#9 Exercise 1, 2, + 3

Exercise and Health

1. Enhanced sense of well-being. 2. Retards loss of work capacity, function and strength that occur with age—aging or deconditioning?? 3. Generally, any given physical activity represents a lower % of the maximum that can be done and, therefore, is less stressful. 4. Greater cardiac efficiency: An aerobically trained person accomplishes any given cardiac output with a lower HR and higher SV thus diminishing the energy demands of the heart at any given work rate. 5. Helps prevent and/or reverse risk factors associated with many chronic diseases prevalent in the general population especially CHD.

Benefits of Regular PA/Exercise

Aerobic capacity (cardiorespiratory fitness, CRF) has inverse relationship with risk of premature death from all causes and specifically CVD, and higher levels of CRF associated with higher levels of habitual physical activity, which in turn are associated with health benefits.

BL Concentration for Trained & Untrained Individuals at Different Levels of PA

BL does not accumulate at all levels of PA. Light-moderate (<50% VO2max), BL formation = lactate disappearance. Anaerobic ATP important as exercise intensity increases beyond anaerobic threshold (AT) as evidenced by onset of muscle & thus BL formation. Untrained individual, AT can be at 50% of VO2max while highly trained individual occur at 85-90% VO2max

Blood Lactate Concentration for Trained and Untrained at Different Exercise Levels

BL threshold occurs at higher % of athlete's aerobic capacity Occurs at a higher percentage of the trained aerobic capacity compared to the untrained. Trained persons perform steady-rate aerobic exercise at 80 to 90% of maximum aerobic capacity due to: Specific genetic endowment—muscle fiber type, muscle BF responsiveness Specific local training adaptations that favor less lactate production More rapid rate of lactate removal at any exercise intensity

Exercise and Obesity

Benefits of Adding Exercise to Dietary Restriction for Weight Loss Role of Exercise: Expends kcals during and after exercise Maintains LBM & so prevents decrease in BMR w/weight loss Although in short term, caloric expenditure during exercise is not great relative to energy potential of adipose tissue store (-3,500 kcals/lb), chronic PA in long term has a plethora of benefits BEYOND weight loss & long term weight loss through diet & exercise has less attrition although it is still quite high.

Fat and Energy Content of the Body

Blood FFA—mobilization stimulated by increased circulating levels of epi, norepi, GH, glucagon and cortisol. Inhibited by insulin & lactate. Major substrate esp. at low exercise intensity Contribution to total energy supply decreases as exercise intensity increases. Blood Triglycerides—5 to 15% energy provision esp. important in high oxidative muscle fibers. Muscle Triglycerides—significant depletion in high oxidative muscle fibers w/prolonged exercise.

Effect of Exercise on Blood Pressure

Blood pressure response depends on factors such as: 1) muscle mass being used in the exercise 2) whether exercise is static or dynamic 3) body position 4) temperature among others. In general CO increases more than TPR decreases so MAP rises. This increases is due to an increase in SBP rather than DBP which is expected to remain near resting levels during exercise in a healthy individual.

Exercise and Cardiovascular Disease

CV risk factors: smoking hyperlipidemia hypertension sedentary behavior diabetes obesity

Cardiac Output

Can vary considerably during rest. Influencing factors include emotional conditions that alter cortical outflow to cardio-accelerator nerves and nerves that modulate arterial resistance vessels. 5 L/min = average cardiac output for males average HR = 70 b/min, average SV = 71 mL/b 4 L/min = average cardiac output for females average HR = of 70 b/min, average SV = 50 to 60 mL/b

Determining Caloric Expenditure During Exercise

Total ATP turnover can't be measured directly in an exercising human so valid estimate of energy cost is usually made by measuring O2 consumed during exercise. This assumes that all energy is being derived aerobically. MET=Multiples of Resting Metabolic Rate (RMR) Exercise at 2 METs requires twice the resting metabolism, 3 METs equals three times rest, etc. To consider variations in body size, express METs in VO2 per unit body mass. ox consumption as enrgy expenditure - MET Respiratory quoteint - Vco2/Vo2

Fat Dynamics During Exercise

When exercising at similar work rates, exercising skeletal muscle in trained individuals takes up and oxidizes more free fatty acids that have been mobilized from adipose tissue to support ATP synthesis. This increased fat use is, in part, due to the increased circulating levels of FFA's. The higher lactate levels in untrained individuals inhibit FFA release from adipose tissue. This increased capacity to utilize energy from fat conserves crucial muscle and liver glycogen stores and can contribute to increased endurance

Blood Pressure Response to Resistance Exercise

When leg work is performed, vasodilation occurs in a large active muscle group and vasoconstriction occurs in a relatively small inactive muscle mass. When arm work is performed eliciting the same VO2, the blood pressure response is higher than with leg work. TPR increases more during arm exercise so MAP is higher for the same VO2. Exercise with arms produces higher SBP and DBP than leg exercise performed at a given percentage of VO2max in each exercise mode. Individuals with cardiovascular dysfunction should rhythmically exercise relatively large muscle groups in contrast to exercise that engages a limited muscle mass.

