Fitness professionals routinely assess the cardiorespiratory fitness level of clients. Cardiorespiratory fitness assessments include submaximal and maximal exercise tests designed to provide baseline information and progress measurements throughout the duration of the training program.

Cardiorespiratory fitness is the maximal capacity of the body’s circulatory and respiratory systems to provide oxygenated blood to the muscles during physical activity.¹ It is vital to prolong good health and optimize activities of daily living. Studies have shown a pronounced effect from the role of cardiorespiratory fitness in chronic disease prevention and as a result, it should be a priority in any fitness regimen.^{1, 2}

Properly gauging cardiorespiratory fitness can be accomplished through a battery of tests with data readily available to compare results based on age, gender, and potentially body weight. The key measurables for most tests include heart rate and breathing rate to determine maximal oxygen uptake or VO₂ max.²

The VO₂ max is the maximum amount of oxygen the body can utilize during intense exercise, measured in milliliters of oxygen used per kilogram of body weight per minute (ml/kg/min). Overall, a correct assessment of VO₂ max is the gold standard in terms of measuring aerobic fitness.

When determining the optimal sequencing of assessments, the National Strength and Conditioning Association recommends the following:

1. Resting measures such as heart rate, body composition, and blood pressure.
2. Agility tests
3. Maximal power and strength tests
4. Muscular endurance tests
5. Fatiguing Anaerobic tests
6. Aerobic tests

The reasoning behind this sequence is based on exercise fatigue and recovery along the energy metabolism pathway. The earlier tests fatigue the fast-acting metabolic pathways and require a short rest period to be replenished.

As the assessments begin taxing the glycolytic pathways, recovery requirements grow to several minutes between tests. The aerobic tests tax the oxidative metabolic pathway and may take up to 24 hours to fully recover.

This sequencing of tests based on energy metabolism is designed to optimize performance throughout every stage of testing.³

Optimal test sequencing yields the most accurate results; however, fitness professionals should know that some flexibility exists when sequencing these assessments depending on the needs of the participant, the timing involved, and access to equipment.

Test selection for determining cardiorespiratory fitness depends on the overall status of the participant and the availability of specific modalities, as some may prove to be cost-prohibitive or hard to access.

Test selection for determining cardiorespiratory fitness will equate to the overall status of the participant and the availability of specific modalities as some may prove to be cost prohibitive or hard to access.

The relationship between heart rate and oxygen uptake is mostly linear. As a result, relatively accurate estimates of VO2 max can be made employing submaximal testing and ventilatory thresholds.^4,5,6 Usage of submaximal testing, as opposed to maximal testing, is more user friendly and greatly reduces the risk of injury or harm to the user. Specifically, when thinking of untrained or sedentary individuals, the risk associated with maximal VO2 testing far outweighs the benefit when a submaximal test can provide a solid estimate. 

Submaximal testing can be under predictive of VO2 scores when working with highly trained and athletic participants.⁷ Therefore, maximal testing is recommended for athletic and well-trained populations.⁴

VO₂ Max Testing

The relationship between heart rate and oxygen uptake is mostly linear. As a result, relatively accurate estimates of VO₂ max can be made utilizing submaximal testing and ventilatory thresholds.^{4, 5, 6}

The utilization of submaximal testing is more user-friendly and greatly reduces the risk of injury or harm to the user compared to maximal testing.

Specifically, when thinking of untrained or sedentary individuals, the risk associated with maximal VO₂ testing far outweighs the benefit when a submaximal test can provide a solid estimate. Submaximal testing often underpredicts VO₂ scores when working with highly trained and athletic participants.⁷ Therefore, maximal testing is recommended for athletic and well-trained populations.⁴

YMCA 3-Minute Step Test

Purpose: Sub-maximal VO₂ max test

Equipment: 12-inch step, stopwatch, metronome, and optional heart rate monitor

Metronome should be set to 96 beats per minute.

Notes:

• Allow the participant to practice stepping to the beat of the metronome.
• After completion of the 3 minutes, the participant sits down immediately onto the bench and remains still.
• The score of the test is the participants’ one-minute post-test heart rate.
• Compare the score to the YMCA step test published chart.

A full cycle of 4 beeps equals one complete step. The participant should perform 24 steps per minute.

