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Metabolic equivalents (METS) in exercise testing, exercise prescription, and evaluation of functional capacity

Metabolic equivalents (METS) in exercise testing, exercise prescription, and evaluation of... SIDNEY.* G . BLUMCHENt Department of Kinanthropology,School of Human Kinetics, University of Ottawa, Ottawa, Canada; *Present affiliation: Laurentian University, Sudbury , Ontario, Canada tKlinik Roderbirken, Leichlingen, Federal Republic of Germany Summary: One metabolic equivalent (MET) is defined as the amount of oxygen consumed while sitting at rest and is equal to 3.5 ml O2per kg body weightx min. The MET concept represents a simple, practical, and easily understood procedure for expressing the energy cost of physical activities as a multiple of the resting metabolic rate. The energy cost of an activity can be determined by dividing the relative oxygen cost of the activity (ml O,/kg/min) x by 3.5. This article summarizes and presents energy expenditure values for numerous household and recreational activities in both METS and watts units. Also, the intensity levels (in METS) for selected exercise protocols are compared stage by stage. In spite of its limitations, the MET concept provides a convenient method to describe the functional capacity or exercise tolerance of an individual as determined from progressive exercise testing and to define a repertoire of physical activities in which a person may participate safely, without exceeding a prescribed intensity level. Key words: metabolic equivalents, energy cost, oxygen consumption, exercise prescription, functional capacity Introduction cost of activities. METS are also routinely utilized to describe the functional capacity or aerobic power of an individual and to provide a repertoire of activities in which he or she can safely participate. Since the term METS appears frequently in the North American literature and since some persons may not be completely familiar with the concept, a definition of the term and its utilization could prove useful. Our purpose, therefore, is to ( I ) define the concept of METS, (2) compare METS and watts of selected household and recreational activities, and (3) describe the use of METS in the formulation of an exercise prescription. Definition A MET is defined as the resting metabolic rate, that is, the amount of oxygen consumed at rest, sitting quietly in a chair, approximately 3.5 ml 02/kg/min (1.2 kcallmin for a 70-kg person).* As such, work at 2 METS requires twice the resting metabolism or 7.0 ml O,/kg/min and three METS requires three times the resting metabolism (10.5 ml 02/kg/min), and so on. Metabolic Equivalents of Activities Metabolic equivalents (METS) are a simple, practical, and easily understood procedure to quantify the energy Tables I and I1 provide the energy cost in METS and the comparative values in watts for common household chores and leisure activities, respectively. The values for watts have been calculated for a 70-kg person. The METS values were adapted from an expert committee report submitted to the Canada Fitness Survey.' Most physical activities can be performed at a variable intensity ranging from light to heavy. Accordingly, Tables I and I1 also in- Address for reprints: Dr. Maurice JettC School of Human Kinetics University of Ottawa Ottawa, Ontario Canada K I N 6N5 Received: January 17, 1990 Accepted with revision: March 5, 1990 *Since one liter of oxygen is equal to 5 kcal, I W is equal to 0.01435 kcal or 14 ml. One MET is equal to 17.5 W for a 70-kg person. Clin. Cardiol. Vol. 13, August 1990 TABLE Metabolic equivalents of household chores I Intensity Activity Gardening digging raking weeding Heavy housework y carpen t t grocery shopping painting remodel I ing repairing washing floor washing windows Light housework cooking dishes ironing making beds mowing lawn with power mower Mowing lawn (push mower) Farm chores Snow shovelling Wood cutting METS" 4.4 3.5 3.5 5-7 2-7 4-5 4-5 4-5 3.3 4.9 2.5 2.1 2 .o 3-5 3-5 5-1 4-5 5.1 5-7 Wattsb Light METS Moderate METS w Heavy METS 3 88- I23 35-123 70-88 70-88 70-88 58 86 2 44 37 35 53-88 53-88 88-123 70-88 89 88- I23 88 88 I40 I23 "Indicates energy expenditure as a multiple of resting metabolic rate. bValue indicated is for a 70-kg individual. TABLE Approximate metabolic costs of recreational activities 11 Intensity Activity Aerobic dancing Low Medium Alpine skiing Archery Backpacking (km/h) (5% slope, 20 kg) 6.4 7.2 8.0 9.6 11.2 Badminton Doubles Singles Competitive Ballet Ball games METS' 3.9 6.0 5-9 4.3 8.0 9.6 11.6 13.1 15.5 3-4 4-5 6-7 6-8 Wattsb 68 I05 88-158 75 I40 168 203 229 27 1 Light METS W Moderate METS W Heavy METS W I40 175 3 53-70 70-88 105-123 105-140 I05 I05 70 I40 88 (1'ON riflltrd) M. Jette er al.: METS in exercise testing TABLE (continued) I1 ~~~ Intensity Activity Ball hockey Ballroom dancing Baseball Bas ketbal I Bicycling (km/h) 10 15 20 25 30 Bocce Body building Bowling Boxing Broomball Canoeing Car driving Catch (ball) Cricket Croquet Cross-country skiing (km/h) 4 6 8 METS" Wattsb Light W METS Moderate METS W Heavy METS W 3-5 4-7 53-88 70- 123 I94 84 I03 124 I47 172 70 70 70 I40 I23 5 5 5 II 10 88 88 88 I93 I75 2-4 13.4 6.3 3-1 1 2 6.1 2-3 5.5 7.7 9.9 12.2 14.3 16.5 7.4 3-8 7 6-10 12.9 2-3 3-4 2-3 10.3 4.8 6-7 7-8 35-70 235 53-193 35 107 35-53 96 135 173 214 250 289 130 53-140 123 105-175 226 35-53 53-70 35-53 180 84 105-123 123-140 44 88 44 158 I23 70 70 70 44 I58 12 14 Curling Disco and popular dancing Equestrianism Exercise classes Fencing Figure skating Fishing From bank In stream From boat Floor hockey (forwards) Fol kdancing Football (American) Football (touch) Freestyle skiing Frisbee Golf Carrying clubs Pulling cart Riding cart Gymnastics Handball (4-wall) Hiking Home calisthenics 88 88 88 105 123 I05 105 I23 123 158 175 I75 140 88 I05 I05 I 05 70 175 123 123 I 40 158 88 5.1 3-4 2-3 7 8-12 6 2-6 89 53-70 35-53 123 140-210 I05 35-105 I23 140 I05 88 (con rinued) Clin. Cardiol. Vol. 13, August 1990 TABLE (continued) 11 Intensity Activity Horseback riding Walk Trot Gallop Horseshoes Hunting Ice hockey Jogging (level) (kmlh) 9 METSO 3.2 6.9 8.6 2-3 3-7 12.9 Wattsb 56 121 151 