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Car diopulm Phys Ther J. 2012 June; 23(2): 19–29. PMCID: PMC3379719

The Submaximal Clinical Exercise Tolerance Test (SXTT) to Establish Safe Exercise

Prescr iption Parameters for Patients with Chronic Disease and Disability

Eduard Gappmaier , PT, PhD

Author information Copyright and License information

Abstract

Purpose

To describe how to perform a Submaximal Clinical Exercise Tolerance Test (SXTT) as part of an exercise

evaluation in the physical therapy clinic to determine an appropriate exercise prescription and to establish

safety of exercise for physical therapy clients.

Summary of Key Points

Physical activity is crucial for general health maintenance. An exercise evaluation includes a comprehensive

patient history, physical examination, exercise testing, and exercise prescription. The SXTT provides

important clinical data that form the foundation for an effective and safe exercise prescription. Observations

obtained during the exercise evaluation will identify at-risk patients who should undergo further medical

evaluation before starting an exercise program. Two case examples of SXTTs administered to individuals with

multiple sclerosis are presented to demonstrate the application of these principles.

Statement of Recommendations

Due to their unique qualifications, physical therapists shall assume responsibility to design and monitor safe

and effective physical activity programs for all clients and especially for individuals with chronic disease and

disability. To ensure safety and efficacy of prescribed exercise interventions, physical therapists need to

perform an appropriate exercise evaluation including exercise testing before starting their clients on an

exercise program.

Key Words: exercise evaluation, clinical exercise testing, exercise prescription

INTRODUCTION AND PURPOSE

The health benefits of regular physical activity have been widely publicized. On the other hand, many clinical

observations indicate that negative physical effects occur with inactivity. According to the 2008 Physical Activity Guidelines for Americans, published by the United States Department of Health and Human Services,

adults should perform at least 150 minutes a week of moderate-intensity, or 75 minutes a week of vigorous-

intensity aerobic physical activity, or an equivalent combination of moderate- and vigorous-intensity aerobic

activity. Moderate-intensity aerobic physical activity has been defined as 40% to 59% of aerobic

capacity reserve and vigorous-intensity activity as 60% to 84% of reserve. Healthy, asymptomatic,

previously inactive adults may begin moderate-intensity activity safely without the need to consult a health

care provider. However, individuals with symptoms, chronic conditions, or disabilities are advised to begin an

exercise program after appropriate medical evaluation and with guidance of a health care provider.

The American Physical Therapy Association (APTA) enthusiastically endorses the national effort to increasephysical activity in all sedentary persons. Due to their extensive clinical background, their expertise in

exercise physiology and the movement sciences and the physical therapy patient management model with a

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focus on client-centered care, the physical therapist is uniquely positioned to assist people of all ages and

abilities to design and monitor safe and effective physical activity programs that help establish life-long habits

of physical activity.

Since persons with symptoms, chronic conditions, or disabilities may have limited exercise tolerance and are

at increased risk for adverse events associated with physical activity, they require a clinical exercise evaluation

to screen for potentially dangerous signs or symptoms of exercise intolerance and to establish safe and

appropriate parameters for their exercise prescription.

A maximal exercise test or clinical “stress test” is considered the gold standard to determine maximal exercise

capacity as a baseline for exercise prescription and to reveal potential signs and symptoms suggesting

myocardial ischemia due to coronary artery disease or other abnormal physiological responses to exercise.

These tests however require advanced expertise and equipment. They are associated with a higher risk for

complications due to exercise to the point of volitional exhaustion or occurrence of signs or symptoms of

cardiovascular compromise and thus may require medical supervision.

Standard submaximal exercise tests as described in ACSM's Guidelines for Exercise Testing and Prescription

and summarized by Noonan et al to estimate maximal oxygen uptake are based on several assumptions.

One primary assumption is that the maximal heart rate of the individual undergoing the test is similar to a

predicted maximal heart rate based on a formula such as “220-age.” Such formulae may be applied with

caution to healthy individuals as long as one is aware of the significant inter-individual variability (SD=10-12

beats/min) of maximal heart rate. However, many studies that measured maximal aerobic capacity of

persons with a variety of medical conditions such as cardiovascular, metabolic, neurologic or neuromuscular

disease found significantly lower maximal heart rates in these patient populations.

