PaceSetter Book

Warm-Up & Cool-Down Activities 3

3.7.2 Centre Of Gravity Young athletes also need to understand the concept of the ‘Centre of Gravity’, which plays an important role in many different events within track & field athletics. A simple exercise to find the body’s centre of gravity can be seen below. WEB COPY ©EVEQUE Move arms over head The young athlete lies on a bench on his or her front and finds the point where the body is balanced with neither forward nor backward movement. Once the body reaches the point of balance, the centre of gravity has been found. If the young athlete sweeps his or her arms forwards towards a position in front of the head, the top part of the body will then move down towards the ground. The young athlete should now lie on the bench on his or her back and once again find the point where the body is balanced. If the young athlete slides down the bench with his or her lower body, the legs will move down towards the ground and the centre of gravity has then passed over the edge of the bench. Compare the weight of a 3kg medicine ball with the weight of a young athlete. Although the medicine ball is quite heavy to lift, the young athlete’s body weight can be 12 to 18 times heavier, so the legs are constantly carrying a large weight. Ask the young athlete to walk on tiptoe without a medicine ball. Lifting the body weight should be quite easy as such weight is normal to the legs. Then ask the young athlete to carry a 3kg medicine ball, holding it out in front. The legs should feel the difference when trying to move around with 3kg additional weight as more work is been done by legs and hips to stabilise the shift in the centre of gravity of the body. Another easy exercise that highlights the difference in effort required to lift the body with additional weight is as follows. The young athlete should crouch down and then move into a standing position. Then holding the 3kg medicine ball out in front, the young athlete should be asked to perform the same task. The additional effort required by the legs to move the body weight and the medicine ball to a standing position should be quite noticeable and once again due to the effort required to stabilise the shift in the centre of gravity. WEB COPY ©EVEQUE Bench Slide down bench Bench

The vertical jump, explained in section 5.2.1, is a simple indicator of how far the centre of gravity has been raised from the floor.

46