Using your legs and moving them regularly is critical for maintaining strength and mobility. However, many situations can lead to long periods of not using your legs, such as being bedridden due to illness or injury. Not moving your legs for an extended time can have serious consequences on your muscle health, bone density, joints, circulation, and overall wellbeing. Understanding what happens when you don’t move your legs is important for recovery and prevention.
Muscle Atrophy
One of the most prominent effects of not using your legs is muscle atrophy. Muscle atrophy refers to the wasting away or loss of muscle tissue. It occurs when muscles are not active and load bearing for prolonged periods. Without regular use, muscle cells start to degrade and the fibers shrink in size.
Several key factors lead to muscle atrophy from disuse of the legs:
– Lack of muscle contraction – Contracting muscles is necessary to maintain muscle protein synthesis. Without this stimulation, synthesis drops while degradation rises.
– Reduced protein synthesis – Disuse suppresses the signaling pathways that control muscle growth and sustain proteins.
– Increased protein degradation – Inactivity enhances processes like apoptosis and ubiquitin-proteasome activity that break down proteins.
– Oxidative stress – Greater free radical damage occurs in inactive muscles.
– Unloading – Loss of mechanical loading and tension on muscles activates degradation.
– Nerve withdrawal – Loss of signaling from motor neurons worsens atrophy.
– Circulation changes – Altered blood flow to inactive muscles exacerbates wasting.
Research shows noticeable atrophy can occur in a matter of days or weeks of inactivity. Without moving the legs against gravity or resistance, muscle mass can decline at a rate of 0.5% per day. Complete immobilization can elicit decreases up to 4% per week.
The degree of atrophy depends on the duration and extent of disuse. However, even two weeks of immobilization was shown to reduce muscle size by 10% and strength by 30%. Atrophy advances most rapidly in the early stages then progresses more slowly over time. Muscle wasting follows a distinct pattern, affecting certain leg muscles earlier and more severely.
Differential Atrophy Patterns
Studies reveal differential atrophy of individual leg muscles with immobility:
– Soleus – The soleus of the calf atrophies first and most extensively. As a postural antigravity muscle, it’s highly dependent on weight bearing signals. After a few weeks of immobilization, soleus muscle fibers can decrease up to 50%.
– Quadriceps – Thigh muscles, particularly the vastus lateralis and medialis, undergo rapid atrophy without leg use. Electromyography shows greatly reduced quadriceps activity after just 96 hours of disuse.
– Adductors – Muscles on the inner thigh are significantly altered by 2 weeks of inactivity.
– Hamstrings – These large posterior thigh muscles demonstrate significant wasting with leg immobilization.
– Tibialis anterior – This dorsiflexor muscle in the shin loses cross-sectional area and strength with unloading.
– Gastrocnemius – Though less affected than the soleus, this calf muscle still shows declines.
– Gluteals – Early atrophic changes occur in gluteus muscles with immobility.
Overall, antigravity muscles that constantly work to stabilize and move the body undergo the most drastic atrophy without weight bearing activity.
Effects of Muscle Atrophy
The loss of muscle mass and strength from atrophy contributes to many impairments. Consequences are wide-ranging and impact physical function, metabolism, circulation, and overall health. Effects include:
– Strength loss – Wasting decreases force generation capabilities for daily activities. Leg press power can drop 20-50% after immobilization.
– Fatigue – With smaller cell size, fewer mitochondria, and altered metabolism, fatigability increases.
– Coordination – Motor control and balance are compromised without precise muscle movements.
– Mobility loss – Physical flexibility declines as muscle fibers become stiffer and joints can’t move as freely.
– Postural instability – Weak postural muscles reduce stability and control of leg joints.
– Fall risk – Diminished strength and motor control raise risks of falling and injury.
– Circulation – Less muscle pumping activity can slow blood flow, pooling fluids in the legs.
– Insulin response – Metabolic changes like insulin resistance result, elevating diabetes risk.
– Bone loss – Mechanical unloading of bones speeds osteopenia and osteoporosis.
– Rehabilitation – Overcoming muscle deficits makes recovery and rehab more difficult.
– Quality of life – Activities of daily living and independence are hampered.
– Mortality – Those with lower muscle mass have higher long-term mortality rates.
Muscle atrophy impairs overall physical functioning. Recovery requires gradually reintroducing activity through range of motion, strengthening exercises, and eventual weight bearing.
Neural Changes
Along with structural muscle changes, lack of use causes alterations in the nervous system. Neural control of muscles is disrupted from disuse. Key effects include:
– Reduced signaling – Without activity, motor neurons decrease synaptic signals to muscle fibers.
– Nerve withdrawal – Motor axons retract from the neuromuscular junctions.
– Decreased excitability – Muscles show higher stimulation thresholds and reduced activation with voluntary effort.
– Altered reflexes – Diminished excitatory reflex sensitivity due to changes in spinal cord signaling pathways.
