Exercise/Sports Physiology
Dr. shafali singh
Learning objectives
■ CARDIOVASCULAR RESPONSES
■ RESPIRATORY RESPONSES
■ Physical Training and Conditioning
• The cardiovascular adjustments that occur
during exercise consist of a combination of
neural and local (chemical) factors.
Neural factors include
• (1) central command,
• (2) reflexes that originate in the contracting
muscle, and
• (3) the baroreceptor reflex
Mild to Moderate Exercise
• Anticipation of physical activity inhibits vagal
nerve impulses to the heart and increases
sympathetic discharge.
• The result is an increase in heart rate and
myocardial contractility which increase cardiac
output.
Cardiac Output
• Increased because of increased heart rate.
• If the workload increases, the heart rate
increases concomitantly until a plateau of
about 180 beats/min is reached during
strenuous exercise.
• In contrast to the large increase in heart rate,
the increase in stroke volume is only about
10% to 35%, the larger values occurring in
trained individual.
Olympic athletes who run marathons or perform cross country
skiing have much higher maximum cardiac outputs than nonathletes. Which of the following statements about the hearts
of these athletes compared to non-athletes is most accurate?
A) Stroke volume in the Olympic athletes is about 5% greater at
rest
B) Percentage increase in heart rate during maximal exercise is
much greater in the Olympic athletes
C) Maximum cardiac output is only 3% to 4% greater in the
Olympic athletes
D) Resting heart rate in the Olympic athletes is significantly
higher
Approximate distribution of cardiac output at rest and at different levels of
exercise up to the maximal O2 consumption ((VO2max) in a normal young man
VO2 max – maximal O2 consumption
• The level (point) where further increase of
workload does not bring about further
increase in VO2 .
• The VO2 max of an individual determines the
maximal aerobic work capacity;
• Contracting muscle avidly extracts O2 from the
perfusing blood and thereby increases the
arteriovenous O2 difference .
• This release of O2 from blood is facilitated by the shift
in the oxyhemoglobin dissociation curve during
exercise.
• Oxygen consumption may increase as much as 60-fold,
with only a 15-fold increase in muscle blood flow.
• Muscle myoglobin may serve as a limited O2 store
during exercise, and it can release the attached O2 at
very low partial pressures. However, myoglobin can
also facilitate O2 transport from capillaries to
mitochondria by serving as an O2 carrier
Venous Return
• sympathetically mediated constriction of the
capacitance vessels in both exercising and non
exercising parts of the body,
• pumping action of the working skeletal
muscles and the muscles of respiration
Peripheral resistance
• Sympathetic-mediated vasoconstriction increases
vascular resistance and thereby diverts blood
away from the skin, kidneys, splanchnic regions,
and inactive muscle.
• The local accumulation of metabolites relaxes the
terminal arterioles, and blood flow through the
muscle may increase 15- to 20-fold above the
resting level. This metabolic vasodilation of the
precapillary vessels in active muscles occurs very
soon after the onset of exercise.
• Overall there is a decrease in TPR
Blood pressure
• Mean blood pressure increases only slightly
because, the effect of enhanced cardiac
output is offset by an overall decrease in TPR
• The actual mean arterial pressure attained
during exercise represents a balance between
cardiac output and TPR
• Systolic pressure usually increases more than
diastolic pressure, which results in an increase
in pulse pressure . The larger pulse pressure is
primarily attributable to a greater stroke
volume
Blood pressure
1. In systemic circulation
a) Systolic blood pressure:
Increase in linearity with severity of exercise.
b) Diastolic blood pressure:
No change in mild to moderate exercise( total resistance
falls considerably due to drastic vasodil in working muscle)
Slight increase in severe exercise( due to vasoconstriction
in non working muscles and skin)
c)Mean blood pressure increases during heavy
exercise
Severe Exercise
• The compensatory mechanisms begin to fail. The heart rate
attains a maximal level of about 180 beats/min, and stroke
volume reaches a plateau.
