REF-1134 · Spiering, Weakley & Mujika, 2023 · Sports Medicine · Paper · PubMed · Free full text

I spent a week in bed — how long before I'm back to normal?

Plan at least 2-4 weeks of progressive rebuilding with strength work in it — the authors' advice after up to 28 days in bed, possibly longer after illness or injury. No study has measured real athletes; in exercise-trained men upright endurance fell within 3 days (VO2max −16.5% in 3 days on an upright test; −3.9% in 7 days on supine tests in another laboratory). A week in bed is not a week off.

Blimited evidenceMeasured on non-to trained athletes

Spiering, Weakley and Mujika set out to describe what bed rest does to athletes, which countermeasures work and how long recovery takes. Their pre-registered search of four databases (October 2022) for horizontal bed rest of at least 72 h in Tier 3-5 athletes aged 18-50 found zero studies.

They then discussed seven studies of apparently healthy, previously exercise-trained (Tier 2) men, and data from sedentary or recreational people where nothing better existed.

Upright endurance performance, VO2max and lactate threshold fell after just 3 days, and the endurance-trained lost more than the strength-trained; VO2max fell fastest in the first 1-2 weeks; the loss was larger on upright than on supine tests. None of the seven measured strength; in Tier 0-1 people strength falls within 5 days.

Fluid and salt loading preserved supine VO2max and plasma volume in one laboratory's studies. None of the seven measured recovery; from Tier 0-1 data the authors recommend at least 2-4 weeks of progressive rehabilitation, including strength training, after bed rest of up to 28 days, longer when illness or injury is the reason.

Their primary conclusion is that the question is unanswered for real athletes.

Included studies

Systematic search: SPORTDiscus, Web of Science, Scopus, MEDLINE/PubMed, October 2022; protocol registered on the Open Science Framework (osf.io/d3aew). Criteria: healthy adults 18-50, strict horizontal bed rest (no head-down tilt), at least 72 h, objective performance or physiological outcomes, participants Tier 3-5. 501 records, 190 duplicates, 381 screened, 97 full texts, 0 included.

Narrative evidence: seven studies in Tier 2 men (reporting quality at least 6 of 9 on a modified Downs and Black checklist): Smorawiński (endurance-trained n = 10, strength-trained n = 10, 3 days, upright tests), Zorbas and colleagues (endurance-trained, 7, 15 and 30 days, supine tests, results averaged across their homogeneous studies, n = 30-40), Balsam and Leppo (n = 7, 17 days), Sketch (recreational team sport, n = 8, 18 days, upright).

Tier 0-1 evidence used sparingly for strength (Marusic), countermeasures and recovery (Lee and others).

Key Results

Study (Table 1)	Participants	Bed rest	Outcome (% change in the group mean)
Smorawiński	Tier 2 endurance-trained men, n = 10	3 days, upright test	max incremental load −14.3%, VO2max −16.5%, lactate threshold −24.8% (both larger than in strength-trained)
Smorawiński	Tier 2 strength-trained men, n = 10	3 days, upright test	max incremental load −10.0% and VO2max −10.4% (both significant), lactate threshold −10.1% (not significant)
Zorbas	Tier 2 endurance-trained men, n = 40	7 days, supine test	VO2max ~−3.9%, plasma volume ~−12.3%, fat-free mass ~−1.1% (inconsistent)
Zorbas	n = 30	15 days, supine	VO2max ~−4.7%, plasma volume ~−9.0%, fat-free mass ~−1.9% (inconsistent)
Balsam and Leppo	Tier 2 endurance-trained men, n = 7	17 days, position not reported	VO2max −19.5%
Sketch	Tier 2 recreational team-sport men, n = 8	18 days, upright	max incremental duration −8.1%, VO2max −9.2%
Zorbas	n = 30	30 days, supine	VO2max ~−8.4%, plasma volume ~−18.2%, fat-free mass ~−2.4% (not significant)

Recovery (Tier 0-1 evidence and one older study cited in the introduction)

After 21 days of bed rest, sedentary subjects needed about 7-10 days to regain their aerobic performance, previously exercise-trained subjects about 4-5 weeks (introduction, the authors' reference 7).

Lee's review (Tier 0-1): about 2 weeks of bed rest needs about 1 week of recovery; longer bed rest may need 2-4 weeks; fitter people need longer.

After 28 days of bed rest, 14 days of re-ambulation plus resistance exercise fully recovered strength (not size); re-ambulation alone did not (Brooks). After 14 days of bed rest, 14 days of rehabilitation with resistance exercise restored size and strength (Pišot).

Recommendation: at least 2-4 weeks of progressive rehabilitation, including strength training, after bed rest of up to 28 days; possibly longer for higher-level athletes and for medical bed rest.

Countermeasures: in Tier 2, only fluid and salt loading was tested (26-30 mL water and 0.1 g sodium chloride per kg body mass daily, started 7-15 days before and continued through bed rest): it preserved, and even increased, supine VO2max and plasma volume — all from one laboratory.

Tier 0-1 candidates: passive mechanical loading, protein or essential amino acids, motor imagery, passive blood-flow restriction, electrical muscle stimulation, lower-body negative pressure, "anti-gravity suits", drugs (with doping rules).

Mechanisms

Measured: plasma volume fell about 12% in 7 days and 18% in 30 days in the Zorbas studies, alongside the VO2max loss; fluid and salt loading that kept plasma volume kept supine VO2max.

Authors' interpretation (citing Lee): the rapid early VO2max loss mirrors plasma volume and lower exercise cardiac output; the slower later loss adds cardiovascular structural and muscular changes such as fewer oxidative enzymes.

