Chapter 5: Understanding Our Body

The tendon of the calf muscles inserted into the calcaneus, or heel bone, is called the Achilles tendon because of the Greek mythological hero Achilles. According to the story, Achilles was a great warrior, but his only weak point was his heel. Therefore, the tendon near the heel came to be known as the Achilles tendon.

The values we learn from this story are:

1. Every person may have some weakness, even if they are very strong.
2. We should not become overconfident about our abilities.
3. We should protect our weak areas and work to improve them.
4. Strength should be used with wisdom and discipline.

A similar story from the Indian epic Mahābhārata is the story of Duryodhana. His body was made very strong, but his thighs remained his weak point. During the final fight, Bhima struck Duryodhana on his thigh and defeated him. This story also teaches that even a powerful person can have a weak point.

When we touch the Achilles tendon below the calf muscle and above the heel bone, it feels like a hard, strong, and rope-like band. It is not very soft because it connects the calf muscles to the heel bone and helps in movements like walking, running, jumping, and standing on toes.

When we touch the ear, it feels softer and more flexible because the ear is mainly made of cartilage.

Similarities

1. Both Achilles tendon and ear cartilage are connective tissues.
2. Both are flexible to some extent.
3. Both help in giving support to body structures.

Differences

Yes, all three types of levers are present in the human body. In our body, bones act as levers, joints act as fulcrums, and muscles provide effort or force.

1. First-Class Lever

In a first-class lever, the fulcrum is between effort and load.

Example in body: Movement of the head at the neck joint.

When we nod the head, the neck joint acts as the fulcrum, muscles provide effort, and the head acts as the load.

2. Second-Class Lever

In a second-class lever, the load is between fulcrum and effort.

Example in body: Standing on toes.

In this movement, the toes act as the fulcrum, the body weight is the load, and the calf muscles provide effort.

3. Third-Class Lever

In a third-class lever, the effort is between fulcrum and load.

Example in body: Bending the elbow.

The elbow joint acts as the fulcrum, the biceps muscle provides effort, and the hand or object held in the hand acts as the load.

Most movements in the human body are examples of third-class levers.

Five activities that help improve mobility and function of specific joints are:

These exercises are useful during warm-up because they prepare the joints and muscles for physical activity and reduce the risk of injury.

When heel raises are performed in a standing position, we feel tension mainly in the calf muscles. The movement is easier because the legs are straight.

When heel raises are performed in a mid-squat position, the tension in the calf muscles feels greater. This is because the knees are bent and the muscles have to work harder to lift the heels.

Muscles involved

1. Gastrocnemius
2. Soleus
3. Achilles tendon helps transfer the force of calf muscles to the heel bone.

The gastrocnemius is more active when the leg is straight, while the soleus works more when the knee is bent, such as in the mid-squat position.

A. Kicking a Ball

Joints involved

1. Hip joint
2. Knee joint
3. Ankle joint
4. Toe joints

Muscles involved

1. Quadriceps
2. Hamstrings
3. Gluteus maximus
4. Gastrocnemius
5. Soleus
6. Hip flexors

Explanation

While kicking a ball, the hip joint helps move the leg forward, the knee joint helps in bending and straightening the leg, and the ankle joint helps in controlling the foot. The quadriceps help extend the knee, while the hamstrings and gluteus muscles support leg movement and balance.

B. Throwing a Ball

Joints involved

1. Shoulder joint
2. Elbow joint
3. Wrist joint
4. Finger joints
5. Spine and hip joints for body rotation

Muscles involved

1. Deltoids
2. Biceps
3. Triceps
4. Pectoralis major
5. Trapezius
6. Forearm muscles
7. Abdominal muscles

Explanation

While throwing a ball, the shoulder joint helps move the arm, the elbow joint helps bend and straighten the arm, and the wrist and fingers help release the ball. The deltoids, biceps, triceps, and chest muscles help produce force, while abdominal and back muscles help in balance and body rotation.