Aerobic assessment Flashcards
What are the three main energy systems assessed in exercise?
- Anaerobic Alactic (ATP-PCr) System (Phosphagen): High power, short capacity.
- Anaerobic Lactic (Lactic Acid) System (Glycolysis/Glycogenolysis): Intermediate power and capacity.
- Aerobic Oxidative System: Lower power, long capacity.
We can only assess which energy system predominates during exercise
Explain the relationship between power and capacity in the context of energy systems.
Higher power energy systems (like anaerobic alactic) can produce energy very quickly but for a short duration (short capacity), while lower power systems (like aerobic) produce energy more slowly but can sustain it for much longer (long capacity)
Why is aerobic assessment important?
It is important for both performance in aerobic sports and for overall health.
What does VO2 help predict?
◦ It is a better predictor for long-term cardiometabolic health.
◦ It can somewhat predict success in endurance activities.
◦ It can somewhat indicate the ability to recover from a task.
◦ It has been linked to an increased risk for a variety of diseases
What is considered the gold standard for assessing overall aerobic fitness?
The maximal oxygen consumption test or VO2max test is considered the single best measure of overall aerobic fitness
Define VO2max
VO2max is defined as the maximum rate at which O2 can be inspired, transported, and utilized to perform muscular work
What is the Fick Equation related to?
The Fick Equation defines how much VO2 we have based on cardiac output (HR x stroke volume) and arteriovenous oxygen difference (a-vO2 diff)
What is the difference between absolute and relative VO2? Which is generally more useful and why?
◦ Absolute VO2 is the total volume of oxygen taken up by the body in liters per minute (L/min).
◦ Relative VO2 is the volume of oxygen taken up by the body per unit of body weight in milliliters per kilogram per minute (mL/kg/min).
◦ Relative VO2 is generally more useful because it accounts for differences in body size. Individuals with more muscle mass will have a higher absolute VO2 simply because more muscle takes up more oxygen to do work. However, it does not tell you about an individual’s body composition
What primary equipment is used to directly assess aerobic power (VO2max)?
A metabolic measurement system (“Metabolic cart”) is used. It is based on the relationship between the volume of oxygen inspired versus the volume of oxygen expired.
Why is a treadmill considered the “gold standard” machine for eliciting VO2max?
◦ It typically elicits VO2max 5-11% higher than cycling.
◦ It allows for greater functional engagement of additional muscle mass.
◦ “True” VO2max requires utilizing a large(st) overall muscle mass and working against gravity (non-body mass supported), which is best accomplished on a treadmill
What is important to consider regarding treadmill test protocols for VO2max?
Protocols that increase grade are generally better at eliciting VO2max than those that only increase speed. Many different standard treadmill protocols are available and can be modified for different populations (e.g., slower initial speed for inexperienced individuals)
What criteria are required for a valid measurement of VO2max?
- Peak and plateau (<150 ml/min) in oxygen consumption with an increase in work rate.
- A respiratory exchange ratio (RER) greater than 1.15.
- Achievement of predicted maximum heart rate (HRmax).
- Venous lactate concentration > 8 mM.
- Rating of perceived exertion (RPE) > 17 (6-20 original) or 10 (0 to 10 revised) Borg Scale.
- Volitional exhaustion.
What are some general end-of-test criteria for a maximal VO2max test?
Should max out HR, and signs of intolerance such as a drop in systolic BP, hypertensive response, chest pain, signs of poor perfusion (cyanosis or pallor), abnormal ECG, cramping, or extreme fatigue
What is the difference between “True” and “Peak” VO2max?
- “True” VO2max is thought to be achieved when a test utilizes a large(st) overall muscle mass and requires working against gravity (primarily on a treadmill).
- “Peak” VO2max refers to the highest rate of oxygen consumption achieved on other exercise machines/modalities like cycle ergometers
What should be checked after a progressive maximal aerobic test to assess the validity of the data?
A post-gas check using gas analyzers should be performed. The parameters (VE, FECO2, FEO2, VO2) should be close to expected/normative values and follow the desired trends during the incremental exercise
Describe how various physiological parameters change during a progressive maximal aerobic test.
- VE (Ventilation): Increases significantly (up to 150+ L/min).
- TV (Tidal Volume): Increases during exercise and plateaus at around 4.0 L.
- RR (Respiratory Rate): Rapidly increases at high intensities (up to 50+ bpm).
- VO2: Increases linearly up to 30+ mL/kg/min (untrained) and 50+ mL/kg/min (trained).
- VCO2: Increases linearly, closely matched with VE.
- RER: Increases from 0.75-0.80 at rest to values exceeding 1.1-1.2 at max.
- VE/VO2: Initially decreases from rest to submax, followed by a rapid increase during more intense exercise.
- VE/VCO2: Initially decreases, remains relatively constant throughout submax, followed by a steady increase beyond the anaerobic threshold (AT).
What is the general reliability of VO2max testing?
VO2max testing generally shows good test-retest reliability, especially when performed on a treadmill. Studies have shown high correlation coefficients (e.g., r = 0.96 for rowing VO2max) and relatively small variability between repeated tests
How can VO2max be assessed if a metabolic cart is not available?
