When people get very sick and go to the intensive care unit (ICU), their muscles start to shrink quickly—sometimes losing 10% of their size in just one week. Researchers used ultrasound (the same technology used during pregnancy) to watch what happens to leg muscles in 95 critically ill patients. They found that patients who were already at risk for poor nutrition lost muscle even faster. Interestingly, the type of nutrition support patients received didn’t seem to slow down the muscle loss, suggesting doctors may need to find better ways to protect muscles during critical illness.

The Quick Take

  • What they studied: How quickly do leg muscles shrink in people who are very sick in the hospital, and does the food and nutrition they receive help prevent this muscle loss?
  • Who participated: 95 patients (average age 56 years old, mostly men) who were admitted to intensive care units. These were people with serious illnesses or injuries requiring close hospital monitoring.
  • Key finding: Leg muscles shrank by about 10% in just the first week after hospital admission. Patients who were already malnourished or at nutritional risk lost muscle even faster than others. The type of nutrition support given didn’t significantly slow down the muscle loss.
  • What it means for you: If you or a loved one becomes critically ill and needs ICU care, muscle loss happens very quickly and may not be prevented by standard nutrition support alone. This suggests doctors need to develop better strategies to protect muscles during critical illness. However, this is early research and more studies are needed before changing treatment approaches.

The Research Details

Researchers watched 95 patients during their first week in the intensive care unit and measured their leg muscles using ultrasound—a safe imaging technique that uses sound waves to create pictures of muscles. They took measurements when patients arrived and again a few days later to see how much the muscles had changed. They also looked at each patient’s nutrition status and what type of food and nutrition support they received.

Ultrasound was chosen because it can detect muscle changes much earlier than traditional strength tests. The researchers measured several things: how thick the muscle layer was, how big the muscle was across its width, and even how the muscle tissue looked and felt (its texture and stiffness). This gave them a complete picture of what was happening to the muscles.

Understanding how fast muscles shrink in critically ill patients is important because muscle loss can make recovery slower and harder. If doctors can detect muscle loss early using ultrasound, they might be able to try different treatments sooner. This study helps answer the question: does the nutrition support we’re currently giving patients actually help preserve their muscles?

This study observed what naturally happened to patients rather than randomly assigning them to different treatments, which means we can see patterns but can’t prove that nutrition support directly caused or prevented muscle loss. The sample size of 95 patients is moderate—large enough to find some patterns but not huge. The researchers measured muscles in a standardized way using ultrasound, which is more objective than just looking at a patient. However, we don’t know details about all the factors that might have affected muscle loss, such as how active patients were or their exact calorie intake.

What the Results Show

All the muscle measurements showed shrinkage during the first week in the ICU. The quadriceps muscle (the big muscle on the front of the thigh) got about 10% thinner. The cross-sectional area of the rectus femoris muscle (another thigh muscle) shrank by about 10.5%. These changes happened in almost every patient studied.

Patients who started out at nutritional risk—meaning they were already malnourished or at high risk for malnutrition—lost even more muscle than other patients. This finding was statistically significant, meaning it’s unlikely to have happened by chance. The researchers found that the worse a patient’s nutritional status was at the beginning, the more muscle they lost during that first week.

Surprisingly, when the researchers looked at the type of nutrition support patients received (such as feeding tubes or intravenous nutrition), they didn’t find a strong connection between the type of support and how much muscle was lost. This suggests that current nutrition strategies may not be effective enough at preventing muscle loss in critically ill patients.

The researchers also measured other muscle characteristics like the angle of muscle fibers, how the muscle tissue looked on ultrasound, and the stiffness of the muscle tissue. These measurements showed changes too, though they were more variable between patients. The texture and stiffness changes suggest that the muscle tissue itself was changing in quality, not just getting smaller.

Previous research has shown that muscle loss in critically ill patients is a real problem, but most studies relied on indirect measurements or waited until patients recovered to assess damage. This study is notable because it used ultrasound to detect changes in real-time during the first week—the earliest period when muscle loss happens fastest. The finding that nutritional risk predicts muscle loss aligns with previous research, but the finding that standard nutrition support didn’t prevent muscle loss suggests that current approaches may need improvement.

This study watched what happened naturally but didn’t randomly assign patients to different nutrition plans, so we can’t say for certain that nutrition support caused or prevented muscle loss. We don’t know all the details about each patient’s activity level, exact calorie intake, or other medical conditions that might have affected muscle loss. The study only looked at the first week—we don’t know what happens to muscles over longer periods. The researchers measured muscles in a standardized way, which is good, but different doctors might measure slightly differently. Finally, this was a single study in one hospital system, so results might be different in other places or patient populations.

The Bottom Line

Based on this research (moderate confidence): Doctors should monitor muscle loss early in critically ill patients using ultrasound, especially in patients already at nutritional risk. Current standard nutrition support may not be enough to prevent muscle loss, so doctors should consider additional strategies such as early mobilization (getting patients moving), resistance exercises when possible, or investigating new nutrition approaches. Patients and families should understand that muscle loss happens quickly in critical illness and recovery may take time.

This research is most relevant to: doctors and nurses caring for critically ill patients in intensive care units, patients and families facing critical illness, and researchers studying how to improve recovery from severe illness. People with chronic illnesses who might someday need ICU care should also be aware that maintaining good nutrition before illness may help protect muscles. This research is less directly relevant to generally healthy people, though it highlights the importance of good nutrition for overall health.

Muscle loss begins within hours of critical illness and the fastest loss happens in the first week. Recovery of lost muscle takes much longer—weeks to months depending on how much was lost and how well the patient recovers. Even after leaving the hospital, patients may need physical therapy and good nutrition for several months to regain muscle strength and function.

Want to Apply This Research?

  • For patients or caregivers using a health app: Track daily calorie and protein intake during or after critical illness recovery. Set a goal of 1.2-1.5 grams of protein per kilogram of body weight daily (ask your doctor for your specific target). Log this weekly to monitor whether nutrition goals are being met.
  • Work with your healthcare team to: (1) Eat adequate protein at each meal during recovery, (2) Engage in gentle movement or physical therapy as soon as approved by doctors, (3) Keep a simple food diary to ensure you’re meeting calorie and protein targets, (4) Schedule follow-up appointments to monitor muscle recovery progress.
  • After hospital discharge, use the app to: Track weekly protein intake and total calories, record any physical activity or therapy sessions, note energy levels and strength improvements, and share monthly summaries with your doctor. This helps identify whether your nutrition and activity plan is supporting muscle recovery.

This research describes what happens to muscles in critically ill patients and suggests that current nutrition support may need improvement. However, this is a single observational study and should not be used to change medical treatment without consulting with your healthcare team. If you or a loved one is in critical care, all nutrition and treatment decisions should be made by the medical team caring for that patient based on their individual condition. This information is for educational purposes and is not a substitute for professional medical advice, diagnosis, or treatment.