WHY DO MUSCLES CRAMP?   Excerpt From IDEA Fitness Journal August 2021

Muscle cramps can stop athletes in their tracks. These cramps usually dissipate within seconds or minutes; however, the abrupt, harsh, involuntary contractions can cause mild-to-severe agony and immobility, often accompanied by knotting of the muscle. And cramps are common; 50%–60% of healthy people suffer muscle cramps during exercise, sleep or pregnancy or after vigorous physical exertion. They appear to occur more often in endurance athletes and in the elderly, but there is no gender difference in incidence of skeletal muscle cramps.

Types of Muscle Cramps

  • Nocturnal cramps occur during sleep without any clear trigger.
  • Pathological cramps are a consequence of having diabetes, nerve dysfunctions or metabolic disorders.
  • Exercise-associated muscle cramps occur during or after exertion. The first scientific confirmation of these types of cramps dates to 1908, when they were described in miners working in hot and humid conditions.

Risk Factors for Muscle Cramps – With marathon runners, research has found certain risks associated with the occurrence of a muscle cramp. These risks include a longer history of running, advanced age, higher body mass index, shorter daily stretching time, irregular stretching habits and a family history of cramping. The top two factors associated with cramps in marathoners are muscle fatigue (linked to longer runs) and poor stretching habits..

Theories on the Cause of Muscle Cramps-  Early theories on the source of muscle cramps focused on electrolytes, dehydration and the environment.

  • Serum Electrolyte Theory – Blood plasma contains electrolytes, such as sodium, potassium, chloride, bicarbonate, calcium and phosphate. Electrolyte depletion is often blamed for causing cramps. Currently, however, there is no solid explanation for how low serum electrolyte concentrations could have this effect.
  • Dehydration Theory – In the past, studies have suggested treating muscle cramps in workers and firefighters with fluids and electrolytes.  More recent studies that have estimated blood volume and plasma volume do not support the theory that dehydration has a direct link to exercise-associated cramps.
  • Environmental Theory – This theory sprang from the condition referred to as “heat cramps.” While exercising in a hot, humid environment may  correlate with the development of muscle cramps, there is no evidence linking cramps to an increase in core body temperature.

Current Theory On Muscle Cramps – The newest concept of muscle cramps is a neuromuscular theory. This theory has evolved to point to two origins: a central origin (spinal column) and a peripheral one (neuromuscular junction).

The central or spinal origin theory suggests that the involuntary contraction of a muscle occurs when nerve messages to the spinal column change, perhaps due to muscle fatigue. This results in an imbalance of excitatory (from muscle spindles) and inhibitory (from Golgi tendon organs) spinal messages to muscles . This neural signaling imbalance leads to enhanced muscle cell excitability and cramping.

The scientific evidence of a neuromuscular theory is mounting. The research appears to show that, in some cases, fatigued muscle can’t fully relax. This condition leads to an imbalance between excitatory signals and inhibitory messages to the muscle. So, the most recent research appears to support the central origin theory of the muscle cramp.

What Are Muscle Spindles and Golgi Tendon Organs?

Muscle spindles and Golgi tendon organs are referred to as proprioceptors. A proprioceptor is a sensory receptor that receives stimuli from within the body, particularly signals related to body position and movement. The neuromuscular theory of muscle cramps suggests that muscle spindle and Golgi tendon organ signaling play a role in the development of a muscle cramp.

Muscle spindles are stretch receptors within a muscle that serve to detect changes in the length of the muscle and/or the speed of length change. They convey muscle length information to the spinal column via specialized afferent nerve fibers. The muscle spindle activates the stretch reflex. This happens when a muscle is stretched quickly to its endpoint of movement. The muscle spindle sends a rapid message to the spinal column, which tells the muscle to contract, preventing it from overstretching.

Golgi tendon organs, also called Golgi organs, are neurotendinous sensory organs that sense changes in tension within a muscle. The Golgi tendon organ lies at the origin and insertion of skeletal muscle fibers into the tendons. If there is too much tension (i.e., too much force) placed on a muscle, the Golgi tendon organ will inhibit the muscle from creating any more force (via a reflex arc), protecting it from injury.

PREVENTING MUSCLE CRAMPS – Intense, extremely long workouts (relative to the fitness of the exerciser) clearly lead to more skeletal muscle cramps. Lack of training and training in a hot, humid environment also predispose a person to muscle fatigue and potential cramping. As mentioned previously, research also shows muscle cramps are more common in the elderly.

Although studies show that poor or inadequate stretching may spark muscle cramps, there are no evidence-based stretching recommendations for warding off cramps. But encouraging clients to stretch regularly and with proper body alignment after exercise seems logical.

RESEARCH TAKEAWAYS – From a health and teaching perspective, the latest research shows no evidence that muscle cramping is due to electrolyte imbalances or water depletion in muscle. Studies also fail to support the use of particular supplements to impede cramps. What is imperative is avoiding intense or long workouts for which clients are not properly prepared. Teaching and encouraging proper stretching exercises, particularly of the limbs, is also essential. And finally, although studying cramps is difficult, we need more research to better understand their mechanisms and to develop evidence-based prevention strategies.


DEBORA’S EXPERIENCE – I have experienced severe muscle cramps in my adductor (inner thigh) muscles, especially after skiing.  What seemed to help was to drink about a ½ cup of the brine from a pickle jar. I know this seems strange, but it worked 85% of the time to relieve the cramp. My husband has experienced similar relief by this method.