Work tests with the bicycle ergometer by Per-Olof Åstrand, M.D. Dept. of Physiology, Gymnastik- och Idrottshögskolan, Stockholm, Sweden Original text from 1964

ERGOMETRY - test of ”physical fitness”

Exercise is the key to fitness In the 1950-ies Dr W von Döbeln developed a principle for accurate determination of the brake power of the bicycle ergometer. At the same time our institution was involved in a program of education with a fixed aim: to teach gymnastics teachers, athletics leaders and interested “amateurs” the foundations required to be able to inform and instruct in many health questions. It came natural to instruct how to make a simple test of the heart function and state of physical fitness with the help of the bicycle ergometer. In other words, we moved out the ergometer from the traditional laboratory and hospital environment to schools, clubs and enterprises. It became such a success that the existing resources to manufacture the bicycle ergometer were inadequate. The popularity of the athletics movement and to some extent our institution persuaded Monark to take up the production of the bicycle ergometer. Bicycling is a simple work form. Studies have shown that different persons, female or male, trained or out of condition, young or old, get the same energy output at a given load (power). It means that the demand of oxygen is relatively alike, i.e. the mechanical efficiency is quite alike for different individuals. The load on the bicycle ergometer gives a good idea about the demands put on the oxygen transport organs, especially on the heart and on the circulation of the blood. The blood volume which the heart has pumped out in the aorta is to a great extent fixed by the oxygen demand. The technical term for the blood volume that the left heart pumps out per minute is called the minute volume of the heart. The emptying for each beat is called the stroke volume of the heart. We then get the formula Minute volume = stroke volume x heart frequency (“the pulse”). A person with a small stroke volume has to compensate for this with a high pulse to reach a certain minute volume. The pulse during a given work on the bicycle ergometer will thus be high. If this person had been relatively untrained at the test occasion, physical training can give an increased stroke volume. A new work test on the same load some months later is then done with a lower pulse frequency. The heart can therewith work with better power and with less consumption of energy. The maximum oxygen uptake capacity has also increased. The ergometer test can thus reveal variations in the state of physical fitness. In connection with a medical examination or other medical studies more or less sophisticated methods can supplement the simple pulse taking. The Importance of Exercise The human body is built for action – not for rest. This was a historic necessity; the struggle for survival demanded good physical condition. But optimal function can only be achieved by regularly exposing the heart, circulation, muscles, skeleton and nervous system to some loading, i.e. training. In the old days the body got its exercise both in work and at leisure. In our modern society, however, machines have taken over an ever increasing share of the work elements which were formerly accomplished with muscular power alone. Our environment has come to be dominated by sitting, riding and lying. Thus, the natural and vital stimulation that tissues and internal organs receive through physical work has largely disappeared. Certain tissues such as muscles, bone and blood and also a number of bodily functions can adapt to inactivity – and to stress. Studies at the GIH’s Physiological Institution have proved that if you use 30 minutes for exercise in form of running, bicycling, swimming or skiing 2-

3 times a week, your condition has been improved by 15 per cent after a few months. The pump capacity of the heart muscle will increase and joints and muscles grow in strength. The body adapts to the new demands. The spare energy comes and you feel less tired and worn out. With increased physical activity fatness is counteracted, the appetite functions “safer”, you can eat more without risk for overweight and thereby the risk of lack of important food substances decreases. For many the effect of the exercise also means that the psychic balance increases. The feeling to have more energy often means that you can more easily keep your temper and endurance in strained situations. What kind of exercise to choose? You ought to think of two things:

1. You should have fun when exercising. Choose something you find pleasure in doing regularly. 2. To get a good effect out of the training you should choose a form of exercise that engages

large muscle groups. Not until this happens, the demand of increased blood transport and by that the demand for delivered oxygen will be so great that heart will be exposed to a work which increases the pump capacity. Running, bicycling, swimming, skiing and walking are excellent examples of exercises meeting this requirement.

P.O. Åstrand Department of Physiology Gymnastik- och Idrottshögskolan Stockholm, Sweden

