• Types of muscle fibre.Types of muscle fibre.• Muscle fibres & Sport.Muscle fibres & Sport.• How muscles work in pairs.How muscles work in pairs.

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Trapezius

Triceps

Gluteals

Hamstrings

Gastrocnemius

Quadriceps

Abdominals

Latissimus Dorsi

Biceps

Deltoid

Types of Muscle FibreTypes of Muscle FibreThere are two different types of muscle fibre which can be found in muscles.•Fast twitch fibres.•Slow twitch fibres.Fast Twitch FibresThese contract faster than slow twitch fibres & with much more force. They are used whenever rapid, powerful movements are needed. They do not have a good supply of oxygen, so they tire very quickly. They are suited to activities that need bursts of strength & power such as sprinting & weightlifting.

Slow Twitch FibresThese work for long periods of time because they have a good supply of oxygen. Slow twitch fibres are not as big or as strong as fast twitch fibres, & they also take longer to contract. They are most suited to activities that need endurance such as long-distance running & cycling.

Every muscle contains a mixture of these different fibres.For example, in the gastrocnemius, there is a high percentage of fast twitch muscles.  Athletes will have a different mix of fast & slow twitch fibres depending on the sport they play. Distance runners have about 80% slow twitch fibres while some weight lifters have 80% fast twitch fibres.

activity average % ST range of % STmarathon 81 50 - 98cross country skiers 64 52 - 75cyclists 59 52 - 72800m runners 52 40 - 62untrained 47 42 - 76shot putters 39 19 - 57sprinters 40 20 - 53

The table above shows the average % & range of slow twitch muscle fibres in sports performers. Use the data to explain the differences in muscle fibre relevant to the events they perform.

How Muscles Work Muscles usually work in pairs or groups.

To flex the elbow the biceps contracts & the triceps relaxes.

To extend the elbow the biceps relaxes & the triceps contracts. This is called ANTAGONI STI C MUSCLE ACTI ON. The working muscle is called the prime mover or agonist. The prime mover is helped by other muscles called synergists. These contract at the same time, reducing unnecessary movement when the prime mover contracts.

Muscle Action Study the sequence of photographs of the standing long jump & determine the state of contraction/ relaxation of the Quadriceps, Hamstrings & Gastrocnemius muscles. Place an ‘X’ in the appropriate spaces in the table to indicate which muscle is contracted, & which is relaxed in the various positions.