Reliability of a new test battery for fitness assessment of the European Astronaut corps

Abstract

Background: To optimise health for space missions, European astronauts follow specific conditioning programs before, during and after their flights. To evaluate the effectiveness of these programs, the European Space Agency conducts an Astronaut Fitness Assessment (AFA), but the test-retest reliability of elements within it remains unexamined. The reliability study described here presents a scientific basis for implementing the AFA, but also highlights challenges faced by operational teams supporting humans in such unique environments, especially with respect to health and fitness monitoring of crew members travelling not only into space, but also across the world. The AFA tests assessed parameters known to be affected by prolonged exposure to microgravity: aerobic capacity (VO2max), muscular strength (one repetition max, 1 RM) and power (vertical jumps), core stability, flexibility and balance. Intraclass correlation coefficients (ICC3.1), standard error of measurement and coefficient of variation were used to assess relative and absolute test-retest reliability.

Results: Squat and bench 1 RM (ICC3.1 = 0.94-0.99), hip flexion (ICC3.1 = 0.99) and left and right handgrip strength (ICC3.1 = 0.95 and 0.97), showed the highest test-retest reliability, followed by VO2max (ICC3.1 = 0.91), core strength (ICC3.1 = 0.78-0.89), hip extension (ICC3.1 = 0.63), the countermeasure (ICC3.1 = 0.76) and squat (ICC3.1 = 0.63) jumps, and single right- and left-leg jump height (ICC3.1 = 0.51 and 0.14). For balance, relative reliability ranged from ICC3.1 = 0.78 for path length (two legs, head tilted back, eyes open) to ICC3.1 = 0.04 for average rotation velocity (one leg, eyes closed).

Conclusions: In a small sample (n = 8) of young, healthy individuals, the AFA battery of tests demonstrated acceptable test-retest reliability for most parameters except some balance and single-leg jump tasks. These findings suggest that, for the application with astronauts, most AFA tests appear appropriate to be maintained in the test battery, but that some elements may be unreliable, and require either modification (duration, selection of task) or removal (single-leg jump, balance test on sphere) from the battery. The test battery is mobile and universally applicable for occupational and general fitness assessment by its comprehensive composition of tests covering many systems involved in whole body movement.

Keywords: Astronaut fitness assessment; Intraclass correlation coefficients (ICC); Reliability; Space flight; Test battery.

Fig. 1

Instrumented balance board used for balance tasks (L7–10).

Fig. 2

Treadmill protocol (modified Bruce protocol) used for the assessment of aerobic capacity [speed (km h⁻¹); stage time (min)].

Fig. 3

Mean (+SD) core strength test performance time (s) for the ventral, lateral and dorsal position on the three test days.

Fig. 4

Mean (+SD) measured (via spirometry) and estimated (from blood lactate samples and using the ERGONIZER^® software) aerobic capacity on the three test days.