SUBMAXIMAL EXERCISE TESTS
EXERCISE MODES
The most commonly used mode of exercise for submaximal exercise testing is the cycle ergometer. However, any exercise mode that allows for standardization of the work rates with known estimates of V˙O2can be utilized. Both treadmills and steps are other rela-tively common modes of exercise for submaximal exercise testing.
Cycle Ergometer
There are several advantages to using the cycle ergometer that make it the mode of choice for submaximal exercise testing. One advantage to the cycle is the non–weight-bearing mode of exercise provided, making it a good choice for orthopedic injury cases.
Also, the cycle ergometer is a relatively safe mode of exercise as there is less danger of falling off of the apparatus as compared to a treadmill. BP and HR by palpation are eas-ily measured during exercise on the cycle ergometer because of the limited noise that the cycle produces as well as the natural stabilization of the upper body and arm. Addi-tionally, the cycle ergometer is less expensive and is more portable than a treadmill, re-quires little space, and has no electrical needs.
There are a few disadvantages with the use of the cycle ergometer that merit consid-eration. One disadvantage is that a cycle is not a common mode of exercise or activity for many adults in the United States, especially in older populations. Another potential disadvantage is that mechanically braked cycle ergometers require the client to maintain a constant pedaling cadence to keep the work rate constant.
Generally, the mechanically braked Monark cycle ergometer is the most popular brand used for submaximal exercise testing because of the ease in calibrating the er-gometer. An example of a mechanically braked cycle ergometer is shown in Figure 7.2.
Calibration of this ergometer ensures accurate work outputs for the different stages of a submaximal test. The calibration procedure for the Monark cycle ergometer is provided in Box 7.4.
Proper seat height is important for optimal performance when using cycle ergome-ters. The knee should be flexed at approximately 5 to 10 degrees in the pedal-down po-sition with the client seated with toes on the pedals. Figure 7.3 illustrates an incorrect seat height setting. Another way to check seat height is to have the client first place the heels on the pedals. With the heels on the pedals, the leg should be straight in the pedal-down position. Also, the seat height can be aligned with the client’s greater trochanter, or hip, with the client standing next to the cycle. Most importantly, the client should ac-tually sit on the bike, turn the pedals, and evaluate comfort with the seat height. While pedaling, the client should feel comfortable and there should be no rocking of the hips.
Also, the client should maintain an upright posture, which may require an adjustment to the handlebars, and should not grip the handlebars too tightly.
Work Output Determination
Chapter 7 in ACSM’s GETP8 provides a summary of the metabolic calculation equations, which includes information on work output settings. However, because the determina-tion of work output is a critical component of submaximal cycle exercise testing, an
Calibration screw
Force scale Friction belt
Pendulum
Flywheel Force knob
FIGURE 7.2. The features of a mechanically braked cycle ergometer. (Reprinted from Adams, G. Exercise physiology laboratory manual, 3rd ed. New York (NY): McGraw Hill: 1998, 140 p.)
Calibration of the Monark Cycle Ergometer
Prior to calibrating, examine the resistance belt and flywheel for excessive wear and dirt. The flywheel can be cleaned with steel wool and cleanser and the belt can also be cleaned with a mild detergent. However, you should not conduct a test if either is wet, so plan ahead. Most resistance belts have a lifespan of several years before they need replacing depending on usage.
The ergometer needs to be on a level surface for the calibration procedure.
1. Loosen or unfasten the resistance belt from the pendulum so that the pendu-lum hangs free. The line in the center of the pendupendu-lum should be in exact alignment with the zero line on the measurement scale. If not, loosen the lock nut to allow movement of the measurement scale to the correct zero point, and then tighten the lock screw to hold this position.
2. Using certified calibration weights (between 3 and 7 kg), hang a known weight to the balancing spring (shorter belt) and check the reading on the measurement scale. If it is not reading the exact weight, adjust the pendulum to the correct weight on the scale by means of the adjusting weight inside the pendulum. To change the position of the adjusting weight, loosen the lock screw of the weight. Should the index of the pendulum weight be too low, move the adjusting weight upward in the weight, and if the index should be too high, the adjusting weight is moved somewhat downward and locked in the new position. Repeat until the correct reading is achieved.
When the calibration is completed, reattach the belt to the mechanism and be sure to pull the belt somewhat tightly without too much slack. Check the Monark ergometer handbookafor more detailed information about the calibration proce-dures.
aFound at www.monark.net/eng/pdf/manual828.pdf.
BOX 7.4
FIGURE 7.3. An example of a seat height set too low for cycle ergometry testing.
overview is provided here. Work is determined by multiplying force and distance. Work output, or power, is expressed in terms of how much work is performed per unit of time. Thus, to calculate work output (kp m min–1), the following equation is used:
Work output Resistance (kp) Revolutions per min (rpm)
Flywheel distance (m rev–1)
Resistance in this equation refers to the resistance caused by the flywheel by pendu-lum weight and friction belt and is measured in kiloponds (kp) or kilograms (kg). A kp is the force exerted by the Earth’s gravity by the swinging pendulum weight applied to the friction belt on the flywheel of the cycle. Resistance can be increased during the test to apply standardized work outputs to the client. Because kp and kg are somewhat in-terchangeable, the measure of work on the cycle ergometer is commonly expressed as kg m min–1.
Revolutions per minute (cadence) is simply the number of pedal revolutions per minute (rpm). Most common submaximal cycle protocols require a constant rate of 50 rpm. Newer ergometers usually have an electronic console that measures rpm; other-wise, the pedaling rate needs to be in cadence with a metronome set at 100 bpm (100 bpm for 100 downstrokes to produce 50 rpm). It is a good practice to periodically ver-ify that the console measure is reading accurately by cross-checking it with a metronome as shown in Figure 7.4.
Flywheel travel distance (meters per revolution) is a constant for each type of cycle.
The Monark cycle ergometer has a 6-m rev–1ratio. This means that the flywheel on the Monark cycle will travel 6 m per complete revolution of the pedal (the flywheel is 1.62 m in circumference and travels 3.7 circuits per pedal revolution). If another brand of cy-cle is used, the flywheel travel distance will need to be verified.
Because the rate is standardized to 50 rpm on the Monark cycle, the client will always be covering 300 m per minute (50 rpm 6 m rev–1). Some examples of some common cycle ergometer work output calculations using the Monark cycle at 50 rpm are as follows:
Resistance setting of 1 kg: 300 kgmmin–1 1 kp50 rpm6 mrev–1 Resistance setting of 1.5 kg: 450 kgmmin–1 1.5 kp50 rpm6 mrev–1
Resistance setting of 2 kg: 600 kgmmin–1 2 kp50 rpm6 mrev–1
It is also important to understand another unit, called watts, used to express work output. Watts can be determined from kg m min–1 by dividing by 6.12 (usually rounded to 6). For example, 600 kg m min–1is approximately equal to 100 watts.