In the original article, there was an error. The International Space Station Expedition was incorrectly referred to as "the Skylab Expedition 18."
A correction has been made to the In-Flight Protocols section ...

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Corrigendum: Application of Blood Flow Restriction to Optimize Exercise Countermeasures for Human Space Flight.

Space sojourns are challenging for life. The ability of the human body to adapt to these extreme conditions has been noted since the beginning of human space travel. Skeletal alterations that occur during spaceflight are now better understood owing to tools such as dual-energy X-ray densitometry and high-resolution peripheral quantitative CT, and murine models help researchers to understand cellular and matrix changes that occur in bone and that are difficult to measure in humans. However, questions remain with regard to bone adaptation and osteocyte fate, as well as to interactions of the skeleton with fluid shifts towards the head and with the vascular system. Further investigations into the relationships between the musculoskeletal system, energy metabolism and sensory motor acclimatisation are needed. In this regard, an integrated intervention is required that will address multiple systems simultaneously. Importantly, radiation and isolation-related stresses are gaining increased attention as the prospect of human exploration into deep space draws nearer. Although space is a unique environment, clear parallels exist between the effects of spaceflight, periods of immobilization and ageing, with possibly irreversible features. Space travel offers an opportunity to establish integrated deconditioning and ageing interventions that combine nutritional, physical and pharmaceutical strategies.

Skeletal changes during and after spaceflight.

To counteract microgravity (µG)-induced adaptation, European Space Agency (ESA) astronauts on long-duration missions (LDMs) to the International Space Station (ISS) perform a daily physical exercise countermeasure program. Since the first ESA crewmember completed an LDM in 2006, the ESA countermeasure program has strived to provide efficient protection against decreases in body mass, muscle strength, bone mass, and aerobic capacity within the operational constraints of the ISS environment and the changing availability of on-board exercise devices. The purpose of this paper is to provide a description of ESA’s individualised approach to in-flight exercise countermeasures and an up-to-date picture of how exercise is used to counteract physiological changes resulting from µG-induced adaptation. Changes in the absolute workload for resistive exercise, treadmill running and cycle ergometry throughout ESA’s eight LDMs are also presented, and aspects of pre-flight physical preparation and post-flight reconditioning outlined. With the introduction of the advanced resistive exercise device (ARED) in 2009, the relative contribution of resistance exercise to total in-flight exercise increased (33–46 %), whilst treadmill running (42–33 %) and cycle ergometry (26–20 %) decreased. All eight ESA crewmembers increased their in-flight absolute workload during their LDMs for resistance exercise and treadmill running (running speed and vertical loading through the harness), while cycle ergometer workload was unchanged across missions. Increased or unchanged absolute exercise workloads in-flight would appear contradictory to typical post-flight reductions in muscle mass and strength, and cardiovascular capacity following LDMs. However, increased absolute in-flight workloads are not directly linked to changes in exercise capacity as they likely also reflect the planned, conservative loading early in the mission to allow adaption to µG exercise, including personal comfort issues with novel exercise hardware (e.g. the treadmill harness). Inconsistency in hardware and individualised support concepts across time limit the comparability of results from different crewmembers, and questions regarding the difference between cycling and running in µG versus identical exercise here on Earth, and other factors that might influence in-flight exercise performance, still require further investigation.

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Exercise in space: the European Space Agency approach to in-flight exercise countermeasures for long-duration missions on ISS

INTRODUCTION Exposure to microgravity causes alterations in multiple physiological systems, potentially impacting the ability of astronauts to perform critical mission tasks. The goal of this study was to determine the effects of spaceflight on functional task performance and to identify the key physiological factors contributing to their deficits. METHODS A test battery comprised of seven functional tests and 15 physiological measures was used to investigate the sensorimotor, cardiovascular, and neuromuscular adaptations to spaceflight. Astronauts were tested before and after 6-month spaceflights. Subjects were also tested before and after 70 d of 6° head-down bed rest, a spaceflight analog, to examine the role of axial body unloading on the spaceflight results. These subjects included control and exercise groups to examine the effects of exercise during bed rest. RESULTS Spaceflight subjects showed the greatest decrement in performance during functional tasks that required the greatest demand for dynamic control of postural equilibrium which was paralleled by similar decrements in sensorimotor tests that assessed postural and dynamic gait control. Other changes included reduced lower limb muscle performance and increased HR to maintain blood pressure. Exercise performed during bed rest prevented detrimental change in neuromuscular and cardiovascular function; however, both bed rest groups experienced functional and balance deficits similar to spaceflight subjects. CONCLUSION Bed rest data indicate that body support unloading experienced during spaceflight contributes to postflight postural control dysfunction. Further, the bed rest results in the exercise group of subjects confirm that resistance and aerobic exercises performed during spaceflight can play an integral role in maintaining neuromuscular and cardiovascular functions, which can help in reducing decrements in functional performance. These results indicate that a countermeasure to mitigate postflight postural control dysfunction is required to maintain functional performance.

