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Medicine & Science in Sports & Exercise:
Basic Sciences: Symposium: Physiological Effects of Bed Rest and Restricted Physical Activity: an Update

An overview of the issues: physiological effects of bed rest and restricted physical activity

CONVERTINO, VICTOR A.; BLOOMFIELD, SUSAN A.; GREENLEAF, JOHN E.

Section Editor(s): Convertino, Victor A. Writing Group Chair

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Author Information

Physiology Research Branch, Clinical Sciences Division, Brooks Air Force Base, TX 78235; Department of Health and Kinesiology, Texas A & M University, College Station, TX 77843; and Laboratory for Human Environmental Physiology, Life Sciences Division, NASA, Ames Research Center, Moffett Field, CA 94035

Submitted for publication February 1995.

Accepted for publication December 1995.

Address for correspondence: Victor A. Convertino, Ph.D., Physiology Research Branch, Clinical Sciences Division, AL/AOCY, 2507 Kennedy Circle, Brooks Air Force Base, TX 78235-5117

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Abstract

Reduction of exercise capacity with confinement to bed rest is well recognized. Underlying physiological mechanisms include dramatic reductions in maximal stroke volume, cardiac output, and oxygen uptake. However, bed rest by itself does not appear to contribute to cardiac dysfunction. Increased muscle fatigue is associated with reduced muscle blood flow, red cell volume, capillarization, and oxidative enzymes. Loss of muscle mass and bone density may be reflected by reduced muscle strength and higher risk for injury to bones and joints. The resultant deconditioning caused by bed rest can be independent of the primary disease and physically debilitating in patients who attempt to reambulate to normal active living and working. A challenge to clinicians and health care specialists has been the identification of appropriate and effective methods to restore physical capacity of patients during or after restricted physical activity associated with prolonged bed rest. The examination of physiological responses to bed rest deconditioning and exercise training in healthy subjects has provided significant information to develop effective rehabilitation treatments. The successful application of acute exercise to enhance orthostatic stability, daily endurance exercise to maintain aerobic capacity, or specific resistance exercises to maintain musculoskeletal integrity rather than the use of surgical, pharmacological, and other medical treatments for clinical conditions has been enhanced by investigation and understanding of underlying mechanisms that distinguish physical deconditioning from the disease. This symposium presents an overview of cardiovascular and musculoskeletal deconditioning associated with reduced physical work capacity following prolonged bed rest and exercise training regimens that have proven successful in ameliorating or reversing these adverse effects.

Historically, the research emphasis in exercise physiology has been placed on the study of physiological mechanisms underlying limitations of physical work performance and adaptations associated with increasing work capacity through exposure to exercise training regimens. Indeed, if exercise is repeated by ambulatory subjects for weeks or months, the capacity to perform work is increased while general strain on body systems is diminished. For instance, when exercising at the same absolute work rate following endurance training, heart rate and blood lactate are lower while stroke volume, cardiac output, blood volume, and muscle blood flow are increased compared with the pretrained state. These responses to exercise after training are manifestations of increased physiological capacity to perform physical work. However, less attention has been given to the lower end of the activity continuum, i.e., to the deconditioning induced by chronically-reduced activity and its implications for rehabilitation in diseased patients. Since it is reasonable that alterations in physiological responses to exercise following deconditioning should be opposite of those observed during training, understanding mechanisms of exercise training in ambulatory subjects has contributed significantly to providing direction for investigation of the physiological adaptation associated with chronic exposure to bed rest with many practical applications for health maintenance and for athletic performance.

The adverse effect of prolonged bed rest deconditioning in humans, with its accompanying physical inactivity, was known to Hippocrates who reported loss of strength and exercise performance after prolonged bed rest and inactivity(7). Few well-designed bed rest studies were performed prior to World War II which stimulated interest in the possible adverse effect of inactivity and deconditioning in the treatment of hospitalized patients(21,35). Shortly after the war, Taylor et al.(46,47), Deitrick et al. (18), and Whedon et al. (48) conducted their now classic human bed rest studies concerning blood volume, work performance, and metabolic function. With the advent of manned space flight in the early 1960's, there was significant stimulation of research using prolonged bed rest where some physiological responses to microgravity acclimatization could be simulated(12,27,32,38,41). In the recumbent position, there is loss of most hydrostatic pressure in the vasculature below the heart, virtual elimination of longitudinal compression on the spine and long bones of the lower extremity, reduced muscular force on virtually all bones, and reduced total energy utilization (i.e., reduced exercise). Confinement to bed rest may also lead to socio-psychological changes if patients or subjects move into new isolated surroundings and associate with different people in a more psychologically stressful environment.

