Question

1. Briefly explain why bone density is related to an individual’s body weight.
2. Discuss the type of mechanical loading associated with the various types of bone fractures.
3. Speculate about what exercise or other strategies may be employed in outer space to prevent the loss of bone mineral density in humans.
4. Discuss the relative importance of joint stability and mobility for athletes participating in gymnastics.
5. Identify a joint in the body for each of the following categories: Gliding, Hinge, Condyloid, Saddle, and Ball & Socket.

Answer 1

Body weight is directly associated with bone mineral density (BMD). A low body mass index otherwise known as BMI has been cited as an important risk factor for lower BMD and predicts greater bone loss in older age and in younger persons in the basence of menses or an eating disorder.

Osteocytes are present inside the mineralised matrix of bone called lacunae and travel through the canaliculae channels. When the loading increases on the bone, the extracellular fluid is moved through the extracellular space with the help of pressure gradients. This fluid movement exerts a drag force within the pericellular space and the bone walls. The moving fluid also produces a shearing stress on the plasma membrane of the osteocytes.

The exercises that help in decreasing the loss of bone mineral density in humans is regular weight bearing exercise such as walking , jogging and dancing. Also the strength resistance training such as lifting weights , push ups and squats also help in decreasing the loss of bone mineral density in human.

Joint mobility is defined as the state to which an articulation can move before being restricted by surrounding tissues and joint stability is defined as the ability to maitain or control joint movement or position. Stability is achieved by coordinating actions of surrounding tissues and the neuromuscular system.

These are very much important for gymnasts as they peform a lot of stretching in their body. When a joint is stretched beyond a tonned range , is likely to dislocate. Balanced and strict movement are required in gymnasts movement. Hence, joint mobility and stability are very important for gymnasts.

Gliding joint is found between the bones of wrists and ankles .

Hinge joint is found in ankles, elbows , fingers , knees and toes.

Condyloid joint is found between the joints of the wrist and fingers.

Saddle joints is found in the carpometacarpal joint of the thumb.

Ball and socket joints are found in hip region where the round head of the femur rests in the cup like acetabulum socket of the pelvis.

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