Physiological and Functional Alterations after Spaceflight and Bed Rest.

STUDY DESIGN Prospective case series OBJECTIVE Evaluate lumbar paraspinal muscle (PSM) cross-sectional area and intervertebral disc (IVD) height changes induced by a 6-month space mission on the International Space Station The long-term objective of this project is to promote spine health and prevent spinal injury during space missions and here on Earth SUMMARY OF BACKGROUND DATA National Aeronautics and Space Administration (NASA) crewmembers have a 43 times higher risk of herniated IVDs, compared with the general and military aviator populations The highest risk occurs during the first year after a mission Microgravity exposure during long-duration spaceflights results in approximately 5 cm lengthening of body height, spinal pain, and skeletal deconditioning How the PSMs and IVDs respond during spaceflight is not well described METHODS Six NASA crewmembers were imaged supine with a 3 Tesla magnetic resonance imaging Imaging was conducted preflight, immediately postflight, and then 33 to 67 days after landing Functional cross-sectional area (FCSA) measurements of the PSMs were performed at the L3-4 level FCSA was measured by grayscale thresholding within the posterior lumbar extensors to isolate lean muscle on T2-weighted scans IVD heights were measured at the anterior, middle, and posterior sections of all lumbar levels Repeated measures analysis of variance was used to determine significance at P < 005, followed by post-hoc testing RESULTS Paraspinal lean muscle mass, as indicated by the FCSA, decreased from 86% of the total PSM cross-sectional area down to 72%, immediately after the mission Recovery of 68% of the postflight loss occurred during the next 6 weeks, still leaving a significantly lower lean muscle fractional content compared with preflight values In contrast, lumbar IVD heights were not appreciably different at any time point CONCLUSION The data reveal lumbar spine PSM atrophy after long-duration spaceflight Some FCSA recovery was seen with 46 days postflight in a terrestrial environment, but it remained incomplete compared with preflight levels LEVEL OF EVIDENCE 4

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Lumbar Spine Paraspinal Muscle and Intervertebral Disc Height Changes in Astronauts After Long-duration Spaceflight on the International Space Station

INTRODUCTION Physical training has been conducted on the International Space Station (ISS) for the past 10 yr as a countermeasure to physiological deconditioning during spaceflight. Each member space agency has developed its own approach to creating and implementing physical training protocols for their astronauts. We have divided physical training into three distinct phases (preflight, in-flight, and postflight) and provided a description of each phase with its constraints and limitations. We also discuss how each member agency (NASA, ESA, CSA, and JAXA) prescribed physical training for their crewmembers during the first 10 yr of ISS operations. It is important to understand the operational environment, the agency responsible for the physical training program, and the constraints and limitations associated with spaceflight to accurately design and implement exercise training or interpret the exercise data collected on ISS. As exploration missions move forward, resolving agency differences in physical training programs will become important to maximizing the effectiveness of exercise as a countermeasure and minimizing any mission impacts.

Physical Training for Long-Duration Spaceflight.

BACKGROUND Postflight reconditioning of astronauts is understudied. Despite a rigorous, daily inflight exercise countermeasures programme during six months in microgravity (μG) on-board the International Space Station (ISS), physiological impairments occur and postflight reconditioning is still required on return to Earth. Such postflight programmes are implemented by space agency reconditioning specialists. Case Description and Assessments: A 38 year old male European Space Agency (ESA) crewmember's pre- and postflight (at six and 21 days after landing) physical performance from a six-month mission to ISS are described. ASSESSMENTS muscle strength (squat and bench press 1 Repetition Maximum) and power (vertical jump), core muscle endurance and hip flexibility (Sit and Reach, Thomas Test). INTERVENTIONS In-flight, the astronaut undertook a rigorous daily (2-h) exercise programme. The 21 day postflight reconditioning exercise concept focused on motor control and functional training, and was delivered in close co-ordination by the ESA physiotherapist and exercise specialist to provide the crewmember with comprehensive reconditioning support. OUTCOMES Despite an intensive inflight exercise programme for this highly motivated crewmember, postflight performance showed impairments at R+6 for most parameters, all of which recovered by R+21 except muscular power (jump tests). CONCLUSIONS Regardless of intense inflight exercise countermeasures and excellent compliance to postflight reconditioning, postflight performance showed impairments at R+6 for most parameters. Complex powerful performance tasks took longer to return to preflight values. Research is needed to develop optimal inflight and postflight exercise programmes to overcome the negative effects of microgravity and return the astronaut to preflight status as rapidly as possible.

Natalie Hirsch

Papers

Physical Training for Long-Duration Spaceflight.

Postflight reconditioning for European Astronauts - A case report of recovery after six months in space.