week2 day1 - exercise testing

Purpose – What is the purpose of exercise testing?

Evaluation of physical capacity and effort tolerance; detection/diagnosis of cardiovascular disease; prediction of cardiovascular events and mortality; assessment of symptoms and response to treatment.

VO2 Assessment – What are the two ways to determine VO2?

Metabolic equations (estimate VO2) and ventilatory expired gas analysis (direct measurement, most accurate to measure but expensive).

Metabolic Equations – What do they measure?

They estimate how much oxygen (VO2) is used during a given exercise workload.

Metabolic Equations – What is the walking VO2 equation?

VO2 = (0.1 × S) + (1.8 × S × G) + 3.5

Metabolic Equations – What is the running VO2 equation?

VO2 = (0.2 × S) + (0.9 × S × G) + 3.5

Metabolic Equations – What is the cycling VO2 equation?

VO2 = 1.8(work rate / BM) + 3.5 + 3.5

Metabolic Equations – What do these abbreviations mean?

S = speed (m/min); (1 mph = 26.8 m min-1)
BM = body mass (kg); (1 kg = 2.2 lbs.)
G = grade (decimal); (e.g. 10% = 0.1)
VO2 = oxygen consumption (mL/kg-1/min-1)

Metabolic Equations – What is 1 MET?

1 MET = 3.5 mL/kg/min (resting VO2)

Metabolic Equations – What constants must you remember?

Walking = 0.1
Running = 0.2

VO2 Assumptions – What are the key assumptions?

• Steady-state HR and VO2 at each workload

• Linear HR–work rate relationship

• Max workload reflects VO2max

• Max HR = 220 – age (same for everyone of same age)

• Mechanical efficiency during cycling/treadmill is equal or constant among individuals

Subject Preparation – Why no food 3 hours before test?

Digestion increases metabolism and VO2, leading to inaccurate results

Subject Preparation – What are key prep steps?

Explain test, no food 3 hrs prior, allow meds, proper clothing, brief history/physical, ECG for clinical populations

Field Tests – What is the 6-minute walk test?

Walk as far as possible in 6 minutes; used in clinical/chronic disease populations (100ft)

Field Tests – What is the 1.5 mile test used for?

Healthy adults (18–29), running is recommended/walk as fast as possible

Field Tests – What is the 1-mile walk test?

Walk 1 mile as fast as possible; measure HR immediately after (good for anyone 20-69yrs)

Treadmill – What are the pros?

Natural movement, higher VO2 (5–10%), walking/jogging/running options

Treadmill – What are the cons?

Less precise/accurate work rate estimate, fall risk, unfamiliar, handrail use reduces accuracy, only incremental (cannot use ramp)

Cycle Ergometer – What are the pros?

Precise work rate, safer, less movement artifact, can use ramp/graded protocols, minimal fall risk, can be performed sitting/supine

Cycle Ergometer – What are the cons?

Unfamiliar, leg fatigue before max if protocol is too agressive

Lab Testing – What affects results?

eating food before, dehydration, elevated body temperature, emotional state, meds, physical activity before test, temp or humidity of testing environment

YMCA Protocol – What is the key assumption?

Linear relationship between HR and VO2

YMCA Protocol – How long are stages?

3 minutes (take HR in last 10sec of 2nd and 3rd minutes of each satge)

YMCA Protocol – What do you do if HR difference (greater than) >5 bpm?

Add another minute to the same stage; BUT if less than 5bpm, then steady state is assumed and you can start another stage

YMCA Protocol – What RPM must be maintained?

50 RPM

YMCA Protocol – When do you stop?

At 85% of age-predicted HRmax or signs of termination

VO2 Graph – What does the graph show?

Relationship between heart rate (Y-axis) and work rate (X-axis) to estimate VO2max

Astrand Protocol – Key feature?

Constant speed (5mph), first 3 mins at 0%, increase grade every 2 minutes (by 2.5%); for healthy individuals

Bruce Protocol – What changes?