Energy Released from Protein

When used for energy, amino acids most be converted—i.e. "deamination"—nitrogen removal. Protein catabolism yields waste products that are eliminated in urine, therefore, protein catabolism requires an increase in body's water needs (facilitates water loss)—dehydration or hot environment. Excess dietary protein accumulates as fat—amino acids after deamination convert to pyruvate.

CHANGES IN STRENGTH WITH RESISTANCE TRAINING

With resistance training, initial strength gains are primarily due to neural mechanisms and later gains due to hypertrophy (increased actin and myosin content). Genetic limitations can be stretched by the use of anabolic steroids. Hyperplasia is not a usual mechanism by which an increase in strength occurs in response to strength training. Atrophy and loss of strength occurs with disuse and can be alarmingly rapid especially with immobilization or complete bed rest.

DOES THE CV SYSTEM LIMIT VO2max?

• In most of us, VO2max appears to be limited by left ventricular output (cardiac output) • If the heart could deliver more oxygen to exercising muscle, muscle would use it • "Blood doping" experiments support this contention Exceptions—LV dysfunction/low EF; CHF; cardiomyopathy; valve stenosis

Stronger muscles can:

• generate more force • generate more power (F x D/T) • do more work • for a given submaximal effort, do all of the above at a lower motor unit recruitment level—therefore reducing fatigue with repeated contractions (muscle strength training). Favorably impacting: • balance and fall prevention • ability to perform ADL's • performance in most athletic endeavors • bone mineral density THE HUMAN BODY NEEDS MUSCLE TO MOVE—BODIES DESIGNED FOR MOVEMENT

Whole Body Arteriovenous Oxygen Difference at Rest and During Intense Aerobic Exercise

•An active muscle's uncompromising capacity to use available O2 in its large blood flow supports position that O2 supply, not muscle oxygen use, limits aerobic capacity. Exceptions is highly deconditioned individuals---such as severe bedrest; COPD; dialysis patients

Energy for Skeletal Muscle Contraction

1. Immediate Energy: ATP-PCr •Each kg skeletal muscle contains 3-8 mmol ATP (enough to power 2-3s maximal exercise) •PCr-- 4-5X more PCr then ATP (enough to power up to 10s maximal exercise) - do not need oxygen 2. Short-term Glycolytic (Lactate Forming) •Muscle glycogen breakdown via rapid anaerobic glycolysis w/lactate formation that allows ATP to form rapidly without O2. Rapid & considerable accumulations of BL occur during large muscle, maximal exercise between 60-180s. Greatest capacity of anaerobic mechanisms. 3. Long-term Energy: Aerobic System (can use CHO, fatty acid & amino acid oxidation) •Results in pyruvate-to-acetyl-CoA-to-citric acid cycle and electron transport of the remaining energy within the original glucose molecule. Slower to turn on & less powerful than anaerobic mechanisms but much greater capacity to sustain prolonged bouts of muscle contraction.

Factors that Affect VO2max

1. Mode of Activity—Concept of specificity. TreadMill usually produces highest values among diverse activity modes. Arm crank is about 70% TM & bike-5 to 25% lower then TM. 2. Heredity—genetic effect about 20-30% VO2max, 50% Hrmax, 70% physical work capacity. 3. State of Training—vary 5-20% 4. Gender—women 15-30% lower values than male counterparts. Elite females 15-20% lower than male elites—mostly due to increased %body fat in females & lower hemoglobin 5. Body composition—variations in body mass can explain up to 70% differences in VO2max scores among individuals 6. Age—VO2max declines steadily after 25-30 years at about 1% per year however strong evidence that habitual exercise & intensity exert greater influence on aerobic capacity than chronological age per se.

Current Exercise Recommendations for Health & QOL

150-300 minutes of moderately intense exercise, 75-150 minutes of vigorous exercise weekly or equivalent combination-------preferably spread out during the week. 60 minutes of physical activity for children and teens daily (Play 60 initiative). Activity may be broken down into shorter activity sessions during the day. Any activity better then none. 200-250 minutes/week when weight loss is a major goal. Moderate intensity can be 50%VO2 max for healthy adults or as low as 40% VO2 max in patients with low fitness. Include moderately intense resistance training for major muscle groups 2X per week. Recognize the dose-response relation between physical activity and health. Older adults—include flexibility exercise & neuromotor exercise. There are similar recommendations for all adults regardless of health status (there are special considerations based on specific diagnoses, however, the guidelines are the goal). It is estimated that only about 20% of Americans are currently meeting these guidelines—study demographics impact results. Even more concerning is that in certain demographics this percentage is even lower. Exercise spread out over multiple days rather then "weekend warrior" demonstrated to have better health benefits especially for middle-age & older adults

Exercise and Obesity

2/3 adults in US are overweight/obese. Estimated 140 million Americans are either overweight or obese. Overweight/Obese associated w/CHD, HTN, T2DM, Dyslipidemia, Metabolic Syndrome (and a plethora of other negative health outcomes). Obesity is second leading cause of preventable deaths in the United States. In the last 30 years obesity has tripled among American children ages 6 to 11 to nearly 15% and more than 17% in youth ages 2 to 19. Overweight children and adolescents, regardless of final body weight as adults, exhibit higher risk of illnesses as adults than counterparts of normal weight.

