ENDURANCE

Definition:: Endurance is the ability to work for prolonged periods of time and the ability to resist fatigue. (It is a measure of fitness) Fitness is a general term indicating a level of cardiovascular functioning that result in heightened energy reserves for optimum performance and well being.Endurance is dependent on the transport of oxygen which influenced by: a-Pulmonary function including ventilation and diffusion b-The oxygen-binding capacity of the blood (depends on blood volume and haemoglobin. c-Cardiac function which is stroke volume and heart rate d-Oxygen extraction capabilities including total muscle blood flow and capillary density. e-Muscular oxidative potential, which is dependent on the level of mitochondrial enzymes..

Determination of EnduranceThe determination of an individual’s endurance is based on maximum aerobic power (VO2 max), which is the measure of oxygen transport system.*VO2 max is the maximum oxygen volume that can be consumed per minute. It is also called aerobic capacity, aerobic power, maximum oxygen uptake, maximum consumption and cardiovascular endurance capacity. The maximum aerobic power (VO2 max) is influenced by: a- age, b- sex c- heredity factors d- disease

e- Conditioning f- DeConditioning..

CONDITIONING: is an augmentation of the energy capacity of the muscle through an exercise program. It depends on exercise of sufficient intensity, duration and frequency.DECONDITIONING: occurs with prolonged bed rest and in the individual who is sedentary because of life style and increasing age.Types of Endurance:1-Local (muscular endurance): concerns restrictive muscle group and is manifested by repeated or continuous use of the muscle group.2-General (cardiovascular endurance): concerns with many muscle groups situated in various areas of the body or total body that sustain muscle tension against low-intensity exercise as walking

over an extended period of time

**Types of Local Endurance:1-Sustained Isometric Endurance:It is determined by the length of time an isometric contraction is maintained against a given resistance.2-Repeated Isometric Endurance:The number of isometric contractions of a short duration at a given frequency and against a given resistance.3-Isotonic Endurance:The work produced by a muscle group when moving a constant resistance at a given frequency.*Endurance Evaluation:1-Isometric endurance: it is done by calculating the number of seconds an isometric contraction is maintained against a maximal resistance of the percentage of a maximal resistance.2-Isotonic endurance: it is done by recording the number of times a maximal or percentage of maximal resistance can be moved in a measurable distance.*N.B: in evaluating isotonic endurance it is important to consider:1-resistance 2-distance 3-frequency 4-speed

Guidelines for Endurance exercise:1- Local (muscular endurance): in which patient performs active exercise repeatedly against a moderate load to the point of fatigue, but don’t push to the point of stress.2- General (cardiovascular endurance): in which patient performs active loaded exercise that is directed to the cardiopulmonary fitness. The exercise is usually done to large groups of muscles as during walking, running.- Establish the exercise heart rate and the maximum heart rate. Maximum Heart Rate = 220 - Age - Warming up exercise gradually for 5-10 minutes that include stretching and repetitive motion at slow speeds with gradually increasing the effort. - Increase the activity so that the exercise heart rate can be maintained for 20-30 minutes.- cool down for 5-10 minutes with slow, low total body repetitive motions and stretching activities.

- Exercise can be repeated 3-5 times per week

- - To avoid injuries, use appropriate equipments and proper biomechanical support.The maximum heart rate: can be determined directly from a maximal performance teat, extrapolated from a heart rate achieved on a predetermined sub-maximal test, or can be calculated as 220- age -The exercise heart rate: determined as percentage of the maximum heart rate. This percentage depends on the level of the fitness of the individual. It is based on the heart rate reserve, which is the difference between the resting heart rate and the maximal heart rate.Exercise heart rate = HR rest +60 to 70% (HR max- HR rest).

• Warming up before starting the exercises and cooling down after finishing the exercises are very important aspect of the program.

Warmining up are important in:1- Stretch the muscles, tendons and connective tissues.2-Prepare the heart, CVS, muscles for activity.3- Divert the blood to the exercising muscles.4- Increase the body temperature that facilitates many physiological

process. The lack of warm up may lead to:a- Result in Premature fatigue.b- Increase the risk of rupture and strains.c- Increase risk of overuse injuries (like tendonitis).Cool-down are important in:a- Regain the body to its normal metabolic and physiological level.b- Reduce the risk of post-exercise dizziness or fainting.c- Reduce the post-exercise soreness.