35-53 53-123 226 I54 196 184 140-210 137 I93 22 1 84 39 123-140 140-210 22 1 100 133 166 184 Light METS Moderate METS w Heavy METS Judo Karate Kayaking (km/h) 12.5 15.0 Lacrosse (forward) Modem dancing Motorcycling Mountaineering Orienteering Racquetball Ringette (forward) Rollerskating ( k d h ) 12.9 13.9 16.1 17.7 Rope skipping (/min) 66 84 100 120 125 I30 135 145 Rowing (kmlh) 4 8 12 16 20 Rugby Running (level) (kmlh) 13 15 Sailing (small boat) Scuba diving Sculling skateboarding 8.8 11.2 10.5 8-12 7.8 11.0 12.6 4.8 2.2 7-8 8-12 12.6 5.7 7.6 9.5 10.5 9.8 10.5 11.0 11.4 11.7 11.8 12.0 12.1 5.5 10.3 13.5 16.4 19.1 12.6 12.9 14.6 34 II 4-10 7 172 184 193 200 205 207 210 212 7 96 180 236 287 334 22 I 226 256 5 3-70 193 70-175 (continued) M. JettC et al.: METS in exercise testing TABLE (continued) I1 Intensity Activity Skating (ice) (km/h) 18 25 28 32 36 Snorkeling Snowmobiling Snowshoeing (4 km/h) Soccer Softball Squaredancing Squash Swimming (beach) Swimming (pool) (km/h) 2.0 2.5 3.0 3.5 4.0 Synchronized swimming Legs only Arms only Table tennis Tag games Tennis Singles Doubles Tobogganing Track and field Marathon High jump Long jump Shot put Trail biking Volleyball Walking for exercise (km/h) 3 5 7 Walking upstairs Waterpolo Waterskiing Weightlifting Weight training Windsurfkg Wrestling Yoga METS" 4.0 4.8 9.2 10.8 15.2 2-3 9.5 10.3 3-6 4.8 8-12 Wattsb Light METS Moderate METS w Heavy METS 4 70 84 161 189 266 35-53 I66 180 53-105 84 140-210 4 3 5 5 3 3 6 2 3 88 61 I23 I23 70 88 158 53 88 I1 5 7 12 4 9 I05 88 I75 193 88 I23 210 70 158 4.3 6.8 8.9 11.5 13.6 8.7 9.8 4.7 6.8 6-7 4-5 7.0 13.3 4.1 15.0 3.8 6-8 6 1.8 3.2 5.3 4.7 9.8 7.9 3-7 10.9 8-12 3.2 75 I19 156 20 1 238 4 152 172 82 119 105-123 70-88 123 233 72 263 67 105-140 I05 32 56 93 82 172 138 53- 123 191 140-210 56 70 I05 70 I05 70 105 88 53 53 70 I05 105 140 123 88 88 88 I58 8 I1 9 7 7 7 12 140 I93 158 123 123 123 210 "Indicates energy expenditure as a multiple of resting metabolic rate. bValue indicated is for a 70-kg individual. Clin. Cardiol. Vol. 13, August 1990 clude for the various activities, the MET values, as assigned by the expert committee, for three levels of intensity: light; when the activity results in only minimal perspiration and only a slight increase in breathing above normal; moderule; when the activity results in definite perspiration and above normal breathing; heavy; when the activity results in heavy perspiration and heavy breathing. These MET values indicating intensity level enable the clinician to be more specific when prescribing exercise by providing the patient with subjective, yet specific, feelings as to the desired intensity of participation. For instance, a person participating in a game of tennis with only a slight change from normal state would be exercising at approximately 4 METS. A patient showing slight perspiration, accompanied by increased breathing, would be exercising at 6 METS. However, a person who shows heavy perspiration and heavy breathing while performing would be working at 10 METS. This procedure, however, is not without limitations. One major inconsistency in Table 11, which should be oted, is that some activities of relatively low intensity, such as bowling, bocce, and croquet are shown in the “heavy” intensity category with an intensity of 3 METS. Other activities, on the other hand, such as badminton, baseball, hiking, and folk dancing, are classified in the ‘‘light’’ intensity category also with an intensity of 3 METS. In Tables I and 11, activities classified as “heavy” range from a low of 3 METS to a high of 16 METS. Activities classified as ‘‘light’’ have a similar range of 3 to 12 METS. Classification of Activities McArdle et ul. * have presented a classification system (Table 111) for rating the difficulty of sustained physical activity in terms of its intensity. In addition to METS, the exercise intensity classifications are expressed V 0 2 and watts. For men, light work is considered as that eliciting an energy expenditure of up to 4 METS ( 1 liter of O,/min). Today, most industrial jobs and household chores require less than three times the resting energy expenditure (i.e., 3 METS) and can thus be regarded as light work. Heavy work is defined as that requiring 6 to 8 times the resting oxygen consumption (i.e., 6-8 METS). Unduly heavy work is any task requiring an increase in metabolism greater than tenfold above resting value (i.e., 1 METS). Compared with men, the classifications of 0 physical activity in terms of exercise intensity are lower for women accounted for by their lower level of physical work capacity. With respect to physical training, activities demanding only 1-4 METS are generally considered to be of low intensity, and therefore, not suitable for developing cardiorespiratory fitness in normals. However, they may provide a sufficient training stimulus for persons whose functional capacity is less than 6 METS. Activities in the 5-8 METS range are considered to be of moderate intensity, and for most sedentary persons, especially patients and elderly individuals, generally provide a suitable training stimulus. Naturally, activities should be considered in light of the fitness level of the participant: they may TABLE Five-level classification of physical activity in terms of exercise intensity I11 Energy expenditure Level Men Light Moderate Heavy Very heavy Unduly heavy Women Light Moderate Heavy Very heavy Unduly heavy kcal/min ml/kg/min W METS 2 .O-4.9 5.0-7.4 7.5-9.9 10.0- 12.4 12.5- 6. I-15.2 15.3-22.9 23.0-30.6 30.7-38.3 38.4- 28-69 70-104 105-139 140-174 175- 1.6-3.9 4.0-5.9 6.0-7.9 8 .O-9.9 10.0- 1.5-3.4 3.5-5.4 5.5-7.4 7.5-9.4 9.5- 5.4-12.5 12.6- 19.8 19.9-27.1 21.2-34.4 34.5- 21-48 49-76 77- 104 105-132 133- 1.2-2.7 2.8-4.3 4.4-5.9 6.0-7.5 7.6- Note: ml/kg based on 65-kg man and 55-kg woman; one MET is equivalent to 250 m l 0 , per minute, o r the average resting oxygen consumption. Source: Adapted from Ref. 2, McArdle er al., Exercise Physiology: Energy, Nutrition, and Human Performuncr, Lea & Febiger, 1986, reprinted with permission. M. JettC et al.: METS in exercise testing be too vigorous for the unfit person and not sufficiently vigorous for the very fit person. Activities