Risks Associated With A Sedentary Lifestyle

A sedentary lifestyle is an INDEPENDENT RISK factor for cardiovascular disease. Abnormal glucose metabolism leading to Type 2 DM Weight gain leading to obesity Development of metabolic syndrome Development of CVD Increased CVD mortality All cause mortality Increase risk of Colon, Lung & Endometrial Cancers Women >30 years old, sedentary lifestyle has been demonstrated to be a stronger RF for CVD then smoking. The bad news----Individuals are engaged in TOO MUCH SEDENTARY ACTIVITY and it is contributing to poor health. The good news---even small breaks in activity behavior can reverse negative metabolic outcomes. The bad news---Physical activity does not guarantee protection if individuals are engaged in long periods of sedentary activity.

RER and Exercise Intensity

AEROBICALLY PROVIDED ATP The relative proportion of fat and CHO oxidized can be estimated from the measured respiratory exchange ratio (RER). The RER value during exercise depends on 1) exercise intensity, 2) prior dietary history, 3) exercise duration and 4) fitness level. The RER increases as VO2 increases. Under steady state conditions this reflects increased CHO use. At high intensities (or any non steady state conditions) the RER also indicates that hyperventilation is occurring.

ACSM Recommendations for Weight Loss

Aerobic Exercise: 5 or more days/week at moderate to vigorous intensity for 30 min/day (150 min/wk) progressing to 60 min/day or more (250-300 min/wk). Continuous, rhythmic activities using large muscle groups—walking, cycling, swimming. Resistance Exercise: 2-3 days/week, 60-70% 1-RM with progressive increase; 2-4 sets of 8-12 reps for each of major muscle groups. - burns calories at rest Flexibility: 2-3 days/week stretch to point of tightness; hold static stretch for 10-30s; 2-4 reps of each exercise; can use static, dynamic or PNF stretching.

Endurance performance continues to increase with prolonged training despite a leveling of VO2max

Aerobically trained muscle displays an increased mitochondrial content and, thus, an increased capacity to synthesize ATP aerobically especially from free fatty acids. • All muscle fiber types can increase mitochondrial content if used and stressed appropriately during the training program—especially Type I Slow Twitch & Type IIa FOG • The increase in mitochondrial content is associated with a marked improvement in endurance capacity (the ability to work at a high percent of VO2max for a prolonged period of time) and a greater reliance on fat as a metabolic fuel at any given work rate. With long term training, VO2max may not further increase but the ability to sustain a progressively higher % of VO2max does, resulting in improved endurance performance.

The rate of glycogen utilization by skeletal muscle increases exponentially as VO2 increases.

Aerobically trained muscle exhibits greater capacity to oxidize CHO than untrained muscle. During submaximal effort, endurance trained muscle relies less on muscle glycogen & BG as fuel sources & uses more lipids. Desirable training adaptation conserves body's limited glycogen reserves.

BP: Graded Aerobic Exercise (Increasing Intensity)

After an initial rapid rise from resting level, SBP increases linearly with exercise intensity. DPB remains stable or decreases slightly at higher exercise levels. SBP may increase to 200 mm Hg or higher in healthy, fit individuals during maximum exercise (despite reduced TPR). ◦This blood pressure most likely reflects the heart's large cardiac output during maximal exercise by individuals with high aerobic capacity. - need venous return now

Recommendations for Weight Loss

Aim for a 500-1000 Kcal/day deficit - 250-500 Kcals decreased intake - 250 -500 Kcals increased activity To achieve 1-2# weight loss/week. • Obese will need greater calorie restriction and greater calorie expenditure. • Avoid sudden, large decreases in caloric intake. •Weight loss of 3-5% demonstrated to result in clinically meaningful reduction in CVD RF including TG, blood glucose, HbA1c & risk of developing T2DM. • Include resistance exercises to maintain LBM. • Expect pattern of fat loss to mirror pattern of fat gain. Spot reducing does not exist! • Remember small things add up over time. •Set short-and long-term goals of 3-10% BW loss over 3-6 months. •Target changing eating & exercise behaviors because both result in better long-term wt. loss & maintenance.