ERGOMETRY Introduction Many physiological and medical studies indicate the beneficial effect of regular physical training. By regular physical training is meant the creation of a work capacity well encompassing the demands of routine work. The concept of physical condition should refer to the status of cardiac and circulatory function (the oxygen transport organs, see below). Thus the individual with a lower physical work capacity may be in better condition than the individual who, due to a good constitution, can perform better. One objective way of following variations in physical condition is to determine the heart rate during standardized work, for instance on a bicycle ergometer. It is intended to report the physiological background for this work test, describe the bicycle ergometer and methodology, and give some viewpoints on the evaluation of work test results. The term “ergometry” stems from the Greek “ergon” (work), and “metron” (measurement), and may be translated rather literally as “work measurement”. The instruments of work measurement, ergometers, vary in construction according to the form of analysis. The muscles’ capacity for variation in metabolism surpasses that of any other tissue, and calculations indicate that the muscular metabolic rate can increase by a factor of 100 from the resting condition. In this situation, major demands are placed upon the “service organs”, particularly upon the respiratory and circulatory apparatus. Otherwise the function would be impaired due to too great a change in the cell environment through an accumulation of waste products and carbon dioxide, as well as over-heating. No other cell activity can load the respiratory muscles and heart to such a high degree as can muscular activity. During prolonged work (minutes and more), a “combustion engine” is a necessity. The available energy is obtained via the combustion of fat and carbohydrates in the muscles, a process which requires oxygen. In research directed at the regulation of respiration and circulation, the investigation must be extended to work tests, including both submaximal and maximal work. Observation of the subject during muscular work can yield important information in an evaluation of circulatory function. A decrease in the heart’s pumping capacity may not be detectable at rest, with a demand for a cardiac output of 4-5 liters, but certainly will be so if the load, as a result of work, is a cardiac output of 10-15 liters per min. or more. Within the clinic, as well as in preventive medicine, it may be worthwhile to apply a work load corresponding to the subject’s normal daily energy expenditure. If this test load can be measured exactly, one can follow how the reaction to the load changes as a result of illness, convalescence, training, etc . These examples indicate that studies of the adjustment during muscular activity are important from the theoretical as well as the practical point of view. The methodology is here illustrated with a simple work test and some view-points are given on the evaluation of the results. Study within this area is still so new that there do not yet exist any inernational or even national norms. The methods and norms reported here are based primarily upon the exercise physiology research conducted at the Department of Physiology of Gymnastik- and Idrottshögskolan, Stockholm, during its more that 20-year existence. Type of Exercise Large muscle groups must be engaged if a work test is centered upon an analysis of the oxygen transport function. At submaximal work levels the work time should be at least four minutes, so that respiration and circulation have time to adapt. At that time a steady state, “second wind”, occurs, that is to say the rate of oxygen uptake in the lungs corresponds to the tissues’ oxygen demands. The steady state concept implies that such easily measured functions as heart rate and pulmonary ventilation have attained stability. It is advantageous if the absolute work load can be widely varied, so that subjects with differing capacity can have approximately the same relative load. If work is too light, (heart rate below 100-120 beats per minute), physiological factors, such as nervousness, can

influence the pulse reaction. If work is too heavy, a strain is placed upon the subjects’ desire to cooperate , and overloading also implies a certain risk. Bicycling has proved to be a very suitable work form, since, among other things, at a given load, (submaximal), it demands about the same energy output, whether the subject be young or old, trained or out of condition, elite bicyclist or unfamiliar with the sport. The bicycle ergometer was invented several decades ago, and has been widely used in physiological laboratories ever since. This instrument provides an exact measurement of the performed external work, and thus a graded and measureable load can be applied to the subject. Changes in circulation, respiration, and metabolism can be studied during and after work. During the last ten years, ergometry has been applied within sport, physiology, hygiene, industry, and medicine. Consequently the bicycle ergometer has become an important aid in the evaluation of the physical work capacity and of the physical condition. Bicycle ergometers of varying construction and price are available. That produced by MONARK in Sweden (Fig 1) is a modification of a construction by Associate Professor W von Döbeln (1), with the technical assistance of Mr. H Hagelin. If the bicycle ergometer is fixed to a stand in front of a bed, it may be used for work in the supine position. Work Test with the Bicycle Ergometer Whether or not a medical examination should be done before a work test depends, of course, upon the subject and the questions to be answered. Often the work test does not have the character of a clinical examination, but sometimes it does.

Monark Bicycle Ergometer Fig 1 For an active sportsman, the exercise test usually implies less of a load than do training and competition. Obviously in older, completely untrained subjects, or patients, a thorough medical history should be taken and a clinical examination regarding in particular the circulatory apparatus ought to be done before the test. (In such circumstances, the work test usually is combined with ECG recording an ECG being recorded and interpreted immediately previous to exercise. Whether or not a physician is to be present during testing depends upon the subject’s health and the object of the test.)

Here is presented a description of the construction of the MONARK BICYCLE ERGOMETER and an instruction on how to conduct a simple work test. For physiologists the use of a bicycle ergometer is certainly well known, and for them a special instruction is not considered necessary. For a work test are required: 1) a bicycle ergometer, 2) a metronome, 3) an ordinary clock or stop-watch for “work time”, 4) a stop-watch accurate within 1/10 of a second, or a special watch for heart rate measurement, and if possible, 5) a table fan.