Procedure:

1. Demonstrate the alternating step cadence to be performed.
2. Step one foot up onto the bench with the first beat.
3. Step the second foot up with the second beat.
4. Step one foot down onto the floor with the third beat.
5. Step the second foot onto the floor with the fourth beat.
6. Tester starts counting heart rate manually within 5 seconds of completion of test. 
7. Continue counting heart rate for one full minute post-test.
8. If using a heart rate monitor, take the heart rate 1-minute post exercise. This is the “score” used for calculations.
9. Compare the score to the YMCA step test published chart.

Rockport Walk Test

Purpose: Sub-maximal VO₂ max test

Equipment: Accurate weight scale, mile track or treadmill, stopwatch, and optionally a heart rate monitor

Procedure: 

1. Have the participant warm up properly for 5 to 10 minutes prior to the test.
2. Start the stopwatch and have the participant begin walking as fast as possible without slipping into a jog.
3. Upon completion of 1 mile, stop the stopwatch and record the time in decimals. (Ex. 12 minutes and 30 seconds equals 12.5).
4. Calculate heart rate immediately either manually or utilizing a heart rate monitor if available.
5. Calculate the VO₂ max using the following formula:

VO₂ max = 132.853 – (0.0769 x your weight in pounds) – (0.3877 x your age) + (6.315 for a male or 0 for a female) – (3.2649 x walking time) – (0.1565 x heart rate at the end of the test)

The following is an example for a 135-pound, 30-year-old female, that walked the mile in 11.5 minutes and had an end heart rate of 150 beats per minute:

• 132.853 – (0.0769 x 135 lbs.) = 122.4715
• 122.4715 – (0.3877 x 30 years old) = 110.8405
• 110.8405 + (0 for female) = 110.8405
• 110.8405 – (3.2649 x 11.5 minutes) = 73.5011
• 73.5011 – (0.1565 x 150 bpm) = 50.0261

After rounding off to the first three digits, the VO₂ max is 50.0.

1-Mile Run Test

Purpose: Aerobic fitness assessment and VO₂ max estimator. (This is the best option for VO₂ max estimation).

Equipment: Stopwatch, 1.5 mile (2.4 km) flat and hard running course.

Procedure: 

1. Have the participant complete a proper warmup prior to the start of the test.
2. The goal is to complete the course distance in a run as quickly as possible.
3. Have the participant line up on the starting point and at the testers “go” they will begin running. 
4. Walking is allowed, if necessary, but the goal remains to finish as fast as possible.
5. Have the participant perform a cool-down walk following the completion of the test.
6. Calculate the participant’s VO₂ max using the formula:

For males:

• VO₂ max = 91.736 – (0.1656 x body mass in kg) – (2.767 x time in minutes)

For females:

• VO₂ max = 88.020 – (0.1656x body mass in kg) – (2.767x time in minutes)

Note: time should be converted to a decimal (9 minutes and 30 seconds = 9.5).

12-Minute Run/Walk

Purpose: Developed by Dr. Kenneth Cooper, the 12-minute run/walk test is an easily performed test used to measure aerobic fitness and estimate a participant’s VO₂ max. It is the maximum distance a participant can travel in 12 minutes.

Equipment: Level track, stopwatch, cones for marking distance, or a treadmill set to 1% incline if a running track is not available.

Procedure: 

• Have the participant complete a proper warm up prior to the start of the test.
• The goal of the test is to complete the maximum possible distance in 12 minutes at either a run or a walk depending on the participant’s ability level.
• When the participant is ready, have them start, optional to the participant if time is read out during the test.
• Have a cone or other marker ready when time is running out and immediately mark the participant’s position or notate their distance traveled when the 12-minute timer completes.

Notate the distance traveled in either kilometers or miles then calculate the VO2 max using one of the formulas below:

• Kilometers: VO₂ max = (22.351 x kilometers) – 11.288
• Miles: VO₂ max = (35.97 x miles) – 11.29

Compare the participant’s results to readily available online charts with standardizations for age and gender.

Astrand-Rhyming Cycle Ergometer Test

Purpose: The Astrand-Rhyming cycle ergometer test is a submaximal aerobic fitness test. The Astrand test uses heart rate and estimated percentage of maximal aerobic capacity to calculate VO₂ max.

Equipment: Cycle ergometer, stopwatch, heart rate monitor, or optional ECG monitor.

Procedure:

1. Have the participant warm-up on the cycle ergometer for 2 to 3 minutes at a cadence of 50 with no resistance.
2. The goal of the test is for the participant to achieve steady state heart rate over a 6-minute period of cycling.
3. Ideal heart rate range will fall between 125 and 170 beats per minute.

