Future exploration missions Reduced muscle mass, strength and performance in space

1 future exploration missions

1.1 lunar sortie missions
1.2 lunar outpost missions
1.3 mars transit
1.4 mars outpost

future exploration missions

it must stated @ outset risk(s) related loss of skeletal muscle mass, strength, , endurance depends not on level of loss on starting point , relative physiologic expense required complete requisite set of tasks within fixed period. thus, crewmember must capable of completing task before being exposed microgravity, amount of functional loss cannot allowed fall below level needed complete assigned tasks, , physical performance requirements completion of tasks should known. without information relating physical performance requirements of tasks, not possible determine risk of failure.

additionally, if task not completed crewmember before microgravity exposure, can reasonably stated risk of failure during mission 100%. however, if crewmember has capability complete every possible task, composite of tasks completed on finite period presents entirely different requirement because might possible select composite of tasks completed within work period exceeds capabilities of single crewmember or perhaps every crewmember. additionally, possible contingencies might arise must considered, crewmember able deal such off-nominal scenarios near end of duty day. thus, approach basic thoughtful scheduling of daily tasks serve mitigate risk.

from above discussion, several important items emerge must known respect risks related loss of skeletal muscle mass, strength, , endurance. these include:

baseline level of crewmember functional performance (strength, endurance, level of functional performance, etc.)
magnitude of functional loss baseline @ point during mission
physiological demand of task or set of tasks completed
the time period in tasks should performed
all possible contingency events affect functional performance
any other interfering conditions affect functional performance (such nutritional , psychological status, eva suit specifications, equipment malfunction or failure, illness, injury, etc.)

an indication of importance of individual baseline performance obtained illustrative example edomp program. losses in trunk flexor , extensor strength greater crewmembers exercised on shuttle treadmill during flight crewmembers did not exercise during mission (see figure 6-7). although @ first seems counterintuitive, simple logic provides explanation. crewmembers chose exercise during flight did because exercised regularly part of daily routine before flight. since @ higher level of fitness non-exercising crewmember cohorts, lost more strength during flight. however, cannot ascertained from % change data absolute strength levels. instance, exercising crewmembers lost twice abdominal , muscle strength non-exercising counterparts still have greater strength in muscles if started off 3 times stronger non-exercising colleagues.

lunar sortie missions

with respect future missions involving humans, lunar sortie missions represent lowest risk of planned missions , no greater in risk apollo missions (at least respect skeletal muscle performance) unless unusual surface operations planned differ markedly apollo lunar surface operations. longest cumulative time of lunar surface eva crew during apollo program 22 hours. (combined 3 separate days) , longest total duration of crew on lunar surface 75 hours during sixth , final apollo mission (apollo 17).

the answer question of whether exercise equipment should available crewmembers short missions moon , easy 1 , answer resounding “yes.” during of apollo missions, small, lightweight device called “exer-genie,” required no external power, made available crewmembers (see figure 6-1) , encouraged use it. specific comments apollo crewmembers collected during recent “apollo summit” particularly relevant , can summarized follows:

exercise not necessary on short trip , crews did not feel suffered noticeable deconditioning, did demand exercise capability available as possible rest , relaxation phases of mission. exercise device used crewmembers varying amounts , intensities. lunar surface crews (maximum time spent on surface operations [evas] 22 hours during 75-hour stay apollo 17) felt activities on lunar surface provided enough exercise short-duration mission have welcomed simple, robust device stretching , forearm exercise. (note: exer-genie remained on command module command module pilot; did not accompany 2 astronauts descended lunar surface in lunar excursion module.)
apollo crewmembers felt crew surgeons , mission planners should not hard-schedule exercise prescriptions such short-duration missions allow crew perform them @ leisure.
they stated more robust , lightweight piece of in-flight exercise equipment needed flown during apollo. exer-genie limited, ropes friable, , device generated lot of heat , smell, alternative exercise device needed.
most crewmembers felt pre-mission timeline should provide adequate time maintain musculoskeletal strength , stamina. astronauts attributed capabilities on lunar surface pre-mission training because in cases more force needed on lunar surface while wearing eva suit needed in 1g on earth.
the crew felt exer-genie or alternative needed, , because of fear break it, tapered off intense use save use in reconditioning on return trip before re-entry.
the strongest comment many exercise capabilities possible should built future vehicles because used , crew further felt exercise capability throughout flight critical , variety of exercises should provided.

lunar outpost missions

lunar outpost missions present greater challenge shorter “sortie” missions, respect current risk topic represent risks similar experienced on iss. lunar gravity, although 1/6 of earth gravity, still more conducive providing sufficient loading maintain muscle mass , function microgravity. exercise regimens , hardware required, not countering muscle atrophy reasons stated apollo astronauts above well. how exercise needed , proper way implement knowledge gaps require innovative research fill. part of research unquestionably define level of risks crews exposed helpful in mitigating risks.

mars transit

without doubt, transport between earth , mars return trip represent greatest risks humans encountered in history of human spaceflight. notwithstanding risks of radiation exposure, deterioration of musculoskeletal system must prevented or mission mars (and back) not successful. highly refined exercise protocols , robust exercise equipment , methods monitor functional capacity mandatory mitigation of risks inherent in long-duration exposure of humans microgravity. huge challenge provide above within current design of crew exploration vehicle (cev), provides trivial space equipment , crew. cramped confines afford little room stretching or exercise. modest or no power equipment , human life support system design may marginal support full complement of exercise efficiently dealing heat, water vapor, , carbon dioxide byproducts of human exercise additional challenges must overcome.

mars outpost

knowledge gained during lunar outpost missions highly relevant successful establishment of martian outpost. if challenges posed long transit mars , extended period of microgravity exposure can met, outpost phase should represent lower risk comparison, since lunar outpost experience have allowed significant opportunity develop risk-mitigation strategies phase. gravitational environments similar; in fact, martian gravity field, being greater of moon, provide less formidable setting. however, capability provide sufficient exercise capacity during martian outpost phase essential in preparing crew long-duration exposure microgravity on transit earth. represents greatest challenge respect maintaining safe level of skeletal muscle performance exploration-class missions.