Fig 2 Construction of the bicycle ergometer and calculation of the work load (see Fig 2). The gearing and circumference of the wheel have been so dimensioned that one complete turn of the pedals moves a point on the rim 6 meters. The metronome should be set to make exactly 100 beats per minute (make this setting with a stop-watch; if possible, the sliding weight should be fixed by a screw or other device). If the metronome timing is followed so that 50 complete pedal turns per minute are made, the “track distance” covered will be 300 metres per minute. The wheel is braked mechanically by a belt running around the rim. Both ends of this belt are attached to a revolving drum to which a pendulum, A in Fig 2, is fixed. The device thus acts as a pendulum scale, measuring the difference in force at the two ends of the belt. The belt can be stretched with the lever B, which is adjusted with the handwheel, and the deflection of the pendulum is read off on the scale D, graduated in kiloponds (kp). (1 kp is the force acting on the mass of 1 kg at normal acceleration of gravity; 100 kpm/min = 723 foot-ponds/min = 16.35 watts.) The braking power (kp) set by adjustment of belt tension, multiplied by distance pedalled (m), gives the amount of work in kilopond metres (kpm). If the distance is expressed per minute, then the rate of work in kpm per minute will be obtained. Setting of Load. The bicycle ergometer should stand on a level, firm foundation. With the subject mounted, but not touching the pedals, adjust the “0” mark on the scale D with the screw E so that it coincides with the mark on the pendulum weight A. N.B.: This setting must be made accurately if the load is to be precisely set. Work is started with a slack brake belt. Thereafter the belt should be stretched with the aid of the handwheel until the required work load is obtained (1 kp = 300 kpm/min., 2 kp = 600 kpm/min., 3 kp = 900 kpm/min., and so on, provided that the pedalling frequency is 50 turns per minute). Start, (or read off), the “work-time” clock. As the belt and wheel get warmed up the friction will change, necessitating readjustment, especially if the apparatus has been unused for any length of time. Check the load at least once a minute.

If the bicycle ergometer has been used for a long time without an interval the belt may tend to “jerk” and the pendulum weight will not become stabilized, especially in the case of a small load. Generally, the setting can be re-stabilized by stopping and turning the brake belt 180o (so that the outside comes against the rim). If the brake band is very worn, or if it has parted, it can easily be substituted, thanks to the “Swedish straps”. Webbing is the best material to use for this replacement, but as a temporary measure a piece of ordinary thick string or something similar can be used. By means of the “Swedish straps” the length of the belt can also be adjusted, enabling the load to be varied between approx 0,5 and 7 kp by means of the handwheel. If this is not possible the spring F no longer has the proper tension, (it gets weakened in time), and must be replaced. The entire scale can be stripped down for transportation. If not done, the pendulum weight A must be fixed with wrappings.

Fig 3 It should be noted that friction in the transmission, mainly in the chain, increases the work load by about 8 % above the one calculated from breaking force and distance moved. (This also holds true for many other ergometers, e.g. Krogh’s bicycle ergometer.) However, this extra friction is considered in table 2, where the oxygen uptake at various loads is presented. “Therefore a work load of 600 kpm is actually 650 kpm, and of 1200 kpm is actually 1300 kpm. This added load must be considered when comparing work load, oxygen uptake, pulse rate relationships on the Monark and calibrated electronically braked ergometers. As both the oxygen uptake data (Table 2) and subsequently the predicted maximum uptake data were obtained assuming a negotiable friction effect, no correction is required for the tables in this book although the work loads are actually 8 % higher than stated.” (The oxygen uptake 1.5 liter/min listed for 50 watts or 600 kpm/min is actually attained at about 54.5 watts or 650 kpm/min.) If you suspect incorrect calibration, check that the adjusting screw G for the pendulum weight has an unbroken color seal. Make sure that the roller to which the belt is fixed runs freely – it is carried in ball bearings. The calibration can then be checked in the following manner. Set the mark on the pendulum weight at “0” (as in Fig 2). Attach a weight known to be accurate as shown in Fig 3. Then a 1 kg weight should give a reading of 1 kp on the scale D, a 2 kg weight should show 2 kp, etc. The center of gravity of the pendulum weight can be moved by means of the adjusting screw G (which is locked with the screw H). Before making any adjustment, check again that the weight being used really is accurate, that it hangs freely, and that the initial position of the pendulum weight is at “0” on the scale. This calibration is, in fact, made with the utmost precision at the MONARK works and provided that the adjusting screw has not been moved or the mechanism of the pendulum scale damaged, there should be no need whatsoever for recalibration. The weight and scale may be modified to order so that the maximal reading would be 3 kp, or any other force desired. The chain should be tightened as much as on an ordinary bicycle, i.e. it should be possible to move it about half an inch.

