Moderation: M. Heer, Bonn; M. Gogol, Coppenbrügge
Aging, particularly to the 80ies and above, usual show an association with dynapenia, sarcopenia, bone density loss including osteoporosis, functional decline and mobility problems. This process is often accompanied by malnutrition, low fluid intake, metabolic and endocrine changes which accelerate the process. Even chronic conditions of the cardiovascular, pulmonary and endocrine system, which show an age-associated increase itself, contribute to the phenotype of muscle and bone loss and vice versa. Successful intervention on earth as well as in space focus on countermeasures and rehabilitation which we too can name primary and secondary prevention, and comprising improvement or restoration of organ dysfunction, optimizing nutrition, and participation in a training program to improve strength, endurance, flexibilty, postural control, and functional abilities. The progress in our understanding about (patho-)physiological processes as well as the development of different training devices grant the possibility today to delay deconditioning due to aging and microgravity.
The introduction will provide a link between biological changes in the human body which often is similar to that which occurs with aging, e.g. bone loss and sarcopenia, and countermeasures which are proved in head down bedrest studies as well as in clinical settings and nowadays spaceflight missions. As lot of research questions further exists, from the spaceflight field as from the aging research field, this session will be an opportunity to bring researcher from all fields together and provide the unique opportunity to develop new cooperations.
The musculoskeletal system is one of the most affected systems in spaceflight and bed rest. Reduced mechanical loading is the main reason for an early onset of significant muscle and bone losses. However, the hypocaloric nutrition in astronauts, which on average is 25% below their energy expenditure supports the muscle wasting during their mission. Thereby, the reduced muscle mass in spaceflight is mainly induced by a reduction in muscle protein synthesis rather than an increase in degradation.
Using biochemical markers of bone turnover, bone metabolism in astronauts show a similar pattern of changes in bone turnover markers as in aging: increase in bone resorption and decrease in –formation. These increases in osteoclast activity or reduced protein synthesis are very rapid changes and are observed after a couple of days in bed rest. Inadequate nutrient intake may exacerbate the effects of bone loss. High salt intake, as often seen in astronauts during their mission, increases bone resorption while bone formation is unchanged. This effect seems to be induced by changes in acid-base balance and/or higher glucocorticoid levels.
The often-recommended increase in protein intake to counteract muscle loss and to improve glucose tolerance in inactivity seems to be highly effective. Doubling protein intake to twice the recommended intake was able to keep insulin sensitivity during 60 days of bed rest. However, in practice rising protein intake in the Western World mostly leads to increases in animal protein intake. High animal protein content in general consists of a significant amount of sulfur- and phosphor containing amino acids. Metabolizing those reveal sulfuric and phosphoric acids, which concomitantly lead to subtle metabolic acidosis. Since an acidic environment is a pre-requisite to activate osteoclasts, inducing a subtle metabolic acidosis increases bone resorption. Improving the relation between animal protein intake and base precursors prevents the further loss in bone mass in ambulatory conditions but also bed rest. In summary, optimizing nutrient intake during lower mechanical loading such as in spaceflight may play a significant role in maintaining the musculoskeletal system.
Within a sedentary society, a lack of physical exercise is well known to provoke vascular, metabolic, and metastatic diseases. Regular physical exercise has been successfully proven to counteract this deconditioning. More recently, human and animal studies have demonstrated that regular physical activity also targets brain function by increasing cognitive abilities and therefore improving life-quality. Besides these functional, short-term changes, there is good reason to speculate that structural changes caused by exercise may prevent the genesis of neurodegeneration.
Just recently data of a one-year isolation study in a space like analogue, the CONCORDIA Antarctic station, showed a decline in mood and resting state brain cortical activity in a sedentary group, whereas a physically active group did not show any changes at all (ABELN, 2015, PLOS ONE). In a parallel study on the effects of exercise on the progression of Alzheimer disease in a group of 120 elderly participants, we could show (unpublished data), that a decline in cognitive performance (Montreal Cognitive Assessment Test, MOCA) showed a high correlation with the individuals’ general activity level.
Living in space is regarded as a time-lapse of the aging human being, as degenerative processes caused by weightlessness are extremely accelerated, which allows studying the underlying physiological mechanisms as well as defining adequate countermeasures. Whereas the positive impact of exercise in space on the cardiovascular and musculoskeletal system is well documented and its relevance has been shown for an aging population, recent research also shows a beneficial effect of exercise on brain cortical activity, cognitive function and mood improving mission success and safety. A transfer of these results into everyday life, especially an aging population, allows emphasizing the importance of regular physical activity for brain health and stressing its relevance for a healthy life-style.
Introduction: It is of common understanding that physical activity is an effective method to counteract the aging process. Especially the subdomain of physical activity –exercise- is playing an important role in rehabilitation. This common knowledge has led to numerous guidelines and recommendation over the last years also for the special group of older persons. Less is known about the dose-response relationship in specific groups of older person e.g. in frail older community-dwelling persons. The presentation will give an overview of possible musculoskeletal rehabilitation methods of exercise for frail older persons. The overview will be supported by the results of two different exercise interventions (PREFALL and FORMOSA) in this specific cohort.
Methods: In the PREFALL study physical limited older persons were recruited by their local general practitioners and cluster randomized to either the usual care group or the multi-component exercise group. In the FORMOSA study older sarcopenic obese females (70 years and above) were recruited by local news and information and randomized to either an Whole-Body Electromyostimulation exercise group (WB-EMS) or a WB-EMS group in combination with protein supplement or control group.
Results: In the PREFALLID intervention the participants of the multi-component group showed significant improvements in physical function after 12 months compared to the control group and maintained this elevated function after a 24 months retention phase. In the FORMOSA study the WB-EMS group showed significant improvements compared to the control group in variables of physical function.
Conclusion: Evidence is emerging that in older and frail persons exercise interventions can help restore or maintain physical function.
Age-related decreases in physiological performance can be thought of as arising from the combination of senescence, i.e. an irreversible time-linked biological process, from accumulated effects of damage and disease, and from the more sedentary lifestyle depicted by many older people. To disentangle these different trait in humans is not trivial and requires several combined approaches. Studying the fittest survivors can yield insights into the general limitations of human performance as a function of age. However, such studies are inapt to make inferences upon single individuals. To this end, we propose experimental immobilization studies.
Experimental bed rest studies have been performed since more than a century, and the ‘antiorthostatic hypokinesia’ model has become a standard ground-based model for the study of space-related physiological effects. As matter of fact, bed rest and spaceflight induce very similar degrees of muscle atrophy, of bone loss, of cardiovascular de-conditioning, of back pain and others. Alternative models of human immobilization include cast studies, lower leg suspension and the usage of exoskeletons. These localized models of immobilization induce local de-conditioning effects without the more general effects, which is both the strength and the weakness of such localized models. It should be noted here that all of these bed rest-induced changes are reversible after re-ambulation. This circumstance clearly demonstrates that senescence and de-conditioning differ from each other.
Experimental bed rest and other human immobliziation models do not only serve as models of spaceflight and ageing, they also offer the unique opportunity to study the effectiveness of countermeasures for spaceflight and against aging effects. Results in young humans have clearly demonstrated that resistive exercise, either with or without superimposed whole-body vibration can counteract muscle and bone atrophy. Combined resistive and endurance exercise can additionally safeguard cardiovascular function. These recognitions now need to be transferred to geriatric medicine.
In this session we will bring together researcher and physicians from different areas and „spaces“ which allow to view of similary interventions and countermeasures and discuss what we can learn from each other.