Confinement to bed is not an uncommon treatment for patients with chronic disease or injury. The resultant physiological adaptation includes diminution in work capacity(3,4,6,8-10,13-15,17-19,22,25,29,30,42,43,45,47) associated with impairment of cardiovascular(3,9,10,14-15,17,34,36,39,42-45,47), hematologic (10,11,26), musculoskeletal(1,2,5,10,23-25,33,37), metabolic (4,18,42,45), thermoregulatory(16,31), immune (28), neuroendocrine and psychological (19) functions. Health care professionals may perceive the diminution in physical work capacity in chronically ill patients as a result of their infirmity; thus exercise is not commonly used for patients as an integral part of their treatment. However, a reasonable explanation for the reduced work capacity in patients is absence of regular daily physical activity that can present the physiological challenge necessary to maintain the capacity for many normal life functions upon reambulation. This bed rest-induced debilitation is apparent when comparing functioning of the trained athlete, who performs moderate to high intensity work with little strain, with that of the individual who has been confined to bed and cannot sustain even a minimal work output. Maximal exercise testing provides a tool to quantify bed rest deconditioning by assessing maximal capacity of physiological mechanisms underlying the most inherent functional response of the body - human movement.

Measurement of physiological responses to exercise in healthy subjects allows for distinction of deconditioning induced by bed rest to be separated from effects induced by the infirmity. Assumption of the horizontal body position provides an opportunity to examine the impact of reduced hydrostatic pressure gradient within the cardiovascular system, unloading of force on the muscles and bones, and lower energy utilization on physiological reserve capacity. Although most nonclinical investigations have involved young, healthy subjects 18-25 yr old(6,8,15,26,31,33,39,43,45,47), bed rest experiments conducted over the past decade have included older subjects and longer durations of bed rest similar to those of patients recovering from long-term illness(5,13,14,17,25,34,36,37). It is apparent that bed rest deconditioning, independent of disease effects, contributes significantly to the reduced reserve capacity to perform physical work that may be largely obviated by regular physical activity during periods of relative immobility. For example, reduction in resting and exercise stroke volume and cardiac output during bed rest occurs without any apparent pathologic change in ventricular function (12,36). Likewise, loss of skeletal muscle mass and subsequent strength reduction occur during bed rest in healthy subjects with normal functional force-velocity relationships (12). The premise that bed rest deconditioning can be partly explained independent of disease underscores the importance of early intermittent ambulation and physical activity that might significantly limit many debilitating effects during hospital confinement.

In addition to the clinical application of findings from bed rest experiments, these results from deconditioining have implications for understanding mechanisms of adaptation to sedentary life styles. Although bed rest does not completely model sedentary living habits, many physiological changes that occur during bed rest are qualitatively similar to those observed during detraining (40,44). Thus, bed rest may be a helpful short-term research tool for examining deleterious effects of sedentary living on exercise performance and for developing and testing the effectiveness of exercise countermeasures. Such countermeasures have included the successful application during bed rest of acute exercise to enhance blood pressure regulation and orthostatic stability (20), daily endurance exercise to maintain aerobic capacity(11,12,25,39), specific resistance exericses to maintain the integrity of musculoskeletal structure and function(1,24,25,33), and post-bed rest exercise to enhance recovery (17,43).

The following reports provide a history and update of physiological consequences of prolonged bed rest confinement. Convertino presents an overview of cardiovascular function with special emphasis on maximal oxygen uptake and functional working capacity. Bloomfield discusses structural alteration in the musculoskeletal system during bed rest and its impact on body function. Finally, Greenleaf provides data from an extensive experiment with evidence that specific high-intensity exercise training interventions during bed rest can attenuate many adverse effects of deconditioning. Emphasis of these papers is placed on the time course and magnitude of physiological changes; the degree to which these physiological changes can be prevented, counteracted, or attenuated; specific interventions (countermeasures) applied in an experiment that proved effective for attenuating or reversing the changes; and the implications of superimposed chronic illness or injury.