requiring an energy expenditure of 8 METS and above are considered to be of high intensity. Utilization of METS in Describing Functional Capacity The exercise intensity in METS for activities such as walking, jogging, running, cycle ergometer, and stepping is directly related to speed of movement, resistance, or mass lifted (see Tables IV to VII). In exercise testing, er- gometers present the patient with a defined quantity of work. The exercise intensity is gradually and progressively increased from stage to stage in either a continuous mode or at intervals. At each stage, observations of heart rate, ECG, blood pressure, and signs and symptoms are noted. The increases in intensity from stage to stage are normally about 1 to 2 METS (or more) in healthy populations and as small as one half to one MET in individuals with disease. Using a test protocol with smaller increments in exercise intensity is preferable to a protocol using larger increments, since it is possible to more precisely define the subject's exercise tolerance (functional capacity) and/or the TABLE IV Energy requirements in METS for horizontal and uphill jogging/running" %Grade mPh m/min 5 134 8.6 10.3 12.0 13.8 15.5 17.2 8.6 9.5 10.3 11.2 12.0 12.9 13.8 6 161 10.2 12.3 14.3 16.4 18.5 20.6 10.2 11.2 12.3 13.3 14.3 15.4 16.4 7 188 11.7 14.1 16.5 18.9 21.4 23.8 11.7 12.9 14.1 15.3 16.5 17.7 18.9 7.5 29 1 12.5 15.1 17.7 20.2 22.8 25.4 12.5 13.8 15.1 16.4 17.7 19.0 20.3 Outdoors on solid surface 0 2.5 5.0 7.5 10.0 12.5 On the treadmill 0 2.5 5.0 7.5 10.0 12.5 15.0 "Differences in energy expenditures are accounted for by the effects of wind resistance. Source: From Ref. 9, ACSM, 1980, Guidelinesfor Graded Exercise Testing and Exercise Prescription. Lea & Febiger, reprinted with permission. V TABLE Energy expenditure in METS and W during cycle ergometry Exercise rate Body weight (kg) 50 300 50 5.1 4.3 3.7 3.2 2.9 2.6 450 75 6.9 5.7 4.9 4.3 3.8 3.4 8.6 7. I 6.1 5.4 4.8 4.3 (kg/m/min-l) (W) Note: VO, for zero load pedaling is approximately 550 rnllmin for 70-80-kg subjects. Source: From Ref. 9, ACSM, 1980, Guidelinesfor Graded Exercise Testing and Exercise Prescription, Lea & Febiger, reprinted with permission. Clin. Cardiol. Vol. 13. August 1990 TABLE VI Approximate energy requirements in METS for horizontal and grade walking %Grade mPh (m/min) I .7 45.6 2.5 67.0 2.9 3.8 4.6 5.5 6.3 7.2 8. I 8.9 9.8 10.6 3.4 91.2 3.6 4.8 5.9 7. I 8.3 9.5 10.6 3.75 100.5 3.9 5.2 6.5 7.8 9. I 10.4 11.7 12.9 14.2 15.5 16.8 2.3 2.9 3.5 4. I 4.6 5.2 5.8 6.4 7.0 7.6 8.2 Source: From Ref. 9, ACSM, 1980, Guidelines jbr Gruded Exercise Testing and Exercise Prescription, Lea & Febiger, reprinted with permission. TABLE VI1 Energy expenditure in METS during stepping at different rates on steps of different heights Step height (cm) 0 4 8 12 16 20 24 28 32 36 40 Stepdrnin 12 30 3.0 3.8 4.6 5.5 6.3 7. I 7.9 8.7 9.6 10.4 11.2 1.2 I .5 1.9 2.2 2.5 2.8 3.2 3.5 3.8 4. I 4.5 Source: From Ref. 9, ACSM, 1980, Guidelinesfor Graded Exercise Testing und Exercise Prescription. Lea & Febiger, reprinted with permission. onset of adverse signs and symptoms. This, in turn, makes exercise prescription more precise, more effective, and safer. Protocols such as the Balke3 and JettC4 types advance exercise intensity in constant increments. These protocols provide a satisfactory number of possible workloads for patients, with the early (and easier) exercise intensities serving as a warm-up for more strenuous exercise stages that follow. The exercise tolerance of a patient should be determined from the exercise intensity achieved in METS rather than by total treadmill time. Alternatively, functional capacity can be measured directly if oxygen uptake measurements are made. Figure 1 shows the exercise intensity equivalents in terms of METS and milliliters of oxygen for various testing protocols. The METS system can thus be utilized to explain to a patient hidher functional capacity. For example, a 40year-old, 70-kg male whose maximal aerobic power is measured at 2 1 ml O,/kg/min (1.5 I/min O2 or 105 W) would have a functional capacity equivalent to 6 METS (21 ml 0 2 + 3 . 5 ml 0 2 = 6METS). This could then be interpreted to the patient that he/she has achieved a rate of energy expenditure equal to 6 times resting metabolic rate. On the basis of normative data, this value would be classified as poor (Table VIII). This patient could be classified as Functional Class 2 (Table IX). Having determined functional capacity from the exercise test, the patient could be advised, after consulting tables of energy expenditure (Tables I and II), which physical activities can be considered safe and/or suitable (i.e., M. JettC et al. : METS in exercise testing Bench stepping Treadmill protocols Bicycle CAFT'lO Fox8 Balkej ergometer 3-min stages Bruce JeW Naughton 3-min stages Functional O2 cost (W) Male Female 3-min stages 2-min stages 2-min stages 3 MPH class7 mllkglmin METS (70-kg man) Aa stage Aa stage MPH %GR MPH %GR MPH %GR %GR METS Class I 4 l9 l4 3.50 125 7 6 5 4 3 2 1 75 50 25 Class II 21.o 17.5 14.0 Class 111 10.5 7.0 Class IV 3.5 l4 FIG.I Metabolic equivalents in exercise testing and evaluation of functional capacity. *CAFT=Canadian Aerobic Fitness Test; Au=ascents per minute (double 20 cm step). TABLEVIII Normative data for cardiorespiratory fitness for males aged 30-49 30-39 O,ml/kglmin Excellent Above average Average Below average Poor METS 0,mllkglmin 40-49 ~~ METS >53 45-52 38-44 30-37 < 30 > 15 13-15 11-13 9-12 <9 >53 43-52 33-42 23-32 c 23 > 15 12-15 9-12 7-9 <7 Source: From JettC M : Clinical Fitness Research Appraisal Program, Norms for Fitness Tests. Department of Kinanthropology , University of Ottawa, November 1983. Clin. Cardiol. Vol. 13, August 1990 TABLE Summary of criteria for specific activity scale classifications IX Class I : Class 2: Class 3: Class 4: Patient can perform to completion an activity requiring 2 7 metabolic equivalents Patient can perform to completion any activity requiring 2 5 metabolic equivalents but cannot or does not perform to completion activities requiring L 7 metabolic equivalents Patient can perform to completion any activity requiring 2 2 metabolic equivalents but cannot or does