Table 1. Search strategy.
| Main category | Specific category | Keywords in Boolean search format | Search number | Search mask | |
|---|---|---|---|---|---|
| Microgravity | Synonyms | "space analogue" OR "ground-based analogue" OR "terrestrial analogue" OR "space flight" OR space-flight OR spaceflight OR "Space mission" OR "space station" OR “micro gravity” OR micro-gravity OR microgravity OR spaceflight OR weightless* OR "orbital flight" OR "zero gravity" OR "space shuttle" | 1 | Abstract/ Title | |
| Methods & simulations | "bed rest" OR bed rest OR "dry immersion" OR dry-immersion | 2 | Abstract/ Title | ||
| #1 AND #2 | 3 | ||||
| Population of interest | Astronaut* OR astronaut [Mesh] OR cosmonaut* OR taikonaut* | 4 | Abstract/ Title | ||
| #1 OR #3 OR #4 | 5 | ||||
| Countermeasures | Active countermeasures | Countermeasure* OR exercis* OR exercise [Mesh] OR sport* OR "physical activity" OR "physically active" | 6 | All Fields | |
| Passive countermeasures | Centrifug* OR suit* OR "lower body negative pressure" OR LBNP or "fluid loading" OR garment OR stimulation OR "artificial gravity" OR "axial loading" OR electromyostimulation OR "electrical muscle stimulation" OR EMS OR "neuromuscular electrical stimulation" OR NMES OR "whole body vibration" OR WBV | 7 | All Fields | ||
| Nutritional countermeasures | Diet, food, and nutrition [Mesh] OR nutrition* OR diet* OR food* OR supplement* OR protein* OR salt OR saline OR bi-phosphonate OR phosphonate OR nucleotide* OR vitamin* | 8 | All Fields | ||
| #6 OR #7 OR #8 | 9 | ||||
| Operationally relevant outcome parameters | Cardiopulmonary & -vascular | Physical performance | "endurance" OR Vo2 OR Vo2max OR Vo2peak OR "maximal oxygen uptake" OR "peak oxygen uptake" OR "resting heart rate" OR "peak power" OR "maximal work load" OR "orthostatic tolerance" OR "orthostatic intolerance" OR "time until presyncope" OR "exercise tolerance" OR "central fatigue" OR "threshold" OR "onset of blood lactate accumulation" OR "OBLA" | 10 | All Fields |
| Musculoskeletal / Biomechanical | Physical performance | "muscle strength" OR "muscular strength" OR "muscle function" OR "muscular function" OR "muscle power" OR "muscular power" OR "muscle force" OR "muscular force" OR fatigability OR "fatigue resistance" OR "peripheral fatigue" OR "joint moment" OR "joint moments" OR "postural stability" OR posture OR "postural control" OR balance OR sway OR motion OR locomotion OR gait OR walk* OR run* OR jump* OR hop* OR "movement quality" OR "movement pattern" OR "motion pattern" OR coordination OR "motor control" OR "core stability" OR "core strength" OR "trunk stability" OR "trunk strength" OR "lumbopelvic stability" OR "lumbo-pelvic stability" OR "lumbopelvic control" OR "lumbo-pelvic control" | 11 | All Fields | |
| Anthropo-metrics | Anthropometr* OR "skeletal strength" OR "bone mineral density" OR "bone density" OR "bone mineral content" OR flexib* OR "range of movement" OR "range of motion" | 12 | All Fields | ||
| #10 OR #11 OR #12 | 13 | ||||
| #5 AND #9 AND #13 | 14 | ||||
| Apply human filter | |||||
Keywords were divided into main and specific categories for better survey. They were combined using the Boolean operators OR and AND. In order to not mistakenly exclude relevant studies, the Boolean operator NOT was excluded. Medical Subject Headings [Mesh] as a controlled vocabulary thesaurus for indexing and cataloging biomedical literature was applied.