Effects of Endurance Training:I. Cardiovascular Changes:1- increase myocardial contractility, increase HR and reduce pulse rate.2- increase cardiac output.3- increase oxygen extraction by working of muscles.II. Respiratory changes:1- Increase lung volume.2- Increase diffusion capacity3- Increase ventilatory efficiency.III. Metabolic changes:1- Increase metabolism and metabolizing enzymes.2- Decrease rate of depletion of muscle glycogen.3- Increase capability to oxidize carbohydrate..

IV. Other system changes:1- Decrease body fat.2- Decrease blood cholesterol and triglyceride levels.3- Increase bone strength, ligament and tendonN.B:▲Muscular endurance increases by the rapid repetition of exercises or activities performed against a resistance being as maximal as possible.▲The greater the intensity, the shorter the duration needed.▲Optimal frequency of training is 3 or 4 times a week.▲As frequency is increased to greater than the optimal range, the risk of musculoskeletal complication increases.▲If exercise is not progressed every 2 to 3 weeks, there

will be no training effect.

Skeletal Muscle Fatigue

Fatigue is a complex phenomenon that affect muscle performance and must be considered in a resistance training program. Skeletal muscle cells can increase their force production up to 40 N/cm2 in less than 100 ms. However, repeated activation of muscle cells leads to decreased force production and slower contractions.Fatigue may occurs acutely during high-intensity exercise, which is mainly caused by factors related to increased energy metabolism.

There are also other long-lasting types of fatigue in which metabolic factors appear to be of little importance. Contractions that involve stretch of the muscle which cause muscle weakness and damage, that takes many days to recover from.This explains why exercising long and hard enough to feel the burn for an extended period leaves muscles sore for one or more days afterwards. This is called Delayed-Onset Muscle Soreness (DOMS).

Types of Fatigue

  A. According to its incidence:- Acute Muscle soreness: - Muscle pain develops during or directly after strenuous exercise due to lack of adequate blood flow & oxygen and accumulation of lactic acid and potassium in the exercised muscle.- it is transient and subside quickly when adequate blood flow & oxygen are restored to the muscle.- Delayed-onset Muscle soreness: Muscle tenderness and temporary stiffness develop 12-24 hours after exercise. This may be due to microtrauma to muscle fibers and/or connective tissues that result in tissues degeneration.B. According to its typeI. Local Muscle Fatiguethe diminished response of a muscle to repeated stimulus, that is normal physiological response due to decrease in the amplitude of

motor unit potential.

Causes1- High or low-intensity exercises applied over prolonged period of time during either static or dynamic mode.2- Disturbance in the contractile mechanism because of a decreased in the energy stores, insufficient oxygen and accumulation of lactic acid.3- Inhibitory influence from CNS.4- Pain and muscle spasm..

Causes of Fatigue

1 -The depletion of energy stores

Physical activity for short time (several minutes) Energy used is glucose and glycogen. Exercise for more than 90 minutes decrease glycogen decrease blood

glucose level

Decrease energy more dependent upon fat fat cannot be used to produce ATP.

e.g. marathon’s runners, hitting the wal

Causes of Fatigue

2 -The accumulation of inhibitory metabolic waste products

•Accumulation of lactic acid making muscle more acidic inhibitory effect of the process of muscle contractility burning sensation or pain within the muscle.

Causes of Fatigue

3 -Dehydration•During prolonged forms of exercise the body will sweat to

regulate body temperature dehydration (reduce body fluid) affect the efficiency of cardiovascular system reduce oxygen supply to the muscle.

If the state of dehydration persists sweating Stops in order to conserve body fluid over

Heating impaired metabolic reactions

collapse, if not treated may be fatal .

Causes of Fatigue

4 -neurological causes

Depletion of acetylcholine at the neuromuscular junction or neurotransmitter at the synapses.

II. General Muscle Fatigue:is diminished response of a person during prolonged physical activity as walking.Causes1- Decreased in blood glucose (sugar) level.2- Decreased in glycogen stores in muscle and lever.3- Depletion of potassium especially older persons.4- Dehydration due to prolonged form of exercise that lead to excessive sweating.5- Depletion of acetylcholine at the neuro-muscular junction or neurotransmitter at synapsess..

Signs and symptoms of Muscle fatigue1-Pain and muscle cramp.2- Decreased in active motion.3- Use of substitute motion.4- Inability to continue low-intensity physical activity.5- Decline in the beak torque during Isokinetic testing.Recovery from fatigue:adequate time for recovery from fatigue must be built into every resistance training in order to:1- Replenish energy store.2- Removal of lactic acid from the muscle.3- Replenish of oxygen store in muscle.4- Replacement of glycogen