Acute Response to Exercise: Heart Rate and Factors Influencing it

Heart rate increases from about 60 beats/min to a maximum of about 200 beats/minute during intense ______.

Maximal heart rate is calculated as 220 minus the subject's ______.

Stroke Volume (SV) is the amount of blood ejected by the ventricle with each ______.

SV of normal healthy trained athletes is twice as large as that of normal ______.

The factor affecting SV includes Contractility: How hard the heart ______?

Cardiac output (Q) is the total amount of the blood ejected from one ventricle per minute and may be defined with help of formula- Q = SV X HR. HR stands for heart rate and SV stands for ______

Resting cardiac output is 4-6 l/minute. It increases with increased oxygen consumption. Maximal cardiac outputs of 40 l/min are measured in highly trained endurance athletes. Most people have maximal Qs between 20 – 30 l/min. Large cardiac output is related to ventricle size and is largely inherited. Ventricular size can be increased through training, but true increase without genetic makeup is not achievable. Arteriovenous Oxygen Difference (A-VO2 diff.) helps explain the ability of the body to increase energy output from rest to maximal exercise. The difference between arterial blood and mixed venous blood at rest is about 50 ml of O2/litre of blood. This difference increases as work is increased until the difference is 150 or 160 ml/litre of blood. In heavily worked muscles, the difference may even exceed these figures. A-VO2 diff. in the heart is fairly large even at rest (150 ml/litre). During work, the increased oxygen demand is mostly met by increased flow. Blockage of coronary arteries poses challenges due to this reason. Oxygen consumption is largely related to the ______ size.

Pre-load is the amount of blood returned to the heart to stretch the fibres. After-load is the pressure the heart works against. The heart works at its largest size when a person lies down or exercises. The smallest size is during standing. During exercise, venous return is large and the heart beats with more force, yielding the largest stroke volume that can be achieved. Large venous return is associated with the training effect of the heart. Most exercise physiologists have guidelines for intensity that ensure large stroke volumes to overload the myocardium. These programmes are more effective for cardiovascular training than programs of low intensity. The idea that the heart significantly enlarges during exercise is false. The increase in stroke volume occurs due to exercise, not due to an increase in the size of the heart, because the ventricle is only partially emptied at rest. When exercising, the heart beats with more force due to the large venous return, thus yielding the largest ______ that can be achieved.

Cardiac output (Q) is the total amount of the blood ejected from one ventricle per minute. Resting cardiac output is typically 4-6 l/minute. It increases with increased oxygen consumption. Maximal cardiac outputs of 40 l/min are measured in highly trained endurance athletes. Most individuals have maximal Qs between 20 – 30 l/min. Large cardiac output is inherited and is linked to ventricle size. Although ventricle size can be increased through training, true increase without genetic makeup is not possible. Arteriovenous Oxygen Difference (A-VO2 diff.) helps explain the body's ability to enhance energy output from rest to maximal exercise. The difference between arterial blood and mixed venous blood at rest is about 50 ml of O2/litre of blood. This difference escalates with increased work until it reaches 150 or 160 ml/litre of blood. In heavily worked muscles, the difference may surpass these figures. The body is capable of augmenting oxygen extraction from haemoglobin and doesn't solely rely on increased flow for its supply. A-VO2 diff. in the heart is quite substantial even at rest (150 ml/litre). During work, the augmented oxygen demand is largely satisfied by increased flow. Coronary artery blockage poses significant challenges due to this reason. Oxygen demand is closely related to the size of the ______.

Pre-load is the amount of blood returned to the heart to stretch the fibres. After-load is the pressure the heart works against. The heart generally operates at its largest size when a person is lying down or exercising. The smallest size is observed during standing. When exercising, the venous return is substantial, and the heart contracts with more force, resulting in the highest stroke volume that can be attained. The training effect of the heart is associated with the large venous return. Most exercise physiologists establish intensity guidelines that ensure large stroke volumes to stress the myocardium. These programs are more beneficial for cardiovascular training than low-intensity programs. The notion that the heart significantly enlarges during exercise is misconstrued. The escalation in stroke volume is a consequence of exercise, not the result of the heart's size increase, as the ventricle is only partially emptied at rest. During exercise, the heart contracts with greater force due to the substantial venous return, thereby yielding the highest ______ that can be reached.