Acute effect of steady level exerise on H.R,B.P,BLOOD FLOW,R.R,ACID BASE BALANCE,TEMPERATURE,FLUID ELECTROLYTR BALANCE

Acute effect of steady level exercise on H.R,B.P,BLOOD FLOW,R.R,ACID BASE BALANCE,TEMPERATURE,FLUID ELECTROLYTE BALANCE

Dr.NIKITA MANJANWAL(MPT Orthopedics))

CONTENTSIntroductionAerobic exercisePost exercise oxygen consumptionEffect on heart rateEffect on blood flowEffect on blood pressureEffect on respiratory rateEffect on temperatureEffect on acid base balance.

INTRODUCTION:When we begin to study exercise physiology , we must first learn how body respond to single bout of exercise which is called acute response.

Many factors can alter bodys acute responses to a bout of exercise.

As the body shifts from rest to exercise the energy need is increased.

Steady level is a state at which O2 consumption requires several minutes at which the aerobic process are fully functional, but bodys oxygen requirement increases immediately when exercise begins.

A state obtained in moderate muscular exercise when removal of lactic acid by oxidation keeps pace with its production.

Pertaining to the time period during which a physiological functions remains constant is called steady state.

Aerobic exercise:Aerobic exercise is augmentation of energy utilization of muscle by means of an exercise program.

Training produce cardiovascular or muscular adaptations which is reflected in an individuals endurance.

A carefully planned exercise program results in higher level of fitness.

There are 3 components of exercise program 1) a warm up period 2) aerobic exercise period 3) cool down period

Warm up period:A time lag exist between onset of physical activity and bodily adjustments needed to meet the physical requirements.

There is increase in muscle temperature. Extraction of hemoglobin is greater at higher muscle temperature.

Dilatation of previously constricted capillaries with increase in circulation & minimizing lactic acid formation

Purpose: To enhance the numerous adjustments that must take place before physical activity.

To decrease the susceptibility of musculoskeletal system injury.

To prevent occurrence of ischemic (ECG) changes and arrhythmias.

Aerobic exercise period:This exercise period is conditioning part of exercise program.

Exercise must be in patients tolerance , above threshold level for adaptation to occur and below the level of exercise that evokes clinical symptoms.

The intensity be great enough to stimulate an increase in stroke volume , cardiac output ,and to enhance local circulation.

These are generally submaximal, repetitive and rhythmic.

Methods of training:

Cool down period:The purpose is to:

1) Prevent pooling of blood in extremities by continuing to use the muscles to maintain venous return.

2) Prevent fainting by increasing the return of blood to heart and brain as cardiac output and venous return decreases.

3) Enhance the recovery period with oxidation of metabolic waste.

4) To prevent MI , arrhythmias etc.

Post exercise oxygen consumptionOxygen consumption requires several minutes to reach steady state, bodys oxygen requirement increase immediately the moment exercise begins.

Because O2 needs and its supply differ during transition from rest to exercise..there occurs OXYGEN DEFICIT.

CALCULATIONS:Oxygen Deficit= (oxygen requirement- oxygen consumed).

Despite insufficient oxygen, muscle still generate the ATP needed through anaerobic pathway(ATP-PC system , glycolysis).

After exercise during initial minutes even though muscles are no longer working..demand for oxygen does not immediately decreases.

Instead oxygen consumption remains elevated temporarily.

This consumption , which exceeds usually required oxygen when at rest is referred as OXYGEN DEBT.

The common terminology used is excess postexercise oxygen consumption [EPOC].

The EPOC is the volume of oxygen consumed above normally consumed at rest.

Recent studies have given a classical explanation about EPOC.

During initial phase some oxygen is borrowed from oxygen stores(hemoglobin and myoglobin).

That oxygen must be replenished during recovery.

Also respiration remains temporarily elevated following exercise ..in an effort to clear CO2 that has accumulated in tissues as a by product.

Also body temperature is increased which keeps metabolic and respiratory level high hence requiring more oxygen.

FACTORS FOR EPOC:

EFFECTS:Steady state exercise have mainly effect on following parameters:

Heart rate:

Studies have monitored, O2 consumption of heart has shown that heart rate both at rest and during exercise is good indicator of how hard heart is working.

As active muscle require more oxygen than resting muscle..heart O2 consumption and amount of work it does is directly related to its contraction rate.