In addition, patients may be on medications that alter heart rate response to exercise. Another

assumption underlying standard submaximal exercise testing is that mechanical efficiency (oxygen

consumption at a given work rate) is the same for every person undergoing the test. However, many studies

on persons with chronic disease and disability, especially if neuromuscular symptoms are present, have found

a significant difference in oxygen cost for a given work rate as compared to healthy controls. Since

these assumptions which underlie aerobic capacity predictions based on standard submaximal exercise tests

are frequently not met when testing persons with clinical conditions, these tests are usually not appropriatefor these populations. The author therefore suggests that a “Submaximal Clinical Exercise Tolerance Test

(SXTT)” is most appropriate in the standard physical therapy clinic to provide baseline data and to determine

safe and effective exercise prescription parameters. The purpose of this paper is to describe how an exercise

evaluation including a SXTT is performed and to discuss how the resulting data and observations are used to

determine an appropriate exercise prescription for clients seen in the physical therapy clinic.

THE EXERCISE EVALUATION

The objectives of an exercise evaluation include: first, to establish safety for exercise participation, second, to

collect the necessary information to write an appropriate exercise prescription and lastly, to collect baseline

data for outcome assessment. The components of an exercise evaluation are summarized in Figure 1. It is

recommended that clients obtain a referral for an exercise evaluation and prescription from their physician.

The physician may note valuable special precautions or considerations on the referral or may recommend

prior medical evaluation and testing of high risk patients. The pretest evaluation includes a comprehensive

patient history including a complete medical history, medication list, screening for heart disease risk factors,

signs and symptoms, and an activity history. This information is best obtained through a comprehensive

questionnaire that is completed by the patient before the appointment and then reviewed and clarified if

necessary during the patient interview. The physical therapy examination includes a standard

musculoskeletal and neurological screening examination as well as a careful cardiovascular and pulmonary

screening examination including assessment of resting heart rate and pulse, blood pressure, peripheral

vascular status, auscultation of heart and lung sounds, pulse oximetry, and ideally, in patients with increased

cardiac risk, a resting ECG. Special tests dependent on the client's specific diagnoses, impairments, andfunctional limitations may include functional mobility testing, quantitative strength assessment, body

composition analysis, pulmonary function testing, health-related quality of life assessment, and disease

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specific assessments such as fatigue assessments for patients with chronic fatigue syndrome, cancer, or

multiple sclerosis. While many of these tests may be optional, the minimum information that must be

obtained through the patient history and physical examination before conducting the exercise test includes

information to satisfy safety and test protocol considerations. Based on the cardiac screening and risk

assessment and initial risk stratification following ACSM guidelines, the physical therapist determines if

it is safe to proceed with an exercise test or if the patient needs to be referred back to the referring physician

for further medical evaluation and medical exercise testing. Contraindications to exercise testing are

summarized in Table 1. Based on the activity history, musculoskeletal exam, and cardiovascular and

pulmonary screening the therapist determines the optimal exercise test mode and the appropriate test

protocol. Finally, as should be standard practice today for any physical therapy intervention, an informed

consent document is reviewed and discussed with the client and signed before proceeding with the exercise

test.

Figure 1

Components of an Exercise Evaluation

Table 1

Contraindications to Exercise Testing

Test Protocol

When performing exercise evaluations in the physical therapy clinic, the clinician may face major challenges

when considering the “optimal exercise protocol.” The clinician will encounter a dramatic range of maximal

exercise capacities. We sometimes test patients with a peak exercise capacity of as low as 2 METs (ie, person

with severe cardiopulmonary disease who barely endures 2 minutes of walking at 1.5 mph) and occasionally

test physically active chronic disease patients with mild disability who easily achieve a peak intensity greater

than 10 METs. Furthermore, the clinician encounters a great variability in cardiovascular risk profiles. An

otherwise healthy client with chronic disease and disabilities may have no significant cardiovascular risk

factors while another client may have serious signs and symptoms of cardiovascular, pulmonary, or metabolic

disease. In addition the clinician may work with people with chronic disease and a wide range of

musculoskeletal or neuromuscular impairments. Conditions such as degenerative joint disease, chronic low

back pain, or other musculoskeletal pain syndromes may “flare up” when subjected to unaccustomed

increased physical demands. It should be obvious that no single “gold standard” clinical exercise testing

protocol (ie, Bruce Treadmill Protocol) will meet the demands of such a heterogeneous patient population.