Lubrication. Make sure that the chain does not run dry. Lubricate with a few drops of light machine oil. Procedure of the Work Test. Energetic bodily activity should not be engaged in during the hours preceding the work test, nor should the test be performed earlier than about an hour after a light meal, or after a longer time if a heavier meal has been taken. Furthermore, the subject should not smoke for the last 30 minutes prior to the commencement of the test. Experience shows that the basal resting heart rate does not normally give any information over and above that provided by the work test. The available time will thus have to help the operator to decide whether the test is to be preceded by rest in a reclining or sitting position. Adjust the saddle and handle-bar to suit the subject. Studies have shown that mechanical efficiency, (expenditure of energy), does not vary with the height of the handle-bar and saddle, provided that this is kept within reasonable limits. The most comfortable position, and in the case of very heavy work the most effective one, is the saddle height that, when the subject has the front part of his foot on the pedal, gives a slight bend of the knee-joint in the lower position (i.e. with the front part of the knee straight above the tip of the foot). Provided that the work is not too heavy, respiration and circulation increase during the first few minutes and then attain a steady state. The increase in heart rate can be established by counting the heart rate once every minute. After 4-5 minutes the heart rate has generally reached the steady state. (In order to work the muscles need oxygen and nutritive substances, carbon dioxide and waste products have to be removed. This transport exerts a load on respiration and circulation.) As a rule, about 6 minutes is thus sufficient to adapt the heart rate to the task being performed. The heart rate should be counted or recorded every minute, the mean value of the heart rate at the 5th and 6th minutes being designated the working pulse for the load in question. If the difference between these last two heart rates exceeds 5 beats pr minute, the working time should be prolonged one or more minutes until a constant level is reached. The pulse rate is most easily felt over the carotid artery just below the mandible angle, (do not press too hard) or on the chest over the heart, and the most exact value is obtained by taking the time for 30 pulse beats (start a stop-watch showing tenths of a second at the “0” pulse beat). Using Table 1, the time recorded for 30 beats can be converted into the heart rate per minute. Example: if it takes 12.4 seconds for the heart to beat 30 times the heart rate is 145 beats per minute. N.B.: For the inexperienced it is rather difficult to count the pulse rate: the metronome is distracting, the subject is in motion, and the pulse may be of variable intensity. Training under experienced leadership is important. The pulse rate may be measured preferably during the last 15-20 seconds of every working minute. Choice of Load. For trained, active sportsmen, the risk of strain in connection with a work-test is very slight. For female subjects a suitable load is 600 kpm/min. (2 kp and 50 pedal turns), for male subjects, 900 kpm/min, (3 kp). If the heart rate exceeds about 130 beats per minute the load can be considered adequate and the test can be discontinued after 6 minutes. If the heart rate is slower than about 130 beats per minute, the load should be increased after 6 minutes by 300 kpm/min (to 3 kp and 4 kp braking power respectively). If time permits testing at several loads, increase by 300 kpm/min in 6-minute periods for as long as the heart rate remains below about 150 beats per minute (time for 30 heart beats = 12.0 seconds). The next working period may be continued for 6 minutes, even if the heart rate then exceeds 150 beats per minute.

