Why Bike Cramps Happen (And How To Prevent Them), According to a Physical Therapist

Cramping in triathlon and cycling is common, with up to two-thirds of athletes experiencing these painful muscle spasms that can quickly derail a race or ride. While triathletes may more commonly cramp on the run course, cramping on the bike can and does happen frequently as well, even to the best of the best.

At the 2023 PTO U.S. Open, Olympic and multiple-time Ironman champion Kristian Blummenfelt experienced leg cramps the final 20K of the bike that ultimately cost him the victory, and more recently reported that he thankfully was able to rebound during his record-setting victory at Ironman Texas after he had “started cramping in the quads” toward the end of the bike.

Even professional cyclists aren’t immune to cramps – world and Tour de France champion Tadej Pogacar, arguably one of the greatest cyclists of all time, was seen grabbing at his hamstring during the grueling Paris-Roubaix bike race.

Before the weather and your racing season heat up, learn what causes cramps on the bike and what you can do to avoid these potentially race-derailing calamities.

Why bike cramps happen

When it comes to the causes of exercise-associated muscle cramping (EAMC), two main theories prevail: dehydration and electrolyte depletion, and fatigue.

Bike muscle cramp cause #1: Dehydration and electrolyte imbalance

The dehydration and electrolyte imbalance theory dates back a century to observations of industrial workers in the 1920s and 1930s, where both dehydration and hyperhydration with water only were associated with an increase in cramping, and saline solutions appeared to help.

Increased cramping has also been seen with prolonged physical activity in hot, humid environments. But numerous studies, including several looking at Ironman triathletes, have not found an association between EAMC and alterations in serum electrolyte levels or fluid losses.

Serum levels, however, do not tell the whole story, as more localized intracellular and extracellular alterations that cannot be easily measured may still alter neuromuscular excitability and lead to cramps.

Additionally, a more recent study of 30 years of data from the Ironman World Championship medical tent did find that cramping athletes had greater fluid loss, while serum electrolytes did not differ. So, while electrolyte and fluid loss may not explain all EAMC, it likely still may be a contributing factor.

Bike muscle cramp cause #2: Fatigue

The second prevailing theory on the cause of muscle cramping is related to fatigue-induced changes in neuromuscular control. Shortened muscle lengths and intense, fatigue-inducing exercise can cause an increase in muscle-activating muscle spindle activity, while inhibiting muscle-relaxing Golgi tendon organ activity, leading to localized cramping.

Indeed, faster cycling (and overall) times in Ironman athletes have been associated with increased cramping rates, and cramping is most common in the final quarter of bike races, lending support for this theory.

Still, this theory does not account for individual differences in athletes (certainly, not every athlete is cramping during a ride) or the seemingly increased prevalence of cramping in hot, humid environments, meaning that both theories have credence, and cyclists should evaluate their own histories and circumstances surrounding cramping.

Triathlon riding also includes some unique considerations when it comes to cramping, with the foremost being the swim that starts off every race. Sure, swimming might not be overly stressful on the leg muscles, but a hard swim (and T1) still puts a fatigue-inducing stimulus on the body that’s hard to replicate in training.

Wetsuits and water temperature can play a role, as well, especially in long-course competition. Borderline wetsuit legal temperatures combined with an hour or two of tough swimming without access to (drinkable) fluids or electrolytes can easily set the stage for fluid or electrolyte loss heading onto the bike, without the athlete necessarily realizing it.

In addition to exercise-associated causes of cramping, underlying diseases and medications can make athletes more cramp-prone, some of which are cycling-specific. One of these is a vascular condition called external iliac artery endofibrosis (EIAE).

EIAE is most commonly seen in cyclists, and it occurs when the vessel wall of the external iliac artery, an artery that runs along the front of the hip and supplies the leg, thickens likely in response to the repetitive mechanical stresses and compression placed upon it while cycling.

Symptoms include cramping and unexplained weakness. Diagnosis can be difficult (popular pro Fenella Langridge recently detailed her struggles with the condition), but it should be considered when cramping does not fit with other causes.

Sometimes, cramping causes are just elusive. After unexplained, severe quad cramping during 70.3 worlds last December and again recently at Ironman Texas, in both instances, almost immediately after getting onto the bike, top pro Matthew Marquardt took to Instagram to detail his treatment trial of scar tissue and adhesion release around some of the nerves in his quads. When nutrition and fatigue issues alone don’t add up, seek out further medical investigation.

Common areas where you can get cramps while biking

With fatigue being an important contributing factor to EAMC, it follows that the muscle groups most active during cycling would be those most prone to cramping.