This environment requires a highly individualized approach based on either a large menu of standardized

facility protocols or a custom design method driven by the pretest assessment of the individual client.

The first decision for the examiner to make is to choose the most appropriate mode of exercise for the exercise

test. While treadmills and cycle ergometers are most commonly used for clinical exercise testing, these

standard exercise devices are frequently not optimal for physical therapy clients if lower extremity

impairments or balance problems are limiting their lower extremity work capacity. For such individuals

combined arm- and leg ergometry results in higher peak work load, heart rate, and oxygen uptake

values. Due to testing and training specificity issues, it is recommended that the client, if possible, is

tested on an exercise device that is consistent with the preferred and available mode of training for the

subsequent exercise program. The main requirement for an exercise device used for a progressive testing

protocol is a reliable, repeatable, stepwise workload adjustment, ideally with the option to calibrate the power

input to assure accuracy. Based on experience and clinical judgment, the evaluator then defines an

individualized work rate progression for the respective client that will achieve the desired end-point within an

optimal exercise time of 8 to 12 minutes after a low intensity warm-up or chooses an appropriate testingprotocol from a series of previously defined facility protocols (see Table 2). When performing a treadmill test

on previously inactive, deconditioned clients, the author customizes the protocol to the individual as follows:

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the testing protocol is started with 2 minutes at a “slow” walking pace to allow accommodation to the

treadmill. The treadmill speed may range from 1.0 mph (in rare cases even slower) to 2.5 mph. Over the next

few 2-minute stages the walking pace is advanced in 0.5 mph increments to a “brisk but comfortable” walking

speed. During subsequent 2-minute stages, intensity is increased by raising the treadmill grade in 2%

increments until criteria for test termination are achieved. This occurs in most cases within the recommended

time period of 10 to 20 minutes (including incorporated low-intensity warm-up) with a well-tolerated,

comfortable work load progression. When testing on upright or reclined leg cycle ergometers or all-extremity

ergometers (ie, Schwinn Airdyne™ cycle ergometer, NuStep™ recumbent cross trainer) we select one of 5

workload progressions based on the pretest assessment of the client that usually results in an appropriate test

duration with a well-tolerated work load progression (see Table 2).

Table 2

Generic Exercise Testing Protocols (Workload in Watts)

Measurements

Measurements obtained during each stage of a SXTT always include workload, heart rate, blood pressure,

and ratings of perceived exertion (RPE) and dyspnea. In addition, the client is continuously monitored for

abnormal signs or symptoms. When indicated by the client's history and diagnoses, oxygen saturation and the

electrocardiogram (ECG) may also be monitored.

Peak workload obtained with a maximal exercise test (“stress test”) is the best indicator of fitness and physical

work capacity. When evaluated in relationship to indicators of relative intensity and effort (heart rate, RPE,

dyspnea), the peak workload obtained during a SXTT may be used effectively to determine an appropriate

intensity for the exercise prescription and may allow for an estimate of physical work capacity (see discussion

of test endpoints and exercise prescription below).

Heart rate may be reliably monitored through palpation of a radial or carotid pulse or may be obtained

through auscultation, however, inexpensive telemetric heart rate monitors are very accurate and reliable as

long as electric interference is avoided and are much easier to use. Heart rate may also be obtained with anECG. Increasingly affordable ECG systems have the advantage of also monitoring heart rhythm and allow for

detection of abnormalities suggestive of myocardial dysfunction, both at rest and during exercise, which may

warrant further medical evaluation. In his wellness practice, the author has been detecting such rhythm

abnormalities during exercise evaluations on average in 1-2 clients (out of 50-60 exercise evaluations) each

year. All of these clients have been referred with negative cardiac history and medical clearance for exercise

evaluation and prescription by their physicians. Due to these abnormal findings these patients subsequently

have been referred back to their referring physicians with the recommendation for further cardiac evaluation.

Physical therapists can be at times intimidated by this technology, although essential ECG monitoring skills

can easily be acquired through a basic ECG interpretation course offered by many medical facilities,

publishers, or online education providers and some practice in the clinic.

Blood pressure should be measured at rest in sitting and in the exercise position followed by measurements

during each test stage and during recovery. Since most standard automated units are not reliable during

exercise, these measurements are best obtained through manual auscultatory methods.