not perform to completion any activities requiring 2 5 metabolic equivalents Patient cannot or does not perform to completion activities requiring 2 2 metabolic equivalents Source: From Ref. 6 , Goldman e al., 198 1, Circularion 64, 1227, reprinted with permission from the American Heart Association, Inc. f effective) for physical training. It is also appropriate to explain which activities should either not be performed, or performed only with due caution. Utilization of the METS Procedure in the Formulation of an Exercise Prescription Work intensity is a most important factor in the establishment of a conditioning or rehabilitation exercise program. For aerobic training, a proper dosage of exercise is considered to vary from 40% of maximum METS for poorly conditioned and/or symptomatic persons to perhaps 85% of maximum METS for well-conditioned athletic persons. A training intensity of 60-70% of maximum METS, the average level of anaerobic threshold, is typically prescribed for most healthy, asymptomatic individuals when performing continuous aerobic training. Balke3 recommends the following sliding scale for prescribing an acceptable training intensity: Training intensity=60+max METS x max METS For example, if the functional capacity of a patient is 6 METS, the training intensity would be (60+6)/100~6=4 METS. For aerobic training, the patient would be counselled to engage in activities which demand an average energy expenditure of 4 METS. The exercise prescription could be accompanied by a recommended or target heart rate (or range) corresponding to 4 METS as determined during progressive exercise t e ~ t i n g . ~ The advantage of the sliding scale method is that it allows persons with higher levels of functional capacity to automatically train at a greater relative exercise intensity than persons with a lower functional capacity. For the patient with an exercise tolerance of 6 METS, the prescribed average conditioning intensity would be 4 METS; individuals with functional capacities of 5, 10, and 15 METS would train at average intensities of 3.25, 7.0, and 11.25 METS, respectively. For the first few weeks of training, the exercise prescription is normally adjusted 1 MET lower than the calculated exercise intensity until the participant has become ac- customed to exercise and the exercise leader has become familiar with the participant’s exercise response.6 Such precaution minimizes muscle soreness and the potential for debilitating injuries and discomfort, and thereby enhances program adherence. Usually, such activities as walking, jogging, cycling, and swimming are prescribed during the early phases of conditioning since the energy cost of these activities is well known and effort can be simply controlled by telling the participants to cover a fixed distance in a given time. On the other hand, games and sports often involve an element of competition and require a variable or intermittent expenditure of energy. Such activities are not recommended in the initial phases of conditioning, but can be included later to sustain motivation once a minimal function capacity of 5 METS has been attained. Patients with a functional capacity of less than 3 METS, often seen following major surgery or debilitating illness, are usually encouraged to exercise several times each day, with sessions lasting for only about five minutes. Persons with a functional capacity of 3 to 5 METS, on the other hand, are advised to exercise once or twice daily. Individuals with a functional capacity from 5 to 8 METS may exercise on alternate days, three days per week. Once a functional capacity of 8 METS is attained, a less rigorously supervised exercise program can be recommended. Physical conditioning lowers heart rate and rating of perceived exertion (RPE) for a given MET level. Consequently, the participants have to increase the exercise MET level progressively by walking, running, cycling, or swimming faster in order to elicit heart rates (or RPE values) in the desired training range. Limitations of the METS System A number of limitations affect the utility of METS as a method of describing exercise intensity and estimating the energy expenditure of physical activities. A larger person would be expected to have a larger resting oxygen uptake compared with a smaller person. Individuals with the same body mass, but differing in percent body fat and lean body mass (LBM), will have different resting metabolic rates, with resting energy expenditures proportion- M. JettC et al. : METS in exercise testing al to the quantity of muscle present (i.e., LBM). For simplicity, however, individual differences in resting energy expenditures are disregarded. Moreover, even when oxygen uptake is expressed relative to body weight, the baseline value of 3.5 ml 02/kg/min is only an approximate average value for sitting at rest. As is true for the other units, energy expenditure values for a given activity vary not only according to body size, but also level of fitness, skill, and whether or not the activity is performed in a competitive situation. Activities involving high levels of skill, such as swimming, crosscountry skiing, squash, and tennis are particularly subject to a wide range of energy expenditure. The published energy cost of activities is also significantly affected by various environmental conditions, including cold, heat, humidity, wind, altitude, playing surface, and terrain, as well as clothing and equipment worn. Even with these limitations, the MET concept represents a simple, practical, and easily understood procedure for expressing the energy cost of physical activities as a multiple of the resting metabolic rate. Its utilization provides a convenient method to describe the functional capacity or exercise tolerance of an individual as determined from progressive exercise testing and to define a repertoire of physical activities in which a person may participate safely, without exceeding a prescribed intensity level. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Clinical Cardiology Wiley

Metabolic equivalents (METS) in exercise testing, exercise prescription, and evaluation of functional capacity

Jetté, M.; Sidney, K.; Blümchen, G.