• Sympathetic vasoconstrictor activity supersedes the
vasodilator influence on vessels of the skin such that the
rate of heat loss is decreased.
• A reduction in heat loss through cutaneous
vasoconstriction can lead to very high body temperatures
and to acute distress during severe exercise.
• Tissue pH and blood pH decrease as a result of increased
lactic acid and CO2 production. The reduced pH may be a
key factor that determines the maximal amount of exercise
that a given individual can tolerate.
• Muscle pain, a subjective feeling of exhaustion, and loss of
the will to continue determine exercise tolerance
Post exercise Recovery
• Reduced cardiac output
• Persistence of vasodilation in the muscles
• Therefore arterial pressure falls, often below
pre exercise levels, for brief periods.
• Blood pressure is then stabilized at normal
levels by the baroreceptor reflexes
Limits of Exercise Performance
• The two main factors that limit skeletal muscle
performance in humans are the rate of O2
utilization by the muscles and the O2 supply to
the muscles
Physical Training and Conditioning
• Training progressively increases Vo2max,
which reaches a plateau at the highest level of
conditioning.
• greater stroke volume, and lower peripheral
resistance
• Low resting heart rate -is caused by a higher
vagal tone and a lower sympathetic tone.
• Greater extraction of O2 from the blood
(greater arteriovenous O2 difference) by the
muscles.
• Capillary density in skeletal muscle increases..
• The number of mitochondria increases, as do
the oxidative enzymes in mitochondria. In
addition, levels of ATPase activity, myoglobin,
and enzymes involved in lipid metabolism
increase in response to physical conditioning
• Which of the following parameters is
decreased during moderate exercise?
(A) Arteriovenous O2 difference
(B) Heart rate
(C) Cardiac output
(D) Pulse pressure
(E) Total peripheral resistance (TPR)
Respiratory changes
1.Pulmonary ventilation  due to
1.Cortical stimulation
2. Increase in body temperature
3.Increased catecholamines level
4.Increased PCO2 level
5.Increased impulses to ARAS
• In exercise, there is increased ventilation and
pulmonary blood flow. The ideal VA/Q is no
longer 0.8; it is greater than 0.8.
• Thus, during exercise, ventilation increases
more than cardiac output. Also, the base–apex
flows are more uniform.
2. O2 usage/consumption
More exercise  More O2 usage
1.  in PV
2.  in O2 uptake in lungs
3.  in blood flow to tissues
4.  in PO2 & PCO2 in tissues
Measuring Maximal Oxygen Uptake Is the most
Common Method of Quantifying Dynamic Exercise
Which of the following statements about respiration in
exercise is most accurate?
A) Maximum oxygen consumption of a male marathon
runner is less than that of an untrained average male
B) Maximum oxygen consumption can be increased
about 100% by training
C) Maximum oxygen diffusing capacity of a male
marathon runner is much greater than that of an
untrained average male
D) Blood levels of oxygen and carbon dioxide are
abnormal during exercise
Which of the following sources can
produce the greatest amount of ATP per
minute over a short period of time?
A) Aerobic system
B) Phosphagen system
C) Glycogen-lactic acid system
D) Phosphocreatine system
E) Stored ATP
Which of the following athletes is able to
exercise the longest before exhaustion
occurs?
A) One on a high-fat diet
B) One on a high-carbohydrate diet
C) One on a mixed carbohydrate–fat diet
D) One on a high-protein diet
E) One on a mixed protein–fat diet
Most of the energy for strenuous exercise that
lasts for more than 5 to 10 seconds but less
than 1 to 2 minutes comes from which of the
following sources?
A) Adenosine triphosphate (ATP)
B) Anaerobic glycolysis
C) Oxidation of carbohydrates
D) Oxidation of lactic acid
E) Conversion of lactic acid into pyruvic acid