Did you know that there are more than 600 different skeletal muscles in the body? These are the muscles that attach to and move our bones. Skeletal muscles are made up of bundles of muscle cells also known as muscle fibers. They contain proteins called actin and myosin that play an important role in muscle contraction. When nerve signals reach a muscle cell, an electrochemical chain of events results in the contraction or shortening of the muscle. The more muscle fibers involved, the stronger the contraction and the more load it will move.

In order to understand muscle weakness, it is important to examine how muscles become stronger. In general, the overload principle is utilized to improve muscle strength. This principle states that gradually increasing the load or resistance against a healthy muscle over time will cause a muscle to adapt by getting stronger. This principle explains why staying at the same level of activity or resistance training will facilitate a plateau while gradually adding more challenge to the exercise will facilitate improvements in strength and performance. An increase in muscle strength is accomplished through a few mechanisms discussed below:

Enhanced neuromuscular drive:When you first start a new workout program or exercise, the initial improvements in strength and power that occur in the first 4-8 weeks can be attributed largely to changes in the neuromuscular system rather than the muscle fibers themselves. In this early stage units of muscle fibers called motor units begin to synchronize, allowing for a stronger muscle contraction. Improved muscle recruitment and activation of the motor nerves also contribute to the early changes in muscle strength and performance.

Increased cross sectional area: Muscle hypertrophy or muscle growth, is often what people think about when they want to get stronger. The process of adding more parallel muscle fibers increases the cross-sectional area of muscle and thus produces a more powerful contraction. The effects of this process become noticeable after about 8-10 weeks of consistent training.

Enhanced mitochondrial activity and capillary density: Mitochondria are the powerhouse of the cell. They produce ATP which acts as the fuel for muscle contraction. Capillaries supply working muscles with much-needed oxygen. Both mitochondrial activity and capillary density are enhanced as a result of regular aerobic and muscle endurance training. Better oxygenation and more fuel allows muscles to contract efficiently for longer periods of time.

If you decide to work with a physical therapist to help with muscle weakness related issues, your entire treatment plan could consist of around 8-20+ different physical therapy sessions that will each last 60-90 minutes. Once you complete your customized physical therapy treatment plan, you will be able to continue to do the prescribed stretches and exercises utilized during your PT sessions yet in the comfort of your own home.

WHAT CONDITIONS ARE ASSOCIATED WITH MUSCLE WEAKNESS?

Just as regular exercise or activity will spur a healthy muscle and nervous system to become stronger and more efficient, a period of inactivity or an injury or medical condition that affects the muscles or nerves can cause the reverse to occur. Some examples of conditions under which muscles often become weak are as follows:

Injury or surgery: pain, swelling, immobilization or movement restrictions often lead to weakness in muscles around the injured area or surgical site

General deconditioning: a period of inactivity often leads to reduction in muscle strength. In this case muscle weakness may be mild and only impact activities like running or cycling or it might also be severe and affect a person’s ability to sit, stand or care for themselves.

Muscle disorders or myopathies: a group of medical conditions that impact the health and function of the muscle itself can lead to varying degrees of muscle weakness and impact its ability to respond to training. Examples would be muscular dystrophy, ALS, Myasthenia Gravis, Myositis. Muscle strengthening needs to be undertaken carefully in these cases.

Nerve disorders: Impaired nerve signals to the muscle can cause weakness. Examples of central nervous system disorders associated with weakness are stroke and spinal cord injury while examples of peripheral nervous system disorders associated with weakness are peripheral neuropathy and guillain barre syndrome.

HOW DO PHYSICAL THERAPISTS TREAT MUSCLE WEAKNESS

Physical therapists use the overload principle to treat muscle weakness but their specialized training prepares them to adapt and apply these principles safely no matter the cause of the muscle weakness. My team of physical therapists and I do not believe in a one-size-fits-all approach and understand that muscles and nerves that have been injured or are affected by medical conditions like ALS, multiple sclerosis or muscular dystrophy, for example, need to be managed differently. Muscle strengthening may look like practicing rolling in bed or standing up from a chair and it may look like squats and deadlifts. My team of therapists is ready to meet you where you are because no matter your circumstances we want to help improve your function and quality of life.