exercise physiology for the practicing clinician

EXERCISE PHYSIOLOGY FOR THE PRACTICING

CLINICIANRay F. Moss, Ph.D.

Professor Health SciencesFurman University

Director of Molnar Human Performance Laboratory

Years of Training.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 10.0+

%Pe

rfor

man

ce C

apac

ity

VO2MAX

100%

Lactate ThresholdRunning Economy

Components Of Running Performance

Cash Currency for Performance

ATP used

CP reforming ATP

Eventually all paid for aerobically

PCr Shuttle

PCr + ADP ATP + Cr

ATP ADP

CPK

mitochondria

sarcoplasm PCr Cr

CPK

ADP ATPATPase

Sarcomere

Major Regulators of Cell Metabolism

MAXIMUM OXYGEN UPTAKE

(VO2Max)

Maximal Oxygen Uptake

• Maximal amount of oxygen that can be consumed during physical activity at sea level

• VO2 = Cardiac Output x arterial – venous O2

Endurance athletes have VO2Max levels as high as

94 mlO2/kg/min for 76 kg athlete

212 b/min x 200 ml/beat x 20 Vol% - 3 Vol% = 7.2 L/min

Average 25 year old male has VO2Max of

42 mlO2/kg/min

Contributing Factors

• Very large stroke volumes

Over 200 ml/beat (42 L/min)

• Increased blood volume

• Increased capillarization of skeletal muscle

• Increase myoglobin All of these permit greater delivery of O2 to

skeletal muscle to generate ATP

Maximal Oxygen Consumption VO2MAX

Increasing Workload

O

xyge

n U

ptak

e in

ml/m

in

10.0

20.0

30.0

40.0

50.0

60.0

VO2Max

Hea

rt R

ate

beat

s/m

in

6070

80

90

100

110

120

130

140

150

160

170

180

Generating ATP

Mitochondria and Training

• Increases in Number/size of mitochondria May actually be a reticulum

Density of mitochondria

More protein per volume

This reduces the “strain” on mitochondria during heavy exercise

Mitochondria greater capacity to produceATP

Adaptability / Trainability

Fat(%)

60

40

20

0

CHO(%)

100

80

60

40

Aerobic Power (%)0 (Rest) 50 100 (Max)

Untrained

Untrained

“Cross-Over”

FAT

CHO

1-mile Pace (min/mile)

15 10 8 5

100 (Max)Trained

Trained

“Cross-over”

LACTATE THRESHOLD

Lactate Threshold (LT)

• When the body’s requirements of O2, surpass the body’s ability to deliver that O2, there begins a rapid rise in blood lactate

Considered to be best predictor of endurance

performance

LT in untrained occurs about 50% of VO2Max

LT in trained occurs as high as 90% of VO2Max

Determination Of Lactate ThresholdL

acta

te

Running Velocity

Lactate Threshold

Lactate Increase by 1 mM from previous stage

Sample blood after every 4 minute stage of work

% VO2MAX

30 40 50 60 70 80 90

Lactate Untrained Trained

Lactate Threshold in Trained and Untrained Runners

LT

0 0.5 1.0 1.5 2.0 2.5 3.0

La

cta

te A

pp

ea

ran

ce

(m

g/k

g m

in-1

VO2 (L/min)

0

2

4

6

8

10

12

14

Lactate Appearance During Exercise

Pre-Training

Post-Training

Brooks et al 2000

La

cta

te C

lea

ran

ce (

mg

/kg

min

-1)

Lactate (mM)

0

2

4

6

8

10

12

14

1.0 2.0 3.0 4.0 5.0

Pre-TrainingPost-Training

Lactate Clearance During Exercise

Brooks et al 2000

Lactate Shuttle Systems

LactateMono Carboxylate Transport Protein

Lactate OxidizedInside Mitochondrion

PERFORMANCE ECONOMY

Running Economy And Performance

Defined as the Cost of Running a Particular Pace Improving Economy Decreases the Cost of Running

There are Many Areas in which to Improve Running

Economy

a. Biomechanically

b. Metabolically

c. Psychologically

Why Does It Take 10 + Years To Improve Economy?

1. Sarcoplasmic Reticulum and Associated Pumps

2. Sarcolemmal Transport Protein Carriers a. Sodium Pump

b. Monocarboxilic Transport Protein

3. Glucose Receptor Density

a. Glut 4 Receptors

4. Mitochondrial Matrix/Membrane Proteins

5. Biomechanics of Stride Rate/Length

a. Stretch-Shortening Cycle of Connective Tissue

6. Heat Shock Prevention of Glycolytic and Oxidative

Metabolic Enzymes

Increase in Glut 4 Receptors; Skeletal and Adipose Tissue

Questions? Ha, Ha, Ha