Inverse Stretch Reflex
Contained in the tendon of each muscle is the Golgi tendon receptor. This receptor is sensitive to the build up of tension when a muscle is either stretched or contracted. The receptor has a tension threshold which causes the tension to be released when it gets to high. As the Bicep contracts and the threshold is exceeded then a signal is sent to the Bicep causing it to relax. This mechanism prevents damage being done to the Bicep should the weight be to heavy or the movement is to fast.
As the Tricep lengthens the combined effect of the stretching action and the stretch reflex contraction will cause a build up of tension in the Tricep tendon. When the threshold is reached the receptor will send a message to the Tricep muscle causing it to relax. This will allow the Tricep to be stretched even further.
Muscle Soreness
Muscle soreness that occurs some 24 to 48 hours after intense exercise usually involves eccentric contractions (). This causes increases in intracellular pressure that irritates the nerve endings, producing swelling and local pain.
Muscle types
All skeletal muscle fibres are not alike in structure or function. For example, skeletal muscle fibres vary in colour depending on their content of myoglobin (myoglobin stores oxygen until needed by mitochondria). Skeletal muscle fibres contract with different velocities, depending on their ability to split Adenosine Triphosphate (ATP). Faster contracting fibres have greater ability to split ATP. In addition, skeletal muscle fibres vary with respect to the metabolic processes they use to generate ATP. They also differ in terms of the onset of fatigue. On the basis of various structural and functional characteristics, skeletal muscle fibres are classified into three types: Type I fibres, Type II B fibres and type II A fibres.
Type I Fibres
These fibres, also called slow twitch or slow oxidative fibres, contain large amounts of myoglobin, many mitochondria and many blood capillaries. Type I fibres are red, split ATP at a slow rate, have a slow contraction velocity, very resistant to to, fatigue and have a high capacity to generate ATP by oxidative metabolic processes. Such fibres are found in large numbers in the postural muscles of the neck.
Type II A Fibres
These fibres, also called fast twitch or fast oxidative fibres, contain very large amounts of myoglobin, very many mitochondria and very many blood capillaries. Type II A fibres are red, have a very high capacity for generating ATP by oxidative metabolic processes, split ATP at a very rapid rate, have a fast contraction velocity and are resistant to fatigue. Such fibres are infrequently found in humans.
Type II B Fibres
These fibres, also called fast twitch or fast glycolytic fibres, contain a low content of myoglobin, relatively few mitochondria, relatively few blood capillaries and large amounts glycogen. Type II B fibres are white, geared to generate ATP by anaerobic metabolic processes, not able to supply skeletal muscle fibres continuously with sufficient ATP, fatigue easily, split ATP at a fast rate and have a fast contraction velocity. Such fibres are found in large numbers in the muscles of the arms.
Characteristics of Muscle Types
Body muscle make up
Most skeletal muscles of the body are a mixture of all three types of skeletal muscle fibres, but their proportion varies depending on the usual action of the muscle. For example, postural muscles of the neck, back, and leg have a higher proportion of type I fibres. Muscles of the shoulders and arms are not constantly active but are used intermittently, usually for short periods of time, to produce large amounts of tension such as in lifting and throwing. These muscles have a higher proportion of type I and type II B fibres.
Even though most skeletal muscle are a mixture of all three types of skeletal, all the skeletal muscle fibres of any one motor unit are all the same. In addition, the different skeletal muscle fibres in a muscle may be used in various ways, depending on need. For example, if only a weak contraction is needed to perform a task, only type I fibres are activated by their motor units. If a stronger contraction is needed, the motor units of type II A fibres are activated. If a maximal contraction is required, motor units of type II B fibres are activated as well. Activation of various motor units is determined in the brain and spinal cord. Although the number of the different skeletal muscle fibres does not change, the characteristics of those present can be altered.
Fibre type modification
Various types of exercises can bring about changes in the fibres in a skeletal muscle. Endurance type exercises, such as running or swimming, cause a gradual transformation of type II B fibres into type II A fibres. The transformed muscle fibres show a slight increase in diameter, mitochondria, blood capillaries, and strength. Endurance exercises result in cardiovascular and respiratory changes that cause skeletal muscles to receive better supplies of oxygen and carbohydrates but do not contribute to muscle mass. On the other hand, exercises that require great strength for short periods of time, such as weight lifting, produce an increase in the size and strength of type II B fibres. The increase in size is due to increased synthesis of thin and thick myofilaments. The overall result is that the person develops large muscles.
Injury prevention
Like most athletes, you undoubtedly want to lower your chances of incurring an injury while participating in your favorite sport. Injuries decrease the amount of time you can spend in leisure activities, lower your fitness, downgrade competitive performance, and can lead to long term health problems such as arthritis.
There are some general rules for injury avoidance which apply to all sports. Sports scientists suggest that injury rates could be reduced by 25% if athletes took appropriate preventative action.
Common Misconceptions
Coaches and athletes believe that males have higher injury rates than females. Male and female athletes have about the same injury rate per hour of training. Among runners it is considered that training speed is the cause of injuries (Speed Kills) but research indicates that there is no link between speed and injury risk.
