Muscles are either… Relaxed Stimulated

Contractions Muscle contractions are “all or none” There are different types of contractions…

Twitches Single brief contraction Not normal muscle function

Tetanus Summation of contractions One contraction is immediately followed by another The muscle does not return to a resting state

Types of Contractions Isotonic Contractions – Equal force – change in length Isometric Contractions – Equal length – change in force Occur continuously in muscles that stabilize the skeleton and hold the body upright

Isotonic Contractions Concentric Contractions Eccentric Contractions

Concentric Contractions

Eccentric Contractions

Isometric Contractions

Example Most body movements involve both isotonic and isometric contraction When walking, certain leg and thigh muscles contract isometrically and keep the limb stiff as it touches the ground, while the other muscles contract isotonically, bending the limb and lifting it. – Walking down the stairs involves eccentric contraction of certain thigh muscles

Example

Muscle Force Dependent upon the number of fibers stimulated – More fibers contracting results in greater muscle tension

How do Muscles get Energy for Exercise? Initially, muscles use stored ATP for energy. – Only 4-6 seconds worth of ATP is stored by muscles After this, other pathways must be utilized to produce ATP

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Other Pathways Aerobic RespirationAnaerobic Respiration

Other Pathways Aerobic RespirationAnaerobic Respiration With Oxygen Glucose broken down to CO2 and H2O, releasing ATP Slower reaction because it requires continuous O2 Occurs in the mitochondria Produces 36 ATP per glucose, CO2 and H2O Without Oxygen Glucose broken down to produce some ATP  lactic acid produced Reaction is fast, not very efficient Need lots of glucose Produces 2 ATP per glucose, lactic acid

The following are used for fuel and ATP production: – 1. Carbohydrates --- stored as glycogen – 2. Fats --- stored as triglycerides Carbohydrates are the most efficient source of energy Glucose can be broken down in aerobic and anaerobic pathways

Why should I exercise? 1. Boosts energy and mood 2. Strengthens cardiovascular and respiratory systems 3. Improves coordination and digestion 4. Reduces risk of injury and other health issues Strengthens tendons Decreases chance of diabetes, heart disease, etc. Lowers cholesterol 5. More efficient metabolism 6. Increases Flexibility

What’s happening to my muscle cells when I exercise? 1. Increases the numbers of mitochondria within your muscles. Mitochondria convert nutrition to energy. 2. Increases the amount of myoglobin within your muscles. Myoglobin transports and stores oxygen 3. Increases your muscles' capacity to store glycogen Glycogen is a form of carbohydrate fuel. 4. Creation of new blood vessels

Types of exercise Short, intense exercises such as sprinting and weight-lifting are anaerobic. (Resistance) – Creates an oxygen debt by using more oxygen than the body provides. – Anaerobic exercise also causes lactic acid. Long-lasting, less intense workouts, such as running a marathon, are aerobic exercises. (Endurance) – No oxygen debt because they only use as much oxygen as the body will provide. – No lactic acid byproduct

Resistance Exercise Resistance exercise increases muscle size and strength These exercises cause individual muscle fibers to tear, rebuild and grow in size. Hypertrophy– increased muscle size and strength – Increased muscle protein synthesis (actin and myosin) Enhanced Nerve-Muscle Interaction – Improves the body's ability to stimulate more muscle fibers and allow them to work in a more organized manner

Endurance Exercise During Aerobic Exercise muscles become: – More efficient – Meaner and longer – More resistant to fatigue Do NOT usually get lager Enables skeletal muscle cells to: 1. Muscle cells use more fat as fuel 2. Increases the number of enzymes in the mitochondria, which speed up this nutrient breakdown and energy formation. 3. Increase in the metabolic rate rather than change size and shape

Oxygen Debt Oxygen debt causes muscle fatiguemuscle fatigue Oxygen must be “repaid” to tissues to remove the deficit Oxygen is required to get rid of the accumulated lactic acid Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less