Clinical Cardiology , Volume 13 (8) – Aug 1, 1990
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Abstract

SIDNEY.* G . BLUMCHENt Department of Kinanthropology,School of Human Kinetics, University of Ottawa, Ottawa, Canada; *Present affiliation: Laurentian University, Sudbury , Ontario, Canada tKlinik Roderbirken, Leichlingen, Federal Republic of Germany Summary: One metabolic equivalent (MET) is defined as the amount of oxygen consumed while sitting at rest and is equal to 3.5 ml O2per kg body weightx min. The MET concept represents a simple, practical, and easily understood procedure for expressing the energy cost of physical activities as a multiple of the resting metabolic rate. The energy cost of an activity can be determined by dividing the relative oxygen cost of the activity (ml O,/kg/min) x by 3.5. This article summarizes and presents energy expenditure values for numerous household and recreational activities in both METS and watts units. Also, the intensity levels (in METS) for selected exercise protocols are compared stage by stage. In spite of its limitations, the MET concept provides a convenient method to describe the functional capacity or exercise tolerance of an individual as determined from progressive exercise testing and to define a repertoire of physical activities in which a person may participate safely, without exceeding a prescribed intensity level. Key words: metabolic equivalents, energy cost, oxygen consumption, exercise prescription, functional capacity Introduction cost of activities. METS are also routinely utilized to describe the functional capacity or aerobic power of an individual and to provide a repertoire of activities in which he or she can safely participate. Since the term METS appears frequently in the North American literature and since some persons may not be completely familiar with the concept, a definition of the term and its utilization could prove useful. Our purpose, therefore, is to ( I ) define the concept of METS, (2) compare METS and watts of selected household and recreational activities, and (3) describe the use of METS in the formulation of an exercise prescription. Definition A MET is defined as the resting metabolic rate, that is, the amount of oxygen consumed at rest, sitting quietly in a chair, approximately 3.5 ml 02/kg/min (1.2 kcallmin for a 70-kg person).* As such, work at 2 METS requires twice the resting metabolism or 7.0 ml O,/kg/min and three METS requires three times the resting metabolism (10.5 ml 02/kg/min), and so on. Metabolic Equivalents of Activities Metabolic equivalents (METS) are a simple, practical, and easily understood procedure to quantify the energy Tables I and I1 provide the energy cost in METS and the comparative values in watts for common household chores and leisure activities, respectively. The values for watts have been calculated for a 70-kg person. The METS values were adapted from an expert committee report submitted to the Canada Fitness Survey.' Most physical activities can be performed at a variable intensity ranging from light to heavy. Accordingly, Tables I and I1 also in- Address for reprints: Dr. Maurice JettC School of Human Kinetics University of Ottawa Ottawa, Ontario Canada K I N 6N5 Received: January 17, 1990 Accepted with revision: March 5, 1990 *Since one liter of oxygen is equal to 5 kcal, I W is equal to 0.01435 kcal or 14 ml. One MET is equal to 17.5 W for a 70-kg person. Clin. Cardiol. Vol. 13, August 1990 TABLE Metabolic equivalents of household chores I Intensity Activity Gardening digging raking weeding Heavy housework y carpen t t grocery shopping painting remodel I ing repairing washing floor washing windows Light housework cooking dishes ironing making beds mowing lawn with power mower Mowing lawn (push mower) Farm chores Snow shovelling Wood cutting METS" 4.4 3.5 3.5 5-7 2-7 4-5 4-5 4-5 3.3 4.9 2.5 2.1 2 .o 3-5 3-5 5-1 4-5 5.1 5-7 Wattsb Light METS Moderate METS w Heavy METS 3 88- I23 35-123 70-88 70-88 70-88 58 86 2 44 37 35 53-88 53-88 88-123 70-88 89 88- I23 88 88 I40 I23 "Indicates energy expenditure as a multiple of resting metabolic rate. bValue indicated is for a 70-kg individual. TABLE Approximate metabolic costs of recreational activities 11 Intensity Activity Aerobic dancing Low Medium Alpine skiing Archery Backpacking (km/h) (5% slope, 20 kg) 6.4 7.2 8.0 9.6 11.2 Badminton Doubles Singles Competitive Ballet Ball games METS' 3.9 6.0 5-9 4.3 8.0 9.6 11.6 13.1 15.5 3-4 4-5 6-7 6-8 Wattsb 68 I05 88-158 75 I40 168 203 229 27 1 Light METS W Moderate METS W Heavy METS W I40 175 3 53-70 70-88 105-123 105-140 I05 I05 70 I40 88 (1'ON riflltrd) M. Jette er al.: METS in exercise testing TABLE (continued) I1 ~~~ Intensity Activity Ball hockey Ballroom dancing Baseball Bas ketbal I Bicycling (km/h) 10 15 20 25 30 Bocce Body building Bowling Boxing Broomball Canoeing Car driving Catch (ball) Cricket Croquet Cross-country skiing (km/h) 4 6 8 METS" Wattsb Light W METS Moderate METS W Heavy METS W 3-5 4-7 53-88 70- 123 I94 84 I03 124 I47 172 70 70 70 I40 I23 5 5 5 II 10 88 88 88 I93 I75 2-4 13.4 6.3 3-1 1 2 6.1 2-3 5.5 7.7 9.9 12.2 14.3 16.5 7.4 3-8 7 6-10 12.9 2-3 3-4 2-3 10.3 4.8 6-7 7-8 35-70 235 53-193 35 107 35-53 96 135 173 214 250 289 130 53-140 123 105-175 226 35-53 53-70 35-53 180 84 105-123 123-140 44 88 44 158 I23 70 70 70 44 I58 12 14 Curling Disco and popular dancing Equestrianism Exercise classes Fencing Figure skating Fishing From bank In stream From boat Floor hockey (forwards) Fol kdancing Football (American) Football (touch) Freestyle skiing Frisbee Golf Carrying clubs Pulling cart Riding cart Gymnastics Handball (4-wall) Hiking Home calisthenics 88 88 88 105 123 I05 105 I23 123 158 175 I75 140 88 I05 I05 I 05 70 175 123 123 I 40 158 88 5.1 3-4 2-3 7 8-12 6 2-6 89 53-70 35-53 123 140-210 I05 35-105 I23 140 I05 88 (con rinued) Clin. Cardiol. Vol. 13, August 1990 TABLE (continued) 11 Intensity Activity Horseback riding Walk Trot Gallop Horseshoes Hunting Ice hockey Jogging (level) (kmlh) 9 METSO 3.2 6.9 8.6 2-3 3-7 12.9 Wattsb 56 121 151 35-53 53-123 226 I54 196 184 140-210 137 I93 22 1 84 39 123-140 140-210 22 1 100 133 