Analysis Of How Muscles Produce Movement

In order for your body to move different part of the muscular skeletal system work under the influence of your nervous system to produce voluntary movements. The skeletal system contracts when stimulated via impulses from the nervous system. At the point of contraction the muscles shorten and pull on the bones to which they are attached. When a muscle contracts, one end normally remains stationary while the other end is drawn towards it. The point that remains stationary is known as the origin, and the end that moves is called the insertion. Muscles are assembled together to work in pairs to create movement. They only act by contraction or pulling.

Some examples of antagonistic pairs are:

• The quadriceps and hamstrings in the leg
• The biceps and triceps in the arm.

Muscle contractions can be divided into four different types:  Isometric, Concentric, Eccentric and Isokinetic.

1. Isometric – During an isometric contraction the length of a muscle does not change and the joint angle does not alter. The muscle is actively engaged in holding a static position. For example when stopping halfway in a press up. This type of muscle contraction can increase blood pressure as blood flow is reduced and rapidly leads to fatigue.
2. Concentric - Concentric contractions are those which cause the muscle to become short as it contracts. An example is the upward phase in a bicep curl causing a concentric contraction of the Biceps Brachialis muscle. Concentric contractions are the most common type of muscle contraction and occur frequently in daily and sporting activities.
3. Eccentric – This occurs when a muscle returns to its normal length after shortening against resistance. For example the downward phase in a bicep curl. At this point your muscles are working against gravity and act like a braking mechanism. This muscle contraction can cause muscle soreness. This muscle contraction occur in many sporting activities such as running downhill involves eccentric contraction on your quadriceps.
4. Isokinetic – During isokinetic contractions the muscle contracts and shortens at a constant speed. For this type of strength training you need specialised equipment that detects when the muscle is speeding up and can increase the load. Describe, explain and analyse the Type I and Type II fibre types, including examples of the types of athletes associated with each: All Skeletal muscles contain a mixture of fibre types. The mix of fibres varies from individual to individual, and within the individual from muscle group. To a large extent this fibre mix is inherited.

However training can influence the efficiency of these different fibre types. Within the skeletal muscle there are three types of fibre:

• Type 1/ Slow twitch
• Type 2a/ Fast twitch-oxidative fibres
• Type 2b/ Fast twitch-glycolytic fibres

Type 1/Slow twitch

These fibres contract slowly with less force. They are slow to fatigue and suited to longer duration aerobic activities. They have a rich blood supply and contain many mitochondria to sustain aerobic respiration. They are recruited for lower-intensity, longer-duration activities such as long distance running and swimming. An athlete associated with this fibre type Michael Phelps.

Type 2a/ Fast Twitch-oxidative fibres

These muscle fibres are fast contacting and able to produce a great force, but are also resistant fatigue. These fibres are suited to middle-distance events such 800m, 1500m and mile run. An athlete that is associated with this fibre type is Mo Farah.

Type 2b/ Fast twitch-glycolytic fibres

These muscle fibres contract rapidly and have the capacity to produce large amounts of force, but they fatigue more readily, making them better suited to anaerobic activity. They depend almost entirely on anaerobic metabolism and recruited for higher intensity shorter duration activities. They are important in sports that include man stop-go or change of pace activities such as basketball. A perfect example of an athlete that uses this fibre type is LeBron James.