Anatomy
The forearm muscles are divided into 3 groups (compartments) of strong muscle membranes (fasciae) that are partially inextensible. An anterior muscle group i.e. the dorsal side of the forearm (volar compartment containing the extensor muscles), an external muscle group (radial/lateral compartment) and a posterior muscle group i.e. the palm side of the forearm (dorsal compartment containing the flexor muscles). Each muscle group has its own blood and nerve supply.
Cause
Hard training of the forearm muscles can trigger Delayed Onset Muscle Soreness (DOMS), especially if you overtrain untrained muscles or do vigorous muscle contraction while stretching the muscle (eccentric muscle training). DOMS is caused by small strain-induced injuries in muscle tissue (Heiss R, et al. 2019) and connective tissue and is relatively common in the forearms.
Heavy exercise (repetitive heavy lifting or racquet sports) can also trigger ‘trigger points’ with localised muscle changes where pressure triggers soreness, possibly radiating to the hand and referred pain. Trigger points in muscles can also be secondary to other painful injuries and are also seen in non-athletes. Trigger point symptoms can last much longer than DOMS.
Symptoms
DOMS is pain, tenderness and stiffness of the forearm muscles. There may be mild cramps and reduced muscle strength and joint mobility. Symptoms peak 1-3 days after exercise, but symptoms last only a few days. Occasionally, elevated muscle enzymes (creatinine kinase) may be transiently measured in the blood as a sign that muscle damage has occurred.
With trigger points, muscle pain is more localised than with DOMS.
Examination
The diagnosis of DOMS and trigger point is primarily based on the characteristic muscle pain after a sudden increase in exercise intensity and a clinical examination, and the localisation of the pain, which in trigger points is very local.
Treatment
Reduction of triggering activity, stretching and slowly increasing rehabilitation within the pain threshold can be initiated. Massage can in some cases reduce symptoms temporarily. For long-term trigger point discomfort, injection of adrenal cortex hormone into the trigger point has been tried, but the documentation of the effect is limited.
Complications
If the progress is not smooth, you should consider whether the diagnosis is correct or whether it is a tendon disorder or nerve entrapment.