Table 1. Conversion of the time for 30 pulse beats to pulse rate per minute 22.0 sec 82/sec 17.3 sec 104/min 12.6 sec 143/min 21.9 82 17.2 105 12.5 144 21.8 83 17.1 105 12.4 145 21.7 83 17.0 106 12.3 146 21.6 83 16.9 107 12.2 148 21.5 84 16.8 107 12.1 149 21.4 84 16.7 108 12.0 150 21.3 85 16.6 108 11.9 151 21.2 85 16.5 109 11.8 153 21.1 85 16.4 110 11.7 154 21.0 86 16.3 110 11.6 155 20.9 86 16.2 111 11.5 157 20.8 87 16.1 112 11.4 158 20.7 87 16.0 113 11.3 159 20.6 87 15.9 113 11.2 161 20.5 88 15.8 114 11.1 162 20.4 88 15.7 115 11.0 164 20.3 89 15.6 115 10.9 165 20.2 89 15.5 116 10.8 167 20.1 90 15.4 117 10.7 168 20.0 90 15.3 118 10.6 170 19.9 90 15.2 118 10.5 171 19.8 91 15.1 119 10.4 173 19.7 91 15.0 120 10.3 175 19.6 92 14.9 121 10.2 176 19.5 92 14.8 122 10.1 178 19.4 93 14.7 122 10.0 180 19.3 93 14.6 123 9.9 182 19.2 94 14.5 124 9.8 184 19.1 94 14.4 125 9.7 186 19.0 95 14.3 126 9.6 188 18.9 95 14.2 127 9.5 189 18.8 96 14.1 128 9.4 191 18.7 96 14.0 129 9.3 194 18.6 97 13.9 129 9.2 196 18.5 97 13.8 130 9.1 198 18.4 98 13.7 131 9.0 200 18.3 98 13.6 132 8.9 202 18.2 99 13.5 133 8.8 205 18.1 99 13.4 134 8.7 207 18.0 100 13.3 135 8.6 209 17.9 101 13.2 136 8.5 212 17.8 101 13.1 137 8.4 214 17.7 102 13.0 138 8.3 217 17.6 102 12.9 140 8.2 220 17.5 103 12.8 141 8.1 222 17.4 103 12.7 142 8.0 225 For persons expected to have a lower physical work capacity, for instance completely untrained, older individuals, or delicate persons, smaller loads should be chosen, and an initial intensity of 300 kpm/min will be suitable. If a physician is not present, work tests on persons over 40 years of age should be discontinued if the heart rate exceeds 150 beats/min (time for 30 pulse beats = 12.0 seconds), and the load should not be raised above 600 kpm/min for female subjects or 900 kpm/min for male subjects, (2 kp and 3 kp respectively).

If the subject experiences pressure or pain in the chest, pain radiating into the left arm and/or jaw, or insistent stitch or troublesome shortness of breath, the test must be discontinued. The test must not be run as a contest to manage the heaviest load. A load giving a heart rate of 130-140 beats/min is sufficient to test the circulatory function when it is intended to compare with results from repeated tests on later occasions. The volumes of oxygen required to cover the energy demand during exercise with different work are presented in Table 2. Table 2. The table gives the oxygen uptake during steady state of various work loads for subjects with a normal mechanical efficiency. The higher work loads listed can be performed aerobically only by individuals with a very high work capacity.

Work load

watt kpm/min

Oxygen uptake

liters/min

50 300 0.9 100 600 1.5 150 900 2.1 200 1 200 2.8 250 1 500 3.5 300 1 800 4.2 350 2 100 5.0 400 2 400 5.7

Interpretation of the Results The work test in the simple form described above, actually gives but few possibilities of judging the subject’s physical capacity for running, skiing, swimming, etc. In the performance of various kinds of sports and athletics, and in physical work in general, the “motor effect” does indeed play an important part, but other important factors include technique and personality characteristics, such as the ability to force oneself (motivation). The test does give some idea of the maximal effect of the “combustion engine”, i.e. the maximal oxygen uptake, but even here there are sources of error. The maximal heart rate varies with age, but there also are wide variations within the same age group (2-4). A heart rate of 150 during exercise implies an almost maximal effort for a person with a maximal pulse rate of 160, but appears relatively light to a person with a pulse ceiling of 200 beats/min. The work output during the actual test will correspond to a variable proportion of the maximum work effect. The most important use for the work test described above is in testing the same individual on several separate occasions, for instance during a period of training. In this way it is possible to determine objectively whether the circulatory training has been effective. Also, the person in training can be considerably motivated by such testing. Effective training is accompanied by, among other things, an increase in cardiac stroke volume, so that a given oxygen transport demand can be satisfied at a lower heart rate. The oxygen uptake capacity increases, and therewith the “combustion engine’s” effect. The ability to “run in high gear” can increase with training also, although this is NOT reflected in the test. (An untrained subject cannot perform at more than about 50 % of his maximal oxygen uptake during one hour of continuous work, while a well-trained skier can maintain a tempo requiring 80-90 % of the “combustion engine’s” maximal effect, ref. 5.)

Fig 4. Heart rate at steady state during work tests on the Bicycle Ergometer throughout 3 ½ months’ training. Work intensity 600, (•), and 900, (o), kpm/min.

Fig 5. Body weight (■), and heart rate during work on the Bicycle Ergometer on various occasions between 1954-1960 for Sixten Jernberg, olympic gold medal cross-country skier. Symbols: C = Cortina, SV = Squaw Valley, open symbols = 900, and closed symbols = 1200 kpm/min. Left triangle = test in low pressure chamber corresponding to 1800 metres altitude = Squaw Valley. –58 = Feb, 1958 World Championship competition in Lahti, where two victories were recorded.