In cycling, these muscle groups include the quadriceps, hamstrings, calves, glutes, and shin muscles.

The quads and glutes produce the most power in the downstroke, assisted by hamstrings and calves closer to the bottom of the pedal stroke, while the hamstrings assist a bit on the upstroke.

The calf and shin muscles work to maintain a stable ankle position for power transfer throughout. Not surprisingly, the quads, which do the lion’s share of the work, are the most prone to cramps while riding. But the hamstrings, which exist in a lengthened position, and the calves, which have little “off” time during the pedal stroke, are also commonly afflicted.

Along with those working leg muscles, triathletes may find themselves susceptible to cramps on the bike in upper body and postural muscles.

Lower back issues, including cramping, are commonly attributed to cycling in triathlon, particularly in athletes not accustomed to prolonged time in the aerobars.

Neck and upper back cramping can result from swimming. Sighting places stress on those areas before even hitting the saddle, and then hours on end of holding the head up in the aero position can easily lead to fatigue, and thus cramps.

Then, there’s the hands. After near constant activation helping push water back during the swim, they’re called upon to steer and brake on the bike, especially on more technical courses, which can contribute to cramping.

Tips for avoiding bike cramps

While suffering cramps while biking is common – even for professionals – there are several steps you can take to avoid them.

1. Get race-specific

This seems straightforward, but it can be overlooked. Athletes will often focus on seeking out hills when training for hilly races, but the sustained aero positioning and nonstop pedaling involved in flat races tends to get discounted, leading to cramping quads and lower backs later in races when fatigue sets in.

This can be seen as Olympic-distance athletes begin to step up to longer non-draft 70.3 and T100 races – at the aforementioned PTO US Open, Blummenfelt attributed his quad cramps to a lack of time at race intensity in the aero position.

Head and neck position should be considered, as well – that $400 aero helmet may look slick sitting flush against your upper back out of T1, but if you spent the winter staring down at the trainer instead of ahead at the road, you could suffer neck and shoulder cramping from holding your head up throughout the race.

Finally, don’t forget that swim component. If possible, incorporate swim/bike bricks that include time spent at race intensities (potentially in wetsuits, if relevant) into training.

2. Dial in nutrition

Hydration and electrolytes might only be one part of the cramping picture, but it’s one that can be more controlled. Calculating sweat rates, sweat tests, and perhaps most importantly, practicing nutrition plans in similar conditions at similar intensities to race day can help athletes figure out and meet their needs, preventing bike cramping.

3. Consider fit changes

If cramping on the bike is a consistent issue, then a fresh look at bike fit may be in order. Overly aggressive positions or too-high saddles place the lower back, hamstrings, and calves at disadvantageous longer lengths, while a too-low saddle can overload the quads.

A bike position is only as good as your ability to maintain it while putting out power, so if you find your rides consistently plagued by cramps, have a professional take another look.

4. Pace realistically

Easier said than done when race adrenaline kicks in, but riding above your ability levels will always catch up with premature fatigue, and, in some cases, cramps. There’s a reason why the pros begin to spread out on the return trip to Kona at the Ironman World Championship every year, as athlete attrition begins due to overpacing to make the group. Know your limits, and stick to your plan!

5. Have a contingency plan

Despite the best preventative measures, cramps will happen, so what can be done in the moment? The first instinct is often to stretch a cramping muscle, for good reason. When done slowly, stretching activates the Golgi tendon organ and sends signals to the cramping muscle to relax.

In the heat of a race, though, stopping to stretch on the bike might not be possible, so what else can you do? When Pogacar started cramping in Paris-Roubaix, he was quickly handed a small vial of liquid from his team car.

Although he eventually lost contact with eventual race winner Mathieu van der Poel after overcooking a corner, he recovered from his cramp to hold onto second place, sparking questions as to what was in that vial. The answer? A “gruesome” mix of highly concentrated electrolytes and salts, similar to pickle juice or the commercially available Hot Shot.

These concoctions don’t necessarily change serum electrolyte concentrations; instead, they’re postulated to work by triggering receptors in the mouth and throat that reflexively inhibit alpha motor neuron firing to cramping muscles. So, if you’re prone to cramps, it may help to come prepared!

So, while cramps on the bike are painful and certainly never welcome, understanding the underlying causes and areas prone to cramping can help you dial in prevention and treatment strategies. Stay smart and logical, control what you’re able to control and practice in training, and you’ll set yourself up for enjoying more cramp-free riding down the road.