Hyponatraemia and Fluid Replacement
Individuals who attempt long distance events such as marathons will recognise the need to maintain adequate hydration. Over-hydration can, however, lead to severe illness in the form of exercise-associated hyponatraemia (EAH), which is defined as serum sodium of less than 135 mmol/l during or up to 24 hours after prolonged physical activity.
It occurs as a dilutional effect of excess fluid consumption beyond that of body fluid losses during prolonged exertion. Low plasma sodium levels reduce plasma osmolality leading to a fluid shift from extracellular to intracellular compartments. This can lead to peripheral oedema, nausea, vomiting and headache, with confusion, seizures and death occurring with unchecked illness progression as a result of cerebral oedema.
Risk factors for developing EAH include excessive fluid consumption during endurance events, renal dysfunction, hot environmental conditions, female sex and slow running with prolonged event duration. Treatment consists of resuscitative measures as well as initial restriction. Intravenous hypertonic saline (3|% NaCl) is required if neurological symptoms predominate.
Recent fluid replacement guidelines suggest cautious rehydration for individuals involved in endurance events. The guidelines advocate ‘drinking according to thirst’ and encouraging individuals to weigh themselves before and after training events to calculate fluid losses with the aim of ‘avoiding weight gain during exercise’. Medical and fitness professionals should be advised to offer such guidance to individuals who are concerned about hydration during endurance events.
Exertional Heat Illness
Exertional heat illness (EHI) encompasses a spectrum of disorders ranging from heat cramps to life-threatening heatstroke (which carries a 7% morality). It occurs in the sporting environment due to an individual’s inability to adequately dissipate the heat generated through muscular exercise and is commonly seen during endurance events. Heatstroke describes the clinical syndrome of neurological disturbance associated with a core body temperature of greater than 40ºC (rectal temperature). Individuals may become dizzy, confused and agitated with a change in personality and collapse with a reduced Glasgow Coma Score (GCS) is not uncommon.
Risk factors associated with heatstroke include dehydration, obesity, high environmental temperature, febrile illness, alcohol ingestion and poor fitness. Rapid cooling at the roadside ensures restoration of core body temperature to normal. In the sporting environment, this is usually achieved through ice-water body immersion, evaporative spray cooling or ice packs to the axillae, neck and groin. Outcomes are greatly improved by cooling the individual as rapidly as possible with survival rates improving when core temperature is restored to below 38.9ºC within 60 minutes.
Individuals should be advised to ensure that they remain hydrated, avoid excessive alcohol consumption prior to endurance activity and avoid running when unwell. Other causes of exercise-associated collapse must be considered including hypotension (low blood pressure), which rapidly responds to leg elevation and hypoglycaemia (low blood sugar), which should be measured in the initial assessment.
Female Athlete Triad
Primary care practitioners are commonly the first medical professional to encounter an individual with the female athlete triad (FAT). FAT describes the syndrome of disordered eating, low bone mineral density and amenorrhoea or menstrual dysfunction. It occurs in females who have a negative energy balance due to excessive physical activity and/or insufficient calorific intake. A significant proportion of females may only suffer from components of the triad, which exists as a continuum between health and disease.
Excessive exercise in combination with a restricted diet can result in suppression of reproductive function and bone formation, which occurs when the body enters ‘starvation mode’. This results in hypothalamic amenorrhoea with subsequent menstrual abnormalities. This process is reversible when energy balance is restored through increased calorific intake.
Reduced energy intake also results in lower bone mineral density and strength due to decreased bone formation and increased resorption. As a result of these bone changes, individuals have a higher incidence of stress fractures.
Screening for FAT relies on the medical professional elucidating a detailed history regarding exercise volume, dietary intake and menstrual irregularities. If amenorrhoea exists, then it is important to exclude other treatable causes before presuming that reduced energy availability is the cause.
Management relies on improving availability through incremental increases in dietary intake or a reduction in output as exercise (or both). The aim is to restore a normal menstrual pattern and reverse low bone density. A dietician and psychiatrist may offer optimal outcomes in individuals who are resistant to therapy. Individuals with a diagnosis of osteoporosis on Dual Energy X-ray Absorptiometry (DEXA) scanning may benefit from calcium and vitamin D replacement as well as bisphosphonates. However, there is little evidence supporting their use in the younger population.
Exercise dependency (ED) develops when an individual becomes addicted to physical activity, resulting in withdrawal symptoms when exercise is withheld, as well as feelings of guilt and low mood. It may lead to interference with relationships and continued participation in physical activity despite medical contraindications.
There appears to be a close relationship between ED and eating disorders, with obsessions regarding weight and body shape commonly described. ED may result in illness due to reduced immune function and musculoskeletal injury when the individual fails to heed warning signs and continues to exercise despite them.
Tolerance may occur whereby increasing levels of physical activity are required to achieve similar psychological benefits. Participation in exercise and obsessive thoughts regarding physical activity may dominate and interfere with social functioning.
It is important for medical and fitness professionals to educate individuals about the dangers of ED as the individual may be able to recognise early signs of the condition and about further progression. Regular rest forms a vital part of the training and recovery process and may practically involve the individual swapping an intense cardiovascular workout for a gentle stretching session. A multidisciplinary approach, including input from psychiatrists and psychologists, may optimise an individual’s outcomes.
- Female Athlete Triad: Problems Caused by Extreme Exercise and Dieting (forthealthcare.wordpress.com)