Fig 6. Heart rate at 900, (o), and 1200,(●), kpm/min during repeated tests on a canoeist trained for the Nov. , 1956 Olympic Games in Melbourne. Cross country running was interrupted in April-May. Arrow indicated broken rib, which hindered training. (Subject = Heurlin). Fig 4 gives an example of the decrease in heart rate at 600 and 900 kpm/min at repeated tests during several months’ training. Fig 5 shows work pulse changes both during training periods and throughout the course of the years for an Olympic Champion cross-country skier. Fig 6 gives the values for a canoeist trained for the 1956 Olympic Games in Melbourne. Physical condition improved during winter and early spring training including cross-country running and skiing. When the lakes were cleared of ice the athlete transferred to paddling almost exclusively. Due to the engagement of smaller muscle groups, the training state could not be maintained, as shown by the “test values” (May). Later on a broken rib hindered training for more than 1 ½ months. (Unsuccessful at the Olympic Games because of broken paddle at start!) Another example is shown in Fig 7. The heart rate is given for five occasions between July, 1957, and Feb, 1958, when the skier (LAR), was in training for a World Championship. The figure also shows the test values before and during the Squaw Valley 1960 Olympic Games. In Aug, 1959, the heart rate at 1200 kpm/min, is about 15 beats slower than at the same season two years earlier. Squaw Valley is located 1800 meters above sea level, leading to a certain oxygen deficiency and generally, for the first few days, a heart rate increase. The subject experienced some days trouble with sore throat and other common cold symptoms, which probably is reflected in a heart rate peak in the work test. The functional tests were however normal during competition, (placed no. 5 in 30 km, and no. 4 in 50 km). In preparation for 1960, he trained, beginning in June, by doing cross-country running once a week at a continuously hard tempo for 20-25 miles, and in addition almost daily training. This may explain the improved test values and a better, and more even, competition season.

Fig 7. Test series as in Fig 5 with Rolf Rämgård and Lennart Larlsson, cross-country skiers. Symbols as in Fig 5.

Fig 8. The figure presents data on 14-year-old boys collected over a period of one year with a work test on a bicycle ergometer (600 kpm/min, oxygen uptake about 1.5 liters/min). The decrease in heart rate, observed in steady state of work, suggests an 8 per cent increase in maximal oxygen uptake per kg body weight from September 1959 until May 1960. After summer vacation for 2 ½ months the heart rate was somewhat higher and so also was the body weight. The maximal oxygen uptake per kg weight was now 5 per cent l o w e r; the boys apparently did not train as hard when on holiday as they did in school. Significance of Oxygen Transport Capacity For every liter of oxygen consumed in combustion 4.7 – 5.05 kilogram calories are liberated. Measurement of the oxygen uptake during work thus estimates the amount of aerobic energy transfer. The greater the maximal oxygen transport (maximal aerobic power), the greater the potential energy output. A high oxygen transport capacity also implies that a given energy output can be accomplished with relatively less physiological strain. A task involving more continuous work, for example, ought not to load the oxygen transport organs to more than 50 % of their capacity. From Tables 3 and 4, (for males and females respectively), the maximal oxygen uptake can actually be derived from the heart rate at a given load. Example: a male subject working at 900 kpm/min has a

heart rate of 147. His maximal oxygen uptake, according to Table 3, is 3.3 l/min. Oxygen uptake per kilogram body weight is given in Table 5. A body weight of 74 kg = 45 ml/kg x min. If more than one load has been used, the maximal oxygen uptake is estimated as the mean of the values calculated for each work load. The tables are based on a maximal heart rate of 195. Since older persons have usually a lower maximum they are often overestimated in regard to maximal oxygen uptake. Hence the values in Tables 3 and 4 must be corrected by multiplication with the age factor from Table 6 a. Example: a subject weighing 79 kg has a work pulse of 139 at 900 kpm/min. Maximal oxygen uptake, according to Table 3, is 3.6 l/min. At 50 years the value becomes 3.6 x 0.75, or 2.7 l/min. Maximal oxygen uptake per kilogram body weight, according to Table 5, is 34 ml/kg x min. If the subject’s maximal heart rate is known the factor presented in Table 6 b should be used.

Table 3. Prediction of maximal oxygen uptake from heart rate and work load on a Bicycle Ergometer (from a nomogram by Åstrand. Acta. physiol. scand. 49 (suppl. 169), 1960, pp. 45-60. Applicable to men. The value should be corrected for age, using the factor given in Table 6.

Table 4. Prediction of maximal oxygen uptake from heart rate and work load on a Bicycle Ergometer (from a nomogram by Åstrand. Acta. physiol. scand 4 (suppl. 169) 1960, pp. 45-60. Applicable to women. The value should be corrected for age, using the factor given in Table 6.

Table 6 a and b. Factor to be used for correction of predicted maximal oxygen uptake: a) when the subject is over 30-35 years of age or b) when the subject’s maximal heart rate is known. The actual factor should be multiplied by the value that is obtained from Table 3 or Table 4.

