The aim of this study is to evaluate the effect of early exercise by cycle ergometry and early targeted feeding in reducing muscle atrophy and improve functional outcomes in the older critically ill patient.

Patients admitted to ICU are normally ventilated due to their critical illness and sedated for their comfort. This prolonged immobility from sedation leads to accelerated muscle atrophy and reconditioning when they recover from their critical illness. This leads to further complications from immobility like bed sores, hospital acquired infections, deep vein thrombosis and pulmonary embolisms. Many patients do not return to their pre-illness level of function and require long term care.

Nutrition is frequently hard to assess when patients is in a catabolic state and sedated. There is a loss of appetite if the patient is awake to express it, and if sedated is depended on nasogastric feeding based on caloric empirical formulas invented more than 50 years ago. These formulas also do not accurately take into account exercise physiotherapy which patients will undergo while on ICU. With indirect calorimetry (IC), patients energy requirements can be estimated on a daily basis and can be fed accordingly. The IC is considered the gold standard in many guidelines for nutritional assessments but it is not commonly used due to cost and practical difficulties in measurements. The investigators intend to use the IC based on international recommendations to assess energy requirements daily and feed patients based on the data provided by the IC.

Early rehabilitative type of exercises have been show to increase muscle mass and reduce length of stay in the elderly geriatric population by preventing deconditioning. There is some evidence that this also applies to the ICU population but in a ventilated patient on multiple therapies, this is extremely labour intensive. By utilising the cycle ergometry, this muscle atrophy may be reduced. Interestingly, studies on intensive physiotherapy have not shown to have a dramatic outcome in the elderly ICU population. This could be due to the catabolic rates and the inadequate feeding of a sedated patient who cannot express their hunger or satiety. By using the indirect calorimetry, a more accurate energy expenditure can be estimated and nutrition can be targeted. By combining these 2 therapies, the lengths of stay in hospital can be reduced and functional outcomes improved in this silver population.

The investigators plan to conduct a randomised controlled trial. Participants will be randomised into 2 groups; the intervention and control group. Participants in the control group will receive standard empiric weight based feeding and standard physiotherapy. Participants in the intervention group will undergo daily IC measurements on admission and fed according to the energy expenditure measured by IC. In addition to standard physiotherapy, the participants in the intervention group will undergo cycle ergometry for up to 60 minutes daily. The participants in the intervention group will undergo 14 days of IC and cycle ergometry or until extubation (for IC), whichever is earlier.

During this 14 day period, participants in both groups will undergo twice weekly quadriceps muscle ultrasounds to assess muscle thickness as a surrogate measure of muscle atrophy. After this 14 day period, the investigators will perform regular assessments of functional status (during the ICU/HD stay, on discharge to general ward, and on discharge from hospital). The investigators will also collect demographic and ICU assessment data from medical records.

Inclusion Criteria:

1. At least 60 years old
2. Mechanically ventilated within 3 days of ICU admission
3. Expected to be mechanically ventilated for more than 3 days at time of recruitment
4. Able to ambulate with or without a gait aid before hospitalization
5. Able to be enterally fed within 48 hours of ICU admission

Exclusion Criteria:

1. Unable to follow commands at baseline before hospital admission (e.g. Severe dementia)
2. Acute condition where cycling is a contraindication (e.g. leg fracture)
3. Not expected to survive the subsequent 48 hours
4. Body habitus unable to fit the cycle ergometry
5. Patients at high risk of refeeding (i.e. NUTRIC score >= 5): malnourished patients with anorexia nervosa, chronic malabsorption syndromes, chronic alcoholism, or patients with massive weight loss.
6. Extremes of BMI: i.e. BMI < 16 or > 30
7. Liver failure
8. Cycling exemptions precluding cycling within the first 4 days of mechanical ventilation
9. Requirement for inspired oxygen content (FiO2) greater than 0.8
10. Expected to be on renal replacement therapy for longer than 12 hours per session
11. PEEP > 15mmHg
12. Air leaks through chest drains
13. Palliative goals of care or limitation of treatment established by the CARE form
14. Readmissions to ICU

Outcome assessor (in our study, person measuring participants' quadriceps muscle thickness) is blinded.