Do not overdo it
The amount of training you carry out plays a key role in determining your real injury risk. Studies have shown that your best direct injury predictor may be the amount of training you completed last month. Fatigued muscles do a poor job of protecting their associated connective tissues, increasing the risk of damage to bone, cartilage, tendons and ligaments. If you are a runner, the link between training quantity and injury means that the total mileage is an excellent indicator of your injury risk. The more miles you accrue per week, the higher the chances of injury. One recent investigation found a marked upswing in injury risk above 40 miles of running per week.
The two best predictors of injury
If you have been injured before you are much more likely to get hurt than an athlete who has been injury free. Regular exercises has a way of uncovering the weak areas of the body. If you have knees that are put under heavy stress, because of your unique biomechanics during exercises, your knees are likely to hurt when you engage in your sport for a prolonged time. After recovery you re-establish your desired training load without modification to your biomechanics then your knees are likely to be injured again.
The second predictor of injury is probably the number of consecutive days of training you carry out each week. Scientific studies strongly suggest that reducing the number of consecutive days of training can lower the risk of injury Recovery time reduces injury rates by giving muscles and connective tissues an opportunity to restore and repair themselves between work-outs.
Psychological factors
Some studies have shown that athletes who are aggressive, tense, and compulsive have a higher risk of injury than their relaxed peers. Tension may make muscles and tendons taughter, increasing the risk that they will be harmed during work-outs.
Weak muscles
Many injuries are caused by weak which simply are not ready to handle the specific demands of your sport. This is why people who start a running programme for the first time often do well for a few weeks but then, as they add the mileage on, suddenly develop foot or ankle problems, hamstring soreness or perhaps lower back pain. Their bodies simply are not strong enough to cope with the demands of the increased training load. For this reason, it is always wise to couple resistance training with regular training.
Muscle imbalance
Screening for is the current cutting edge of injury prevention. The rationale behind this is that there are detectable and correctable abnormalities of muscle strength and length that are fundamental to the development of almost all musculoskeletal pain and dysfunction. Detection of these abnormalities and correction before injury has occurred should be part of any injury prevention strategy. Assessment of and regular sports can be beneficial in this strategy.
Muscle Stiffness
Muscle stiffness refers to the ratio between the change in muscle resistance and the change in muscle length. Muscle stiffness is thought to be directly related to muscle injury risk and so it is important to reduce muscle stiffness as part of a . Research has indicated that only dynamic stretches - slow controlled movements through the full range of motion - decrease muscle stiffness. Static exercises did not decrease muscle stiffness.
This suggest that dynamic stretches are the most appropriate exercises for warming up and not static stretching exercises. Static stretches are perhaps more appropriate for the warm down as they help to relax the muscles and increase their range of movement.
Trigger Points
A "trigger point" (TP), which is often caused by the muscle being overloaded, is a thick knot in a muscle which is palpable and tender (even painful to the touch).
Trigger points can be caused by: training errors, inadequate preparation, worn shoes or equipment, poor biomechanics, muscle fatigue, poor flexibility, nutritional factors (vitamin deficiency), psychological factors (lack of sleep, stress).
Treatment of a TP (separating the fibres of the muscle knot) can be achieved by applying direct pressure to the point for 10 to 20 seconds, gradually releasing the pressure and repeating the process 4 of 5 times. The amount of pressure, which will depend on the sensitivity of the TP, can be applied by using one or both thumbs.
A number of treatments may be required but as the sensitivity (pain) of the TP reduces it will become harder to find. If after a couple of treatments the pain does not reduce then you should seek medical advice. Alternative approach to treating a TP is where petrissage, friction and effleurage techniques can be used to help breakdown the TP.
Trigger points are an early warning to a potential serious injury so checking for TPs is very beneficial. A regular massage is well worth is as the therapists, when conducting a massages, can check for TPs and treat them.
Make it specific
Resistance training can fortify muscles and make them less susceptible to damage, especially if the strength building exercises involve movements that are similar to those associated with the sport. Time should be devoted to developing the muscle groups, strength training, appropriate to the demands of your sport. If you are a thrower then lots of time should be spent developing muscles at the front of the shoulder which increases the force with which you can throw, but you must also work systematically on the muscles at the back of the shoulder which control and stabilise the shoulder joint.
Injury prevention tips
- Avoid training when you are tired
- Increase your consumption of carbohydrate during periods of heavy training
- Increase in training should be matched with increases in resting
- Any increase in training load should be preceded by an increase in strengthening
- Treat even seemingly minor injuries very carefully to prevent them becoming a big problem
- If you experience pain when training STOP you training session immediately
- Never train hard if you are stiff from the previous effort
- Pay attention to hydration and nutrition
- Use appropriate training surfaces
- Check training and competition areas are clear of hazards
- Check equipment is appropriate and safe to use
- Introduce new activities very gradually
- Allow lots of time for warming up and cooling off
- Check over training and competition courses beforehand
- Train on different surfaces, using the right footwear
- Shower and change immediately after the cool down
- Aim for maximum comfort when travelling
- Stay away from infectious areas when training or competing very hard
- Be extremely fussy about hygiene in hot weather
- Monitor daily for signs of fatigue, if in doubt ease off.
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