166 184 Light METS Moderate METS w Heavy METS Judo Karate Kayaking (km/h) 12.5 15.0 Lacrosse (forward) Modem dancing Motorcycling Mountaineering Orienteering Racquetball Ringette (forward) Rollerskating ( k d h ) 12.9 13.9 16.1 17.7 Rope skipping (/min) 66 84 100 120 125 I30 135 145 Rowing (kmlh) 4 8 12 16 20 Rugby Running (level) (kmlh) 13 15 Sailing (small boat) Scuba diving Sculling skateboarding 8.8 11.2 10.5 8-12 7.8 11.0 12.6 4.8 2.2 7-8 8-12 12.6 5.7 7.6 9.5 10.5 9.8 10.5 11.0 11.4 11.7 11.8 12.0 12.1 5.5 10.3 13.5 16.4 19.1 12.6 12.9 14.6 34 II 4-10 7 172 184 193 200 205 207 210 212 7 96 180 236 287 334 22 I 226 256 5 3-70 193 70-175 (continued) M. JettC et al.: METS in exercise testing TABLE (continued) I1 Intensity Activity Skating (ice) (km/h) 18 25 28 32 36 Snorkeling Snowmobiling Snowshoeing (4 km/h) Soccer Softball Squaredancing Squash Swimming (beach) Swimming (pool) (km/h) 2.0 2.5 3.0 3.5 4.0 Synchronized swimming Legs only Arms only Table tennis Tag games Tennis Singles Doubles Tobogganing Track and field Marathon High jump Long jump Shot put Trail biking Volleyball Walking for exercise (km/h) 3 5 7 Walking upstairs Waterpolo Waterskiing Weightlifting Weight training Windsurfkg Wrestling Yoga METS" 4.0 4.8 9.2 10.8 15.2 2-3 9.5 10.3 3-6 4.8 8-12 Wattsb Light METS Moderate METS w Heavy METS 4 70 84 161 189 266 35-53 I66 180 53-105 84 140-210 4 3 5 5 3 3 6 2 3 88 61 I23 I23 70 88 158 53 88 I1 5 7 12 4 9 I05 88 I75 193 88 I23 210 70 158 4.3 6.8 8.9 11.5 13.6 8.7 9.8 4.7 6.8 6-7 4-5 7.0 13.3 4.1 15.0 3.8 6-8 6 1.8 3.2 5.3 4.7 9.8 7.9 3-7 10.9 8-12 3.2 75 I19 156 20 1 238 4 152 172 82 119 105-123 70-88 123 233 72 263 67 105-140 I05 32 56 93 82 172 138 53- 123 191 140-210 56 70 I05 70 I05 70 105 88 53 53 70 I05 105 140 123 88 88 88 I58 8 I1 9 7 7 7 12 140 I93 158 123 123 123 210 "Indicates energy expenditure as a multiple of resting metabolic rate. bValue indicated is for a 70-kg individual. Clin. Cardiol. Vol. 13, August 1990 clude for the various activities, the MET values, as assigned by the expert committee, for three levels of intensity: light; when the activity results in only minimal perspiration and only a slight increase in breathing above normal; moderule; when the activity results in definite perspiration and above normal breathing; heavy; when the activity results in heavy perspiration and heavy breathing. These MET values indicating intensity level enable the clinician to be more specific when prescribing exercise by providing the patient with subjective, yet specific, feelings as to the desired intensity of participation. For instance, a person participating in a game of tennis with only a slight change from normal state would be exercising at approximately 4 METS. A patient showing slight perspiration, accompanied by increased breathing, would be exercising at 6 METS. However, a person who shows heavy perspiration and heavy breathing while performing would be working at 10 METS. This procedure, however, is not without limitations. One major inconsistency in Table 11, which should be oted, is that some activities of relatively low intensity, such as bowling, bocce, and croquet are shown in the “heavy” intensity category with an intensity of 3 METS. Other activities, on the other hand, such as badminton, baseball, hiking, and folk dancing, are classified in the ‘‘light’’ intensity category also with an intensity of 3 METS. In Tables I and 11, activities classified as “heavy” range from a low of 3 METS to a high of 16 METS. Activities classified as ‘‘light’’ have a similar range of 3 to 12 METS. Classification of Activities McArdle et ul. * have presented a classification system (Table 111) for rating the difficulty of sustained physical activity in terms of its intensity. In addition to METS, the exercise intensity classifications are expressed V 0 2 and watts. For men, light work is considered as that eliciting an energy expenditure of up to 4 METS ( 1 liter of O,/min). Today, most industrial jobs and household chores require less than three times the resting energy expenditure (i.e., 3 METS) and can thus be regarded as light work. Heavy work is defined as that requiring 6 to 8 times the resting oxygen consumption (i.e., 6-8 METS). Unduly heavy work is any task requiring an increase in metabolism greater than tenfold above resting value (i.e., 1 METS). Compared with men, the classifications of 0 physical activity in terms of exercise intensity are lower for women accounted for by their lower level of physical work capacity. With respect to physical training, activities demanding only 1-4 METS are generally considered to be of low intensity, and therefore, not suitable for developing cardiorespiratory fitness in normals. However, they may provide a sufficient training stimulus for persons whose functional capacity is less than 6 METS. Activities in the 5-8 METS range are considered to be of moderate intensity, and for most sedentary persons, especially patients and elderly individuals, generally provide a suitable training stimulus. Naturally, activities should be considered in light of the fitness level of the participant: they may TABLE Five-level classification of physical activity in terms of exercise intensity I11 Energy expenditure Level Men Light Moderate Heavy Very heavy Unduly heavy Women Light Moderate Heavy Very heavy Unduly heavy kcal/min ml/kg/min W METS 2 .O-4.9 5.0-7.4 7.5-9.9 10.0- 12.4 12.5- 6. I-15.2 15.3-22.9 23.0-30.6 30.7-38.3 38.4- 28-69 70-104 105-139 140-174 175- 1.6-3.9 4.0-5.9 6.0-7.9 8 .O-9.9 10.0- 1.5-3.4 3.5-5.4 5.5-7.4 7.5-9.4 9.5- 5.4-12.5 12.6- 19.8 19.9-27.1 21.2-34.4 34.5- 21-48 49-76 77- 104 105-132 133- 1.2-2.7 2.8-4.3 4.4-5.9 6.0-7.5 7.6- Note: ml/kg based on 65-kg man and 55-kg woman; one MET is equivalent to 250 m l 0 , per minute, o r the average resting oxygen consumption. Source: Adapted from Ref. 2, McArdle er al., Exercise Physiology: Energy, Nutrition, and Human Performuncr, Lea & Febiger, 1986, reprinted with permission. M. JettC et al.: METS in exercise testing be too vigorous for the unfit person and not sufficiently vigorous for the very fit person. Activities requiring an energy