Arterial blood glucose is well maintained during exercise

Arterial blood glucose is well maintained during exercise unless the exercise is performed for a long period of time (hours) without supplemental CHO intake. Under these circumstances, hypoglycemia can occur and result in fatigue or an inability to continue the exercise. Muscle glycogen: glycogenolysis rate increases exponentially as work rate increases severe local muscle fatigue is apparent when muscles are depleted of their glycogen Glucose uptake by skeletal muscle increases during exercise despite decreased blood insulin due to enhanced insulin sensitivity—what are implications for both T1DM & T2DM? - overweight

Regular physical activity is inversely associated with:

Cardiovascular disease: • coronary artery disease • stroke • peripheral vascular disease CV disease risk factors: • hypertension • high TG and low HDL cholesterol • platelet adhesiveness and aggregation • insulin needs and glucose intolerance Some cancers: • colon • reproductive (especially female) Overweight and obesity Type 2 diabetes mellitus Metabolic Syndrome Osteoporosis/Osteoporosis/Hip Fx Anxiety and depression All Cause mortality Functional Health/Falls Dementia- generally/Alzheimer's-specifically

Benefits of Regular PA/Exercise

Decreased Morbidity & Mortality Primary prevention--prevent initial occurrence. Higher activity/fitness associated with lower death rates from CAD. Higher activity/fitness associated with lower incidence rates for CVD, CAD, stroke, Type II DM, metabolic syndrome, osteoporotic fx, breast & colon Ca, and gallbladder disease. Secondary prevention—interventions after cardiac event to prevent another cardiac event. CR reduce CV and all-cause mortality post MI.

Changes in Respiratory Parameters w/increasing VO2

During a GXT, total minute ventilation (VE) increases linearly to the point of the ventilatory threshold then increases out of proportion to VO2 at high work intensities. The reasons for this linear response phase are many and complex but most likely do NOT involve stimulation of arterial receptors by changes in arterial PO2, PCO2 or H+. The hyperventilation at higher intensities is costly but useful since hyperventilation decreases alveolar and consequently arterial PCO2 thus helping to manage arterial pH (which decreases none-the-less due to lactic acidosis). Note that alveolar and therefore arterial PO2 is well maintained in a healthy individual even during heavy exercise. Other ventilatory responses such as an increase in the V/Q ratio in most alveoli also contributes to effective gas exchange during exercise. The ventilatory threshold (as % of VO2max) increases with increasing levels of aerobic fitness.

Energy Yield from CHO, Fat & Protein

Energy yield per liter of O2 is slightly greater when CHO is substrate. Fat is very efficient storage form of energy in terms of Kcals/g Calculate the caloric content in adipose tissue of a 70kg male who is 25% body fat? 17.5 kg adipose tissue X ~9kcal/gm=157,500 kcals

Distribution of Cardiac Output During Rest and Strenuous Exercise

Environmental stress, level of fatigue and PA mode & intensity affect regional blood flow but major portion of CO diverts to active muscle. Kidney & liver can tolerate substantial reduction in BF, however, heart & brain cannot and their BF increases. The higher CO during exercise is distributed differently than at rest. Arterioles controlling blood flow to active skeletal muscle dilate so that these tissues may receive up to 80-85% of the total CO. Blood flow to inactive muscles and the splanchnic area decreases due to vasoconstriction in those arteriolar beds.

Examples of Portable and Bag Spirometry

Inspired and expired air is passed through a flow meter and O2 and CO2 gas analyzers. All measures of VO2 and VCO2 are computer corrected and reported as volumes occupied at STPD.

Examples of appropriate activities include

Examples of appropriate activities include, walking briskly, swimming cycling, running etc. If weight loss is primary goal, then increase increase kcal burned (usually duration first then intensity). Dose-response relationship indicating additional health benefits with 300 min/wk or more of moderate intensity aerobic activity; 150 min/wk or more of vigorous intensity aerobic activity; or combination of both. Use of the RPE scale (exertion level of 11-16 on the Borg 15 point scale) is common especially when more objective measures of exercise intensity are not possible or unreliable. • the overload principle means that, in order to improve, body systems must be exposed to sufficient stress. As training adaptations occur the exercise stress must increase in order to continue to provide an adequate stimulus for adaptation. Demonstrable cardiopulmonary adaptations are normally seen in a few weeks. However, several to 6 months may be needed to achieve a meaningful fitness level. NOTE: It is much easier to maintain a satisfying level of fitness than to develop it from a poor fitness state.

Fast-Twitch Fibers (Type II)

Exhibit four characteristics: 1.High capability for transmission of action potentials. 2.High myosin ATPase activity. 3.Rapid Ca2+ release & uptake by efficient sarcoplasmic reticulum. 4.High rate of cross bridge turnover. These factors contribute to fiber's rapid energy generation for quick, powerful muscle actions. Larger motor neuron but fatigue quicker, fewer mitochondria, low myoglobin. Quick, powerful muscle actions. Rely on well-developed, short-term glycolytic system for energy transfer. Activation predominates in anaerobic-type sprint activities & other forceful muscle actions that rely entirely on anaerobic energy transfer. Activation plays important role in stop-and-go or change-of-pace sports such as basketball, soccer, lacrosse, or field hockey.

Heart Rate to Estimate Energy Expenditure

For each individual (regardless of fitness level), heart rate (HR) and VO2 relate linearly over range of exercise intensities to about 80% of maximum. ◦Exercise HR can provide an estimate of VO2 & thus energy expenditure during aerobic exercise. ◦Many factors independent of & in addition to exercise limit use of exercise HR to estimate energy expenditure. ◦environmental temperature, emotions, food intake, body position, muscle groups used, continuous vs. discontinuous mode, static or dynamic movements.

