What Is a Muscle Strain?
A muscle strain is a partial or complete injury to the muscle fibres caused by sudden overstretching, forceful contraction or direct trauma to the muscle. It is one of the most common sports injuries, particularly in activities involving explosive movements, sprinting or sudden changes of direction, such as football, basketball, athletics and tennis.
Muscle strains are classified into three grades of severity. A grade I strain involves minimal fibre damage, mild pain and negligible loss of function. A grade II strain involves more extensive fibre damage, severe pain, swelling and difficulty moving. A grade III strain is a complete muscle tear, resulting in an inability to contract the muscle and, in some cases, visible deformity.
The hamstrings, quadriceps, calf muscles and adductors are among the most affected muscle groups.
Stages and Characteristics of a Muscle Strain
Muscle healing after a strain occurs in three successive stages: destruction and inflammation during the first 48 to 72 hours, repair and regeneration from approximately day 3 to day 21, and, finally, remodelling over a period of weeks or months.
The quality of each stage determines the final outcome. When the inflammatory phase persists or regeneration is incomplete, the muscle may heal with fibrous scar tissue, which is less elastic and functional than healthy muscle tissue.
A key feature of muscle strains is the haematoma that develops on the site of the injury. When it is not absorbed promptly, it may become organized into a fibrous mass or, in severe cases, lead to myositis ossificans, permanently restricting movement. The presence of haematoma also creates local hypoxia, which can delay the natural tissue repair process.
The risk of recurrence is high, particularly when an athlete returns to activity before biological healing is complete, even if they no longer experience symptoms.
Scientific Basis
Animal studies and clinical research involving athletes have documented the potential benefits of hyperbaric oxygen therapy in the recovery of muscle strains. The main findings include faster haematoma resorption, improved muscle-fibre regeneration through the activation of satellite cells and a reduced fibrotic response, which is responsible for scar-tissue formation within the muscle.
Studies assessing return-to-play time following grade II muscle strains have reported a significantly shorter recovery period among athletes whose treatment protocol included hyperbaric oxygen therapy, compared with those who received conservative treatment alone.
The Role of Hyperbaric Oxygen Therapy
In cases of muscle strain, hyperbaric oxygen therapy may begin within the first 24 to 48 hours as an adjunct to conventional treatment. Early treatment may maximize its effect on inflammation and support an earlier transition to the regenerative phase.
During the acute phase, the primary objective is to reduce the haematoma and prevent secondary ischaemia. The increased amount of oxygen dissolved in the plasma supplies oxygen to the tissues surrounding the injury, which may otherwise be compromised by pressure from the swelling. At the same time, its anti-inflammatory effect may reduce pain and weakness, allowing earlier mobilization.
During the regenerative phase, hyperbaric oxygen therapy activates satellite cells—the muscle stem cells responsible for rebuilding muscle fibres—and reduces the formation of fibrous tissue. This promotes the development of functional muscle tissue rather than scar tissue.
The result may be better-quality healing and a lower risk of reinjury. A treatment course for a grade II muscle strain typically consists of 10 to 20 sessions, always combined with a physiotherapy programme and monitored by a sports medicine physician.