VO2max can be predicted using a variety of indirect tests and formulas. These tests can be maximal or submaximal and use some sort of physiological performance indicator (e.g., time to exhaustion, heart rate) in a formula to provide a predicted VO2max or VO2peak
Provide some examples of maximal indirect tests for predicting VO2max
Leger 20 Meter Shuttle Run Test, Bruce Protocol, Modified Bruce Protocol, Balke Protocol, Cooper Test
Provide some examples of submaximal indirect tests for predicting VO2max.
mCAFT, YMCA cycle ergometer test, Astrand cycle ergometer test, PWC, ACSM submaximal treadmill test, Ebbeling treadmill test, Rockport 1-Mile Walk Test
Describe the Bruce Treadmill Test. How is VO2 prediction performed with this test?
It is a continuous, progressive exercise test to fatigue (volitional exhaustion) that correlates well to actual VO2max. It starts at 10% grade and 1.7 mph, with speed and grade increasing every 3 minutes. VO2 prediction can be performed using a nomogram aligning exercise time with predicted VO2 or using participant-specific equations based on time to exhaustion
Describe the Naughton Treadmill Test and for whom it is particularly useful.
It is a continuous, progressive exercise test to fatigue, specific to higher-risk individuals (e.g., cardiac patients). It starts at 0% grade and 1.0 mph, with speed increasing at 2 minutes (to 2 mph) and grade increasing (+3.5%) every 2 minutes
How can cycle ergometry be used to estimate VO2max?
Cycle ergometry can be discontinuous or continuous. The maximal power output (in Watts) attained is used in equations to estimate VO2max
What are the advantages of using predictive submaximal VO2max tests?
They are generally safer, less expensive, require less sophisticated equipment, require less expertise, are more conducive to “mass” testing, and some have shorter protocol durations compared to maximal tests
On what physiological principles are submaximal VO2max tests based?
- The positive linear relationship between power output, VO2, and heart rate (HR).
- The assumption that maximal HR can be predicted similarly in all individuals.
- The assumption that variability in heart rate (day to day) is minimal.
- The assumption that efficiency of exercise is similar between individuals at a given submaximal workload.
- The best predictive power using HR occurs between HRs of 120 to 170 b/min
What are some limitations of submaximal VO2max tests?
Age-predicted max HR formulas have a degree of error. Protocols are designed for average users and may over- or underestimate VO2max in athletes, sedentary individuals, or older populations. They provide a single snapshot and rely on several assumptions that may not always hold true
Briefly outline the steps involved in predicting VO2max using a multi-stage cycling ergometer test
- Determine power output for each stage.
- Measure heart rate at the end of each stage.
- Use the ACSM metabolic equation for cycle ergometry to calculate VO2 for each stage.
- Determine the slope of the line of best fit for the HR vs. VO2 relationship during submaximal work.
- Extrapolate the line to the age-predicted HRmax to estimate VO2max
Describe the Ebbeling Treadmill Test and its target population.
It is a single-stage submaximal treadmill protocol designed for healthy adults between 20-59 years old. It involves a 4-minute warm-up followed by 4 minutes of exercise at a 5% grade (same speed as warm-up). A specific equation is used to predict VO2max based on speed, heart rate, age, and sex
Describe the Rockport 1-Mile Walk Test and its target population
It is a submaximal field test where the participant walks one mile as quickly as possible without speed walking. Heart rate is measured immediately at the end of the test, and a specific equation (using weight, age, sex, time, and HR) is used to predict VO2max. It may be more appropriate for older and sedentary populations
What are some general protocol considerations for conducting aerobic assessments?
Include a warm-up and cool-down. Monitor HR, BP, RPE, and symptoms before, during, and after exercise. Be aware of factors affecting HR (anxiety, temperature, caffeine, talking, body position). Consider achieving steady state if relevant to the test. Remember the limitations of age-predicted max HR formulas
What is the primary purpose of aerobic stress testing? What measurements are typically included?
The primary purpose is to assess cardiac function by increasing HR and myocardial contractility to see how people respond to exercise. Procedures typically include a graded exercise protocol, 12-Lead ECG plus BP measurements, and monitoring subjective symptoms using scales like the Borg, Angina, and Claudication scales
Why might someone undergo an exercise stress test?
- Part of an annual checkup for physician clearance (screening).
- Prognostic assessment for patients with risk factors.
- Diagnosis of coronary artery disease and related symptoms.
- Functional assessment to evaluate procedures improving circulation.
- Determination of a safe exercise level for rehab or daily living
Define aerobic capacity.
Aerobic capacity is defined as the total amount of work that can be done using aerobic energy sources. It may be more important for activities of daily living (ADL) than aerobic power
What is the key difference between aerobic power and aerobic capacity?
Aerobic power (VO2max) refers to the maximum rate of oxygen utilization, while aerobic capacity refers to the total amount of work that can be sustained aerobically over a longer duration. Ultra-endurance athletes might have similar VO2max to middle-distance athletes, but the former have a much greater aerobic capacity
What are some assessments used to evaluate aerobic capacity?
