Bedrest, a period of prolonged inactivity, is often prescribed for medical reasons, such as recovering from severe injuries or illnesses, or managing certain conditions during pregnancy. While intended to facilitate healing, extended bedrest can lead to various physiological changes throughout the body. The abdominal system, encompassing the digestive, metabolic, renal, and muscular components, experiences several notable effects due to this sustained lack of movement.
Digestive System Changes
Reduced physical activity significantly impacts the gastrointestinal tract, leading to a slowdown in bowel motility, also known as peristalsis. This decreased movement of food through the colon and rectum can result in increased water reabsorption and progressively harder stools, making constipation a common issue for individuals on bedrest. In fact, people confined to bed are up to 16 times more likely to experience constipation compared to mobile individuals.
The supine position also alters the normal gravitational forces that assist in defecation, further reducing the urge to pass stool. Bedrest can also affect appetite, potentially leading to lower food intake. Alterations in physical activity and diet can influence the gut microbiome.
Metabolic and Body Composition Alterations
Bedrest profoundly influences the body’s metabolism and overall composition. Insulin sensitivity, the body’s ability to manage blood sugar, can decrease rapidly. This leads to increased insulin resistance and impaired glucose tolerance, meaning the body processes nutrients less efficiently, potentially leading to higher blood glucose levels.
Prolonged inactivity also alters fat storage and muscle mass. While body weight may not change significantly, fat mass can progressively increase, even under controlled nutritional intake. Simultaneously, bedrest causes muscle atrophy, particularly in the core and abdominal muscles, which contribute to overall body composition and metabolic health. This muscle loss, along with changes in cellular metabolism, contributes to the observed insulin insensitivity and a shift in how the body utilizes energy sources.
Renal and Urinary System Responses
The kidneys and urinary bladder are also affected by prolonged bedrest. Immobility can lead to changes in fluid balance and electrolyte regulation. An early increase in urinary calcium excretion occurs, primarily due to bone demineralization. This increased calcium, along with other urinary solutes, can lead to increased saturation in the urine, raising the risk of kidney stone formation.
Urinary stasis, where urine pools in the renal calyces due to the lack of gravity-assisted drainage, further contributes to the risk of stone formation and urinary tract infections. Bladder function can also be impacted, as the supine position reduces pressure on the bladder, diminishing the natural urge to urinate even when the bladder is full. This can lead to incomplete bladder emptying and increased risk of urine retention.
Abdominal Muscle Weakness
A direct consequence of bedrest is the deconditioning and weakening of abdominal muscles. Lack of use causes these core muscles, including the transversus abdominis and internal obliques, to atrophy. Studies have shown a reduction in transversus abdominis thickness by over 18% in inactive individuals after 60 days of bedrest.
This loss of muscle mass and strength in the abdominal region compromises their ability to support internal organs, maintain proper posture, and contribute to overall trunk stability. The decline in muscle strength can be more rapid than the actual muscle atrophy in the initial stages of bedrest. This weakening affects not only physical movement but also indirectly impacts functions like effective coughing and bowel movements, which rely on strong abdominal contractions.