Inclusion Criteria:  Aged 20-55 years Voluntary and able to provide informed consent Fluent in English Current moderate - severe cannabis use disorder Major history of cannabis use (i.e. ≥3 days per week on average for ≥4 of the past 6 years) Capacity to tolerate physical exercise according to 'Fitness to Exercise'  Exclusion Criteria:  Have a history of cardiovascular disease, high blood pressure, musculoskeletal injury or other condition that would preclude safe engagement in VO2 max fitness testing and/or regular physical exercise Severe claustrophobia, non-MR compatible metallic implant, or other contraindication to MRI scanning Lifetime history of significant neurological illness, or moderate - severe brain injury, Current major unstable medical illness or chronic pain condition Lifetime history of schizophrenia, schizoaffective disorder, OCD, PTSD, bipolar disorder Current significant depression or anxiety that precludes ability to reliably engage in the exercise program Current moderate - severe substance use disorder for substances other than cannabis (excluding nicotine) Currently pregnant or lactating Shift work employment schedule within the prior 6-months Have engaged in ≥5 sessions of HITT or resistance training within the past 12-months History of treatment with antipsychotic medications Current participation in psychosocial treatment for substance use disorder Other psychoactive medications or psychosocial treatments will be considered on a case-by-case basis. Where a current psychoactive medication is deemed acceptable, both dose and type must have been stable for a minimum of four weeks prior to baseline assessment, and remain stable throughout the 12-week exercise phase of the study.