At the end of each test stage, RPE is measured with a standard Borg or Omni RPE scale and

dyspnea ratings are obtained with a standardized dyspnea rating scale (see Table 3). Before the test,

patients are instructed to report any abnormal signs and symptoms they may experience du ring the test.

Throughout the test and the recovery period, the patient is carefully observed for signs and symptoms of

cardiovascular compromise such as substernal chest pain or other angina symptoms, lightheadedness, pallor,

nausea or sudden, unusual sweating or fatigue. Patients with chronic disease and disability also need to be

monitored for other clinical symptom changes such as exacerbation of pain in persons with arthritis,symptom modification due to increased core temperature in persons with multiple sclerosis, onset or increases

in tremor in persons with neurodegenerative disease, etc.

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Table 3

5-Grade Dyspnea Scale

Test termination criteria

One of the most challenging questions when administering a SXTT is when to stop the test. The test is stopped

without hesitation if any of the indications for (maximal or “symptom-limited”) exercise test termination as

defined by the ACSM guidelines are met (see Table 4 and 5). In addition, any exercise test intended to be

classified as a “submaximal” exercise test should be stopped when a heart rate of 85% of age-adjustedmaximal heart rate (AAMHR) is achieved as per definition of “submaximal” by ACSM guidelines.

However due to their clinical condition or due to the great inter-individual variation of maximal heart rate,

the testing subject may reach volitional exhaustion before achieving 85% of AAMHR. This predetermined

“submaximal exercise test endpoint” is thus, in many cases, not relevant. In most cases the SXTT will be

terminated by decision of the tester based on predetermined test objectives, the tester's clinical observations

and the tester's clinical judgment of the individual's risk of adverse events. In order to determine an

appropriate exercise intensity for the exercise prescription, the tester needs an estimate of the subject's

maximal physical work capacity. Based on an integrated assessment of both physiological and subjective

indicators of subject effort (heart rate, dyspnea level, RPE rating), the experienced tester can usually predict a

reliable estimate of the subject's maximal exercise capacity thus meeting one of the primary objectives of thetest. This stage in the test will usually be 1-2 levels above the subsequently prescribed, ideal training intensity,

so that another objective of the SXTT is met: to demonstrate appropriate acute adaptations to exercise to a

level beyond the prescribed training intensity suggesting that the subsequently prescribed exercise parameters

will be safe for the client. Thus the SXTT should be terminated, once based on the administrator's subjective

appraisal the following two objectives are accomplished: first, an estimate of maximal workload is perceptible

and second, the intensity of exercise has been safely progressed beyond apparent moderate to vigorous

exercise prescription parameters. The confidence in making this somewhat subjective decision increases with

tester experience and the novice test administrator is advised to perform a number of tests under the

supervision of a more experienced tester to hone this skill. If this is not possible, then (s)he should proceed

initially cautiously with tests on low-risk individuals until confidence in making this decision appropriately is

gained.

Table 4

General Indications for Stopping an Exercise Test in Low-Risk Adults

Table 5

Indications for Terminating Exercise Testing

Safety considerations and contraindications

In order to ensure safety during exercise testing the tester needs to have adequate knowledge of exercise

testing and management principles, and understand and follow appropriate exercise testing guidelines as

summarized in the ACSMG. Absolute and relative contraindications to exercise testing are listed on Table 1.

Contraindications to exercise testing most commonly seen in our clinic are uncontrolled hypertension and

previously undetected rhythm abnormalities. The author recommends that the physical therapist require a

physician's referral with clearance for exercise participation before proceeding with an exercise evaluation.

However, it is important to understand that such a document does not assure the absence of undiagnosed

cardiovascular disease and risk of adverse events in response to physiological stress in previously sedentary

individuals. These conditions may not be ruled out by a review of the patient's history and a brief physical

exam in the physician's office. It is not unusual that a careful pretest screening and physical examination by the physical therapist reveals signs and symptoms of cardiopulmonary disease that would warrant a

cardiology evaluation in a client who presents with an appropriate physician's referral. In this case the patient

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is sent back to the referring physician with a note documenting the findings and the suggestion that “due to

these findings a medically supervised exercise test is recommended by ACSM guidelines before starting an

exercise program.” Referring physicians usually graciously comply with this proposition.

