I recently read a good article about cramping, as I have them too on longer adventures. Below is a few parts of the article that discuss the neuromuscular fatigue and muscle fatigue that inhibits our muscles.
More recent theories about exercise-induced cramp have investigated fatigue-related disturbances in the neuromuscular system.
You’ll have likely found that the most reliable treatment for a cramped muscle is to stretch it immediately. It’s certainly our instinctive response. If one of the most reliable treatments for cramp involves adding tension to the afflicted muscle, then perhaps one of the underlying causes is a lack of tension. Or more precisely, a lack of tension on specific structures.
Embedded within the tendons of muscles are receptors called Golgi tendon organs (GTOs). The role of the GTO is to measure, feedback and reduce tension within the muscle when necessary. It’s thought that in the fatigued state there is a reduced inhibitory effect from the GTOs. The regulation of tension becomes unbalanced as the muscle is subjected to greater excitatory signals from the alpha motor neuron. Cramp eventually ensues. This theory is supported by the increase in electrical activity that has been demonstrated in cramping muscles.
It’s also been shown that muscles are more prone to cramp when in their shortened ranges. This is particularly true of two-joint muscles such as the hamstrings. It’s thought that the unloading of the GTO also plays a role in this effect.
Exercise-induced muscle cramps
Exercise-induced muscle cramps seem to occur irrespective of weather conditions and fluid loss. Several studies have confirmed this.
In a trial looking at male runners before and after a marathon, no difference was found in fluid and electrolyte balance between the runners who suffered cramps and those who didn’t. In a South African study on Ironman triathletes, those who suffered from cramp had no significant difference in either percentage body mass loss or serum electrolyte concentrations. Post-race serum sodium concentrations were lower in the cramping group, but these were deemed to be within normal clinical ranges.
Interestingly, this research group also measured electrical activity in muscles that had cramped and compared it to those that hadn’t. They noted increased activity in the cramping muscles which they thought may be due to increased neuromuscular activity. More on the significance of this in a moment.
In a further study using more Ironman triathletes, subjects were surveyed before an event and asked questions about personal-best performances, current training loads and cramp history. The researchers found that athletes who experienced cramp during the event had exercised at a higher intensity during the race and had a faster overall time. This was despite having similar preparation and performance histories to those who didn’t cramp.
The researchers concluded that fatigue is a greater predictor of cramp than dehydration or serum sodium changes.
2. Muscle fatigue
It’s no coincidence that most of us cramp more during early season races or when we’re attempting a particularly challenging ride. In this context cramping can be seen as a message that we need to improve our conditioning.
Studies looking at individuals who always cramp in the same muscles, usually in the later part of endurance events, have shown strength work can be effective in eliminating these type of occurrences. A strength training programme which begins by isolating the muscles involved in cycling is a good place to start.
3. Neuromuscular fatigue
Theories on the fatigue of the neuromuscular system as a likely cause of cramp don’t only give us an effective intervention, they also give us potential areas to focus on to avoid it in the first place.
Resistance train into vulnerable position
We know that muscles are more likely to cramp when taken into their short position. We can, however, train muscles to better tolerate these positions.
For example, two-joint muscles like your hamstrings may be prone to cramp when your hip is extended and your knee is flexed. If you find this to be the case then it’s likely you are also weak in this position. Applying resistance to these positions will not only reduce your risk of cramping but may have the additional effect of improving your performance on the bike.
Change positions on the bike frequently
It also seems that having muscles performing over the exact same length and tension for long periods may cause issues.
This is an indication you should switch up your position on the bike intermittently. Get out of the saddle now and again, drop your heels on the pedals to stretch your calves, straighten each leg fully, and push your pelvis towards the handlebars. Move between the brake hoods and the tops as appropriate as well.