Monday, February 04, 2008

(sEMG) Surface Electromyography to refine your stroke??

Many practitioners, using traditional methods debate the use of sEMG techniques?

Many don't understand how we use it!

Through the wonders of contemporay science and technology, a whole series of devices and techniques are becoming available to researchers.

The reasons why people are unable to continue muscular work and why they experience fatigue depend on several general factors, including the nature of the activity, the training and physiological status of the individual, and environmental conditions. Because physiologicaol systems are often matched in their capacities, during exercise stress it is somtimes difficult to identify a single factor that failed in an attempt to maintain exercise intensity.

During athletic contraction, muscular fatigue usually appears to be a peripheral phenomenon and due to fatigue of the muscles. The CNS and associated motor neurons and neuromuscular junctions appear to be "far superior" to skeletal muscle in maintaining function. It has been learned that the heart is not thought to fatigue and cause reduced ecercise power output. In other words, it much like a car, the more gas you give it, the faster the motor will move you down the road, at a cost! But if you don't have any horsepower, well don't get in a race, because the motor that uses more muscle mass will win!

Much research is going on about V02max (maximal O2 consumption) in setting the upper limit for aerobic metabolism and endurance. Two possibilities are considered! One is that V02max is limited by 02 transport from the lungs to contracting muscles. The other possibility is that V02max is limited by the respiratory capacity of contracting muscles. Some believe that endurance is directly related to V02max (i.e., the greater the V02mac, the greater the endurance). Other support the posibility that endurance is determined by peripheral factors like mitochondria to sustain high rates of respiration.

At present, we must conclude that V02max is a parameter set by maximal oxygen transport, but that endurance is determined also by muscle respiratory (mitochondrial) capacity. We also need to understand that it is better to use more muscle mass if one wants to make speed!

Muscle mass of contracting can influence V02 during exercise, once a critical mass of muscle is utilized, V02 is independent of muscle mass! The influence of muscle mass is revealed in the observations that V02max during bicycling with one leg is less than that when cycling with two legs. Running will be greater than bicycling do to gravity and the use of more muscle mass.

V0zmax apparently increases as active muscle mass increases to a point beyound which O2 delivered through the circulation is inadequate to supply the active muscle mass.

The ability of nerve and muscle cells to respond to chemical (neurotransmitter) stimuli ultimately "governs" all human motor behavior.

Electromyography (EMG) is a measurement tool that is used to identify the recruitment of motor units in skeletal muscle. An investigator can measure muscle electrical activity. Both the frequency and amplitude of the electrical activity can be measured, and this provides insight into actual recruitment patterns and the type and number of motor units being used during physical activity. In addition to measuring EMG, measurements of muscle force can be made, thus allowing an analysis of the relationship between force and EMG.

By studying muscle preparations, we have learned that the force of the overall muscle is controlled by two mechanisms during "voluntary contractions." One mechanism is to alter the frequency by which a given motor unit is recruited, a concept that is called "rate-coding."
First it is true that a intact muscle, a single muscle fiber, a single motor unit, the frequency of stimulation increases, so does the force output! The second mechanism to increase overall force output during voluntary contractions is to recruit "more motor units."

Complicated movements involve some part of the brain!

Most learned movement patterns, especially those movements that require sensory input (like hitting a baseball), require the participation of one or several areas of the brain. The motor cortex is in direct control fo the learned movement patterns. The learning of intricate motor tasks involves the programing of the motor cortex. The initiation of motor tasks involves the playing back of stored programs in which motor units in active and supporting muscles are recruited in a precise pattern of time, space, frequency, and amplitude.

Man kind has some essential movement patterns built into the CNS through the process of evolution. These primitive movements involve locomotion (e.g. walking, running, cycling, swimming) and appear to be located in the spinal cord. Even at the youngest age, you can watch a little kid pedal at the basic form! True, these primitive spinal cord movement patterns are activated under the control of higher cortical centers. Even Tiger woods had a golf club in his hands at a early age, but had to learn more!

