Hans Berg

Hans Berg is Visiting Professor of Environmental Physiology at the Department of Physiology and Pharmacology since 1 September 2024.

He presented his thesis ”Effects of unloading on skeletal muscle mass and function in man” at Karolinska Institutet in 1996, using experimental bedrest or unilateral limb unloading to quantify muscle atrophy, cellular changes and performance deficits following inactivity or spaceflight. As a spin-off he invented the flywheel exercise technology (FWE) for gravity-independent strength training, used in space and other microgravity studies with ESA and NASA, now well-documented for athletic training and rehab.

As a research resident, then consultant orthopaedic surgeon at Karolinska University Hospital, Dr Berg assessed strength loss and gait disturbance in relation to muscle atrophy, fat infiltration and bone loss in patients suffering osteoarthritis (OA). A translational project evaluated small joint implants to treat focal cartilage lesions typical for young sports individuals causing chronic disability. Implants inserted in sheep, were monitored for bone ingrowth and cartilage wear up to 1 year, allowing this Swedish-developed method to be introduced and used clinically worldwide.

An international randomized controlled clinical study (RCT) questioned the efficacy of shoulder fracture surgery. Further RCTs quantify atrophy after tendon injury and knee arthroplasty. Several national register studies map the epidemiology of tendon injury, upper and lower extremity fractures and trends in their surgical treatment. A register study uses machine learning to predict mortality after high-energy severe traumatic injuries. A joint study with KTH Royal Institute of Technology aims to merge robotic surgery with new external fixation technologies for fractures.

Increased gravitational (G) force, hypoxia and decompression stress are all risks encountered in modern military jet aviation. Experimental studies using a human centrifuge focus both cardiovascular challenges to human performance and the increased spinal load exposed under increased G-forces. Experiments using a hypobaric chamber, producing reduced ambient air pressure, simulate high-altitude aviation or space walks. Related decompression sickness and/or hypoxia syndromes, reducing optimal performance, can thereby be investigated. Basic physiological reactions are revealed in these unique environments.

Our FWE training model to prevent muscle and bone loss in microgravity during planned long-term spaceflight, has produced a recent thesisis, and is now undergoing biomechanical and metabolic evaluation with the goal to qualify for the planned Gateway moon-orbiting space station.

Muscle physiology, environmental physiology, aviation and space physiology, orthopaedics.