Authors' interpretation: upright exercise suffers more than supine because after bed rest standing raises heart rate and lowers stroke volume more, through gravity's effect on fluid distribution.

Measured (Tier 0-1, Marusic, cited): strength follows a logarithmic decay, rapid within about 5 days; early strength loss exceeds muscle loss (neural factors), while over longer bed rest about 79% of the strength loss is attributed to lost muscle mass.

Measured (Smorawiński, cited): people with a higher starting VO2max lost more of it; endurance-trained men lost more VO2max and lactate threshold than strength-trained men.

Practical Application

I spent a week in bed — how long before I'm back to normal? Plan at least 2-4 weeks of progressive rebuilding with strength work in it — the authors' advice after up to 28 days in bed, possibly longer after illness or injury. No study has measured real athletes; in exercise-trained men upright endurance fell within 3 days (VO2max −16.5% in 3 days on an upright test; −3.9% in 7 days on supine tests in another laboratory). A week in bed is not a week off.

The first sessions after bed rest will show it most in upright work. The loss is larger on upright than supine tests and is driven early by plasma volume (authors' interpretation), so heart rate for an easy effort runs high at first; the base gates the return on easy-effort heart rate (SYNTH-36).

Put strength back in from the start of the rebuild. After 28 days in bed, re-ambulation plus resistance exercise recovered strength in 14 days and walking alone did not (Tier 0-1 data).

While in bed, fluid and salt is the only countermeasure tested in trained people (26-30 mL/kg water and 0.1 g/kg sodium chloride daily, started 7-15 days before bed rest and continued through it; whether starting it only once in bed works is untested; one laboratory, supine VO2max only); anything else, and anything during an illness, is a question for the treating doctor, not the training plan.

Not from this paper: an illness adds its own cost on top of the inactivity — all seven studies used healthy volunteers. Fever and chest symptoms stay a stop (SYNTH-36, REF-609).

Limitations

Zero studies met the criteria. Everything comes from Tier 2 men and, for strength, countermeasures and recovery, from Tier 0-1 people; the authors themselves call the conclusions limited for Tier 3-5 athletes and expect athletes to lose more.

Small, uncontrolled, men only. The seven studies range from n = 7 to about 40, have no control groups, and one laboratory (Zorbas) supplies four of them, averaged by the reviewers into approximate means; the reporting-quality check found missing inclusion criteria (5 studies), missing exact P values (6) and inadequate statistics descriptions (3).

Test position changes the number. Upright tests (−16.5% VO2max in 3 days) and supine tests (−3.9% in 7 days) are not comparable; one study did not report position.

Healthy volunteers, not patients. All bed rest was voluntary and healthy; the authors warn that illness or injury bed rest probably needs longer rehabilitation.

The recovery numbers are not from trained people. None of the seven measured recovery; the 2-4-week recommendation is the authors' synthesis of Tier 0-1 studies and one older study of 21-day bed rest.

Internal slip: the table footnote cites Zorbas as references 16-19 while the table cites 18-21.

Funding: none for writing; no conflicts declared. The first author's affiliation is a commercial sports research laboratory (New Balance Athletics).

How this entry was checked and changed

Why this level

the systematic arm (pre-registered, PRISMA, 501 records) returned nothing; every conclusion rests on a narrative reading of seven small uncontrolled bed-rest studies in exercise-trained men (n = 7 to 40) plus reviews of sedentary or recreational adults, and the strength and recovery recommendations come from Tier 0-1 data only; not B+ like REF-587 because the evidence this entry carries is those seven studies, not a body of maintenance trials; read from the full text

Full text (checked 2026-10-15)

"The systematic search retrieved a total of 501 studies"; "190 were removed as duplicates"; "381 studies were screened, with 97 manuscripts"; "zero studies were identified that met the inclusion criteria" (full text).

Criteria: "between the ages of 18 and 50 years"; "bed rest duration was ≥ 72 h"; "Tier 3–5" (full text).

Smorawiński ET "(n = 10) | 3 days | Upright | MIEL ↓ (− 14.3%)VO2max ↓↓ (− 16.5%)LT ↓↓ (− 24.8%)" (full text).

Smorawiński ST "MIEL ↓ (− 10.0%)VO2max ↓ (− 10.4%)LT ↔ (− 10.1%)" (full text).

"following 21 days of bed rest, sedentary subjects required only ~ 7 to 10 days ... whereas previously exercise-trained individuals required ~ 4 to 5 weeks" (full text).

Fluid/salt: "26–30 mL water per kg body mass and 0.1 g sodium chloride per kg body mass"; "provided prior to bed rest (for 7–15 days)" (full text).

Lee: "short durations of bed rest (approximately 2 weeks) require approximately 1 week of recovery, but longer durations of bed rest might require 2–4 weeks" (full text).

Brooks: "14 days of re-ambulation plus resistance exercise was sufficient to completely recover muscle strength (but not muscle size) following 28 days of best rest" (full text).

"a large fraction (~ 79%) of the strength loss during bed rest can be attributed to losses in muscle mass" (full text).

"Following bed rest of ≤ 28 days, we recommend at least 2–4 weeks of progressive rehabilitation (including strength training)" (full text).

Reporting quality "at least six out of a maximum possible score of nine"; question 3 "n = 5 studies", question 10 "n = 6 studies", question 18 "n = 3 studies" (full text).

"At no point was funding received by any of the authors for the writing of this manuscript"; no conflicts of interest (full text).

Included studies

Key Results

Mechanisms

Practical Application

Limitations

Read with