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DECONDITIONING; EXERCISE TRAINING; CARDIOVASCULAR; MUSCLE; BONE; EXERCISE; DISUSE

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Knee extensor fatigability after bedrest for 8 weeks with and without countermeasure
Mulder, ER; Kuebler, WM; Gerrits, KHL; Rittweger, J; Felsenberg, D; Stegeman, DF; de Haan, A
Muscle & Nerve, 36(6): 798-806.
10.1002/mus.20870
CrossRef
Clinical Rehabilitation
Rehabilitation of decreased motor performance in patients with chronic fatigue syndrome: should we treat low effort capacity or reduced effort tolerance?
Van Houdenhove, B; Verheyen, L; Pardaens, K; Luyten, P; Van Wambeke, P
Clinical Rehabilitation, 21(): 1121-1142.
10.1177/0269215507080769
CrossRef
Archives of Physical Medicine and Rehabilitation
Physical activity in daily life in patients with chronic low back pain
Verbunt, JA; Westerterp, KR; van der Heijden, GJ; Seelen, HA; Vlaeyen, JW; Knottnerus, JA
Archives of Physical Medicine and Rehabilitation, 82(6): 726-730.

Spine
New technologies in spine - Kyphoplasty and vertebrosplasty for the treatment of painful osteoporotic compression fractures
Garfin, SR; Yuan, HA; Reiley, MA
Spine, 26(): 1511-1515.

Aviation Space and Environmental Medicine
Enhancing circulation to lower limbs during head-down tilt by warming upper body and thighs
Koscheyev, VS; Leon, GR; Coca, A; List, N
Aviation Space and Environmental Medicine, 75(7): 596-602.

Behavioural Brain Research
Exercise as a countermeasure to psycho-physiological deconditioning during long-term confinement
Schneider, S; Brummer, V; Carnahan, H; Kleinert, J; Piacentini, MF; Meeusen, R; Struder, HK
Behavioural Brain Research, 211(2): 208-214.
10.1016/j.bbr.2010.03.034
CrossRef
Clinical Rehabilitation
A randomized controlled trial of the effects of intensive sit-to-stand training after recent traumatic brain injury on sit-to-stand performance
Canning, CG; Shepherd, RB; Carr, JH; Alison, JA; Wade, L; White, A
Clinical Rehabilitation, 17(4): 355-362.
10.1191/0269215503cr620oa
CrossRef
Academic Emergency Medicine
Geriatric care in the emergency department
Fernandes, CMB
Academic Emergency Medicine, 12(2): 158-159.
10.1197/j.aem.2004.10.022
CrossRef
Journal of Heart and Lung Transplantation
Comorbidities in end-stage lung disease
Minai, OA; Maurer, JR; Kesten, S
Journal of Heart and Lung Transplantation, 18(9): 891-903.

Age and Ageing
Intensive physical training in geriatric patients after severe falls and hip surgery
Hauer, K; Specht, N; Schuler, M; Bartsch, P; Oster, P
Age and Ageing, 31(1): 49-57.

Journal of Applied Physiology
Effects of 18 days of bed rest on leg and arm venous properties
Bleeker, MWP; De Groot, PCE; Pawelczyk, JA; Hopman, MTE; Levine, BD
Journal of Applied Physiology, 96(3): 840-847.
10.1152/japplphysiol.00835.2003
CrossRef
Experimental Gerontology
Age-related differences in the adaptive potential of type I skeletal muscle fibers
Husom, AD; Ferrington, DA; Thompson, LV
Experimental Gerontology, 40(3): 227-235.
10.1016/j.exger.2004.12.002
CrossRef
Acta Radiologica
Extrapedicular approach of percutaneous vertebroplasty in the treatment of upper and mid-thoracic vertebral compression fracture
Han, KR; Kim, C; Eun, JS; Chung, YS
Acta Radiologica, 46(3): 280-287.
10.1080/02841850510021058
CrossRef
Clinical Orthopaedics and Related Research
Comparison of 5766 Vertebral Compression Fractures Treated With or Without Kyphoplasty
Zampini, JM; White, AP; McGuire, KJ
Clinical Orthopaedics and Related Research, 468(7): 1773-1780.
10.1007/s11999-010-1279-7
CrossRef
Western Journal of Nursing Research
Functional recovery and exercise behavior in men and women 5 to 6 years following coronary artery bypass graft (CABG) surgery
Treat-Jacobson, D; Lindquist, RA
Western Journal of Nursing Research, 26(5): 479-498.
10.1177/0193945904265400
CrossRef
Archives of Physical Medicine and Rehabilitation
Prehabilitation and rehabilitation for attenuating hindlimb unweighting effects on skeletal muscle and gait in adult and old rats
Brown, M; Taylor, J
Archives of Physical Medicine and Rehabilitation, 86(): 2261-2269.
10.1016/j.apmr.2005.06.020
CrossRef
Cochrane Database of Systematic Reviews
Advice to rest in bed versus advice to stay active for acute low-back pain and sciatica
Dahm, KT; Brurberg, KG; Jamtvedt, G; Hagen, KB
Cochrane Database of Systematic Reviews, (6): -.
ARTN CD007612
CrossRef
Scandinavian Journal of Medicine & Science in Sports
Effect of strength training on muscle function in elderly hospitalized patients
Suetta, C; Magnusson, SP; Beyer, N; Kjaer, M
Scandinavian Journal of Medicine & Science in Sports, 17(5): 464-472.
10.1111/j.1600-0838.2007.00712.x
CrossRef
American Journal of Critical Care
Rotational bed therapy to prevent and treat respiratory complications: A review and meta-analysis
Goldhill, DR; Imhoff, M; McLean, B; Waldmann, C
American Journal of Critical Care, 16(1): 50-61.

