13.4 Nutrition, Metabolism & Energy Expenditure in Rehabilitation
Key Takeaways
- Adequate calories and protein are essential for wound healing, muscle recovery, and pressure-injury prevention; protein needs rise to ~1.2-1.5 g/kg/day (and higher in burns/wounds), while starvation and immobility drive sarcopenia.
- Metabolic equivalents (METs) express energy expenditure: 1 MET ~3.5 mL O2/kg/min (resting metabolic rate); light activity is 1-3 METs, moderate 3-6, and vigorous >6.
- Immobility causes a catabolic state—loss of lean mass, negative nitrogen balance, insulin resistance, bone resorption—mitigated by early mobilization, resistance exercise, and adequate nutrition.
- Specific populations need attention: dysphagia texture modification, diabetic carbohydrate control, renal protein/phosphorus/potassium limits, and obesity management to offload joints.
Nutrition, Metabolism & Energy Expenditure in Rehabilitation
Nutrition is a Domain A applied-science topic with direct rehab relevance: wound healing, pressure-injury prevention, muscle recovery, and exercise prescription all depend on substrate availability and energy balance.
Macronutrients & Rehab-Relevant Needs
| Nutrient | Rehab Need | Notes |
|---|---|---|
| Protein | ~1.0-1.2 g/kg/day baseline; ~1.2-1.5 g/kg/day for wounds/healing; up to ~2 g/kg/day burns | Essential for collagen synthesis, immune function, and muscle repair |
| Calories | Meet estimated energy expenditure; avoid both deficit (malnutrition) and excess (obesity) | Pressure injury risk rises with malnutrition |
| Vitamin C | Collagen cross-linking | Wound healing |
| Zinc | Enzyme cofactor, immunity | Deficiency impairs healing |
| Vitamin A | Epithelialization | Caution in pregnancy |
| Iron / B12 / folate | Oxygen transport, anemia | Anemia limits exercise tolerance |
| Vitamin D / calcium | Bone health | Immobility, osteoporosis |
Hypoalbuminemia and weight loss are screening flags for malnutrition (validate with validated tools—MNA, SGA, SNAQ—and recognize that albumin is a negative acute-phase reactant, not a pure nutrition marker).
Metabolic Equivalents (METs)
1 MET ~ 3.5 mL O2/kg/min (resting metabolic rate)
Light: 1-3 METs (slow walking, ADLs)
Moderate:3-6 METs (brisk walking, cycling, swimming)
Vigorous:>6 METs (running, competitive sports)
Cardiac and pulmonary rehab use METs to grade exercise intensity and activities; e.g., 6-minute walk, phase II cardiac rehab targets 50-80% of peak capacity. Cardiopulmonary fitness is discussed in Chapter 12; here the unit and its rehab uses are the foundation.
Immobility-Induced Catabolism
Immobility ──► ↓Muscle Protein Synthesis, ↑Protein Breakdown ──► Sarcopenia
│ ↓Insulin Sensitivity, ↑Bone Resorption
└── Early Mobilization + Resistance Exercise + Adequate Protein/Nutrition ──► Reverses
Bed rest/immobility rapidly induces negative nitrogen balance, ~1-3% muscle loss per week in older adults, insulin resistance, cardiovascular deconditioning, bone resorption, and pressure-injury risk. Early mobilization, resistance exercise, and adequate protein/calorie intake counteract the catabolic state.
Population-Specific Nutrition
- Wound/pressure injury: protein ~1.2-1.5 g/kg/day (higher for severe wounds), vitamins/minerals, hydration; offload and reposition.
- Dysphagia: texture-modified diets (IDDSID levels), thickened liquids, supervised feeding, aspiration precautions (see dysphagia section).
- Diabetes: carbohydrate consistency, glycemic control (wound healing), avoid hypoglycemia during exercise.
- Renal disease: protein tailored to stage, restrict phosphorus/potassium; balance protein needs with renal limits.
- Obesity: caloric deficit, behavior change, joint-preserving exercise; reduces load on painful joints.
- Burns: hypermetabolic state with very high caloric and protein demand; feeding protocols.
Deconditioning, Obesity, and Energy Balance
Both under-nutrition (sarcopenia, frailty, poor healing) and over-nutrition (obesity, joint load, cardiometabolic risk) impair rehab outcomes. The physiatrist coordinates with dietitians to match intake to expenditure, prioritize protein, and address micronutrient deficits—while exercise prescription (MET-graded) restores cardiovascular and muscular capacity.
Hydration, Wound Healing & Micronutrients
Adequate hydration supports perfusion and wound healing; dehydration and dependent edema both impair tissue oxygenation. Specific micronutrients matter: vitamin C and iron for collagen and oxygen transport, zinc for enzyme function, vitamin A for epithelialization, and the B vitamins for neuropathy (B1, B6, B12). Excess supplementation is not better—e.g., excess vitamin A can impair healing, and zinc excess causes copper deficiency and neuropathy. Targeted repletion of documented deficiencies is the principle.
Sarcopenia, Frailty & the Vicious Cycle
Sarcopenia (age-related muscle loss) and frailty interact with deconditioning and immobility:
Sarcopenia/Frailty ──► ↓Activity/Falls ──► Immobility ──► Further Sarcopenia (Cycle)
│
└── Resistance Exercise + Adequate Protein + Nutrition + Fall Prevention ──► Reverses
Resistance exercise and adequate protein (with attention to leucine and vitamin D) are the cornerstones of sarcopenia management. Frailty assessment (e.g., Fried criteria, Clinical Frailty Scale) guides prognosis and the aggressiveness of rehabilitation.
Obesity, Energy Balance & Joint Loading
Obesity raises joint reaction forces (especially knee), worsens cardiometabolic risk, complicates transfers and mobility, and is associated with pressure-injury risk in immobile patients. Management combines caloric deficit, behavior change, joint-preserving exercise (aquatic, cycle), and pharmacotherapy/surgery where indicated. Exercise prescription in obesity starts low and progresses gradually, emphasizing adherence and joint protection. The physiatrist balances the dual needs of weight management and strength/mobility restoration.
Hydration, Thermoregulation & Exercise Safety
Thermoregulation matters for rehab safety—older adults and those with autonomic dysfunction (SCI above T6, MS with Uhthoff) have impaired thermoregulation, requiring hydration, cooling, and timing strategies. Cardiac patients (see Chapter 12) require MET-based intensity and symptom/rate monitoring. Across populations, matching intake to expenditure and recognizing deficits (dehydration impairs performance and increases fall risk) completes the energy-expenditure picture the physiatrist manages.
Which protein intake is most appropriate for a rehab patient with a stage III pressure injury?
An activity performed at 5 METs corresponds approximately to:
Which physiological change is a direct metabolic consequence of prolonged immobility in a rehab patient?