Cramp! A diver's Guide
Posted By Laura Harris on 14 November 2003
One of the potential physiological effects of extended range, cold water and technical diving is the increased risk in the occurrence of muscular cramp. As diving evolves with the use of exotic gas blends and tekkies push ever deeper with extended deco and dive times, the need to be water-fit is more important than ever. Cramp is unpredictable, can be dangerously debilitating and if it hits at an inopportune moment could just be the trigger that sends a diver spiralling into the incident pit.
Although the exact cause of cramp is idiopathic there are some known triggers. These variable factors include poor physical fitness, reduced flexibility, muscle fatigue, electrolyte imbalance and dehydration. Divers also have the additional predisposing considerations of cold water diving, new, restrictive or badly fitting kit and changes in body carbon dioxide levels. Most individuals have a susceptibility to a particular trigger. So to help minimise your risk of suffering from an attack, here is the definitive divers guide to cramp.
Physiology, Muscles and Movement
Skeletal, cardiac and smooth are the three different muscle types found in our body. Of these types, skeletal makes up the largest percentage and is the type most susceptible to cramp. It is the only type that we have voluntary control over, through movement. Most muscles are capable of performing more than one type of movement and most movements require the use of more than one muscle. Movement works on a principle of leverage and is brought about by a combination of the muscle (providing the force), the bone (lever), the fulcrum or pivot (joint) and the load (resistance) which in diving is water.
All muscles attach via a tendon onto a bone, hence the term skeletal. Muscle mass usually constitutes between 40% and 50% of total body weight which in turn equates to strength. The prime function of healthy, strong muscle is to turn chemical energy into mechanical energy. This energy generates the force needed to perform work and produce movement. Muscles are always held in a state of permanent tension, providing postural support and resistance to gravitational pull, so they never fully relax. In order for one muscle to contract and make a movement, another muscle has to slacken to allow the motion. Muscles are therefore categorized into prime mover (agonist), oppositional mover (antagonist), assistor, fixator or synergist (refiners of movement) depending on what they are doing to bring about a specific action. Any muscle that spans or is connected to two joints will be more prone to injury and cramping. This is because these muscles are sometimes expected to perform more than one action simultaneously. They are known as biarticular muscles. It so happens that many of the larger groups of leg muscles used during a dive fit this profile such as the hamstrings, the quadriceps and the gastrocnemius (one of the calf muscles).
Monster Contractions
Cramps can generally be separated into four types and are classified by their causes and the muscles that are affected. These categories include dystonic, contractures, tetany and true. True cramps are overwhelmingly the most prevalent form of cramp and the type we are most likely to encounter as a diver.
True cramp is an abnormal, involuntary, painful and sustained muscle spasm.
It can be severe with spasmodic contractions affecting muscles singularly or
as a group. Attacks can range from short lived twitches lasting for only a
few seconds to prolonged, unremitting spasms of over 30 minutes. A cramp may
involve only part of a muscle or the entire muscle and can recur numerous
times before abating. It is linked to the hyperexcitability of the nerves
that fire muscles. During an episode, the contracted tissue bulges outwards
and becomes painful and unyielding. Localised inflammation can arise as the
involved tissue fibres tear when an already tight muscle starts to cramp,
shortening it further. The surrounding soft tissue responds protectively
with additional spasm intended to minimize movement and stabilise the
damaged tissue. This is why after a deep or particularly painful cramp, the
area can feel tender and swollen for some days afterwards. The best way to
relieve an attack once a muscle starts to involuntarily contract is to
stretch it, along with massage and, if land bound, sometimes gentle heat.
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