Measuring involves taking persons pulse, usually radial or carotid artery sites.

Resting heart Rate: It averages from 60-80beats/min. In highly conditioned athletes RHR ranges from 28-40 beats/min.

Heart rate during exercise: When we begin exercise HR increases directly in proportion to increase in exercise intensity until you are near the point of exhaustion.

At this point your HR begins to level-off. This indicates you are approaching maximum HR. HRmax: 220-(AGE IN YEARS) HRmax: 208-(0.7* AGE IN YEARS)

When the rate of work is held constant at submaximal level of exercise , HR increases rapidly until it reaches a plateau..this plateau is the steady-state heart rate.

It is the optimal heart rate for meeting the circulatory demands at specific rate of work.

Drift: when exercise is performed at constant rate over prolonged period of time, particularly under heat stress, HR tends to drift upwards instead of maintaining its steady-state value.

Here stroke-volume(SV) gradually decreases and HR increases.

With moderate exercise heart rate increases to 140 beats/min.

Even the thought of exercise increases rate.

Increased heart rate is also mainly because of vagal withdrawal.

A= ANTICIPATORY RISE

B= SHARP RISE

D= STEADY STATE

E= RAPID DECLINE

F= SLOWER RECOVERY

Blood Pressure:

When examining blood pressure during exercise , systolic and diastolic must be distinguished because they show different changes.

With exercise systolic B.P starts out at 120mmHG and exceed up to 200mmHG.

Increased systolic pressure results from increased cardiac output that accompanies increased rate of work.

Also blood pressure determines how much fluid leaves the capillaries, entering the tissues and carrying needed supplies. It facilitates delivery process.

Diastolic pressure changes little, regardless of intensity. It represents pressure in arteries when at rest.

Blood pressure reaches a steady state during submaximal steady state exercise.

If steady state is prolonged , the systolic pressure might start to decrease gradually, but diastolic pressure remains constant.

This decrease in systolic pressure, if it occurs in normal response reflect arterial dilation in active muscles

B.P= CARDIAC OUTPUT * PERIPHERAL RESISTANCE

Blood Flow

We know that active muscle needs more oxygen and nutrients..to meet these blood must be brought into these muscles during exercise.

During exercise metabolic rate of muscle tissue increases and begins to accumulate.

At resting condition blood supply is 3-4ml/100 grams of muscle per minute.

It increases up to 60-80ml in moderate steady state exercise.

With steady state exercise the muscles become better trained and cardiovascular system gets adapts to increase blood flow.

Through the action of sympathetic nervous system, blood is redirected away from areas where it not essential(digestive system , kidneys) to areas which is active during exercise.

Sympathetic SympatheticStimulation to Stimulation to Constrictor fiber Vasodilator fiberDecreases Increases

additional blood flows

The metabolic rate of muscle tissue increases , as a result more metabolic waste product begins to accumulate.

Increased metabolism causes increase in acidity , CO2 , temperature in muscles. These local changes trigger vasodilatation increasing blood flow.

Respiratory rate:

The onset of physical exercise is accompanied by two phase increase in ventilation

As exercise begins , but before any chemical stimulation occurs , the motor cortex becomes more active and transmit stimulatory impulses to inspiratory center , which respond by increasing respiration.

Proprioceptive feedback from active skeletal muscle and joints provide additional input about the movement and respiratory center can adjust its activity accordingly.

As exercise progresses , increased metabolism in muscles generates more heat , CO2 , and H+.

This is sensed by chemoreceptors which in turn stimulate the respiratory center, increasing depth and rate of respiration.

Some data suggest that receptors in right ventricle of heart sends information to the inspiratory center to increase the cardiac output , which can stimulate breathing during early minutes of exercise

During mild steady state exercise ventilation appears to match the rate of energy metabolism.

The ratio between volume of air ventilated(VE) and amount of oxygen consumed by tissues(VO2) in given amount of time is called ventilatory equivalent for oxygen

This ratio relatively remain constant over steady state exercise..which means breathing is properly match to bodys need for oxygen.

At rest it ranges from 23-28L of air per liter of oxygen consumed.

There occurs a little change during mild exercise .

Acid-Base Balance

Blood pH can change from moderate to high intensity exercise.

Muscular activity results in production and accumulation of lactate and H+ which can impair energy production and reduce contractile force.