To ensure appropriate responses to potential adverse events during exercise testing, facility emergency

procedures need to be clearly defined and basic emergency equipment such as an automated external

defibrillator (AED) should be readily available in the testing area. The tester and support staff should

have a minimum of basic cardiac life support (BCLS) certification. A physical therapist who may

independently evaluate patients in the high risk category should strongly consider advanced cardiac lifesupport (ACLS) certification.

EXERCISE PRESCRIPTION AND ACTIVITY RECOMMENDATIONS

The exercise prescription for cardiovascular conditioning includes the following exercise parameters: mode,

intensity, duration, and frequency. The exercise prescription needs to be individualized to the respective

physical therapy client based on the data obtained in the exercise evaluation and clinical diagnosis, history,

current health status, risk profile, exercise history, and the client's goals and preferences. A comprehensive,

long-term “rehabilitation and wellness program” should also include resistance and flexibility exercises and, if

indicated, functional mobility and balance training. However, a discussion of these areas is beyond the scope

of this paper and the discussion in this article will be limited to cardiovascular conditioning or aerobic

training.

Due to the principle of specificity of exercise, the exercise prescription will be most specific for the mode of

exercise that was used during the exercise test. However, exercise parameters may be adapted to other

training modes that are appropriate for the respective client. For clients without significant physical

impairments and functional limitations, a wide variety of training modes and exercise equipment may be

considered. For most of such individuals with low to moderate fitness levels, walking can be used for a simple

but effective exercise program or they may use any aerobic exercise equipment as long as the

prescribed exercise parameters can be achieved and controlled. As stated earlier, persons with mobility

impairments may be able to exercise at higher workloads and thus be able to optimize exercise adaptations

and benefits by completing overall higher training volumes when performing combined arm-leg-ergometry.

Some may require special equipment accessories or modifications such as leg stabilizers for persons with lower

extremity muscle imbalance, full foot plate strap-in pedals for persons with motor control problems and

tremors or grip-assist devices for persons with poor grip (see Figures 2 and 3).

Figure 2

Recumbent Cross Trainer with Leg Stabilizers and Grip-Assist Device

Figure 3

Custom Pedal with Straps for Combined Arm/Leg Ergometer

Current standards recommend 2.5 to 5 hours of moderate-intensity or 1.25 to 2.5 hours of vigorous-intensity

aerobic physical activity per week for adults to achieve and maintain good health/fitness and decrease the

risk of diseases related to a sedentary life style. Moderate-intensity aerobic exercise is defined as exercise

between 40% and 59% of aerobic capacity reserve that is comparable to 40% to 59% of heart rate reserve

(HRR) and vigorous-intensity exercise is considered to be at a training heart rate above 60% HRR (equivalent

to > 60% aerobic capacity reserve). In order to appropriately calculate HRR, a person's maximal heart rate

needs to be known. However, actual maximal heart rate is not obtained with the SXTT. As discussed earlier,

the practice to substitute AAMHR is not appropriate for most clients seen in the physical therapy clinic.

However, an appropriate, safe, and effective training intensity can be derived from the measurements and

observations obtained during the SXTT. As described in the section above, the experienced tester will have a

good sense of the maximal work capacity and maximal heart rate of the subject after observation and analysis

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of the stage-by-stage progression of heart rate and work load during the test as well as physiological and

subjective indicators of effort throughout the test and especially during the last stage of the test. Based on this

estimate of maximal heart rate (HRmax-estimate) and work load (WLmax-estimate), the tester then

determines the intensity prescription for moderate-intensity exercise (40-60% WLmax-estimate or 40-60% of

HRR based on HRmax-estimate) for the initial training phase. This exercise intensity may be gradually

progressed to vigorous-intensity exercise (60-80% WLmax-esimate or 60-80% of HRR based on HRmax-

estimate) if tolerated well throughout the prescribed training duration without undue fatigue or exacerbation

of clinical signs or symptoms. Ideally, after completion of the exercise evaluation, the patient is monitored

during a subsequent actual exercise training session performed at the prescribed exercise parameters.

Depending on the physiological and subjective responses during this practice training session, the exercise

prescription can be adjusted if indicated.

Guidelines recommend that moderate-intensity exercise is performed for at least 30 minutes at least 5 times

per week or vigorous-intensity exercise for at least 20 to 25 minutes at least 3 times per week.

