Effect of 14 Day Bed Rest on Health Outcomes in Young and Older Participants (BEDREST)

University of Trieste, University of Udine, University of Padova, Università degli Studi di Ferrara, University of Nottingham, DLR German Aerospace Center, Izola General Hospital, National Institute of Public Health, Slovenia

This investigation aimed to compare the response of older adult and young men to 14 day bed-rest and subsequent 28 day rehabilitation. Sixteen older (OM: 55-65 years) and seven young men (YM: 18-30 years) were exposed to 14-day bed rest (BR) followed by 14-day rehabilitation (R), and 400-day of R. Quadriceps muscle volume, force and explosive power of leg extensors, single fiber isometric force, peak aerobic power, gait stride length, and several metabolic were measured before and after BR and after R.

Twenty-three healthy men, of which 7 young (YM; aged 18-30 years) and 16 older adults (OM; aged 55-65 years) were recruited for the study. All participants underwent medical examination and routine blood and urine analysis. Exclusion criteria were: smoking; regular alcohol consumption; ferromagnetic implants; history of deep vein thrombosis with D-dimer > 500 μg·L-1; acute or chronic skeletal, neuromuscular, metabolic and cardiovascular disease conditions; pulmonary embolism. Participants were informed of the purpose, procedures and potential risk of the study before signing the informed consent. The study was performed in accordance with the ethical standards of the 1964 Declaration of Helsinki and was approved by the National Ethical Committee of the Slovenian Ministry of Health on April 17, 2012. The study was conducted in controlled medical environment of the Orthopedic Hospital of Valdoltra, Slovenia. The participants were housed in standard air conditioned hospital rooms and were under constant surveillance with 24-hour medical care. For 14 days, the participants performed all daily activities in bed and received eucaloric controlled meals three times a day. Dietary energy requirements were designed for each subject multiplying resting energy expenditure by factors 1.2 and 1.4 in BR and ambulatory period, respectively. The resting energy expenditure was calculated as done in previous studies. The macronutrient food content set at 60% of carbohydrates, 25% fat, and 15% of proteins, according to the scheme of the so called "mediterranean diet" and adopted also in previous bed rest protocols. Energy balance was checked weekly by fat mass assessment. The daily protein intake was 1.1-1.25 g kg-1 in both groups, in BR and recovery period respectively, except the subgroups of OM who received a supplementation (see below). After the BR, participants underwent a rehabilitation protocol (R) that consisted of 4-week supervised multimodal exercise program with 3 sessions per week. In each session, participants performed 12-minute warm-up, 15-20 minutes of balance and strength training, and 20-30 minutes of endurance training.

16 old participants (55-65 years) were included in physical inactivity or bed rest with supervised recovery intervent and underwent 14-day of bed rest. Bed rest was followed by 28-day recovery. During the bed rest participants will remain 24-hour horizontal with all daily activities performed lying in a bed. No social isolation will be forced. During the recovery participants will 3-times weekly per 75 minutes perform guided exercises to achieve baseline level.

7 young participants (18-30 years) were included in physical inactivity or bed rest with supervised recovery intervent and underwent 14-day of bed rest. Bed rest was followed by 28-day recovery. During the bed rest participants will remain 24-hour horizontal with all daily activities performed lying in a bed. No social isolation will be forced. During the recovery participants will 3-times weekly per 75 minutes perform guided exercises to achieve baseline level.

All (older and younger) participants underwent 14 day of horizontal bed rest with all 24 hour daily activities were performed lying in a bed. Maximal one pillow was allowed. 28-day supervised recovery was performed 3 times weekly for 75 minutes/session.

Change in area-under-the curve (AUC) of triglycerides plasma concentration (young vs. old) after 14-day bed rest

Inclusion Criteria: Body mass index < 28 kg/m2 Short physical performance battery score >= 9 Exclusion Criteria: smoking; regular alcohol consumption; ferromagnetic implants; history of deep vein thrombosis with D-dimer > 500 μg·L-1; acute or chronic skeletal, neuromuscular, metabolic and cardiovascular disease conditions.

Pisot R, Marusic U, Biolo G, Mazzucco S, Lazzer S, Grassi B, Reggiani C, Toniolo L, di Prampero PE, Passaro A, Narici M, Mohammed S, Rittweger J, Gasparini M, Gabrijelcic Blenkus M, Simunic B. Greater loss in muscle mass and function but smaller metabolic alterations in older compared with younger men following 2 wk of bed rest and recovery. J Appl Physiol (1985). 2016 Apr 15;120(8):922-9. doi: 10.1152/japplphysiol.00858.2015. Epub 2016 Jan 28.

Jurdana M, Jenko-Praznikar Z, Mohorko N, Petelin A, Jakus T, Simunic B, Pisot R. Impact of 14-day bed rest on serum adipokines and low-grade inflammation in younger and older adults. Age (Dordr). 2015 Dec;37(6):116. doi: 10.1007/s11357-015-9848-z. Epub 2015 Nov 13.

Marusic U, Kavcic V, Giordani B, Gerzevic M, Meeusen R, Pisot R. Computerized spatial navigation training during 14 days of bed rest in healthy older adult men: Effect on gait performance. Psychol Aging. 2015 Jun;30(2):334-340. doi: 10.1037/pag0000021. Epub 2015 May 4.

Goswami N, Kavcic V, Marusic U, Simunic B, Rossler A, Hinghofer-Szalkay H, Pisot R. Effect of computerized cognitive training with virtual spatial navigation task during bed rest immobilization and recovery on vascular function: a pilot study. Clin Interv Aging. 2015 Feb 10;10:453-9. doi: 10.2147/CIA.S76028. eCollection 2015.