Maintaining homeostatic balance in blood PO2 , PCO2 and pH requires high degree of coordination between respiratory and circulatory systems.

Chlorine is an important mineral in maintaining blood acid-base balance.

Body fluids have more bases(bicarbonate, phosphates , proteins) than acids under resting condition that results in pH range from 7.1 to 7.4 in muscles.

Even hemoglobin acts as a buffer.

Bodys regulation of acid-base involves more control of respiration.

Acid such as lactic acid and carbonic acid release H+ in body.

To minimize effect of free H+, the blood and muscles contain base substance to neutralize its effect.

H+ + buffer H-buffer.

Blood pH can change significantly , becoming more acidic from slightly alkaline resting value of 7.4 down to 7.0 .

The decrease in pH results from increased blood lactate accumulation.

The pH is kept within relatively narrow range by :

CO2- TRANSPORTMajority of CO2 is carried in form of bicarbonate ions.

CO2 + H2O H2CO3 H+ + HCO3- (carbonic (bicarbonate) acid)

H+ combines with hemoglobin and this binding triggers Bohrs effect.

Hence formation of bicarbonate enhance oxygen unloading and hemoglobin act as a buffer preventing any acidification of blood.

When this blood enters the lungs where PCO2 is lower H+ and bicarbonates rejoin to form carbonic acid which then split in Co2 and H2O.

H+ + HCO3- H2CO3 CO2+H2O

Temperature:

Humans are homoeothermic , which means internal body temperature is kept nearly constant.

The normal range..of 36.1 to 37.8 degree Celsius is deviated during prolonged heavy exercise , illness or extreme condition of heat or cold.

Transfer of body heat:During exercise metabolic needs are increased hence heat is generated..to maintain internal body temperature , heat produced in your body must have access to outside world.

It takes place through following process:

Evaporation:It is the primary process of heat dissipation during exercise.

80% of heat loss occurs through evaporation when you are physically active.

As body temperature increases sweat production increases.

As sweat reaches the skin it is converted from a liquid state to a vapor by heat from skin.

Mechanism %loss Exercise Kcal/minConduction152.2Radiation50.8Evaporation8012.0Total10015.0

COLDHere we define cold stress environment condition that causes a loss of body heat that threatens homeostasis.

The hypothalamus has a temperature set at 37*C.

A decrease in skin or blood temperature provide feedback to activate mechanism to conserve body heat.

Methods:

Fluid-Electrolyte Balance:

Water constitute about 50%-60% of total body weight.

It is referred to as intracellular fluid.

While extracellular fluid include water+blood plasma , lymph, and some other fluids.

Role of water in exercise:

Water balance:Water loss accelerates during exercise..and it depends on the formation and evaporation of sweat.

As bodys temperature increases, sweating increase in an effort to prevent overheating.

Water loss occurs from 4 sources:

Evaporation from skinEvaporation from respiratory tractExcretion from kidneyExcretion from large intestine

Water is also produced during exercise because of oxidative metabolism.

The amount of sweat produced during exercise depends on *environment,temperature,humidity *body size *metabolic rate

Water at same time is produced by oxidative metabolism , unfortunately the amount produced has small impact on dehydration , water loss etc

Example: a 70kg person metabolize about 245g of carbohydrate , this would produce 636 g of water , during this time sweat loss could exceed 1500ml of water.

Electrolyte balance:Normal body function depends on balance between water and electrolytes.

When large amount of water is lost during exercise balance between water and electrolytes is disrupted quickly.

Human sweat is infiltrate of blood plasma, so it contains.

* Sodium(Na)* Chloride(Cl)* Potassium(K)* Magnesium(Mg)* Calcium(Ca)

At elevated rates of sweating during steady state exercise, loss of sweat would lower bodys sodium and chloride content by 5% to 7%.

Sodium and chloride are predominant ions in sweat and blood.

To clear waste from blood and regulating water level kidneys also regulate bodys electrolyte content.

Urine production is major source.

Bodys water loss increase during exercise; urine production rate decreases in an effort to conserve water.

The function of sodium is to maintain osmotic pressure ; nerve and muscle function.

Hence deficiency would cause nausea, vomiting, exhaustion and dizziness.

Chloride imbalance will cause acid-base imbalance in body.

Electrolytes loss during exercise occurs primarily with from water loss during sweating.

References:WilmoreKisnerMccardleSembulingam