Initial workload for men and women will fall in the ranges of:

• Unconditioned men- 300-600 kg-m/min
• Conditioned men- 600-900 kg-m/min
• Unconditioned women- 300-450 kg-m/min
• Conditioned women- 450-600 kg-m/min

If needing to convert from watts to kg-m/min multiply the watts by 6.12.

Record the participant’s heart rate every minute during the test.

If the heart rate is not within 5 beats of each other at minutes 5 and 6 continue for an additional minute.

If the steady state heart rate is not between 125 and 170 beats per minute, adjust the workload accordingly and repeat the 6-minute period.

Calculate the participant’s VO2 max utilizing the “workload” in kg-m/min, and heart rate steady state “HRss.”

• Females VO2max = (0.00193 x workload + 0.326) / (0.769 x HRss – 56.1) x 100
• Males VO2max = (0.00212 x workload + 0.299) / (0.769 x HRss – 48.5) x 100

Ventilatory Threshold Testing

Ventilatory threshold testing is based on the linear relationship of oxygen and carbon dioxide during breathing (ventilation). With the onset of exercise, ventilation will match the cellular demand for oxygen by the body meaning the body will use more oxygen. Initially the body will increase tidal volume pulling in more oxygen per breath while breathing rate remains relatively the same.

When exercise nears maximal intensity, breathing rate disproportionally increases compared to oxygen intake. This increased breathing rate aids in releasing the increased production of carbon dioxide as a byproduct of switching to anaerobic glycolysis as a primary ATP source.^{6, 8}

Two points to consider with ventilatory threshold hold testing are the first ventilatory threshold point (VT1) or “crossover point” and the second ventilatory threshold point (VT2) or “compensation point.”

VT1 is the point at which blood lactate starts accumulating faster than it can be cleared by the body. This point represents the moment oxygen demands on the body outpace the oxygen delivery capabilities and lactate buildup begins.⁶

VT2 represents hyperventilation and the point at which the increased breathing rate can no longer disperse the carbon dioxide at that rate.

The VT2 can otherwise be described as the onset of blood lactate accumulation.⁸

• Relative performance intensity of VT1 corresponds to the highest pace someone can sustain for 1 to 2 hours.
• VT2 represents the maximal sustainable pace for 30 to 60 seconds.

V1 Talk Test

Purpose: The purpose of the VT Talk Test is to establish VT1 and the associated heart rate of the VT1 threshold.

During the test, intensity should be increased incrementally. The purpose of the test is to find VT1, and if large changes in intensity are made, the exerciser may unintentionally pass VT1, invalidating the test. As such, the talk test is best performed using machines with adjustable intensities to allow precise increases in exercise intensity.

Appropriate increases in intensity include an additional .5 mph, 1% grade, or 15 watts. 

With each level increase, the heart rate steady state should also increase by approximately 5 beats per minute.

Level increases usually happen every 60-120 seconds depending on when the heart rate steady state is reached. Ideally, the test can be completed within 8 to 16 minutes overall.

During each level of the test, the exerciser reads or repeats a phrase. Preconstructed cue cards with long complete sentences can be read off or the exerciser can recite a phrase from memory such as the Pledge of Allegiance.

When the exerciser reaches an intensity where they are unable to string together 5-10 words between deep breaths, VT1 has been determined and the test is complete.

This ability will be the determining factor in the duration of the test. At any point while below VT1, the exerciser should be able to string together 5-10 words between deep breaths. Once they struggle to reach 5 to 10 words consecutively the test has been completed and VT1 reached.

Equipment: Cardio modality (treadmill, cycle ergometer, elliptical, etc.), stopwatch, heart rate monitoring equipment (watch and/or strap), cue cards with pre-determined phrases written on them.

Procedure:

1. Measure pre-exercise heart rate.
2. Allow the exerciser to warm up on the modality the test will be performed on. The heart rate should stay below 120 bpm while the tester goes over the predetermined written or memorized phrases.
3. Once the warmup is completed, increase the intensity to bring the heart rate steady state up to 120 bpm. On a perceived rating of exertion scale, this level should feel like a 3 or 4.
4. When a steady state is achieved, have the exerciser talk continuously for 20 to 30 seconds.
5. Ask the exerciser if speaking was challenging or difficult at this level.
6. Proceed with incremental increases and repeat the steps until VT1 is found.
7. Notate the heart rate at VT1.
8. Allow the exerciser to cool down for 3 minutes at the warmup intensity level.

