happens later into a ride of 40 miles or more, depending upon temperature and humidity), I usually stop, let my legs hang off the pedals of my trike for a minute or two, and drink some more water. (I started riding a trike a couple of years ago in part to seek relief from cramping.) Then, I can get out of the trike, and take some small magnesium pills that I carry with me. I take about four of those and within a minute or two, I'm normally good to go for the rest of the ride. The adductors are the only muscles that cramp up.

With the help of the magnesium, I don’t normally cramp during a ride, but 6 to 12 hours later I seize up big time! I stretch after rides and do self-massage. However, the cramps will still strike without warning, most of the time when I get up off a chair or the couch. Those are the really bad ones. Pure agony.

There have been times when sleeping that both adductors seize up at the same time, and I cannot move or do anything but writhe in agony until the 5-6 waves of those cramps subside. The night cramps occur only after riding. Not always, but most commonly if I push it or the temperature and/or humidity are higher than normal.

Constant worrying about cramps has taken the fun out of riding. I don't get my heart rate up for fear of pushing it too hard and ending up with those horrific adductor cramps.

We know that Coenzyme Q10, magnesium, sports drinks, pickle juice and other things help alleviate, reduce, or squelch cramping, correct?

My Response to the Myriad Issues Tom Raised

Ouch! I wouldn’t ride hard either if the result was agony in bed!

Let me work through some of the many issues you raised in your personal cramping story, Tom, starting with the scientific knowledge (or lack of it) about cramps.

What causes cramps?

Scientists don’t really understand what causes cramps. According to the Mayo Clinic, “Overuse of a muscle, dehydration, muscle strain or simply holding a position for a prolonged period can cause a muscle cramp. In many cases, however, the cause isn't known.”

Often cycling problems such as cramping may be the result of a cascade of different factors: electrolyte depletion, dehydration, fatigue, heat, poor bike fit and age, possibly compounded by an underlying medical condition or side effects from a medication. Any one of these may not cause cramping, but the combination of several can result in a perfect storm of pain!

That's what makes cramping such a consternating issue for sufferers.

There are two dominant theories on what causes cramps:

1. Dehydration and electrolyte imbalance
2. Neuromuscular fatigue

An excellent paper on Exercise Associated Muscle Cramps (EAMC) is a macro review of many studies and discusses the merits of both theories. The paper was published in the National Center for Biotechnology Information PubMed (NCBI PubMed), a database of 26 million peer-reviewed scientific articles.

Dehydration and electrolyte imbalance

Many health care professionals and organizations, including the Mayo Clinic, attribute cramps to dehydration and/or electrolyte imbalance. (This is based on inference from field observations, not double-blind experiments.)

However, research on runners and other athletes doesn’t support this. Runners and other athletes are more prone to cramping in hot and/or humid conditions. However, runners in marathons in cool conditions also cramp.

Dehydration isn’t the cause. Runners who cramp drink about the same amount as runners who don’t cramp. Changes in plasma volume aren’t significantly different between runners who cramp and those who don’t, and runners who cramp have about the same percent weight loss as runners who don’t cramp.

The paper cites four separate studies, “sweat rate and sodium/fluid losses are often not different in athletes who develop EAMC” from athletes who do not cramp. In another study, “when carbohydrate-electrolyte fluids were ingested at a rate that matched sweat loss, EAMC still occurred in 69% of athletes.”

If dehydration and/or electrolyte imbalance were the causes, then drinking more and taking supplemental electrolytes would solve the problem.

Neuromuscular fatigue

The neuromuscular theory of cramping proposes that the combination of muscle overload and neuromuscular fatigue cause a cramp. The muscle spindles send messages for the muscle to act and the Golgi tendon organs (GTOs) send messages for the muscles not to act. As the neuromuscular system fatigues, the GTOs may sense that the muscle is in danger of injury and send strong signals to contract to protect the muscle — it cramps! Cramps occur when the muscle is contracting in an already-shortened position.

The results from research studies on neuromuscular fatigue are stronger than the observational studies of athletes’ experiences. However, the latter studies have also produced inconsistent results.

The paper concludes, “Because EAMC occur in a variety of situations, environmental conditions, and populations, it is unlikely that a single factor (e.g., dehydration, electrolyte imbalance, or neuromuscular factors) is responsible for causing them directly. It is more likely that EAMC are due to a combination of factors that simultaneously occur under specific physiological circumstances in each athlete.”