For severely deconditioned clients with chronic disease or disabilities, this volume of exercise will most likely

be unrealistic–at least during the initial conditioning phase–and duration and frequency must be adjusted

according to the individual capacity. It is crucial to start with a conservative exercise volume to avoid the

development of overuse injuries. It is always easier to increase an overly conservative training load than to be

forced to reduce training parameters or even abort the exercise program to allow for recovery from overuse

injuries. We usually start new clients with a conservative estimate of exercise duration based on our

observations of exertion and subjective fatigue during the SXTT with a recommended frequency of 3 times per

week with a rest day between exercise sessions. We tell clients to expect to be moderately tired after the

exercise session, but that we expect them to recover within a couple of hours after exercise. If fatigue or any

signs of discomfort persist into the next day, we recommend a reduction of exercise parameters. Depending

on the specific diagnosis, severity of disease, and level of disability additional special considerations may affect

the exercise management of the physical therapy patient. For example, patients with diabetes, especially if

dependent on exogenous insulin, will require more frequent glucose monitoring and medication adjustments

to compensate for the effects of increased physical activity. Patients with neurodegenerative disease such as

multiple sclerosis, may experience symptom modification or a temporary worsening of neurological symptoms

in response to an exercise induced increase in core temperature. A discussion of all these special disease-specific clinical considerations is beyond the scope of this paper and readers are referred to relevant literature

such as the ACSM's Exercise Management for Persons with Chronic Disease and Disabilities. Finally, the

physical therapist needs to remain aware about the potential day-to-day variability in the health status and

energy level of persons with chronic disease and disability that requires ongoing reassessment and adaptation

of program parameters and education on appropriate self-assessment and self-adjustment by the patient.

PATIENT CASE EXAMPLE 1 (see Figure 4 & video online at:

http://stream.utah.edu/m/show_grouping.php?g=3f55168646473e2292)

Figure 4

Submaximal Clinical Exercise Tolerance Test - Case Example 1 (Jerry)

Jerry is a 59-year-old architect who received a diagnosis of definite relapsing-remitting multiple sclerosis

(MS) 8 years ago. Two years ago his diagnostic classification was changed to secondary progressive MS. His

EDSS (Expanded Disability Status Scale) score is 7.0, which is defined as “unable to walk beyond

approximately 5 meters even with aid, essentially restricted to wheelchair; wheels self in standard

wheelchair and transfers alone; up and about in wheelchair some 12 hours a day.” He has been sedentary

since time of MS onset and presents with a referral for participation in the University of Utah Multiple

Sclerosis Rehabilitation and Wellness Program. His risk factors include overweight, past smoking history, pre-

hypertension, inactivity, and age/gender (older male). He has an otherwise unremarkable medical history

except complaints of intermittent palpitations for the past several months. His medication list includes a MS

disease-modifying agent, an antispasticity agent, and an antidepressant. None of these medications are

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known to affect the cardiovascular response to exercise. His physical therapy examination reveals normal

strength and function in his upper extremities and marked weakness and spasticity in his lower extremities.

Based on his clinical impression the tester selects the Schwinn AirDyne™ arm/leg cycle ergometer as testing

mode for the SXTT with an individualized testing protocol starting at 20 Watts with a 20 Watt progression

per 2 minute intervals. Due to the patient's risk profile and history of palpitations, the evaluator chooses to

monitor the patient's ECG at rest and during exercise. Exercise test data are summarized in Table 6. Jerry's

resting heart rate is 68, his resting ECG displays a normal sinus rhythm, his resting blood pressure is 136/76,

which is slightly above ideal. During his first test stage, his heart rate increases to 94 and his RPE rating is one(“very light;” Borg 1-10 scale). His workload is increased to 40 Watts which causes a heart rate increase to

