Biology of Exercise Intensity I: Middle Secondary ISBN 978-0-9805758-8-0 © Sport Knowledge Australia

Homeostasis

During exercise At rest

Biology of Exercise Intensity I: Middle Secondary ISBN 978-0-9805758-8-0 © Sport Knowledge Australia

Effects of exercise on circulationThe following variables of the circulation system will be affected by exercise

Heart rate (b/min)The number of times that the heart beats per minute

Stroke volume (mL/beat)The volume of blood that is ejected by the heart each beat

Cardiac output (L/min)The volume of blood pumped by the heart per minute

Blood pressure (mmHg)The forces that are created on a vessel wall by the blood within it

Biology of Exercise Intensity I: Middle Secondary ISBN 978-0-9805758-8-0 © Sport Knowledge Australia

Heart rate

As exercise intensity increases, heart rate increases

Increase in beep-test level and therefore exercise intensity

Incr

ease

in h

eart

rate

(b

/min

)

Maximum heart rate 196 beats per minute

Maximum level on beep-test, level 10–6

Biology of Exercise Intensity I: Middle Secondary ISBN 978-0-9805758-8-0 © Sport Knowledge Australia

Stroke volumeAs exercise intensity increases, stroke volume increases.

In this example, stroke volume has increased from 79 mL/beat to 100 mL/beat.

Increase in time (min:sec)

Note that as time is increasing, exercise intensity is also increasing.

Incr

ease

in s

troke

vol

ume

(mL/

beat

)

Biology of Exercise Intensity I: Middle Secondary ISBN 978-0-9805758-8-0 © Sport Knowledge Australia

Cardiac output

X =stroke volume heart rate cardiac output(SV) (HR) (Q)

A typical graph showing cardiac output against level on the beep-test

As the level on the beep-test increases, the cardiac output increases to provide a greater volume of oxygen to the active muscles.

Biology of Exercise Intensity I: Middle Secondary ISBN 978-0-9805758-8-0 © Sport Knowledge Australia

Blood pressure

Two values are provided for blood pressure – systolic blood pressure (SBP) and diastolic blood pressure (DBP), therefore the graph plots two sets of values.

Systolic blood pressureThis is the pressure that is recorded when the heart contracts to eject blood from the heart and is always the highest blood pressure value.

Diastolic blood pressure This is the pressure that is recorded when the heart relaxes as the ventricles are being filled with blood and is always the lowest blood pressure value.

The graph shows that as exercise intensity increases, blood pressure also increases.

Biology of Exercise Intensity I: Middle Secondary ISBN 978-0-9805758-8-0 © Sport Knowledge Australia

Effects of exercise on respiration

Minute ventilation (L/min)The volume of blood that is taken into (or out of) the lungs each minute

Breathing rate / respiratory rate (b/min)The rate of breathing, recorded as the number of breaths per minute

Depth of breathing / tidal volume (mL)The volume of air in each breath

The following variables of the respiratory system will be affected by exercise

Biology of Exercise Intensity I: Middle Secondary ISBN 978-0-9805758-8-0 © Sport Knowledge Australia

Rate and depth of breathing

At low to moderate intensity there is an increase in depth

of breathing and then this decreases.

At low to moderate intensity there is a gradual increase in the

rate of breathing and then it increases more rapidly.

Depth of breathing or tidal volume

Rate of breathing or respiratory rate

Biology of Exercise Intensity I: Middle Secondary ISBN 978-0-9805758-8-0 © Sport Knowledge Australia

Minute ventilation

minute ventilation(VE)Xtidal volume respiratory rate

(VT) (fR) =

An exponential graphDuring the early stages of the beep-test changes are slow, but at higher work rates breathing increases very rapidly.

Biology of Exercise Intensity I: Middle Secondary ISBN 978-0-9805758-8-0 © Sport Knowledge Australia

Effects of exercise on metabolism

Heat generated (kJ/min)A by-product of energy release

Metabolic rate (kJ/min)The rate of energy turnover used in a given period of time. It is the conversion of chemical energy into mechanical and heat energy to produce ATP and to perform work.

Lactic acid (mMol)A molecule in the body produced as a by-product of anaerobic energy

The following variables of the muscular system will be affected by exercise

Biology of Exercise Intensity I: Middle Secondary ISBN 978-0-9805758-8-0 © Sport Knowledge Australia

Lactic acid

The graph of lactic acid against level on the beep-test shows a non-linear graph – a slower rate of change at lower exercise intensity followed by an accelerated increase as exercise intensity increases.

A slow rate of increase at low

levels of intensity

A rapid increase in lactic acid at high levels of intensity

Biology of Exercise Intensity I: Middle Secondary ISBN 978-0-9805758-8-0 © Sport Knowledge Australia

Metabolic rate and sweat loss

The metabolic rate is the rate of energy used in the muscles. At a low exercise intensity, metabolic rate is low. As the exercise intensity increases the muscles work harder to produce greater force, therefore the metabolic rate increases.

A by-product of aerobic respiration is heat. Heat generated increases with exercise intensity. The face goes red and the body sweats to help to reduce an increase in body temperature.