Boulay et al. “Aerobic Capacity Test”, Anaerobic Threshold assessments, Submaximal Endurance Tests
Describe Boulay’s Aerobic Capacity Test.
It involves 90 minutes of continuous exercise on a cycle ergometer at an intensity set at a HR 10 b/min below the individual’s previously determined anaerobic threshold (AT). The resistance is adjusted to maintain the HR, and the results are expressed as total kJ/kg attained
What is the rationale behind Boulay’s Aerobic Capacity Test? What are its limitations?
- Rationale: VO2max doesn’t predict the total aerobic energy production. 90 minutes stresses aerobic mechanisms without requiring food intake or engaging significant anaerobic glycolysis (if below AT). It has shown good reliability.
- Limitations: Length of the test, requires prior determination of AT (not practical), precise resistance control needed, susceptible to dehydration and cardiovascular drift, influenced by glycogen depletion, and lacks extensive comparative data.
Define Anaerobic Threshold (AT).
The exercise VO2 above which anaerobic high-energy production supplements aerobic high-energy production, leading to a lower cellular redox state, increased lactate/pyruvate ratio, and a net increase in lactate production. It has two primary components: Lactate Threshold and Ventilatory Threshold
Define Lactate Threshold and how it is typically assessed
Lactate Threshold is the speed or power output at which lactate starts to accumulate in the blood. It is assessed using graded, incremental protocols to near maximal effort with 3-4 minute increments to accurately measure blood lactate levels.
What are common methods for determining Lactate Threshold from blood lactate data?
Graphical method (identifying the point preceding a sustained >1.0 mM increase in blood lactate), regression analysis (intersection of two lines), the “D-max” method (largest deviation from the lactate-workload curve), and the Onset of Blood Lactate Accumulation (OBLA) at 4 mM. Maximal Lactate Steady State (MLSS) assesses the maximal BLa that can be maintained
Define Ventilatory Threshold and how it is typically assessed
Ventilatory Threshold is a non-invasive estimate of AT, reflecting changes in breathing patterns due to increased CO2 production from buffering of lactate. It is assessed using graded, incremental protocols with 2-3 minute increments, requiring equipment to measure ventilatory responses (e.g., VCO2, VE)
What is a common method for determining Ventilatory Threshold?
The V-Slope method, which analyzes the relationship between carbon dioxide production (VCO2) and oxygen consumption (VO2), is common
What is the typical relationship between Lactate Threshold (LT) and Ventilatory Threshold (VT)?
In general, LT usually occurs at a similar time or precedes VT by one workload increment
Describe the Conconi Test and what it predicts.
It is a field test using repeated intervals of exercise with increasing speed over a set distance, measuring HR and velocity at the end of each interval. By graphing HR vs. Velocity, the deflection point in the HR response is used to predict AT. It has shown good concurrent validity and reliability
Describe the PWC170 test and what it suggests to assess.
It involves two consecutive 6-minute bouts on a cycle ergometer at different power outputs, maintaining a pedal rate of 50-60 rpm and achieving heart rates between 120 and 140 bpm. HR is plotted against power output, and the line is extrapolated to a HR of 170 bpm to determine the power output at 170 (PWC170). It is suggested to be a “capacity test”.
What are some limitations of submaximal endurance tests like PWC170 for assessing aerobic capacity?
They may not be long enough to significantly stress aerobic capacity. The selected variables (like HR at a specific workload) might not directly indicate aerobic capacity. Some submaximal intensities could even be above an individual’s AT, making them less indicative of purely aerobic function
How does Anaerobic Threshold relate to Aerobic Capacity?
If exercise below AT primarily uses aerobic energy, and above AT relies more on anaerobic glycolysis, then AT may set the upper limit for sustainable aerobic exercise and thus aerobic capacity. Endurance athletes with high ATs often demonstrate high aerobic capacit
How has Anaerobic Threshold been used to predict endurance performance (e.g., marathon time)?
Studies have used the running velocity at Ventilatory Threshold to predict marathon finishing times with remarkable accuracy, suggesting a strong link between AT and endurance performance
According to Michael Joyner’s model, what are the three key physiological parameters that limit marathon performance?
- VO2max: The maximal rate of oxygen uptake and utilization.
- Lactate threshold (LT): The exercise intensity at which lactate accumulation exceeds clearance (expressed as a percentage of VO2max).
- Running economy (RE): The amount of VO2 used for a given running speed
Define running economy and what factors influence it
Running economy is the amount of VO2 required to run at a given speed. A higher running economy means using less oxygen for the same pace. It is influenced by internal factors (joint biomechanics, respiratory entrainment, VO2 drift) and external factors (wind resistance, friction, shoe energy absorption, clothing)
What physiological characteristics did Joyner suggest an ideal runner would need to break the 2-hour marathon barrier?
A VO2max of 84 mL/kg/min, a lactate threshold at 85% of VO2max, and exceptional running econom
