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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 Endurance
The 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 capacity
3- Increase ventilatory efficiency.
III. Metabolic changes:
metabolism and metabolizing enzymes. 1- Increase
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 tendon
N.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).
Fatigue of Types
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 type
I. Local Muscle Fatigue
the diminished response of a muscle to repeated stimulus, that is
normal physiological response due to decrease in the amplitude of
motor unit potential.
Causes
1- 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.
Causes
1- 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 synapses.
Signs and symptoms of Muscle fatigue
1-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