Age

Factor

Max heart rate

Factor

15 25 35 40 45 50 55 60 65

1.10 1.00 0.87 0.83 0.78 0.75 0.71 0.68 0.65

210 200 190 180 170 160 150

1.12 1.00 0.93 0.83 0.75 0.69 0.64

Table 7 attempts to classify the capacity to perform endurance work according to maximal oxygen uptake. For the 50-year-old mentioned above, with a predicted oxygen uptake of 2.7 l/min, or 34 ml/kg x min, the classification will be “average”. (Such is the methodological variability, however, that of those estimated at 2.0 l/min, 95 % of the actual cases will lie between 1.4-2.6 l/min. The spread at the 3.0 liter level is between 2.1 and 3.9 l/min, and at 4.0 l/min, between 2.8 and 5.2 l/min.) Whether or not a given maximal oxygen uptake is due to natural endowment, or to endowment plus effective training is impossible to say. One also must consider the possibility that a completely untrained subject may receive a “high” classification, while a well-trained subject may receive one of “low”. The cause of this lies, of course, in the unreliability of the method, and also in that the untrained subject might improve his or her capacity if trained, and that the trained subject’s maximal oxygen uptake would be even lower if untrained. It is this evaluation that demands judgement and experience.

Table 7. Classification of Maximal Oxygen Uptake (maximal aerobic power) by Age Group. The upper figure, e.g. 1.69, refers to maximal oxygen uptake in l/min, the lower, e.g. 28, refers to ml/kg x min. “Normal weights” used were: 58 kg for females and 72 kg for males. (Ref 2.)

Fig 9. Mean values for heart rate for 204 athletes representing Sweden, and in some events other countries, in Olympic Games and competitions for World Championships. Values obtained on a group of students have been included for comparison. Work was performed on a bicycle ergometer with a work load of 1200 kpm/min (oxygen uptake about 2.8 l/min). (“Cross country” = skiing.)

The tables 3 and 4 are actually derived from studies on fairly well-trained individuals. Further studies have shown that untrained subjects have usually a somewhat higher maximum for oxygen uptake than the predicted one, and that top trained athletes in events calling for endurance have often a lower capacity than that one predicted.

The data given in Fig 9 are rather good estimates of the load placed upon the oxygen transport organs by various sports, and, to a certain extent, of the athlete’s physical condition. It should be mentioned that the intragroup variation is rather wide. It should be clear from the preceding discussion that the actual test values are not very useful in the estimation of the subject’s chances in a sport requiring endurance. Constitution, technique and ambition play obviously large roles in any sporting event. The oxygen uptake capacity expressed per kilo body weight primarily reflects the ability to cover distances at a fast tempo. It is not at all remarkable that skiers place first in Fig 9. A few kilos variation in body weight is no handicap to rowers, canoers and swimmers, but a high body weight, e.g. due to excess body fat, must be considered when evaluating the individual’s capacity in events where the body is lifted (and in that respect the comparison between the various sports is completely unfair). Record-keeping, graphic plotting of results A record is given in Table 8. After repeated work tests on the same subject, the results are interpreted most easily if plotted on graphic paper (see Figs 4-8). In addition to date, birth date, height and weight, short descriptions should be included of: 1) health, with emphasis on the last 3-4 weeks, (infections, bed-rest, fever etc), 2) training state – physical condition, with amount of training per week, 3) smoking habits, hours of sleep the previous night, time of last meal, activity during the hours just previous to testing etc. (A 5-step scale is useful for the classification of training state: 1, completely untrained, 2, sporadic muscular activity = a few times per month, 3, regular but light exercise = once to twice per week, 4, rather intensive training one or more times per week, 5, hard training for competition several times per week.) The mean of the two final heart rate measurements is recorded as the final heart rate at each work load. Space is reserved for the predicted maximal oxygen uptake in l/min, and in relation to body weight, (ml/kg and min) as well as the correction factor, if used. Directions for record-keeping. The figures refer to the corresponding number in the left column. (See Table 8.)

1) If the record is to be used on only ONE occasion, place the date on line 1 a, if on repeated occasions, (e.g. one work load per time), on line 1 b.

2) If weight equals naked weight, cross out gross; if shoes, gym shorts etc are included, cross out net. 3) Size of work load. 4) Time for 30 pulse beats AND pulse rate per minute, (Table 1), as the test proceeds. 5) Mean of the two last heart rate measurements. 6) Maximal oxygen uptake capacity predicted from Tables 3 and 4. 7) If several loads are used upon one testing occasion, record in the column for the heaviest work the

MEAN of the predicted values (loads with a heart rate of 120-170). Note the correction to be made for older persons (see interpretation of results, and Table 6). If correction is made for age, (or maximal heart rate), underline “corr”, (see line 6): otherwise cross out “corr”.

