PDHPE: Core 2 – Body in Motion

IMMEDIATE PHYSIOLOGICAL RESPONSES TO TRAINING

Heart Rate (HR)• An average resting heart rate is 72 beats/minute. Resting heart rates (RHR) of 30 beats/ minute or less is not uncommon in elite athletes.•HR will rise sharply from an inactive state to an active state.• At the cessation of exercise there will be a quick decline in HR. This decline will be rapid in a fit person.

Stroke Volume (SV)• SV is the amount of blood ejected by the left ventricle of the heart during a contraction. SV is measured in mL/beat.• SV increases during exercise with most of the increase being when the person moves from rest to moderate exercise. As intensity increases to a high level there is less change in SV.• A sedentary person will maintain a SV of 60 – 80 Mls/beat while a well trained athlete will reach 160mls/beat at submaximal loads.•WHAT WILL BE THE RESULT OF THIS?• Important to remember that while our HR steadily increases, our SV levels off at a moderate level of exercise. SEE TABLE ON PG. 193

Cardiac Output (CO)• CO is the amount of blood pumped by the heart /minute.• CO = HR X SV• CO for both trained and untrained people at rest is approximately 5L/minute.• How can this be if the trained athletes have a lower resting heart rate?• As we move from rest to exercise the muscles being used demand a greater supply of oxygen. SEE pg. 194

Lactate Levels (LL)• Lactate is the chemical formed during the breakdown of CHO in the absence of sufficient oxygen.• It is measured in millimoles/litre of blood.•With each molecule of Lactate formed, 1 HYDROGEN ION is also formed. It is this ion that increases the acidity level of the blood and subsequently makes it difficult for muscles to perform.

Ventilation Rate (VR)• VR has two phases inspiration and expiration.•Minute Ventilation is the measurement of air breathed in one minute – APPROX. 6L• At rest we breathe about 12 breathes/min = 500 mls/breath.•Our breathing increases even before exercise begins. Our body anticipates the need for more oxygen and thus our breathing becomes more rapid.• At the end of exercise our breathing remains rapid for a short period and gradually returns to normal.