New England Journal of Medicine
Lack of effectiveness of bed rest for sciatica
Vroomen, PCAJ; de Krom, MCTFM; Wilmink, JT; Kester, ADM; Knottnerus, JA
New England Journal of Medicine, 340(6): 418-423.

Clinical Biomechanics
Techniques for measuring weight bearing during standing and walking
Hurkmans, HLP; Bussmann, JBJ; Benda, E; Verhaar, JAN; Stam, HJ
Clinical Biomechanics, 18(7): 576-589.
10.1016/S0268-0033(03)00116-5
CrossRef
Minerva Anestesiologica
Osteoporotic vertebral compression fracture pain (back pain): our experience with balloon kyphoplasty
Guglielmino, A; Sorbello, M; Barbagallo, G; Murabito, P; Naimo, J; Zingale, SF; Lo Giudice, E; Palumbo, A; Castiglione, A; Patti, F; Pero, G; Mangiameli, S
Minerva Anestesiologica, 73(): 77-100.

International Angiology
Why is training effective in the treatment of patients with intermittent claudication?
Remijnse-Tamerius, HCM; Duprez, D; De Buyzere, M; Oeseburg, B; Clement, DL
International Angiology, 18(2): 103-112.

Osteoporosis International
Factors related to variation in premenopausal bone mineral status: A health promotion approach
Tudor-Locke, C; McColl, RS
Osteoporosis International, 11(1): 1-24.

Science & Sports
Effects of physical activities on postural control in the elderly
Jeandel, C; Vuillemin, A
Science & Sports, 15(4): 187-193.

Journal of Applied Physiology
Exercise throughout 6 degrees head-down tilt bed rest preserves thermoregulatory responses
Shibasaki, M; Wilson, TE; Cui, J; Levine, BD; Crandall, CG
Journal of Applied Physiology, 95(5): 1817-1823.
10.1152/japplphysiol.00188.2003
CrossRef
Health Psychology
Cognitive and psychological outcomes of exercise in a 1-year follow-up study of patients with chronic obstructive pulmonary disease
Emery, CF; Shermer, RL; Hauck, ER; Hsiao, ET; MacIntyre, NR
Health Psychology, 22(6): 598-604.
10.1037/0278-6133.22.6.598
CrossRef
Pain
Disuse and physical deconditioning in the first year after the onset of back pain
Bousema, EJ; Verbunt, JA; Seelen, HAM; Vlaeyen, JWS; Knottnerus, JA
Pain, 130(3): 279-286.
10.1016/j.apin.2007.03.024
CrossRef
Physiotherapy
An observational study of sitting out of bed in tracheostomised patients in the intensive care unit
Bahadur, K; Jones, G; Ntoumenopoulos, G
Physiotherapy, 94(4): 300-305.
10.1016/j.physio.2008.08.003
CrossRef
Cerebrovascular Diseases
Very Early Mobilisation and Complications in the First 3 Months after Stroke: Further Results from Phase II of A Very Early Rehabilitation Trial (AVERT)
Sorbello, D; Dewey, HM; Churilov, L; Thrift, AG; Collier, JM; Donnan, G; Bernhardt, J
Cerebrovascular Diseases, 28(4): 378-383.
10.1159/000230712
CrossRef
Sports Medicine
Effects of exercise and training on blood rheology
El-Sayed, MS
Sports Medicine, 26(5): 281-292.

Journal of Neurocytology
Persistence of tight junctions and changes in apical structures and protein expression in choroid plexus epithelium of rats after short-term head-down tilt
Masseguin, C; Mani-Ponset, L; Carcenac, C; Herbute, S; Tixier-Vidal, A; Gabrion, J
Journal of Neurocytology, 30(5): 365-377.

Spine
Apical lordosating osteotomy and minimal segment fixation for the treatment of thoracic or thoracolumbar osteoporotic kyphosis
Chang, KW; Chen, YY; Lin, CC; Hsu, HL; Pai, KC
Spine, 30(): 1674-1681.

