Muscle protein synthesis response largely preserved after critical illness

In a study of 20 ICU survivors and 20 matched controls, researchers measured muscle protein synthesis after resistance exercise paired with 24 g of protein. Survivors had a smaller increase from baseline, but post-intervention synthesis rates were similar between groups; the findings are mechanistic and do not establish rehabilitation outcomes.

Twenty ICU survivors were compared with 20 matched controls.
Baseline muscle synthesis was higher in survivors.
Post-intervention synthesis rates were similar between groups.
The study assessed acute physiology, not rehabilitation outcomes.

Researchers compared 20 adults 3–6 months after intensive care unit discharge with 20 age- and sex-matched controls. Participants underwent muscle biopsies before and after a flywheel leg-extension resistance exercise session combined with 24 g of hydrolysed protein. The primary outcome was the change in muscle protein fractional synthetic rate; muscle size, handgrip strength and anabolic and proteolytic signalling pathways were also assessed.

ICU survivors had lower quadriceps muscle thickness and handgrip strength than controls. Their baseline muscle protein synthesis rate was higher (0.041%/hour vs. 0.030%/hour), and the increase after the intervention was smaller (0.031 vs. 0.040 percentage points per hour). However, post-intervention rates were similar (0.071%/hour vs. 0.070%/hour). The intervention increased anabolic signalling in both groups.

The results suggest that survivors retained the capacity to achieve post-exercise, post-protein synthesis rates comparable to controls, despite persistent muscle deficits. This small study measured an acute physiological response, not longer-term changes in strength, function or recovery; it therefore does not establish the effectiveness of a rehabilitation programme.

In practice

For adults with persistent muscle loss or weakness 3–6 months after ICU discharge, the study suggests that muscle protein synthesis can reach rates similar to those of matched controls after one bout of resistance exercise paired with protein. The smaller increase from a higher baseline in survivors does not show that they are unable to respond. Because only 20 survivors were studied and the endpoint was an acute muscle-synthesis measure, the findings do not establish that this intervention improves strength, function or longer-term recovery, or support a specific rehabilitation regimen.

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Source

Critical Care: Preserved anabolic skeletal muscle capacity in response to exercise and protein intake after critical illness ↗

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