107. His blood pressure is recorded just slightly above resting at 138/78 and his RPE rating is 2 or “light.” The

ECG displays sinus tachycardia without abnormalities. During stage 3 at an intensity of 60 Watts, it becomes

obvious that Jerry relies primarily on his arms to maintain the work load. His heart rate increases to 117 and

his RPE rating is 4 or “somewhat hard.” His exercise ECG remains normal. The work load is further increased

to 80 Watts for stage 4 of the test. Jerry is obviously exerting significant effort at this intensity, which is also

reflected in his RPE rating of 7 or “very hard.” His heart rate increases to 136 bpm and his blood pressure is

recorded at 152/80. Mild to moderate exercise induced dyspnea is evident, rated by the tester as 2 (5-point

scale: “mild, some difficulty;” see Table 3). The ECG continues to show sinus tachycardia without any

abnormal waveforms. At this point it is obvious to the tester that Jerry has reached a workload clearly above a

reasonable training intensity for his current fitness level. One of the objectives of the SXTT has thus been

achieved: since there have been no abnormal signs or symptoms observed throughout the test, the

assumption, that Jerry will be “safe” when exercising at the (lower) intensity, which will be later prescribed for

his exercise program, should be warranted.

Table 6

Submaximal Clinical Exercise Tolerance Test - Case Example 1 (Jerry)

Based on the tester's integrated assessment of the stage-by-stage observations of the physiological and

subjective indicators of subject effort (heart rate, dyspnea level, tester observation of patient effort, RPErating), the tester also feels quite confident at this point to provide a good estimate of Jerry's maximal exercise

capacity thus meeting the second objective of the SXTT. Based on the stage-by-stage observation of subject

effort by the tester, consistent with the apparently reasonable RPE ratings given by the subject, the tester has

the impression that Jerry would be able to advance to and probably complete the next 2-minute stage at an

intensity level of 100 Watts. However, by the end of this stage, he would probably reach volitional fatigue with

an RPE rating of 9 or 10 (very, very hard or maximal) and would most likely not be able to continue to the

next stage. The tester also estimates that his heart rate, which increased quite linearly during the first 3stages

and then increased in slope during stage 4, may have risen another 20-25 bpm during maximal effort. Based

on this SXTT, he thus predicts a maximal workload of approximately 100 Watts and a maximal heart rate of

approximately 160 bpm.

Based on these estimates he determines the following exercise prescription: Target Heart Rate (THR) Range:

105-125 bpm (40-60% HRR based on HRmax-estimate, rounded to nearest 5) with recommended THR: 115

bpm (50% HRR); initial work load: 50 Watts (50% WLmax-estimate). Recommended RPE during training:

3-4 (moderate to somewhat hard), not to exceed 4 (somewhat hard). Initial duration: 15 minutes plus 2-3

minutes warm-up and cool-down, gradually increased as tolerated to 30 minutes. Initial frequency: 3 times

per week with at least one rest day between exercise days. Jerry will be closely monitored during his first

training session and exercise parameters may be modified if necessary.

PATIENT CASE EXAMPLE 2 (see Figure 5 & video online at:

http://stream.utah.edu/m/show_grouping.php?g=3f55168646473e2292)

Figure 5

Submaximal Clinical Exercise Tolerance Test - Case Example 2 (Linda)

http://stream.utah.edu/m/show_grouping.php?g=3f55168646473e2292











Linda is a 53-year-old research pharmacologist who received a diagnosis of definite relapsing-remitting MS24 yrs ago. Several years ago her diagnostic classification was changed to secondary progressive MS. Based on

her walking ability her EDSS score is 6.5, which is defined as “constant bilateral assistance (canes, crutches,

braces) required to walk about 20 meters without resting.” She uses a manual wheelchair or electric

scooter for energy-efficient ambulation when she leaves her home. In the past she has been moderately active,

however, she became more sedentary when she started to use a wheelchair one year ago and now presents

with a referral for participation in the University of Utah Multiple Sclerosis Rehabilitation and Wellness

Program. Except for MS she has an unremarkable medical history. Her medication list includes a MS disease-

modifying agent, an analgesic drug, and multiple dietary supplements. None of these medications are known

to affect the cardiovascular response to exercise. Her medical history and physical examination do not reveal

any significant heart disease risk factors, however, she reports a “history of PVCs” (premature ventricular

contractions) on her health history questionnaire. Her physical therapy examination reveals normal strength

and function in her upper extremities and marked weakness and mild spasticity in her lower extremities.