Speed AND grade increase every 3 minutes; (if healthy person the 0-5% grades are omitted)

Bruce Protocol – Main con?

Large workload jumps reduce accuracy and limit use in elderly

Progressive Exercise Test — Protocols for clinical exercise testing generally

include:

• Warm up

• Progressive graded exercise with increasing workload at

the same time intervals.

• Cool-down: Post-maximum effort recovery period at a low

workload.

treadmill testing = US
cycling = Europe

Ramp Protocol – What is unique?

Continuous increase (no stages), ends in about6–12 minutes

Naughton/Balke – Who are they for?

Elderly or deconditioned patients

Exercise Testing – What are key measurements?

HR, BP, ECG, pulse oximetry, RPE

RPE – Why is it important?

Measures perceived effort; correlates with intensity

Termination – When must you stop immediately?

• ST segment elevation

• Drop in systolic BP ≥10 mmHg

• Chest pain (angina)

• CNS symptoms (dizziness, etc.)

• Poor perfusion (cyanosis/pale)

• Arrhythmias

• Equipment failure

• Patient request to stop

VO2max – What must be met?

VO2 plateaus = (vo2 max)
and at least 1 of:

• RER ≥ 1.15

• HR near max

• RPE ≥ 17

• Subject stops

BUT two of these is (vo2peak)

Fatigue – Definition?

a loss of muscle power that results from the decline in bother force and velocity, which is reversible by rest.

E-C Coupling – What are the steps?

Steps…Action potential (happens in neuron) - 7 steps i think i messed up on step 3

1. Action potential moves down motor neuron and triggers influx of calcium

2. Acetylcholine(ach) released into synaptic cleft (ach enters the neuromuscular junction and bind to R on motor end plate → membrane potential)

3. Ach binds receptors; enters neuromuscular junction and bind to R on motor end plate → membrane potential;MP (happens in on membrane)

4. MP travels down sarcolemma and then to t tubules (actually step 3 according to professor)

5. MP causes calcium to be released from sarcoplasmic reticulum (SR)

6. Calcium binds to troponin to → shifts tropomyosin, exposing myosin binding sites

7. Actin and myosin bind (phosphate needs to be lost) forming a cross bridge → causes power stroke (myosin pulls on actin)

8. Atp breaks cross bridge, and the cycle repeats

Fatigue is caused by different things that occur in this system

Fatigue – Central vs Peripheral?

Central = before NMJ (brain/spinal cord)

• Depression of motor neuron excitability.

• Loss of excitation at branch points.

• Pre-synaptic failure.

Peripheral = after NMJ (muscle issues)

• Lack of Ca++ release from sarcoplasmic reticulum.

Peripheral Fatigue – Causes?

Na⁺(sodium)/K⁺(potassium) imbalance, reduced Ca²⁺(calcium) release, Pi (phosphate) buildup, H⁺(hydrogen) buildup

Mechanical Fatigue – What affects contraction?

Actin-myosin interaction, Ca²⁺ availability, ATP availability

Energetics – What causes fatigue?

Imbalance between ATP supply and demand

Fibers – What happens at <40% VO2max?

Type I fibers dominate

Fibers – What happens at 40–75%?

Type IIa recruited

Fibers – What happens >75%?

Type IIx recruited

Performance – What fuels short-term exercise?

Phosphocreatine + anaerobic energy

Performance – What limits long events (>1 hr)?

Carbohydrate depletion

Altitude – What happens to oxygen?

Lower partial pressure → less oxygen available

Altitude – What happens to VO2max?

Decreases linearly with altitude

Altitude – What happens to HR?

HR increases (even at rest)

Heat – What is hyperthermia?

Elevated body temp due to failed heat regulation

Heat – What are stages of heat illness?

Hyperthermia → syncope → cramps → exhaustion → heat stroke

Heat – What increases risk?

Low fitness, poor hydration, heat, humidity, high metabolic rate