The heart rate limit established from the VT1 test delineates the base heart rate for sports conditioning and should operate as a guide for purely aerobic conditioning vs the beginning stages of anaerobic conditioning.⁹

VT2 Talk Test

The VT2 Talk Test will determine the point at which blood lactate rapidly accumulates inside an exerciser’s body. The VT2 test is optimally performed using lactate analyzers that continuously measure blood lactate levels. In general, the talk test is used to gauge exercise intensity.

The equipment required is both cost and procedurally-prohibitive for most fitness training professionals, so VT2 field tests are a practical alternative to estimate VT2.

Equipment: Cardio modality (treadmill, cycle ergometer, elliptical, etc.), stopwatch, and heart rate monitoring equipment (watch and/or strap).

Procedure:

1. Before starting, review the test purpose and discuss the intensity level the test will be performed at. The goal is maximum sustained intensity for 20 minutes.
2. Have the participant perform a 3–5-minute warmup on the modality being used for the VT2 test. Heart rate should remain at or below 120 bpm.
3. Increase the intensity to the predetermined level.
4. The participant can adjust the intensity as needed during the first few minutes of the test so they can finish the entire 20-minute test.
5. During the last 5 minutes of the test, record the participant’s heart rate each minute.
6. Once completed, find the average heart rate for the last 5 minutes of the test.
7. Multiply the average heart rate by .95 to determine the VT2 estimate.

VT2 results:

The limit established by the VT2 test should mark the maximum efficiency of the individual in their ability to buffer lactic acid out of the body through oxygen delivery.¹⁰

The VT2 limit establishes guidelines for high-intensity interval training (short-duration sprint repeats) which can improve lactic acid buffering efficiency. The improved efficiency has been shown to increase VO₂ max over time.¹¹

Subjective Measurements of Aerobic Intensity

Subjective measurements of aerobic exercise intensity are also available, such as the talk test, the rate of perceived exertion (RPE), and the Borg scale.

The Talk Test

The Talk Test measures intensity based upon the ease with which the client can carry a conversation during aerobic exercise.

If a client can carry a full conversation with no difficulty, intensity is likely low. On the other hand, if they are unable to speak at all, intensity is high, bordering on maximal.

The Talk Test breaks down as follows:

Low intensity: If the client can easily carry on a full conversation, sing, or recite a poem during exercise, they are likely working at a low intensity level.

Moderate intensity: If the client can still talk comfortably but need to take breaths between sentences or phrases, they are likely working at a moderate intensity level.

High intensity: If the client can only speak a few words or a short sentence before needing to catch their breath, they are likely working at a high intensity level.

The Borg Scale

The Borg Scale, also known as the Borg Rating of Perceived Exertion (RPE) scale, is a widely-used tool for measuring aerobic exercise intensity. Developed by Swedish psychologist Gunnar Borg in the early 1980s, this subjective scale helps individuals gauge their own level of exertion during physical activity.

The Borg Scale ranges from 6 to 20, with each number corresponding to a description of perceived exertion. The scale breaks down as follows:

• 6: No exertion at all, equivalent to resting.

• 7-8: Very, very light exertion.

• 9-10: Very light exertion, similar to light walking or stretching.

• 11-12: Fairly light exertion, comfortable and easy to maintain.

• 13-14: Somewhat hard exertion, noticeable but manageable effort.

• 15-16: Hard exertion, challenging and requires a lot of effort.

• 17-18: Very hard exertion, very strenuous and difficult to maintain.

• 19: Extremely hard exertion, close to maximal effort.

• 20: Maximal exertion, cannot continue for more than a few seconds.

Modified Borg/RPE Scale

A more common RPE scale is the modified 0—10 scale. In either case, clients subjectively report their level of exertion, which can be correlated to low, medium, or high intensity.

• 0: No exertion at all, equivalent to resting.

• 1: Very light exertion, barely noticeable effort.

• 2: Light exertion, similar to a slow walk or gentle stretching.

• 3: Moderate exertion, comfortable and easy to maintain, such as a brisk walk.

• 4: Somewhat hard exertion, noticeable effort but still manageable.

• 5: Hard exertion, challenging but sustainable for some time.

• 6: Very hard exertion, very strenuous and difficult to maintain for long periods.

• 7: Extremely hard exertion, near maximal effort, only sustainable for short durations.

