Monthly Archives: February 2013

Energy and Work

We are now moving on to exercise Physiology…

Energy is what makes our body go, There are several kinds of energy that exist in the biological systems.

Energy in Biological Systems-

Electrical Energy-Nerves, muscles, cardiac rhythms.

Chemical energy: Synthesis of molecules, hormones.

Mechanical Energy: Muscle contraction (actual movement)

Thermal Energy: Regulation of body temperature.

The ultimate sourse of energy in all biological systems is Radiant Solar Energy  Captured in plants to convert simple molecules into fats, carbohydrates and protein. Trapped within the chemical bonds of food molecules.

“Energy cannot be created or destroyed, it can only  be changed from one form to another”. ~Albert Einstein

Use of Energy- The body must break down food to a usable form, the final product must be a molecule the cell can use (ATP) “YOU MUST EAT FOOD”

ATP- (Adenosine Triphosphate) is your main source of energy, electrical, mechanical, or chemical. In ATP, three phosphates are linked by high-energy state, becoming adenosine diphosphate (ADT) and inorganic phosphate (P).

Three phosphates linked by high energy bonds. When a bond is broken, energy is released.

ATP and Activity-

ATP is constantly converted to energy and must be replaced as fast as it is used in order for muscles to continue to generate force. Muscle cells have the capacity to regenerate ATP under a variety of work conditions, using multiple sources.

Immediate sources of energy: ATP and Creatine Phosphate

Short-term sources of energy: Glycolysis (anaerobic)-does not require oxigen and Glucose

Long-term sources of energy: Aerobic metabolism of glucose and fat, produced in the cells mitochondria.

Anarerobic energy Sources (Short-term): Cellular energy produced in the absence of oxygen, sources of anaerobic energy are:

ATP-Small amount already available, good for about 1 second.

Phosphocreatine (PC)– Stored in muscle cells, good for about 3-5 seconds

Glycolysis– glucose obtained from teh muscles glycogen stores, good for about 2 minutes.

Aerobic Sources of Energy (long-term): Oxygen must be present in the cell to create long-term energy.

Sources of long-term energy are muscle glycogen, blood glucose, fatty acids and intramuscular fats.

Aerobic Energy is used for activities lasting more that 2 minutes and up to 2 hours or more.

Exercise Intensity and Duration and Energy Production:

Energy from both anaerobic and aerobic sources is on-going. Short duration, high-intensity activity relies on a greater proportion of anaerobic energy and long duration, lower-intensity exercise relies on a greater proportion of aerobic energy.


** Disclosure- Everything from this article was found in the book Fitness Professional’s handbook Sixth Edition**


Muscle groups in Selected Activities

Muscle work in groups to produce specific joint movements. Efficiency of movement can be improved upon by studying the mechanics of movement at a joint, and making necessary changes. (Muscle Memory)

Training for strength and flexibility can influence the efficiency of movement.

Lifting and Carrying Objects-

Place the object close to or between spread feet, squat with an erect trunk, activate abdominal muscles and tilt pelvis backward. Use the hip and knee extensors to generate slow, smooth force. Carry the lifted object close to you body.

Common Mechanical Errors: Walking and Running

Stiff-legged running increases rotational inertia, and increases joint stress. Keep joint movements in the anterior-posterior direction to eliminate trunk rotation. (running strait)

Do not propel too high off the ground and reduce impact by running softly and quietly.

Common Mechanical errors: Throwing and Striking

The more joints involved in a throwing motion, the more speed can be produced. Lack of trunk rotation and poor coordination of timing with shoulder movement can result in low velocity.

When striking, rotate the trunk to increase impact of the strike. Hip, trunk and upper limb movements should follow each other with fluid timing.

Beginners often stop one movement before beginning the next. Increased bat velocity results in increased impact on the ball, and greater transfer of momentum.


** Disclosure- Everything from this article was found in the book Fitness Professional’s handbook Sixth Edition**

Basic Biomechanical Concepts fro Human Movement

Biomechanics is the study of tho our joints in our body move and some forces that contribute to those movements. Learning to understand the Biomechanics of the human body is necessary to fully understand our movement.


Torque is an expression of rotational force and all human movement is rotational in nature. Our Limbs act as levers that rotate around fulcra.

Torque is the product of magnitude of force and the {force arm}

The equation for Torque is T=F X FA [Torque equals Force x Force Arm]

When two for es produce rotation in opposite directions, one is the resistance force (R) and its force arm is called the resistance arm (RA). Force generated by R x RA is called Resistance Torque (TR)

Force Arm- is the perpendicular distance from the axis of rotation of the joint to the direction of the force from its point of application (where the muscle attaches to the bone being moved).

Resistance arm-is the distance from the axis of rotation to the center of gravity of the moving limb.

Torque and Exercise-

While exercising, the force arm is the distance from the axis pint (joint axis of rotation) to the point of attachment of the muscle on the bone being moved. The resistance arm is the distance from the axis of rotation to the center of gravity of the moving limb.

Holding a dumbbell lengthens the resistance arm by moving the center of gravity further away from the fulcrum, the longer the resistance arm, the more torque is needed to produce movement.

Torque varies as a limb a limb moves through the joint’s range of motion due to change in the length of the force arm.

Rotational Inertia-

Rotational Inertia the resistance to change in the rotation of a body segment around a joint axis. It depends on the mass of the segment and its distribution around the joint.

For example a lower limb has more rotational inertia than an upper limb not only because it is heaveier but also because its mass is concentrated a greater distance away from its axis of rotation.

Inertia can be manipulated by changing the joint angle (for example) by flexing the knees during running, we move the mass closer to the axis, decreasing inertia.

Angular Momentum-

Angular momentum is the product of angular inertia x angular velocity. The faster a body segment moves, and the greater its rotational inertia, the greater its angular momentum.

The amount of force needed to change angular momentum is proportional to the magnitude of momentum.

Angular Momentum and Exercise-

A faster movement, a greater mass, or a greater desired decelerate requires grater muscle force to slow down the body segment.

Muscles can be injured if they are not strong enough to decelerate the force generated from ballistic movements.

Ballistic Movement-a high-velocity musculoskeletal movement, such as a tennis serve or boxing punch, requiring reciprocal coordination of agonistic and antagonistic muscles



***disclosure: everything in the article I found in the book Fitness Professional’s Handbook Sixth Edition***