Hyperbaric Oxygen Therapy in HAMstring Injury (HOTHAM) Trial

Inclusion Criteria: * The participant is male or female, of any ethnic origin * The participant is between 18 and 65 years old * The participant has a clinical diagnosis of an acute hamstring injury ≤7 days old, defined as: * Anamnestic acute injury * Anamnestic pain in the posterior thigh * Localized pain during palpation of hamstring muscle * Localized pain during passive straight leg raise * Increased pain during isometric contraction * The participant is able to start of HBOT treatment ≤7 days) Exclusion Criteria: * The participant is not capable of doing an active exercise program. * The participant does not have the intention to full sporting activity or duty activities; * The cause of the hamstring injury is an extrinsic trauma on the posterior thigh; * The participant has a chronic hamstring injury \>2 months, defined as recurrent pain or tenderness of the hamstring; * The current injury is a re-injury ≤2months after RTP/RTD after acute ipsilateral hamstring injury; * Clinical suspicion of a complete proximal tendon avulsions; * Presence of other concurrent injuries inhibiting rehabilitation; * The participant is not able to give informed consent; * There are contra-indications for MRI: Pacemaker, pregnancy and claustrophobia * There are contra-indications for HBOT: * Smoking or quit smoking \<3 months prior to injury; * A previous spontaneous pneumothorax. * Implantation of ICD or PM not compatible with hyperbaric pressure * Current or recent (\<6 months) use of cytostatics * Unable to perform a Valsalva manoeuvre to pressurize the middle ear (pre-existent ear-nose-throat complaints or a current upper airway infection). * Pregnancy * Claustrophobia