8) Training state can be evaluated by the code indicated, with the possible addition of type of training (skiing, gymnastics, walking, swimming, etc).

9) For other notes, such as colds, bed rest, smoking in connection with the test, most recent meal, reason for interruption of work.

This form is only offered as a suggestion. Most investigators will develop a recording form compatible with their own desires and experience. Training on the Bicycle Ergometer. Exercise on the bicycle ergometer can, of course, be included in a training program. Weather conditions, access to local sport facilities, limited time, etc, may hinder traditional training methods. Under such conditions, the bicycle ergometer provides an alternative. Effective training, (= training of the oxygen transporting organs), is attained by the performance of relatively heavy work for 3-4 minutes, followed by an equally long rest period, a repeated exercise period etc, for 20-30 minutes. This should be done several times per week. The individual’s capacity must be considered when choosing the size of the load. An untrained but healthy 20-40 year-old subject in the first weeks of training may choose a work load yielding a heart rate of 120-140 beats per minute in the latter part of the work period. The load can be increased with time, but it is an exaggerated ambition for a non-athlete to work to maximal capacity – to “torture” himself to a peak level. Naturally, older persons should be more cautious.

The strength of the leg muscles can be increased by alternating heavy work, (heavier than for endurance training), for 15-30 seconds with equal rest periods during a total of 5-10 minutes. The heart rate should not exceed about 150 beats per minute. Heavy work should be preceded by a few minutes’ warm-up at a lighter load. If the training described above is supplemented by 5 minutes’ calisthenics, the resultant training will be highly comprehensive from a physiological standpoint. The “speedometer” attached to the bicycle serves no purpose in ordinary work tests, since the tempo is set by metronome, and the “distance” is measured according to time. But for the person using the bicycle for training the speedometer can be a good indicator. A “speed” of about 20 km/hr produces a pedalling rate of 50/min (and 2 kp braking power then gives 600 kpm/min). Summary of Test Procedure

a) Check the metronome tempo (100 single beats per min). b) Adjust the height of the saddle and handle-bar. c) With the subject seated on the Bicycle Ergometer, but without touching the pedals, set the

mark on the pendulum weight at “0” on the scale. d) Begin the work, set the desired load, and start the “worktime” clock. Check the load at least

once every minute. e) At the end of each minute, take the time for 30 heart beats. f) Normally, 6 minutes will suffice to give relatively constant pulse values. After that time, either

discontinue the test or increase the load (see “Choice of Load”). References

1. von Döbeln, W. A simple bicycle ergometer. J. Appl. Physiol. 7:222, 1954. 2. Åstrand, Irma. Aerobic work capacity in men and women with special reference to age. Acta physiol. scand.

49 (suppl 169), 1960. 3. Åstrand, P.-O. Experimental studies of physical working capacity in relation to sex and age. Munksgaard,

Copenhagen, 1952. 4. Åstrand, P.-O. and E.H. Christensen. Aerobic work capacity. In Proceedings of the conference on oxygen in

the animal organism. Ed. F. Dickens, E. Neil and W.F. Widdas. Pergamon Press Limited, Oxford, 1964. 5. Åstrand, P.-O., I. Hallbäck, R. Hedman and B. Saltin. Blood lactates after prolonged severe exercise. J. Appl.

Physiol. 18:619, 1963. 6. Åstrand, P.-O. Human physical fitness with special reference to sex and age. Physiol. Rev. 36:307, 1956. 7. Åstrand, P.-O., La Condition Physiqe. Presses de la Cité, Librairie Polytechnique Béranger, Paris, 1964. 8. Rowell, L.B., L. Taylor and Y. Wang. Limitations to prediction of maximal oxygen uptake. J. Appl. Physiol.

19:919, 1964. 9. Saltin, B. Aerobic work capacity and circulation at exercise in man. Acta physiol. scand.62 (suppl. 230), 1964. 10. Glassford, R.G., G.H. Y. Baycroft, A.W. Sedgwick and R.B.J. Macnab, Comparison of maximal oxygen uptake

values determined by predicted and actual methods. J. Appl. Physiol. 20:509, 1965. 11. Teräslinna P., A.H. Ismail and D.F. MacLeod. Nomogram by Åstrand and Ryhming as a predictor of maximum

oxygen uptake. J. Appl. Physiol. 21:513, 1966. 12. Åstrand, P.-O. and K. Rodahl. Textbook of Work Physiology. McGraw-Hill, New York, 1970.