• 8-9: Very, very hard exertion, extremely difficult to maintain.• 10: Maximal exertion, the highest level of effort, cannot continue for more than a few seconds.

Identifying the right cardio modality to use for testing depends on the participant’s profile. Comfort with a particular modality due to prior use or application to their chosen sport will typically be the determining factors.

In certain situations, due to lack of access to equipment or risk of injury, accommodations can be made.

Below is a breakdown of common modalities with the pros and cons for testing based on a user’s capabilities and common checkpoints for form while using the modality.

For upper extremity injuries a traditional cycle ergometer and potentially a stair stepper can be utilized to limit exertion on the injury. 

For lower extremity injuries, an upper body only cycle ergometer can be utilized for a submaximal test.

Treadmill

Pros:

• Direct carryover to real world activities
• Ideal modality for many sports applications
• Ideal for maximal intensity testing procedures

Cons:

• High impact modality
• Potentially too intense for beginners above walking speed·        
• May be unsuitable for clients with lower extremity injuries

Form Checkpoints:

1. Toes pointing straight ahead on foot strike.
2. Foot strike plants directly under the body.
3. Knee points in the same direction as toes.
4. Hips face forward.
5. Torso remains tall without shoulder rounding.
6. Arms swing front-to-back without crossing midline.
7. Eyes stay parallel to the floor with head up.

Coaching Cues:

1. Advise the participant to try to utilize a normal stride, not adjusting for being on a machine.
2. Placing the treadmill at 1% incline greater reflects real world running.
3. Since the belt moves below the participant, remind them to make a full cycle of the legs and pick heels up with each stride.

Stair Stepper

Pros:

• Low impact
• Varied intensity capabilities

Cons:

• The learning curve for proper form
• The bulkiness of the machine can make communication and testing procedures difficult

Form Checkpoints:

1. Body stays upright throughout use.
2. Lightly hold handrails or let arms swing freely, handrails should not support bodyweight.
3. Hips should stay directly under the torso.
4. Plant and step through the entire foot allowing the heel to drop

Coaching Cues:

1. Inform the user to treat the stepper like a real-world stairwell and not rely on the handrail.
2. Fully extend the leg every step in an attempt to drive the stairs down to better simulate moving up stairs.

Elliptical

Pros:

• Low impact
• Total body exercise

Cons:

• Unnatural movement pattern
• Lower overall exertion makes it less ideal for maximal-intensity tests

Form Checkpoints:

1. Always maintain a tall upright posture.
2. Shoulders should stay relaxed and depressed.
3. Maintain a small bend in the elbow.
4. Loose grip on the handles.
5. Hips stay neutral under the torso.
6. Toes and knees point forward.

Coaching Cues:

1. Remind the participant that the elliptical is a total body combination machine. The lower and upper body should work in unison.

Rowing Machine

Pros:

• Low impact
• Effective for high-intensity testing

Cons:

• Steeper learning curve than other modalities
• Potential users more limited due to injury risk
• Not advised for individuals with a history of lower back injury

Form Checkpoints:

1. The starting position is straight arms holding the handle with a prone grip and bent knees with feet in the stirrups. Shoulders should be slightly in front of hips.
2. In the drive phase, the knees extend near-maximally first, followed by hips hinging and the torso leaning back with a neutral spine, and finally, the arms follow through and pull the handle to meet the torso at the lower chest.
3. The recovery phase should be a mirror image of the drive phase.

Coaching Cues:

1. The rowing form should activate the gluteal muscle group and feel similar to a deadlift movement.
2. Maintain a neutral spine throughout the motion.

Cycle Ergometer

Pros:

• Low impact
• High intensity
• Setup facilitates easy monitoring

Cons:

• Test results will vary if a client is a trained cyclist independent of CRS fitness

Form Checkpoints:

1. On the extension phase the driving leg should near maximal extension.
2. Back should remain flat throughout use.
3. Relaxed grip on the handlebars to ensure the upper body doesn’t perform isometric exercise and hold tension.
4. Opposing limbs should look symmetrical from in front or back of the ergometer.

Coaching Cues:

1. If using an upper body cycle ergometer, the same cues apply to the upper extremities vs lower extremities on a traditional cycle ergometer.
2. Align the seat height so at full extension the participant’s knees are only slightly flexed.
3. The handlebars are there for balance support and shouldn’t absorb a lot of body weight. Additionally, keep the feet and legs relaxed for an upper body ergometer.

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