– Poor coordination – Proprioception and motor control declines, affecting balance and movement.
Neural dysfunction contributes to feeling unsteady on the legs after prolonged immobility. Strength gains may outpace control gains during rehabilitation. Supportive footwear, assistive devices, and balance training help overcome nerve-related motor deficits.
Bone Loss
Along with muscle and nerve effects, lack of mechanical forces on the bones leads to significant bone loss and strength declines. This process is known as disuse osteoporosis.
Normally, dynamic and impact forces from muscle activity and body weight put beneficial stress on bones. This stimulates osteoblasts to maintain and renew bone tissue. Inactivity dramatically reduces this osteogenic signal.
Osteoclasts gain prominence and absorb bone matrix, while osteoblast formation and bone growth slows. Bone mineral density can rapidly decline without weight bearing activity. The legs are especially vulnerable since they bear all body weight.
After just one week of immobilization, markers of bone formation are reduced up to 70%. A month of inactivity leads to measurable mineral loss. The effects intensify over longer durations. Bones reshape and degrade without mechanical forces, accumulating microdamage.
The greatest bone changes occur where tensile and compressive stresses are normally highest, such as the long bones of the legs. The quantity of bone declines while the microarchitecture deteriorates, comprised of poorer quality tissue.
Research shows bone mass decreases 1-2% per month of immobilization. Up to half of total bone mineral content can be lost after six months of inactivity. Declines are most pronounced in those who are already osteoporotic. Losing bone density makes the skeletal system brittle and fracture prone.
Regional Osteopenia
Studies reveal regional variations in bone loss down the leg with unloading:
– Femoral neck – This hip area is highly susceptible to osteopenia since it bears weight. Bone density drops 5-6% per month here.
– Proximal femur – Loss also occurs along the thigh bone nearest the hip. Declines up to 4% monthly are reported.
– Distal femur – The distal femur and knee joint lose 2-3% bone mineral per month without activity.
– Proximal tibia – This area can weaken by 1-2% per inactive month.
– Calcaneus – The heel bone loses density but recovers faster during remobilization.
Along with quantity reduction, architectural changes in bone increase fragility after immobilization. Low magnitude forces stimulate osteogenic activity before high impact activity.
Joint Contractures
Reduced mobility of joints is another consequence of not moving the legs. When joints cannot move actively or passively through normal ranges, contractures can develop.
Joint contractures involve a permanent shortening of the muscles, tendons, ligaments, or skin around a joint. This increases passive stiffness and reduces mobility. Studies show a 20-40% decline in knee joint range of motion after just one week of immobilization.
The lack of activity allows connective tissues to adhere and shrink. Flexor muscles usually contract more than extensors without movement. Common leg joint contractures from immobility include:
– Ankle contracture – The ankle exhibits restricted dorsiflexion range. Limited ankle mobility impairs gait.
– Knee flexion contractures – Knee movement is constrained into greater flexion. This impedes walking and transfers.
– Hip flexor contracture – The hip flexors become tight and shortened. This restricts back extension.
– Plantarflexion contracture – The foot points downward due to calf shortening. Weight bearing is altered.
Preventing and managing contractures during immobility requires regular passive joint movements through the full range. Stretching, serial casting, and splinting help once contractures develop.
Blood Flow Effects
Reduced blood circulation is another impact of not moving the legs. Inactivity for even short periods can slow lower limb blood flow and increase risk of clots. Several factors are at play:
– Muscle pump – Less leg muscle activity means reduced pumping to circulate blood back to the heart. Blood can pool in the veins.
– Vessel changes – Arteries and veins alter in size and compliance after progression of inactivity.
– Endothelial dysfunction – Blood vessels can become less responsive. Vasodilation is impaired.
– Hypercoagulability – Immobility leads to thicker, stickier blood more prone to clotting. Clotting factors are elevated.
– Stasis – Lack of movement allows blood to sit stagnant in veins and coagulate. Valves work less effectively.
Together, these factors significantly elevate risks of serious clotting events like deep vein thrombosis and pulmonary embolism. Hospitalized patients are at high risk. Preventive measures include anticoagulants, compression stockings, passive leg movements, and early remobilization.
Balance and Coordination
Being immobile for a long duration also hampers balance, stability, and coordination. The nervous system and muscles need constant practice and training to maintain precise control.
Factors contributing to motor control deficits with leg disuse include:
– Altered reflexes – Diminished spinal and cortical excitability impairs automatic responses.
– Weak postural muscles – Important stabilizers like the soleus atrophy.
– Impaired proprioception – Position sense in the legs declines.
– Stiffer joints – Connective tissue changes reduce mobility needed for balance corrections.
– Cardiovascular deconditioning – Blood pressure control worsens on standing.
– Spatial perception – Situational awareness and perception of objects in space deteriorates.
– Vestibular changes – The balance organs are altered by bed rest.
