exercise physiology Flashcards
define exercise physiology
study of how human body responds to physical stress under either acute or chronic conditions
With any activity there is an increasing demand for oxygen at the tissue level
VO2 is how oxygen uptake or oxygen consumption is referred to as.
A number of changes occur to meet the increased demand for oxygen.
CV system
Increase Heart Rate – resting 60-100 (beats/min). Increases in anticipation of exercise
Increase Stroke volume - amount of blood ejected per beat from left ventricle (ml/beat) Increase Cardiac Output - amount of blood pumped by the heart in 1 minute (L/min) [CO = (SV x HR)] 5L/min. During intense exercise this can increase to 20-40L/min
blood pressure
aerobic exercise
During rhythmic steady state exercise (jogging), systolic blood pressure rapidly increases, then levels off at 140-160 for healthy men and women. As activity continues, systolic blood pressure gradually declines because the arterioles in the active muscle continue to dilate, further reducing peripheral resistance to blood flow.
Diastolic blood pressure remains relative unchanged throughout the activity period
Upon completion of a single bout of submaximal physical activity, BP temporarily falls below pre exercise levels for normotensive and hypertensive individuals from an unexplained peripheral vasodilation.
This hypotensive response to activity can last up to 12 hours.
One explanation for post exercise hypotension proposes that a considerable quantity of blood remains pooled in the visceral organs and/or skeletal muscle vascular beds during recovery. The venous pooling effect reduces central blood volume, which in turn decreases atrial filling pressure and lowers systemic arterial blood pressure.
CV system exercise resistance exercises
Resistance exercises compress the peripheral arterial vessels that supply active muscles.
This increases total peripheral resistance and reduces muscle perfusion. Muscle blood flow decreases proportionally to the percentage of maximum force capacity exerted. In an attempt to restore muscle blood flow substantial increases occur in sympathetic nervous system activity, CO an MAP.
The magnitude of the hypertensive response relates directly to the intensity of effort and quantity of muscle mass activate
For those who train regularly, the elevated blood pressure response become reduced.
CV training adaptations
Endurance athletes: lower resting heart rate and increased stroke volume
Lower resting heart rate is due to increased vagal (parasympathetic) tone and decreased sympathetic drive which slow down the heart.
The increased stroke volume is due to increased blood volume, myocardial contractility and compliance of the left ventricle.
CV system adaptations
Slower heart rate allows for increased venous return i.e. greater ventricular filling during diastole
Increase in end-diastolic volume stretches the myocardium and initiates a powerful ejection during contraction.
Training adaptations expand the blood volume and reduce resistance to blood flow in the peripheral tissues.
muscular adaptations: increased oxygen extraction capacity
Increased skeletal muscle microcirculation: increased capillary-to –fiber ratio.
Increased size and number of mitochondria (can increase by up to 40%)
Increased mygoblin: a proteinfound in musclecells, which provides oxygen to the working muscles.
acute response to exercise in health
pulmonary system Minute ventilation VE :
At rest = 5-7 l.min-1
During exercise = > 100 l.min-1
↑ Alveolar ventilation VA
VT & RR both increase. In early stages VT accounts for most of the rise in VA and VE. When VT approaches approx 60% of vital capacity further increases in ventilation come from increasing RR
↑ VE
→ maintain homeostatic balance PaCO2 + pH in blood
→ ↑delivery of O2
pulmonary system responses
EELV (end expiratory lung volume)
At rest EELV = FRC
During exercise EELV ↓ (200-400ml below FRC)
VD/VT (VD = dead space VT= tidal volume)
rest 25-35%
During exercise 5-20%
Flow rates increase during exercise
Inspiratory flow rate = 1.5 x expiratory
i.e. less time spent on inspiration
MVV = maximum voluntary ventilation
theoretical upper limit
maximum voluntary ventilation
MVV evaluates ventilator capacity with rapid deep breathing for 15 seconds.
The 15 seconds is extrapolated to the volume if the subject continued for 1 minute.
MVV averages at 25% higher than the ventilation during maximal exercise because exercise does not stress how a healthy person breathes.
exercise limitation in COPD
Dynamic hyperinflationoccurs when a breath is initiated prior to complete exhalation of the previous breath, resulting in an increase in end-expiratory lung volume and subsequent restrictions on inspiratory capacity.
The ability to increase ventilation at rest is not a direct determinant of maximal exercise ventilation in COPD. Therefore traditional methods of assessing MVV may not be appropriate for people with COPD.
The concept that it is lung volume, not airflow, that limits ventilation in exercising COPD patients is a crucial one
resp system adaptation
Swimmers have larger static lung volumes and an increased pulmonary diffusion capacity when compared with athletic controls (McKenzie 2012)
The average man has about 4 kg of skeletal muscle that can be recruited for respiration in heavy work. (McKenzie 2012)
To the competitive athlete, whether RM training will improve performance remains a controversial issue. (Mckenzie 2012)
Evidence that respiratory muscle training can increase exercise tolerance in people with COPD (Neves et al. 2014)
Breathing exercises and inspiratory muscle training improve functional capacity in heart failure patients (Cahalin and Arena 2015)
energy system
Energy for exercise does no simply result from activation of a series of energy systems that “switch on” and “switch off” but rather from a smooth blending with considerable overlap of one mode of transfer to another
muscle fibre types in COPD
Peripheral skeletal muscle dysfunction is a well recognised disabling feature of COPD.
Reduced muscle strength and reduced endurance.
Loss of muscle strength can largely be attributed to the loss of muscle bulk which, in turn, is caused by muscle fibre atrophy.
Loss of muscle mass does not account for the reduced endurance.
Shift from type I to II (accompanied by reduced activities of enzymes involved in oxidative energy metabolism)
acute response to exercise summary
Increased HR
Increased stroke volume
Increased BP
Redistribution of blood to muscle and under perfused lung parenchyma (vasodilation and vasoconstriction)
Increased minute ventilation (Increased RR and Tidal)
Reduced VD/VT
Systolic blood pressure decreases by 6mmHg and diastolic blood pressure by 10mmHg with aerobic training in previously sedentary men and women regardless of age
