Muscle cramping is a prevalent issue among athletes, characterized by sudden, involuntary, and painful muscle contractions during or after physical activity. The causes of muscle cramps remain somewhat elusive, although two hypotheses have been proposed. In this article, we will explore the different types and prevalence of muscle cramps, risk factors associated with their occurrence, and the two main theories explaining their origins.
Types and Prevalence of Muscle Cramps
Muscle cramps are a common occurrence among athletes, but estimating their prevalence is challenging due to varying factors such as frequency and severity. Different types of cramps exist, ranging from small and brief muscle contractions to large, whole-body cramps that can cause prolonged pain. Studies have reported different definitions and measurements of cramps, making it difficult to obtain accurate prevalence rates. However, one survey conducted on 2600 triathletes found that 67% reported experiencing cramps during or after exercise, with 4% experiencing severe cramping.
While muscle cramps can happen during any physical activity, they appear to be more prevalent in endurance sports due to their prolonged and repetitive nature. Several risk factors have been associated with cramping, including older age, cardiovascular disease, and exercising in hot and humid conditions. However, it's important to note that these factors are often only correlated with cramping and do not necessarily cause it. Instead, they may contribute to the overall risk of experiencing cramps.
Disturbed Electrolyte Balance and Hydration Status
One traditional explanation for muscle cramps involves the loss of electrolytes and dehydration through sweating. Electrolytes play a crucial role in muscle function, including the process of contraction and relaxation. Depletion of electrolytes in the blood and muscles could potentially disrupt and trigger uncontrolled muscle contractions, leading to cramping. Early studies conducted on physically demanding workers in the 1920s and '30s suggested a connection between electrolyte loss through sweat and the occurrence of cramps.
Hyponatremia, a condition characterized by low sodium concentrations in the blood, was specifically implicated in cramping symptoms. Further research on athletes has indicated that those who experience cramps tend to have larger sodium losses during exercise and often consume plain water instead of electrolyte beverages, potentially exacerbating the issue.
Altered Neuromuscular Control
Muscle cramps can also occur without dehydration or electrolyte imbalance, even in cool environments. In these cases, abnormal activity in the nerves that control muscle contractions, originating from the central nervous system, is believed to be the cause. The precise mechanism behind this abnormality remains unclear, but it is thought to be associated with increasing fatigue. Fatigue may lead to heightened muscle activation while reducing the inhibition that typically controls excessive contraction, resulting in uncontrolled muscle cramping.
Nervous System Control of Cramping
Studying the impact of nervous system control on cramping is challenging due to the unpredictability of cramps during exercise. Researchers have utilized electrical muscle activation to induce cramps in various studies. These studies revealed that individuals prone to cramping required less electrical stimulation to trigger cramps.
Additionally, the administration of anesthetics to block the nerves responsible for muscle activation resulted in a higher threshold for cramp induction. This evidence supports the theory of a nerve-related mechanism contributing to cramps. Although the similarity between electrically stimulated cramps and exercise-induced cramps remains unknown, studying the former provides valuable insights into muscle cramp research.
Muscle cramping can occur due to a variety of factors, with dehydration and electrolyte imbalance being more prominent in exercise under heat conditions. However, cramps can also manifest without these factors, suggesting an altered neuromuscular control mechanism associated with fatigue. While the exact mechanisms behind muscle cramps remain uncertain, understanding their causes is crucial for developing effective prevention and treatment strategies. Stay tuned for our upcoming blog on muscle cramp prevention and treatment.
If you have any further questions about the topic, then just drop us online by clicking here
- Kantorowski P, Hiller W, Garrett W, Douglas P, Smith R, O’Toole M. Cramping studies in 2600 endurance athletes. Med Sci Sports Exerc. 22(2):S104, 1990
- Dill D, Bock A, Edwards H, Kennedy P. Industrial fatigue. J Ind Hyg Toxicol. 18:417-31, 1936
- Maughan RJ, Shirreffs SM. Muscle Cramping During Exercise: Causes, Solutions, and Questions Remaining. Sports Med. 49(Suppl 2):115-24, 2019
- Talbott J. Heat Cramps. Medicine. 14:323-76, 1935
- Jung A, Bishop P, Al-Nawwas A, Dale R. Influence of hydration and electrolyte supplementation on incidence and time to onset of exercise-associated muscle cramps. Journal of Athletic Training. 40(2):71-5, 2005
- Minetto M, Botter A. Elicitability of muscle cramps in different leg and foot muscles. Muscle Nerve. 40(4):535-44, 2009
- Minetto M, Holobar A, Botter A, Ravenni R, Farina D. Mechanisms of cramp contractions: peripheral or central generation. J Physiol. 589(23):5759-7, 2011