Exercise rehabilitation following intensive care unit discharge for recovery from critical illness

Review question

We reviewed the evidence about the effects of exercise rehabilitation on functional exercise capacity and health-related quality of life for patients who have been critically unwell in the intensive care unit (ICU). Functional exercise capacity is a term used to express how well individuals perform activities such as walking or climbing the stairs.


Adults often develop muscle wasting and weakness during ICU admission. This may occur as a result of the illness itself, and because patients tend to be less mobile and physically active whilst they are receiving treatment. As they recover, this muscle weakness can cause difficulty in their ability to exercise and carry out normal activities of daily living. Adult patients can become depressed or low in mood as a result of the illness and the effects of their reduced strength, which can last for many years.

We wanted to measure health-related quality of life to determine whether exercise programmes can help patients recover from critical illness-related physical deconditioning and muscle weakness after they have been discharged from the ICU, and can help them to feel better about themselves.

Study characteristics

We included six studies that involved 483 participants (298 male, 185 female) over the age of 18 years. Participants had received breathing support from a machine (been mechanically ventilated) for longer than 24 hours whilst in the ICU and had begun an exercise programme after leaving the ICU. Studies were carried out in the UK, Australia, the USA and Italy.

Exercise programmes were delivered on the ward in two studies; on the ward and in the community in one study; and in the community in three studies. The duration of the intervention varied according to length of hospital stay after ICU discharge up to a fixed time of 12 weeks. Exercises included arm or leg cycling, walking and general muscle strengthening at home, provision of self help manuals and hospital-based multi-exercise programmes carried out in physiotherapist-led gymnasiums.

Three of the six studies were funded by government health research funding agencies. One study was supported by combined funding from an independent charity and a commercial company (with no interest in the results of the study). One study did not report a funding source, and another was funded by an academic health research agency.

Key results

We were unable to determine an overall result for the effects of exercise-based interventions. Three studies reported improvement in functional exercise capacity following completion of the exercise programme, and the other three found no effects of treatment.

Only two studies measured patient-reported health-related quality of life, and both of these studies showed no effects related to treatment. Again, we were unable to reach an overall conclusion. No study included an evaluation of acceptance of the treatment by patients or the experience of patient participation in an exercise-based programme.

Quality of the evidence

We found considerable differences across included studies regarding types of exercise, how measurements of functional exercise capacity were collected, ways by which results were presented and people who had been critically ill. Exercise programmes were compared with usual care, with lack of acknowledgement of the standard level of rehabilitation and exercise in usual practice. In addition, we found variability in how well the studies were performed. We were unable to perform any statistical tests on study findings or to make firm conclusions because of this variability. The overall quality of the evidence was very low for these reasons. .

Currency of the evidence

Evidence is current to May 2014. We reran the search in February 2015 and will deal with studies of interest when we update the review.

Authors' conclusions: 

At this time, we are unable to determine an overall effect on functional exercise capacity, or on health-related quality of life, of an exercise-based intervention initiated after ICU discharge for survivors of critical illness. Meta-analysis of findings was not appropriate because the number of studies and the quantity of data were insufficient. Individual study findings were inconsistent. Some studies reported a beneficial effect of the intervention on functional exercise capacity, and others did not. No effect on health-related quality of life was reported. Methodological rigour was lacking across several domains, influencing the quality of the evidence. Wide variability was noted in the characteristics of interventions, outcome measures and associated metrics and data reporting.

If further trials are identified, we may be able to determine the effects of exercise-based intervention following ICU discharge on functional exercise capacity and health-related quality of life among survivors of critical illness.

Read the full abstract...

Skeletal muscle wasting and weakness are significant complications of critical illness, associated with degree of illness severity and periods of reduced mobility during mechanical ventilation. They contribute to the profound physical and functional deficits observed in survivors. These impairments may persist for many years following discharge from the intensive care unit (ICU) and can markedly influence health-related quality of life. Rehabilitation is a key strategy in the recovery of patients after critical illness. Exercise-based interventions are aimed at targeting this muscle wasting and weakness. Physical rehabilitation delivered during ICU admission has been systematically evaluated and shown to be beneficial. However, its effectiveness when initiated after ICU discharge has yet to be established.


