Fitness And In-Flight Exercise Training Parameters Predictive Of Functional Task Performance In Astronauts Following Long-Duration Spaceflight

Purpose: The Artemis era of spaceflight aims for surface exploration under more physically-demanding conditions than in previous missions. Understanding fitness, exercise, and functional performance is imperative to prepare astronauts to successfully accomplish mission objectives following microgravity exposure. Methods: A retrospective analysis of 31 astronauts (11F; pre-flight age 47.5±6.2 yrs, pre-flight body mass 78.1±11.6 kg) was completed using NASA flight studies (Functional Task Test, Field Test, Standard Measures) and astronaut medical testing data. Astronauts were tested before and after ∼6 months of spaceflight to capture cardiorespiratory fitness, muscular strength, and sensorimotor functional task performance. In-flight exercise for cycle ergometry (CEVIS), treadmill (T2), and resistive (ARED) exercise was analyzed. Linear mixed models and regressions determined longitudinal changes and relationships between exercise, fitness, and functional outcomes. Results: Peak aerobic capacity (VO _2pk ; -8 to -10%; p<0.001), lower limb isokinetic strength (-12 to -16%; p<0.05), and object translation (-11%; p=0.001) were reduced ∼1-week post-flight. CEVIS and T2 exercise volume loads were associated with aerobic fitness (r= 0.63-0.75; p<0.01). ARED lower body load was associated with lower body strength (r=0.59-0.70; p<0.05). CEVIS workload (normalized watts) predicted aerobic fitness outcomes (p< 0.05) and functional task performance (jump settling time; p=0.007), explaining 8.6-32.7% of variability in outcomes. VO _2pk predicted jump settling time (p=0.013), accounting for 16% of variability. Pre-flight lower body strength accounted for 20-40% of variability in select performance outcomes (p<0.05). Conclusions: Results from this investigation indicate that performance on functional tasks related to ambulation and balance control are influenced by fitness status and in-flight exercise.