expenditure of 8 METS and above are considered to be of high intensity. Utilization of METS in Describing Functional Capacity The exercise intensity in METS for activities such as walking, jogging, running, cycle ergometer, and stepping is directly related to speed of movement, resistance, or mass lifted (see Tables IV to VII). In exercise testing, er- gometers present the patient with a defined quantity of work. The exercise intensity is gradually and progressively increased from stage to stage in either a continuous mode or at intervals. At each stage, observations of heart rate, ECG, blood pressure, and signs and symptoms are noted. The increases in intensity from stage to stage are normally about 1 to 2 METS (or more) in healthy populations and as small as one half to one MET in individuals with disease. Using a test protocol with smaller increments in exercise intensity is preferable to a protocol using larger increments, since it is possible to more precisely define the subject's exercise tolerance (functional capacity) and/or the TABLE IV Energy requirements in METS for horizontal and uphill jogging/running" %Grade mPh m/min 5 134 8.6 10.3 12.0 13.8 15.5 17.2 8.6 9.5 10.3 11.2 12.0 12.9 13.8 6 161 10.2 12.3 14.3 16.4 18.5 20.6 10.2 11.2 12.3 13.3 14.3 15.4 16.4 7 188 11.7 14.1 16.5 18.9 21.4 23.8 11.7 12.9 14.1 15.3 16.5 17.7 18.9 7.5 29 1 12.5 15.1 17.7 20.2 22.8 25.4 12.5 13.8 15.1 16.4 17.7 19.0 20.3 Outdoors on solid surface 0 2.5 5.0 7.5 10.0 12.5 On the treadmill 0 2.5 5.0 7.5 10.0 12.5 15.0 "Differences in energy expenditures are accounted for by the effects of wind resistance. Source: From Ref. 9, ACSM, 1980, Guidelinesfor Graded Exercise Testing and Exercise Prescription. Lea & Febiger, reprinted with permission. V TABLE Energy expenditure in METS and W during cycle ergometry Exercise rate Body weight (kg) 50 300 50 5.1 4.3 3.7 3.2 2.9 2.6 450 75 6.9 5.7 4.9 4.3 3.8 3.4 8.6 7. I 6.1 5.4 4.8 4.3 (kg/m/min-l) (W) Note: VO, for zero load pedaling is approximately 550 rnllmin for 70-80-kg subjects. Source: From Ref. 9, ACSM, 1980, Guidelinesfor Graded Exercise Testing and Exercise Prescription, Lea & Febiger, reprinted with permission. Clin. Cardiol. Vol. 13. August 1990 TABLE VI Approximate energy requirements in METS for horizontal and grade walking %Grade mPh (m/min) I .7 45.6 2.5 67.0 2.9 3.8 4.6 5.5 6.3 7.2 8. I 8.9 9.8 10.6 3.4 91.2 3.6 4.8 5.9 7. I 8.3 9.5 10.6 3.75 100.5 3.9 5.2 6.5 7.8 9. I 10.4 11.7 12.9 14.2 15.5 16.8 2.3 2.9 3.5 4. I 4.6 5.2 5.8 6.4 7.0 7.6 8.2 Source: From Ref. 9, ACSM, 1980, Guidelines jbr Gruded Exercise Testing and Exercise Prescription, Lea & Febiger, reprinted with permission. TABLE VI1 Energy expenditure in METS during stepping at different rates on steps of different heights Step height (cm) 0 4 8 12 16 20 24 28 32 36 40 Stepdrnin 12 30 3.0 3.8 4.6 5.5 6.3 7. I 7.9 8.7 9.6 10.4 11.2 1.2 I .5 1.9 2.2 2.5 2.8 3.2 3.5 3.8 4. I 4.5 Source: From Ref. 9, ACSM, 1980, Guidelinesfor Graded Exercise Testing und Exercise Prescription. Lea & Febiger, reprinted with permission. onset of adverse signs and symptoms. This, in turn, makes exercise prescription more precise, more effective, and safer. Protocols such as the Balke3 and JettC4 types advance exercise intensity in constant increments. These protocols provide a satisfactory number of possible workloads for patients, with the early (and easier) exercise intensities serving as a warm-up for more strenuous exercise stages that follow. The exercise tolerance of a patient should be determined from the exercise intensity achieved in METS rather than by total treadmill time. Alternatively, functional capacity can be measured directly if oxygen uptake measurements are made. Figure 1 shows the exercise intensity equivalents in terms of METS and milliliters of oxygen for various testing protocols. The METS system can thus be utilized to explain to a patient hidher functional capacity. For example, a 40year-old, 70-kg male whose maximal aerobic power is measured at 2 1 ml O,/kg/min (1.5 I/min O2 or 105 W) would have a functional capacity equivalent to 6 METS (21 ml 0 2 + 3 . 5 ml 0 2 = 6METS). This could then be interpreted to the patient that he/she has achieved a rate of energy expenditure equal to 6 times resting metabolic rate. On the basis of normative data, this value would be classified as poor (Table VIII). This patient could be classified as Functional Class 2 (Table IX). Having determined functional capacity from the exercise test, the patient could be advised, after consulting tables of energy expenditure (Tables I and II), which physical activities can be considered safe and/or suitable (i.e., M. JettC et al. : METS in exercise testing Bench stepping Treadmill protocols Bicycle CAFT'lO Fox8 Balkej ergometer 3-min stages Bruce JeW Naughton 3-min stages Functional O2 cost (W) Male Female 3-min stages 2-min stages 2-min stages 3 MPH class7 mllkglmin METS (70-kg man) Aa stage Aa stage MPH %GR MPH %GR MPH %GR %GR METS Class I 4 l9 l4 3.50 125 7 6 5 4 3 2 1 75 50 25 Class II 21.o 17.5 14.0 Class 111 10.5 7.0 Class IV 3.5 l4 FIG.I Metabolic equivalents in exercise testing and evaluation of functional capacity. *CAFT=Canadian Aerobic Fitness Test; Au=ascents per minute (double 20 cm step). TABLEVIII Normative data for cardiorespiratory fitness for males aged 30-49 30-39 O,ml/kglmin Excellent Above average Average Below average Poor METS 0,mllkglmin 40-49 ~~ METS >53 45-52 38-44 30-37 < 30 > 15 13-15 11-13 9-12 <9 >53 43-52 33-42 23-32 c 23 > 15 12-15 9-12 7-9 <7 Source: From JettC M : Clinical Fitness Research Appraisal Program, Norms for Fitness Tests. Department of Kinanthropology , University of Ottawa, November 1983. Clin. Cardiol. Vol. 13, August 1990 TABLE Summary of criteria for specific activity scale classifications IX Class I : Class 2: Class 3: Class 4: Patient can perform to completion an activity requiring 2 7 metabolic equivalents Patient can perform to completion any activity requiring 2 5 metabolic equivalents but cannot or does not perform to completion activities requiring L 7 metabolic equivalents Patient can perform to completion any activity requiring 