Postexertionele

Postexertionele is an adjective used in medical contexts to describe responses that occur after physical or cognitive exertion. It is most commonly encountered in relation to postexertional malaise (PEM), a key feature of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and related disorders.

Postexertional malaise refers to a marked and disproportionate worsening of symptoms following exertion, with onset often delayed by hours to days and lasting 24 hours or more. Common accompanying features include profound fatigue, cognitive difficulties (often described as "brain fog"), myalgia, enlarged or sore lymph nodes, feverish or flu-like sensation, sleep disturbances, headaches, and autonomic symptoms such as dizziness or lightheadedness. The severity and duration of PEM can vary between individuals and across illnesses.

The underlying mechanisms of postexertional malaise are not fully understood. Hypothesized contributors include disruptions in cellular energy metabolism, immune or neuroimmune activation, oxidative stress, and autonomic nervous system dysregulation. Ongoing research aims to clarify the pathways involved and to identify potential biomarkers.

Diagnosis of PEM is clinical, based on patient history and alignment with diagnostic criteria for ME/CFS or related conditions. PEM is considered a defining feature in several consensus criteria, but its presence can also be observed in other chronic illnesses, such as fibromyalgia, multiple sclerosis, and orthostatic intolerance.

Management centers on energy conservation and symptom management. Common approaches include pacing—careful planning and balancing of activity with rest—sleep optimization, and treatment of associated symptoms. Graded exercise or activity programs are controversial in PEM and are generally approached with caution, emphasizing individual limits and verification of tolerability.