Rehabilitation initially focuses on re-establishing static balance. Exercises progress from seated to standing, then to dynamic stability. Maintaining balance and preventing falls requires a gradual return to walking and activities. Assistance is often needed at first.
Psychological Effects
Along with physical problems, long periods without leg use contribute to psychological consequences as well. Emotions and mental health are affected by immobilization.
Potential psychological effects include:
– Anxiety and depression – Mood disorders are more common when inactive and debilitated.
– Boredom and isolation – Confinement leads to feelings of impatience and loneliness.
– Helplessness – Reliance on others for basic care needs increases when mobility is lost.
– Fear and loss of confidence – Concerns about falling or worsening weakness develop.
– Altered body image – Significant atrophy changes muscle appearance.
– Cognitive decline – Attention, orientation, and memory may suffer.
– Social withdrawal – Interactions and engagement with others decreases.
Seeking mental health support is important during periods of prolonged immobility. Counseling, relaxation strategies, cognitive therapy, social interaction, and creative outlets help counter negative psychological effects.
Complications
Without preventive measures, serious medical complications can arise from continuous leg inactivity:
| Complication | Description |
|---|---|
| Pressure ulcers | Unrelieved pressure on the heels, sacrum, hips and other areas restricts blood flow and damages skin. Ulcers form if pressure isn’t regularly relieved. |
| Deep vein thrombosis | Blood clots form in the deep veins of the legs, often in the larger calf veins. Life-threatening pulmonary emboli can result if clots dislodge. |
| Urinary tract infections | Bacteria enter the urinary tract more readily with catheter use and poor mobility. Infections can spread to the bladder and kidneys. |
| Atelectasis and pneumonia | Poor breathing function and mucus clearance increase risk of lung collapse (atelectasis) and bacterial pneumonia. |
| Respiratory failure | Ventilatory capacity declines rapidly with disuse, which can lead to acute hypoxemic respiratory failure if severe. |
| Sarcopenia | Advanced muscle loss and weakness becomes severe, impairing movement and function. Disability results. |
| Osteoporosis | Bone density decreases substantially, greatly raising risk of fractures, disability, and chronic pain. |
| Stroke | Sedentary individuals have higher risk of ischemic stroke from atherosclerosis and blood clots. |
Preventing complications requires diligent care, frequent repositioning, range of motion exercises, and monitoring of affected body systems. Early mobility should occur as soon as possible.
Recovery Process
Reversing the effects of immobility and rebuilding strength and function requires a gradual process of remobilization. Key phases include:
– Range of motion exercises – Gentle movements of the legs through the range first reintroduce activity.
– Isometric training – Tensing muscles against resistance begins strengthening without joint movement.
– Active exercises – Active movement against gravity then added resistance follows.
– Increased loading – Walking and weight bearing exercises progressively load muscles.
– Cardio training – Aerobic activity builds endurance once basic strength allows.
– Power training – High velocity exercises develop power as strength improves.
– Balance exercises – Dynamic activities challenge stability reactions.
– Skill training – Advanced exercises train complex movement patterns.
– Ergonomic adjustments – Assistive devices provide added support where needed.
Underlying conditions are treated, and nutritional support provided. Early physical and occupational therapy maximizes functional recovery. With optimal rehabilitation, most people can regain mobility and prevent long-term impairment.
Prevention
While sometimes unavoidable, taking preventive measures can help reduce risks and consequences of prolonged leg inactivity:
– Move regularly – Perform active and passive range of motion exercises whenever possible.
– Shift positions – Reposition frequently to relieve pressures and improve circulation.
– Take walking breaks – Get up and walk for a few minutes periodically if able.
– Strengthen legs – Do leg exercises during confinement to maintain muscle health.
– Use compression – Compression socks and devices improve circulation.
– Elevate legs – Raising legs above the heart helps venous blood return.
– Watch diet – Adequate protein, calcium and nutrients prevent deficiencies.
– Treat contributing factors – Underlying causes like obesity or neuropathy should be addressed.
– Rehabilitate promptly – Starting physical therapy quickly preserves function.
– Utilize caregiver help – Seek assistance for mobility and self-care when needed.
While complete lack of mobility should always be avoided, total prevention isn’t always realistic. However, minimizing periods of inactivity, maintaining conditioning, and promptly rehabilitating can reduce long-term impairment.
Conclusion
Going for long periods without moving the legs has profound effects throughout the body. Muscle atrophy sets in rapidly once activity stops, along with bone loss, nerve changes, joint stiffness, and circulation deficits. This impairs physical function and health in multiple ways.
With prolonged immobility, the level of disability and dependence increases. Risk of medical complications also rises significantly. Preventing these consequences requires diligent care, range of motion, and early remobilization. A graduated rehabilitation program helps reverse the damage and regain mobility. Seeking medical guidance is key to recovering strength and functionality after extended leg disuse.