Slow-Twitch Fibers (Type I)

Generate energy for ATP resynthesis through aerobic system of energy transfer Four distinguishing characteristics: 1.Low myosin ATPase activity. 2.Slow calcium handling ability & shortening speed. 3.Less well-developed glycolytic capacity than fast-twitch fibers. 4.Large & numerous mitochondria. Smaller motor neuron, produce less force, high oxidative capacity, high concentration of mitochondria & myoglobin so fatigue resistant.

HR & SV Response to Exercise

HR increases fairly linearly with increasing VO2. Sympathetic input to the SA node increases (and parasympathetic input decreases) commensurate with the increasing physical stress of the exercise. Stroke volume increases initially at mild to moderate exercise intensities and then levels off or may even decline slightly at higher work rates. SV increases as venous return and contractility of the heart are stimulated. Why does SV fail to increase further during heavy exercise?? - difference in stroke volume with cardiovascular training

Vision of Exercise Is Medicine

Have healthcare providers (regardless of specialty) assess & record every patient's level of physical activity at every clinic visit. (consider this a vital sign). Determine if the patient is meeting the CDC & WHO National Physical Activity Guidelines. Provide patients with brief counseling to help him/her meet the guidelines and to conclude each visit with an exercise "prescription' and/or referral to a certified health fitness professional or allied health professional for further counseling and support if indicated. Be a Role Model for your patients. One of the most important decisions patients will make regarding their overall health is to incorporate regular physical activity (PA) into their lifestyles. Healthcare provider encouragement has been demonstrated to be one of the greatest influences on this decision. ROLE OF THE PHYSICIAN • As a role model you will not only look like you practice what you preach but you will sound more convincing to patients if you have convinced yourself. • Physical activity habits are as important a health determinant as smoking, alcohol consumption or the practice of risky behaviors. • Patients are often on information overload when talking to a physician so written information which can be reviewed more leisurely is beneficial. • Follow up in subsequent meetings regarding the adherence to a program of regular physical activity. • Good programs, knowledgeable trainers, cost and convenience are all factors when evaluating community resources. Remember: research has shown that the single most compelling reason that motivates individuals to start and adhere to an exercise program is a strong recommendation from their physician!

Cardiovascular Adjustments to Upper-Body Exercise

Higher VO2 during arm exercise at all submaximal power outputs. Two factors that produce additional O2 cost at higher intensities of arm exercise include: 1.Lower mechanical efficiency in upper-body exercise from the additional cost of static muscle actions that do not contribute to external work. 2.Recruitment of additional musculature to stabilize torso during arm exercise. Exercise prescriptions based on running and bicycling do not apply to arm exercise. Low correlations between VO2max− arm versus VO2max− leg exercise do not allow accurate VO2max predictions for arm exercise based on leg exercise and vice versa. Lack of strong association between two exercise modes verifies the exercise specificity concept.

Effect of exercise on SBP and DBP of borderline hypertensives.

Hypertension Regular exercise has a small but potentially important effect of lowering blood pressure (both systolic and diastolic) in normotensive individuals. Severely hypertensive people usually need a pharmacologic intervention and should exercise cautiously preferably with medical guidance. Exercise seems to benefit those with borderline hypertension the most and may obviate the need for drug therapy.

Carbohydrate Dynamics During Exercise

Intensity and duration determine fuel mixture •Intense exercise - 1-hr decreases liver glycogen 55%; 2-hr almost depletes liver + muscle glycogen. CHO provides 2X more rapid energy transfer compared w/lipid or protein. 6% more energy per unit O2 consumed •Moderate and prolonged exercise - Fat serves as main energy substrate during low-intensity exercise Compared w/lipid & protein catabolism, CHO preferential fuel during intense aerobic exercise because rapidly supplies ATP during oxidative processes. Early minutes of intense activity O2 use fails to meet energy demands & stored muscle glycogen primary contributor because rapidly supplies energy w/out O2 As intense activity progresses glucose from liver increases metabolic contribution. During prolonged submaximal activity, lipids provide increasing larger % of total energy output. Blood glucose levels decline & circulating fatty acids increase. Protein also provides increased contribution to energy pool. With CHO depletion, activity intensity decreases after 2 hours—direct result of slower rate of aerobic energy release from lipid metabolism.

What Is a Sedentary Lifestyle?

Lack of physical activity IS NOT THE SAME as a sedentary lifestyle. Why?? Sedentary lifestyle is a strong risk factor for CVD-- INDEPENDENT of physical activity. Energy expenditure <1.5 METS while in a sitting or reclining position during waking hours. In US, estimated 55% of daily waking time.

Exercise Is Medicine

Launched in 2007 by the American College of Sports Medicine (ACSM) with support from American Medical Association (AMA) & Office of Surgeon General. No combinations of medications available today can replicate the benefits associated with consistent physical activity prompting ACSM to develop the "Exercise Is Medicine" initiative.

