PMC

Illustration of possible implementations of Exercise Holidays and possible recovery programme modalities for future head-down-tilt bed rest campaigns. (A) No Exercise: The generic ‘no exercise’ control group wherein participants do not perform any exercise countermeasures through the duration of the bed rest campaign (B) Exercise First: Participants start the bed rest campaign with an exercise countermeasure programme, followed by a period of no exercise until the end of the campaign (C) Exercise—Rest—Exercise: Participants start and end the bed rest campaign with a period of exercise countermeasures, separated by a period of exercise holidays (D) Rest—Exercise—Rest: Participants start and end the bed rest campaign without any exercise (i.e., exercise holiday), separated by a period of exercise countermeasures (E) Rest First: Participants start the bed rest campaign with an exercise holiday, followed by a period of performing exercise countermeasures until the end of the campaign. All of the different iterations of bed rest campaigns described above can be combined with different recovery programme modalities during post-bed rest period: Uncontrolled recovery programme: participants are not subjected to a controlled recovery programme. - Controlled but generic recovery programme: all participants complete the same recovery programme, not adapted to the personal needs of the participant. - Controlled and individualized recovery programme: all participants complete an individualize rehabilitation programme, adapted to the personal needs of the participant. Doing so may provide crucial information on the time and resources needed for an optimal recovery to take place.

Representative Western Blot Images
A, Western blot images are EAA-induced mTORC1 nutrient signalling markers in Young (Y) and Older (O) adults skeletal muscle before bed rest (PRE), after 5 days bed rest (BED REST) and after 8 weeks of exercise rehabilitation (REHAB). Images (in replicate) are representative of fasted (basal) and 1 and 3 h EAA skeletal muscle responses following each intervention. B,representative western blot images (in replicate) for AMPKα and select proteolytic markers in Young (Y) and Older (O) adult skeletal muscle in the fasted state before (PRE), after bed rest (BED REST) and after exercise rehabilitation (REHAB).

CTR, control group, i.e., bed rest only HDBR only (n = 5). RE, bed rest combined with resistance exercise (n = 5). RVE, bed rest combined with resistive exercise superimposed with whole-body vibrations (n = 6). Data are presented as estimated means and standard errors. Individual data are shown as dots. Positive numbers are defined as phase delays and negative numbers as phase advances. Effect sizes are Hedge’s g with 95% confidence intervals.

Representative transcranial Doppler data for each condition before (BDC-3) and after (R + 1) head-down bed rest. CON, control condition; NeX, resistance vibration exercise with nutritional supplementation condition; RVE, resistance vibration exercise condition.