Muscle Imbalance Continuum

Muscle balance is the relative equality of muscle length or strength between an agonist and an antagonist (e.g. your bicep and your tricep) or contralateral muscles (e.g. left and right). This balance is necessary for normal movement and function. Muscle imbalances occur when the length or strength relationship of an agonist and antagonist prevents normal function. For example: a strength imbalance of >20% between eccentric hamstring force production and concentric quadriceps force production results in a 4x increase risk of hamstring injury. This post introduces the bigger picture of the muscle balance continuum before delving into pain science. Keep this picture in mind as we go through the pain science series. Pain makes us move and think differently. For example, a sprained ankle begins at the “tissue damage” end of the continuum. This tissue damage leads to a reduction in walking, which may cause a plantarflexion contracture. Once this person is weight bearing, they will have an altered movement pattern due to tight plantarflexors, limiting dorsiflexion range of motion. Decreased range of motion can be found at the other end of the continuum and can lead to movements that put someone at risk to utilize altered movement patterns. Let’s look at another example. If someone has an altered movement pattern secondary to excessive elevation of the scapula and inadequate upward rotation during arm elevation, then that movement pattern may lead to tight upper traps and weak lower traps and serratus anterior over time. This can eventually cause sub-acromial pain or shoulder impingement. Note: The brain concludes that the tissues are under threat and require action, which may include rest. An added benefit is that memories of pain will hopefully protect you from making the same mistake more than once. Why We Feel Pain Why does pain matter? Understanding pain biology changes the way people think about pain, reduces its threat value and improves their management of it. The brain will give you perception of what is happening. The alarm system–or the pain signal–will tell your brain WHERE the danger is in your body, the AMOUNT of danger, and the NATURE of the danger (meaning what type of pain: sharp, burning, aching, tingling etc…). This alarm system is stored within the safety of the skull, which is comprised of the strongest bones in the body. Nociception is a sensory nerve’s response to a harmful or painful stimulus. Sensory receptors will respond to mechanical stimuli, temperature, and chemical stimuli. They then send a signal to the spinal cord which eventually sends the signal to multiple different areas of the brain. Shown in this video are the numerous areas of the brain affected by pain. It’s no wonder why someone with chronic pain is HYPERSENSITIVE to all sorts of stimuli such as noise, light, and temperature changes. Pain has also been shown to reduce concentration, affect problem solving, alter memory, induce fear, increase stress, and disturb spatial cognition. Fun Facts: -Our brain contains about 100 billion neurons, each of which can make thousands of connections. -Neurons are to keen to make connections. A single neuron placed in a saltwater bath will wriggle up to 30% of it length in search of another neuron. -As you are reading this you will have millions of synapses link and unlink every second. -The life of a sensory neuron is short. They only live for a few days then get replaced by fresh sensors. NOTE: understanding the process behind the experience of pain can provide you with major control of your pain! The sympathetic nervous system, which can be stimulated by pain, primes your big muscles for you in a fight or flight situation. This muscle priming can lead to muscles such as the hamstrings and upper trapezius getting tight and cause muscle imbalance. In this case, the small stabilizing muscles will then become inhibited leading to potential instability. One way to combat this is through the use of diaphragmatic breathing, which will stimulate the phrenic nerve to DECREASE sympathetic activity (fight or flight mode) and INCREASE parasympathetic activity (rest and digest mode) which will allow for cell nourishment and tissue healing. Pain Is Not Tissue Damage! and Painkillers If you aren’t experiencing pain, it means that any changes in tissue are not perceived to be a threat by your brain. However, that does not necessarily mean there is no tissue damage! There are many people who have endured extreme injuries and are asymptomatic. Conversely, there are people who have minor tissue changes who perceive a significant amount of pain. To summarize this point, pain is not directly correlated to a certain amount of tissue damage. Here are some examples
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