Far too many rider's ride their bikes at the primitive level, very basic locomotion. Even the pro baseball player spends much time learning how to picth!!! Why not cycling? You will see people pedal in all sorts of ways?

Human movement during sports, like movement during other human endeavors, is under the ultimate control of the brain and the central nervous system. Therefore, understanding the neural controle of movement, using Myo-facts sEMG/Dartfish is of primary importance.

First, we don't use surface electromyography for assessing pain related problems. We don't use needle EMG or watch nerve conduction velocity suitable for bone and nerve related problems, they are insensitive to muscle, tendon, ligament and articular dysfunctions. We should also point out that traditional methods for assessing soft tissue pain related problems, such as palpation, are ultimately subjective!

We are not in the pain industry, we leave that to the physical medicine practitioner. We do use surface EMG technology to specifically monitor muscle action poentials (MAPs), and this is known to be sensitive to soft tissue injuries. Again, we don't use sEMG for ill care!

We do look for dysfunction homologous muscle pairs (or between agonist and its antagonist or synergist) during the pedal stroke. We can point out to your very eyes an imbalance in relative stiffness in the muscles that participate in a specific movement. These imbalances are thought to faulty CNS motor control problems, along with peripheral factors such as inefficient length-tension relationships and passive myofascial compliance with a poor saddle/cleat setup and bad motor skills. The relationship between muscle impairment and psychologic factors becomes clearer.

Do we not think about the correct golf swing or in our case the correct pedal stoke? Even Tiger Woods uses Butch Harrman, as does Phil Mickelson to refine their golf swing? So what's up with us refining your pedal stroke?

Observed functional limitations can be seen with a poor fitting bike. Surface EMG techniques and associated feedback displays can make the user more efficient. Fore example, sEMG can help identify inappropriate muscel substitution patterns and thus refine the pedal or the exercise. Motor copy templates can be used to assist in learning new recruitment patterns for a more powerful pedal stroke.

In health care, today, it is very common to teach a patient a set of exercises (stretching & strengthening exercises) and give them a handout to remind them of what they are to do until the next visit. We use sEMG to monitor the actual ability to activate the desired muscle. In real time, we can help them refine the pedal stroke to make it more effective.

No question, sEMG monitoring provides objective documentation trail of the impact on muscle function, thus allowing us to demonstrate gains. We see the sum of the effort in watts, and the watts increase with a improved, refined, pedal stroke.

If a posture is bad, movement may be compromised or muscle substitutions may appear.
We can show elevations in muscle activity. One could argue that that its weight placing an undue strain on the peri-articular structures or by the build up of lactic acid associated with muscular efforts required by the posture or movement.

We can teach a better postural alignment, and it is much better to show how the muscles can relax with the new correction. Many have caught onto their needed correction, based upon what the sEMG has taught them.

It has been shown in sports, for many who are professionals that muscle work better if the muscle relaxes during the stretch. When one reads the sEMG, a problem can be seen with assessing! The muscle stretch receptor gets stimulated causing the muscle to become active.
Now think about the speed of the pedal stroke and the speed of the muscle firing?

We can point out to you where you are stretching your muscles too much! Correct that on the fly, all while you pedal. Then we use the Dartfish, to break it down to you, one stroke at a time.
Real motor templates can be used to assist in learning a refined pedal stroke.

The sum of the work then provides you with the recordings of wattage!

It has been pointed out that many in the physical medicine field claim that we don't provide the best feedback, given the use of the muscles e.g. gas exchange of O2 & C02 "ADP to ATP ect....

That is true, we don't use sEMG to to test your blood, we just use it for seeing if a muscle is on/off, for a better model of a better pedal stroke. The results of people learning, taking that biofeedback to their game, putting more focus to their stroke has made a difference!

A poor pedal stroke, used 5,000 times per hour is not good, even if the V02max is at what ever value! Hitting a tennis ball in the sweetspot is always better than to the outside of that sweetspot.

Results are the end results! Every stroke counts no matter what time of year! Its hard work!

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