Based on his clinical impression the tester selects the NuStep Recumbent Cross Trainer as testing mode for

the SXTT with an individualized testing protocol starting at 40 Watts with a 10 Watts progression in 2 minute

intervals. Due to the patient's self-reported history of PVCs, the tester chooses to monitor the patient's ECG at

rest and during exercise. Exercise test data are summarized in Table 7. Linda's resting heart rate is 57, her

resting ECG displays a normal sinus rhythm, her resting blood pressure is 108/60. She tolerates the gradual

increase in work load from stage 1 to 5 well, which is reflected in her RPE rating that gradually increases to 5

(“hard”) by stage 5. Her blood pressure response is appropriate with a workload-related increase of the

systolic value as expected. Her ECG displays a sinus rhythm without abnormal waveforms or beats. Her heart

rate response is blunted from stage 1 to 3, then rises significantly during stage 4 followed again by only a small

increase during stage 5, in spite of a considerable increase in effort by the client (see Table 7 and video). At

this point in the test Linda is working quite hard, as can be observed by the tester and as reflected by her RPE

rating (5, “hard”). The tester may consider terminating the test at this point. The subject is obviously working

at a higher workload/intensity than she will train in the future based on the exercise prescription she will

receive later today. One of the objectives of the SXTT has thus been achieved: since there have been no

abnormal signs or symptoms observed during the test, the assumption that Linda will be “safe” when

exercising at the (lower) intensity, which will be later prescribed for her exercise program, should be

warranted. However, the tester has difficulty interpreting the non-linear, blunted heart rate response of this

client. At the end of stage 5, in spite of significant effort, her heart rate is only 103 bpm, which is only 62% of

her AAMHR. He decides to continue the test and progress to stage 6 with a work load increase to 90 Watts, which will be very strenuous for Linda. Based on his experience, he anticipates two possible responses which

would reveal valuable clinical information important for test interpretation. One possibility may be that the

increased sympathetic stimulation associated with the increased effort necessary to produce this workload

may result in a further significant increase in heart rate. The other possibility may be the absence of an

appropriate heart rate response in spite of the increased effort suggesting chronotropic incompetence,

possibly due to an MS-related autonomic neuropathy. As expected, Linda is exerting significant effort at this

intensity (see video), which is also reflected by her RPE rating of 7 (“very hard”). She is relying heavily on her

arms to maintain the workload. Mild to moderate exercise induced dyspnea is evident, rated by the tester as 2

(“mild, some difficulty”). The ECG continues to show a regular sinus rhythm without abnormal waveforms.

However, there is no further increase in heart rate, in spite of the valiant effort of the client, who reaches

volitional fatigue (“my legs gave out”) by the end of the 2 minute test stage. This SXTT thus evolved into amaximal exercise test that provides the following information: peak work load = 90 Watts, peak HR = 103

bpm.

38








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Table 7

Submaximal Clinical Exercise Tolerance Test - Case Example 2 (Linda)

Based on these measurements, the tester determines the following exercise prescription: Target Heart Rate

Range: 85-95 bpm (60-80% HRR, rounded to nearest 5; based on his clinical judgment the evaluator

determines that the “vigorous intensity” range is most appropriate in this case); initial work load: 50 Watts

(55% peak work load). Recommended RPE during training: 3-4 (moderate to somewhat hard). Initial

duration: 15 minutes plus 2-3 minutes warm-up and cool-down, gradually increased as tolerated to 30

minutes. Initial frequency: 3 times per week with at least one rest day between exercise days. Linda will be

closely monitored during her first training session and exercise parameters may be modified if necessary.

This second real-life case presented by the author was intentionally more complex to demonstrate the

importance of clinical judgment and decision making when engaging in the “art of exercise testing and

prescription.” It is also a good example why AAMHR should never be used when prescribing exercise for

persons with chronic disease and disability. Without an appropriate exercise evaluation, an uninformed

clinician may have prescribed this patient a “conservative” exercise intensity based on 40% to 60% HRR using

AAMHR with a THRR of 101-123 bpm, which would be inappropriate and potentially dangerous.

CONCLUSIONS

Clinical exercise management requires a highly individualized approach to meet the needs of the diverse

patient population seen in physical therapy practice. To ensure safety and efficacy of prescribed exercise

interventions, physical therapists need to perform an appropriate exercise evaluation including exercise

testing before starting their clients on an exercise program. The Submaximal Clinical Exercise Tolerance Test

provides important clinical data that form the foundation for an effective and safe exercise prescription and

which may identify at-risk patients who should undergo further medical evaluation before starting an

exercise program. While based on sound principles of medical exercise science, clinical exercise management

is also an art that requires good clinical decision-making skills as well as experience.

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