Anaesthesia
A prospective observational study of ICU patient position and frequency of turning
Goldhill, DR; Badacsonyi, A; Goldhill, AA; Waldmann, C
Anaesthesia, 63(5): 509-515.
10.1111/j.1365-2044.2007.05431.x
CrossRef
Clinical Orthopaedics and Related Research
Oxidative stress after muscle damage from immobilization and remobilization occurs locally and systemically
Liu, MJ; Li, JX; Lee, KM; Qin, L; Chan, KM
Clinical Orthopaedics and Related Research, (): 246-250.
10.1097/01.blo.0000150464.29883.ca
CrossRef
Rheumatology
Arthritis patients show long-term benefits from 3 weeks intensive exercise training directly following hospital discharge
Bulthuis, Y; Drossaers-Bakker, KW; Taal, E; Rasker, J; Oostveen, J; van't Pad Bosch, P; Oosterveld, F; van de Laar, M
Rheumatology, 46(): 1712-1717.
10.1093/rheumatology/kem236
CrossRef
Diabetes
Physical Inactivity Differentially Alters Dietary Oleate and Palmitate Trafficking
Bergouignan, A; Trudel, G; Simon, C; Chopard, A; Schoeller, DA; Momken, I; Votruba, SB; Desage, M; Burdge, GC; Gauquelin-Koch, G; Normand, S; Blanc, S
Diabetes, 58(2): 367-376.
10.2337/db08-0263
CrossRef
Spine
The cochrane review of bed rest for acute low back pain and sciatica
Hagen, KB; Hilde, G; Jamtvedt, G; Winnem, MF
Spine, 25(): 2932-2939.

Journal of Thermal Biology
Effects of simulated natural air movement on thermoregulatory response during head-down bed rest
Yang, ZZ; Fei, JX; Song, D; Zhao, YL; Yu, J; Yu, XJ
Journal of Thermal Biology, 38(7): 363-368.
10.1016/j.jtherbio.2013.04.006
CrossRef
AJN The American Journal of Nursing
Functional Decline in Hospitalized Older Adults: It’s often a consequence of hospitalization, but it doesn’t have to be
Graf, C
AJN The American Journal of Nursing, 106(1): 58-67.

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American Journal of Physical Medicine & Rehabilitation
Rehabilitation for Hospital-Associated Deconditioning
Kortebein, P
American Journal of Physical Medicine & Rehabilitation, 88(1): 66-77.
10.1097/PHM.0b013e3181838f70
PDF (427) | CrossRef
Critical Care Medicine
One small step for man …*
Milbrandt, EB
Critical Care Medicine, 35(1): 311-312.
10.1097/01.CCM.0000251296.05317.49
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Critical Care Medicine
Physical therapy utilization in intensive care units: Results from a national survey
Hodgin, KE; Nordon-Craft, A; McFann, KK; Mealer, ML; Moss, M
Critical Care Medicine, 37(2): 561-568.
10.1097/CCM.0b013e3181957449
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Critical Care Medicine
Patients with respiratory failure increase ambulation after transfer to an intensive care unit where early activity is a priority
Thomsen, GE; Snow, GL; Rodriguez, L; Hopkins, RO
Critical Care Medicine, 36(4): 1119-1124.
10.1097/CCM.0b013e318168f986
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Obstetrics & Gynecology
Building the Evidence Base for Postoperative and Postpartum Advice
Minig, L; Trimble, EL; Sarsotti, C; Sebastiani, MM; Spong, CY
Obstetrics & Gynecology, 114(4): 892-900.
10.1097/AOG.0b013e3181b6f50d
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Journal of Nursing Care Quality
An Interdisciplinary Approach to Addressing Patient Activity and Mobility in the Medical-Surgical Patient
Markey, DW; Brown, RJ
Journal of Nursing Care Quality, 16(4): 1-12.

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Journal of Orthopaedic Trauma
Kyphoplasty: Report of Eighty-Two Thoracolumbar Osteoporotic Vertebral Fractures
Rhyne, A; Banit, D; Laxer, E; Odum, S; Nussman, D
Journal of Orthopaedic Trauma, 18(5): 294-299.

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Menopause
The effect of ovariectomy combined with hindlimb unloading and reloading on the long bones of mature Sprague-Dawley rats
Tou, JC; Foley, A; Yuan, YV; Arnaud, S; Wade, CE; Brown, M
Menopause, 15(3): 494-502.
10.1097/gme.0b013e318148bbad
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