Does Ventilation Limit Aerobic Endurance?

Less adaptation in pulmonary structure/function occurs in aerobic training than in CV & neuromuscular function. During strenuous exercise, healthy individuals hyperventilate at higher levels of VO2 ◦Hyperventilation response decreases PAco2 and slightly increases PAo2 During intense exercise a breathing reserve exists because VE at VO2max = 60 to 85% MVV. Pulmonary function does not form a "weak link" in the O2 transport system.

WHY DOES MAP INCREASE MORE DURING ARM WORK?

MAP = HR x SV x TPR Leg exercise: vasodilation in large active muscle groups and vasoconstriction in small, inactive muscle groups. Arm exercise: vasodilation in small, active muscle groups and vasoconstriction in large, inactive muscle groups.

Primary Factors Influencing Muscle Strength

Muscle size—muscle fiber alignment Muscle moment arm—changing joint position Stretch of the muscle—# & overlap of cross bridges Contraction velocity—velocity/force relationship between concentric, eccentric & isometric contractions Level of muscle fiber recruitment—frequency of stimulation by motor nerve & number of motor units activated. Fiber types composing muscle—Type I (ST), Type IIa, Ilb, IIx (FT)

Anaerobic ATP Production During Transitions

O2 deficit—aerobic O2 supply does not immediately meet demand during transition from rest to steady state exercise. Anaerobic ATP sources are mobilized creating an O2 deficit which is repaid post exercise. Recovery VO2 called excess post O2 consumption (EPOC)—replace ATP, PCr, return to rest VO2 Table 7.8 b & c Anaerobically provided ATP important: (1) during transition period from low level of activity to higher level of activity and (2) whenever exercise demands exceed anaerobic threshold of individual. At low -moderate exercise intensity, oxygen deficit is minimal but oxygen deficit increases w/higher intensity as more anaerobic ATP is needed.

Components of Total Daily Energy Expenditure (TDEE)

Obligatory thermogenesis: Energy required to digest, absorb, and assimilate food nutrients. Facultative thermogenesis: Activation of sympathetic nervous system and its stimulating influence on metabolism. Reaches maximum within 1 hour following a meal. Considerable variability exist in Diet induced thermogenesis among people: 10-30% of ingested food energy. Physical activity exerts by far the most profound effect on human EE: 15-30% TDEE Regular physical activity stimulates resting metabolism (RMR) Regular CV & resistance exercise offsets decrease in RMR that usually accompanies aging. Each 1-lb gain in FFM increases RMR by 7 to 10 kcal/d. World class athletes nearly double TDEE w/3-4 hrs of intense training.

Benefits of Regular PA/Exercise

Other Benefits Independent living Enhanced feelings of well-being Enhanced performance of work, recreational, sport activities Increase energy/reduced fatigue Muscle strength/endurance Prevention/mitigation of functional limitations & effective therapy for many chronic diseases in older adults.

Typical Values for Minute Ventilation (VE) During Rest and Physical Activity

Physical activity has most profound affect on VE, VO2, and VCO2 dynamics During light to moderate exercise, VE increases linearly w/VO2 and VCO2 VE increases mainly via increases in tidal volume. At higher exercise intensities, breathing frequency takes on more important role. TV - rate has to go up, differences in tidal volume intensity increases rate

Pulmonary Ventilation, Blood Lactate, and VO2 During Graded Exercise to Maximum

Point where pulmonary VE increases disproportionately to VO2 during graded exercise (i.e., disproportionate increase in VE/VO2)—Ventilatory threshold Excess ventilation results from stimulating effects of CO2 release from buffering of the accumulating lactic acid. Excess CO2 causes RER ≥ 1.0 Blood lactate (BL) does not accumulate at all exercise levels. Lactate threshold (LT) describes highest VO2 or exercise intensity before a 1.0 mM increase in blood lactate concentration above the pre-exercise level. During light and moderate exercise (<50% aerobic capacity), blood lactate production equals lactate disappearance, with oxygen-consuming reactions adequately meeting exercise energy demands. For healthy, untrained persons, BL begins to accumulate and rise in an exponential fashion at about 50 to 55% of maximal capacity for aerobic metabolism. BL accumulates only when its disappearance by oxidation or substrate conversion does not match its production. OBLA signifies when blood lactate concentration systematically increases to 4.0 mM. Lactate threshold & OBLA used interchangeably, but each represents an operationally different point for intensityRespiratory compensation represents a further disproportionate increase in ventilation to counter decrease in plasma pH in intense exercise ability to remove lactate - OBLA - 4mm, not same as threshold inflection point - ventilatory threshold respiratory compensation

RESPIRATORY EXCHANGE RATIO (RER)