2 2 metabolic equivalents but cannot or does not perform to completion any activities requiring 2 5 metabolic equivalents Patient cannot or does not perform to completion activities requiring 2 2 metabolic equivalents Source: From Ref. 6 , Goldman e al., 198 1, Circularion 64, 1227, reprinted with permission from the American Heart Association, Inc. f effective) for physical training. It is also appropriate to explain which activities should either not be performed, or performed only with due caution. Utilization of the METS Procedure in the Formulation of an Exercise Prescription Work intensity is a most important factor in the establishment of a conditioning or rehabilitation exercise program. For aerobic training, a proper dosage of exercise is considered to vary from 40% of maximum METS for poorly conditioned and/or symptomatic persons to perhaps 85% of maximum METS for well-conditioned athletic persons. A training intensity of 60-70% of maximum METS, the average level of anaerobic threshold, is typically prescribed for most healthy, asymptomatic individuals when performing continuous aerobic training. Balke3 recommends the following sliding scale for prescribing an acceptable training intensity: Training intensity=60+max METS x max METS For example, if the functional capacity of a patient is 6 METS, the training intensity would be (60+6)/100~6=4 METS. For aerobic training, the patient would be counselled to engage in activities which demand an average energy expenditure of 4 METS. The exercise prescription could be accompanied by a recommended or target heart rate (or range) corresponding to 4 METS as determined during progressive exercise t e ~ t i n g . ~ The advantage of the sliding scale method is that it allows persons with higher levels of functional capacity to automatically train at a greater relative exercise intensity than persons with a lower functional capacity. For the patient with an exercise tolerance of 6 METS, the prescribed average conditioning intensity would be 4 METS; individuals with functional capacities of 5, 10, and 15 METS would train at average intensities of 3.25, 7.0, and 11.25 METS, respectively. For the first few weeks of training, the exercise prescription is normally adjusted 1 MET lower than the calculated exercise intensity until the participant has become ac- customed to exercise and the exercise leader has become familiar with the participant’s exercise response.6 Such precaution minimizes muscle soreness and the potential for debilitating injuries and discomfort, and thereby enhances program adherence. Usually, such activities as walking, jogging, cycling, and swimming are prescribed during the early phases of conditioning since the energy cost of these activities is well known and effort can be simply controlled by telling the participants to cover a fixed distance in a given time. On the other hand, games and sports often involve an element of competition and require a variable or intermittent expenditure of energy. Such activities are not recommended in the initial phases of conditioning, but can be included later to sustain motivation once a minimal function capacity of 5 METS has been attained. Patients with a functional capacity of less than 3 METS, often seen following major surgery or debilitating illness, are usually encouraged to exercise several times each day, with sessions lasting for only about five minutes. Persons with a functional capacity of 3 to 5 METS, on the other hand, are advised to exercise once or twice daily. Individuals with a functional capacity from 5 to 8 METS may exercise on alternate days, three days per week. Once a functional capacity of 8 METS is attained, a less rigorously supervised exercise program can be recommended. Physical conditioning lowers heart rate and rating of perceived exertion (RPE) for a given MET level. Consequently, the participants have to increase the exercise MET level progressively by walking, running, cycling, or swimming faster in order to elicit heart rates (or RPE values) in the desired training range. Limitations of the METS System A number of limitations affect the utility of METS as a method of describing exercise intensity and estimating the energy expenditure of physical activities. A larger person would be expected to have a larger resting oxygen uptake compared with a smaller person. Individuals with the same body mass, but differing in percent body fat and lean body mass (LBM), will have different resting metabolic rates, with resting energy expenditures proportion- M. JettC et al. : METS in exercise testing al to the quantity of muscle present (i.e., LBM). For simplicity, however, individual differences in resting energy expenditures are disregarded. Moreover, even when oxygen uptake is expressed relative to body weight, the baseline value of 3.5 ml 02/kg/min is only an approximate average value for sitting at rest. As is true for the other units, energy expenditure values for a given activity vary not only according to body size, but also level of fitness, skill, and whether or not the activity is performed in a competitive situation. Activities involving high levels of skill, such as swimming, crosscountry skiing, squash, and tennis are particularly subject to a wide range of energy expenditure. The published energy cost of activities is also significantly affected by various environmental conditions, including cold, heat, humidity, wind, altitude, playing surface, and terrain, as well as clothing and equipment worn. Even with these limitations, the MET concept represents a simple, practical, and easily understood procedure for expressing the energy cost of physical activities as a multiple of the resting metabolic rate. Its utilization provides a convenient method to describe the functional capacity or exercise tolerance of an individual as determined from progressive exercise testing and to define a repertoire of physical activities in which a person may participate safely, without exceeding a prescribed intensity level.

Journal

Clinical Cardiology – Wiley

Published: Aug 1, 1990

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