Publications

• The MYOTONES experiment was the first to collect data on muscle health in astronauts during an entire space mission cycle involving inflight measurements at four time points on the ISS.
• Muscle stiffness is a digital biomarker for risk monitoring during future planetary explorations (Moon, Mars), for healthcare management in challenging environments or clinical disorders in people on Earth, to enable effective tailored´exercise programmes.
• Close monitoring of muscle health will be crucial for future Deep Space and Planetary Exploration where gait and postural stability are utmost requirements for human motion in altered gravity conditions (Moon, Mars), as well as for faster recovery on return to Earth.
• The assessment protocol and definition of passive muscle stiffness as a muscle health indicator from the space environment could be helpful for many health professionals undertaking clinical assessments, and widespread uptake may result in a step-change for enhancing healthcare in neuro-musculoskeletal and geriatric medicine, rehabilitation and precision medicine on Earth.
• MyotonPRO offers objective non-invasive measurement suitable for clinical environments to develop clinical scales, and for more accurate and sensitive evaluation of effects of treatments such as drugs and brain stimulation as in Parkinson Disease. Potential future applications also include home monitoring of drug effects, analogous to self-testing blood in diabetes.

Muscle function is compromised by gravitational unloading in space affecting overall musculoskeletal health. Astronauts perform daily exercise programmes to mitigate these effects but knowing which muscles to target would optimise effectiveness. Accurate inflight assessment to inform exercise programmes is critical due to lack of technologies suitable for spaceflight. Changes in mechanical properties indicate muscle health status and can be measured rapidly and non-invasively using novel technology.

A hand-held MyotonPRO device enabled monitoring of muscle health for the first time in spaceflight (> 180 days). Greater/maintained stiffness indicated countermeasures were effective.

Tissue stiffness was preserved in the majority of muscles (neck, shoulder, back, thigh) but Tibialis Anterior (foot lever muscle) stiffness decreased inflight vs. preflight (p < 0.0001; mean difference 149 N/m) in all 12 crewmembers. The calf muscles showed opposing effects, Gastrocnemius increasing in stiffness Soleus decreasing. Selective stiffness decrements indicate lack of preservation despite daily inflight countermeasures. This calls for more targeted exercises for lower leg muscles with vital roles as ankle joint stabilizers and in gait.

Muscle stiffness is a digital biomarker for risk monitoring during future planetary explorations (Moon, Mars), for healthcare management in challenging environments or clinical disorders in people on Earth, to enable effective tailored exercise programmes.

We conclude that stiffness was preserved in the majority of muscle structures studied but selective loss of stiffness of key muscles required for gait, despite daily inflight countermeasures, indicates more targeted exercises are required for effective countermeasures in space. Our work has contributed to the body of evidence for potential to translate Myoton technology to multiple other settings on Earth, from physical conditioning monitoring in remote areas or in extreme environments to clinical rehabilitation enabling more targeted and efficiently tailored interventions. These applications based on muscle stiffness as digital biomarker open up new avenues for improved health status management in future Human Deep Space Exploration and for people on Earth.