Practically, R.Q can't be measured in vivo but can be estimated by measurements of oxygen consumption (VO2) and carbon dioxide production (VCO2) at the mouth. RER = RQ whenever the body's total O2 content stays constant (usual) AND when total CO2 content stays constant (variable depending on breathing strategies). By measuring VO2 and the RER and assuming steady state conditions exist for carbon dioxide, a very accurate measure of caloric expenditure can be made (important for metabolic evaluation of patients on ventilators or nutritional studies). For general exercise studies, to convert from L/min to kcal/min = multiply L/min x 5

RPE Scale

Psychologically, trained individuals also perceive exercise at any given VO2 as less stressful. They will report a lower number on any of the many types of perceived exertion scales. The scale depicted above is the Borg 15 point scale where a "6" represents no feelings of exertion or effort at all and a 20 represents supramaximal exertion. Borg designed the scale so that, roughly, the number reported multiplied by 10 would approximate the heart rate at that exercise level. Similar scales (usually 10 point) are used in medicine to allow patients to report pain levels or severity of dyspnea. higher VO2 - lower RPE as trained

RATE-PRESSURE PRODUCT

RPP = HR x SBP RPP is lower at any given work rate in fit versus unfit Consequences: • heart requires less oxygen • heart requires less blood flow • heart operates more efficiently RPP is a non-invasive index of myocardial blood flow and therefore oxygen needs. The trained heart operates more efficiently by delivering the same cardiac output at a lower heart rate.

Training Response in CHD Patients

Regular exercise & training effects can: 1. Delay onset of angina pectoris. In patients with CHD, work capacity is symptom limited—can exercise up to certain intensity (HR or RPP). ◦At any given submax workload, training effects include: ◦Decreased HR,BP, TPR ◦Increased SV and a-vO2 diff ◦Decreased RPP ◦Increased intensity of work tolerated or longer time at same intensity 2. Lower risk for MI-same reasons as delaying onset of angina. O2 and blood flow demands of heart decreased at any submax exercise intensity & O2 supply enhanced by training induced coronary vascular collaterals.

HYPERLIPIDEMIA

Regular physical activity decreases total serum triglycerides. This effect is especially evident in those with the highest TG's to begin with. Another positive effect of exercise is an increase in circulating HDL's and thus a more favorable HDL/LDL ratio. Total serum cholesterol may be less significantly impacted.

Blood pH and Blood Lactate

Relationship between blood pH & BL concentration during rest and increasing intensities of short-duration exercise to max. Blood pH & BL concentration related to exercise intensity expressed as % of max; decreases in blood pH accompany increases in BL concentration Increased H+ concentration from CO2 production and lactate formation during strenuous exercise makes pH regulation progressively more difficult. Acid-base regulation becomes difficult during repeated, brief bouts of all-out exercise that elevates blood lactate values ≥30 mM. Humans can temporarily tolerate pronounced disturbances in acid-base balance during maximal exercise. A plasma pH ≤7.0 can cause nausea, headache, and dizziness.

Role of exercise in weight loss and maintaining LBM

Research suggests that a combination of diet and exercise is superior to diet or exercise alone when the goal is loss of fat weight and maintenance of fat-free weight. Example: Exercise at 10 kcals/min (VO2 of 2.0 l/min) for 30 minutes/day expends only about 300 kcals, BUT, this exercise performed 3x/week for a year adds up to the equivalent of ~13 pounds of fat!!

Resistance exercise evidence based recommendation

Since there is a large neural component to strength training it is a good idea to use a variety of exercises for any given muscle group Exercise to fatigue ensures that motor units that are most difficult to recruit but with the most potential for hypertrophy are used. However it is a good idea to start out with a less than maximal effort in order to learn to do the exercises properly and to avoid severe DOMS (delayed onset muscle soreness). Performing 1 good set per session has been shown to provide about 80% of the gains as compared to 3 sets. Research indicates that 24-48 hours should elapse between strength training sessions for any given muscle group. Exercise prescription can be modified depending on the specific goals (eg. muscle power, hypertrophy, endurance).

Glycogen

Storage carbohydrate in muscle and liver Body stores about 2000 kcal as carbohydrate. ◦Muscle stores about 400g glycogen ◦Liver stores about 90-100g glycogen Upper limit for glycogen storage averages about 15 g/kg BW. Muscle glycogen used during physical activity, provides the major carbohydrate supply for active muscles.

BP Response to Resistance Exercise

Straining exercises mechanically compress peripheral arteries that supply active muscle—what type of contraction?? Isometric (static) or dynamic. ◦Arterial vascular compression dramatically increases total peripheral resistance and reduces muscle perfusion. ◦In an attempt to restore muscle blood flow, substantial increases occur in sympathetic nervous system activity, cardiac output, and MAP. Acute cardiovascular strain with heavy resistance exercise could prove harmful to individuals with heart and vascular disease. DYNAMIC VERSUS STATIC CONTRACTIONS The BP response depends on the type of contraction being performed because static or isometric contractions begin to occlude blood flow when the contraction exceeds more than ~30% of maximal tension. Total occlusion of blood flow occurs at approximately 70% of a maximal voluntary contraction (MVC). MAP therefore increases as TPR increases. So a minimal BP response occurs when dynamic exercise with large muscle group is performed. Extremely large increases in MAP are seen when static muscle contractions are performed with large muscle groups eg. competitive weight lifting. Valsalva maneuvers can exacerbate the BP response.