To assess the effectiveness of exercise rehabilitation programmes, initiated after ICU discharge, for functional exercise capacity and health-related quality of life in adult ICU survivors who have been mechanically ventilated longer than 24 hours.

Search strategy: 

We searched the following databases: the Cochrane Central Register of Controlled Trials (CENTRAL), Ovid SP MEDLINE, Ovid SP EMBASE and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) via EBSCO host to 15 May 2014. We used a specific search strategy for each database. This included synonyms for ICU and critical illness, exercise training and rehabilitation. We searched the reference lists of included studies and contacted primary authors to obtain further information regarding potentially eligible studies. We also searched major clinical trials registries (Clinical Trials and Current Controlled Trials) and the personal libraries of the review authors. We applied no language or publication restriction. We reran the search in February 2015 and will deal with the three studies of interest when we update the review.

Selection criteria: 

We included randomized controlled trials (RCTs), quasi-RCTs and controlled clinical trials (CCTs) that compared an exercise intervention initiated after ICU discharge versus any other intervention or a control or ‘usual care’ programme in adult (≥ 18 years) survivors of critical illness.

Data collection and analysis: 

We used standard methodological procedures as expected by the Cochrane Collaboration.

Main results: 

We included six trials (483 adult ICU participants). Exercise-based interventions were delivered on the ward in two studies; both on the ward and in the community in one study; and in the community in three studies. The duration of the intervention varied according to length of hospital stay following ICU discharge (up to a fixed duration of 12 weeks).

Risk of bias was variable for all domains across all trials. High risk of bias was evident in all studies for performance bias, although blinding of participants and personnel in therapeutic rehabilitation trials can be pragmatically challenging. For other domains, at least half of the studies were at low risk of bias. One study was at high risk of selection bias, attrition bias and other sources of bias. Risk of bias was unclear for the remaining studies across domains. We decided not to undertake a meta-analysis because of variation in study design, types of interventions and outcome measurements. We present a narrative description of individual studies for each outcome.

All six studies assessed functional exercise capacity, although we noted wide variability in the nature of interventions, outcome measures and associated metrics and data reporting. Overall quality of the evidence was very low. Individually, three studies reported positive results in favour of the intervention. One study found a small short-term benefit in anaerobic threshold (mean difference (MD) 1.8 mL O2/kg/min, 95% confidence interval (CI) 0.4 to 3.2; P value = 0.02). In a second study, both incremental (MD 4.7, 95% CI 1.69 to 7.75 watts; P value = 0.003) and endurance (MD 4.12, 95% CI 0.68 to 7.56 minutes; P value = 0.021) exercise testing results were improved with intervention. Finally self reported physical function increased significantly following use of a rehabilitation manual (P value = 0.006). Remaining studies found no effect of the intervention.

Similar variability was evident with regard to findings for the primary outcome of health-related quality of life. Only two studies evaluated this outcome. Individually, neither study reported differences between intervention and control groups for health-related quality of life due to the intervention. Overall quality of the evidence was very low.

Four studies reported rates of withdrawal, which ranged from 0% to 26.5% in control groups, and from 8.2% to 27.6% in intervention groups. The quality of evidence for the effect of the intervention on withdrawal was low. Very low-quality evidence showed rates of adherence with the intervention. Mortality ranging from 0% to 18.8% was reported by all studies. The quality of evidence for the effect of the intervention on mortality was low. Loss to follow-up, as reported in all studies, ranged from 0% to 14% in control groups, and from 0% to 12.5% in intervention groups, with low quality of evidence. Only one non-mortality adverse event was reported across all participants in all studies (a minor musculoskeletal injury), and the quality of the evidence was low.