Let’s look at the other potential factors:

Heat and humidity

Although these don’t cause cramps, they increase the probability of cramping. In the hot months I recommend that my clients do their intensity workouts either first thing in the morning when it’s relatively cool or in an air-conditioned space on the trainer. For long rides I recommend that they ride more slowly than on cooler days.


Cramps don’t happen when a rider first gets on the bike — they usually develop later in the ride and when the rider is pushing a bit: riding farther, climbing more, riding faster, etc.

But the only way that a rider improves is by asking the body to do more than it’s accustomed to doing! How can a rider push the limits without cramping? By eliminating, or at least reducing, the other contributing factors.

After a 100-mile ride, a cramp-prone client reported, “I was pretty happy with Friday's endurance ride. As per your advice, I slowed the pace down. Friday was hot (93 degrees) and humid. I tend to cramp on long, hot rides, but I guess slowing the pace and becoming fitter maybe prevented the cramping.”

Specific muscle fatigue

As you pedal your muscles get progressively more tired and at some point on that continuum are fatigued enough to cramp. Usually one muscle group is the weakest in the kinesthetic chain that produces power. Tom’s adductors cramp. In other riders the calves are often the culprits. Strengthening a cramp-prone muscle group is another way to reduce the risk of cramps.

Bike fit

The adductors are the muscles on the inner thigh that pull the knees toward each other. When Tom pedals, his knees may naturally track outside of his feet rather than in a straight line. His adductors work to keep the knees in alignment relative to the feet. This is a biomechanical problem that probably can be fixed with a proper bike fit.

In Tom’s case, if he didn’t have a problem with cramping before the saddle width and height were changed, I would suggest that he put the old saddle back in the original position and see if cramping remains a problem.

If you have problems with cramping (or any other recurring pain while riding!) I recommend a bike fit. Bike fit changes over time as your strength and/or flexibility change. Bike fit also changes when your goals and style of riding change. If you haven’t had a bike fit in several years, two fit systems to consider are:

  • Specialized Body Geometry

  • Retul

Both have trained technicians in bike shops around the world. The Specialized techs train in a program developed by Andy Pruitt, the dean of professional bike fitting and founder of the Boulder Center or Sports Medicine (BCSM). The founders of Retul worked at the BCSM. Pruitt just retired as director of the BCSM, and I’ve done probably a hundred bike fits for clients with him.

Shortened muscle(s)

The paper on EAMCs says that cramps are more likely to occur when a muscle contracts in a shortened position. When you pedal, your quads, hamstrings, glutes and other muscles all work through a limited range of motion, which makes them more prone to cramping.

This explains why cramps hit Tom when he gets up off the couch. His muscles are already in a shortened position, and the act of getting up off a chair or couch requires contracting those already shortened muscles.

The EACM paper notes that, “stretching the affected muscle almost immediately relieves EAMC.”


Tom is 68, soon to turn 69. As you age, muscle mass is lost. There are fewer active muscle fibers to do the work, so they fatigue more easily, making cramping more likely. You don’t have to lose that muscle mass, though. Really pushing it on the bike makes your legs hurt; however, it doesn’t load the muscles hard enough to prevent atrophy. A coach who works with Team BMC sends his a rider back to the gym after a grand tour because the rider has lost muscle mass!

Underlying medical condition

If you have recurring cramps, then they may be related to some other medical issue. Since cramps usually have multiple causes, see your health care professional to rule out any medical condition as a contributing factor.

Medication side effects

Cramping is listed as a side effect of many medications. Although the medication alone may not cause cramps, it may increase the potential for cramps, which are then triggered by other factors. If you suspect a medication may be part of the problem, talk with your health care professional about trying a different medication.

Night cramps

According to the Mayo Clinic, “Most of the time, no apparent cause for night leg cramps can be identified. In general, night leg cramps are likely to be related to muscle fatigue and nerve problems.” In athletes, night cramps occur after exercise because the muscles are in a cramp-prone state.

If we can solve the problem of preventing cramps during exercise, then this will help reduce the problem of night cramps.

Part 2 of this article in next week's RBR Newsletter will discuss the role of supplements and other ways of preventing cramps.


Coach John Hughes earned coaching certifications from USA Cycling and the National Strength and Conditioning Association. John’s cycling career includes course records in the Boston-Montreal-Boston 1200-km randonnée and the Furnace Creek 508, a Race Across AMerica (RAAM) qualifier. He has ridden solo RAAM twice and is a 5-time finisher of the 1200-km Paris-Brest-Paris. He has written nearly 30 eBooks and eArticles on cycling training and nutrition, available in RBR’s eBookstore at Coach John Hughes. Click to read John's full bio.

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