Strength-Endurance Continuum

Strength is Specific Muscle strength=maximum strength Muscle endurance=repetition strength Training with heavier loads/fewer reps generally leads to greater muscle strength. Training with lighter loads/more reps generally produces greater gains in muscle endurance. WHY Generally???—Individual differences, sets/reps, volume, intensity, frequency, exercise selection, rest periods, repetition velocity.

Arteriovenous Oxygen Difference

The a- vO2 diff widens with progressively increasing exercise intensity due to 1) better capillary perfusion, 2) a decreased myocyte PO2 and 3) a right shift in the oxygen-hemoglobin dissociation curve. How do these 3 factors affect O2 diffusion? Similar pattern for females except arterial O2 content averages 5-10% lower because of lower Hemoglobin concentration. Arterial blood O2 varies little from rest BUT mixed venous O2 varies from 12-15 at rest to 2-4 during maximal exertion—O2 extraction from arterial blood as circulates thru body.

Average CO, HR, & SV for Endurance-trained and Untrained Men During Maximal Activity

Untrained: 22,000 mL/min = 195 b/min x 113 mL/b Trained: 35,000 mL/min = 195 b/min x 179 mL/b When comparing VO2max between trained & untrained, Hrmax is similar but significant differences in SV. Endurance athlete achieves a large maximal CO solely through a large SV. Low VO2max corresponds with low maximal CO. High levels of VO2max and maximal CO are distinguishing characteristics for endurance athletes. Proportionate increase in maximal CO accompanies increases in VO2max w/endurance training.

ROUGH APPROXIMATION OF CALORIC EXPENDITURE

VO2 (liters/min) x 5.0 Kcals/liter=kcals/min Another useful conversion: 1 MET = 1 Kcal/kg/hour eg. A 70 kg person performing a 3.0 MET activity for 1 hour consumes approximately 210 Kcals. Each 1-MET increase in exercise capacity=13% decrease in all cause mortality & 15% decrease in CV events

VO2 increases linearly with exercise intensity to a point referred to as VO2max. VO2max is considered to be the best single indicator of aerobic fitness or endurance performance. How long person can maintain activity for longer than 4-5 minutes.

VO2 increases with increasing work rate, but platueas need to go 4-5 minutes

Attainment of VO2max

VO2 max called maximal O2 uptake or maximal aerobic capacity----provides quantitative measure of individual's capacity for aerobic ATP resynthesis. Oxygen uptake (VO2) increases with increasing work rate. This increase does not continue indefinitely and, at some point, further increases in work rate will not elicit a further increase in VO2.

Oxygen Extraction: The a-vO2 Difference

VO2, cardiac output, and a-vO2diff relationship expressed in the equation: ◦VO2 = cardiac output × a-vO2diffVO2 = cardiac output × a-vO2diff O2 consumption during PA increases by 2 mechanisms: increased CO & greater use of already existing large quantity of O2 carried by blood (a-vO2diff) The increase in VO2 max with training is attributable to increases in both maximal cardiac output (therefore increased O2 delivery to skeletal muscle) and increased a-vO2 diff (extraction of O2 by trained muscle).

VO2max changes with training and detraining

VO2max decreases rapidly with bed rest and is restored with aerobic training. The decline in VO2 with bed rest is much more pronounced than with simple cessation of training or a decrease in a habitual activity level. law of diminishing returns

VO2max is the product of maximal CO X maximal a-vO2 difference

VO2max is the product of maximal CO X maximal a-vO2 difference, the effect of aerobic training on both these factors should be examined. The increase in VO2 max with training is attributable to increases in both maximal cardiac output (therefore increased O2 delivery to skeletal muscle) and increased a-vO2 diff (extraction of O2 by trained muscle). The increase in maximal CO is due to an increase in maximal stroke volume. Although max HR isn't changed, a trained individual will have a lower HR and higher SV than an untrained individual at any given level of submaximal exercise. This is an important training effect.

What limits VO2 max??

VO2max of elite endurance athletes exceeds sedentary men/women by almost 2X, however, cannot assume that person with highest VO2max will win competition. Other factors such as improved capillary density, enzymes, mitochondrial size & #, muscle fiber type in addition to psychological component, motivation, pain tolerance.

Strength-Endurance Continuum

WHY does this occur? Muscle strength—increases in inter-muscular coordination during multi-joint exercises, changes in fiber contractile properties, larger increase in neural drive. Muscle endurance—increased capillarization (capillary to fiber ratio), changes in type I muscle fiber area, changes in buffering capacity & rate of ion (Na+, K+, Ca2+) transport.

Heart Rate to Estimate Energy Expenditure

•Linear relationship between heart rate and VO2 for two female basketball players of different aerobic fitness levels •Note differences in the slopes of the two lines, indicating different fitness levels (yellow line more fit person)