Oxygen consumption during calisthenic exercise in women with coronary artery disease.

Oxygen Consumption During Calisthenic Exercise in Women with Coronary Artery Disease Calisthenic exercises are frequently included in cardiac rehabilitation exercise programs; however, little information is available concerning the physiologic stress of these activities. [1] Most studies on the energy costs of calisthenic exercises have involved healthy young male subjects. [2-5] Patients with coronary artery disease (CAD), however, differ from healthy subjects in their response to exercise. [6-8] Maximal oxygen consumption ([VO.sub.2 max]) is markedly decreased in the patient with ischemic disease. Stroke volume at all levels of exertion is also decreased in the presence of cardiac disease. [9] In addition, women often respond to various work loads differently than men. [10,11]

When calisthenics are prescribed, it is often on the basis of oxygen requirements or metabolic equivalents (METs) (*1) calculated from healthy subjects. Few reports have documented work requirements for this type of exercise in patient populations. [2-5,12] The purpose of this study, therefore, was to compare the oxygen consumption ([VO.sub.2]) of apparently healthy, middle-aged women with that of women with documented CAD when performing four calisthenic exercises.

Method and Materials

Subjects

Thirty female volunteers (aged 43-63 years) were recruited for this study (Tab. 1). Fifteen subjects had CAD, documented via angiography. Eight of these subjects had a myocardial infarction (MI), and five had undergone coronary artery bypass surgery. All subjects in the CAD Group were either currently participating in a cardiac rehabilitation program or had completed the program. Current participants in the program were following a regimen similar to that described by Atwood and Nielsen [13]: 10 minutes of warm-up activities; 20 minutes of aerobic exercise in the form of walking, jogging, or cycling at an intensity of 70% of their estimated maximal heart rate; and 10 minutes of "cool-down" activities. This program was followed three times per week. Those women who had completed the program were continuing to exercise regularly, in a similar manner, at home. Subjects who had experienced a MI or had undergone surgery were eight months to four years post-incident.

Fifteen healthy subjects were age-matched and served as controls. The Control Group subjects engaged in some form of aerobic activity two or three times per week. The CAD Group and the Control Group were also matched according to activity level and length of participation in their current activities. Informed consent was obtained from all subjects, and the protocol was approved by both the rehabilitation center's review board and the university's institutional review board.

Procedure

Subjects were asked to refrain from consuming any form of caffeine, food, or tobacco for at least 2 hours prior to the test and to abstain from any form of alcohol for at least 12 hours. Each subject was fitted with a headset attached to a rubber mouthpiece, a one-way respiratory valve, a Wright respirometer, (*2) a flexible connecting hose, and a gas collection bag to collect expired gases and to determine minute volume.

Following a five-minute rest period, with the subject in the sitting position, expired gases were collected, resting heart rate was determined via palpation of the radial artery, and the minute volume was measured. The oxygen and carbon dioxide content of the expired gases were measured using a Beckman OM-14 oxygen analyzer (*3) and a Beckman LB-2 carbon dioxide analyzer, (*3) respectively. The values obtained for oxygen and carbon dioxide content, as well as the minute volume, were used to calculate [VO.sub.2] according to the standard formula. [14]

Each subject performed each exercise for four minutes, with the order of performance of each exercise randomized between subjects. The recorded beat of a metronome was used to mark cadence for each subject. Expired gas was collected and minute volume was recorded from the third to the fourth minute of each exercise. There was a five-minute rest period between each exercise, with a return to resting heart rate, [+ or -] 5 bpm, determining resting state. Exercise heart rate and blood pressure were not assessed. The exercises performed were as follows: 1) alternating, unilateral knee extension, in the sitting position, at 30 repetitions per minute; 2) standing hip flexion with knee raised to 90 degrees at 40 repetitions per minute; 3) standing, bilateral upper extremity range of motion in a diagonal pattern at 33 repetitions per minute; and 4) standing, lateral trunk bending at 26 repetitions per minute. [4] In all exercises, except for standing ROM, one repetition indicated the completion of the motion to one side.

Data Analysis

A two-way analysis of covariance (ANCOVA) for repeated measures was used to compare group means of [VO.sub.2] for each exercise and to compare each individual exercise with the other exercises. [15] The covariate was resting (initial) [VO.sub.2]. When a significant difference was found between the exercise means of [VO.sub.2], the Newman-Keuls multiple-range test was used. Statistical significance was established at the .05 level.

Results

The means and standard deviations of [VO.sub.2] for each group, during rest and exercise, are given in Table 2. The results of the ANCOVA are presented in Table 3. Although the two groups of women were matched as closely as possible, we found a significant difference in the [VO.sub.2] at rest between the two groups. The CAD Group had a mean [VO.sub.2] at rest of 2.70 [mL.kg.sup.-1.min.sup.-1] (s = 0.73), and the Control Group had a mean of 2.90 [mL.kg.sup.-1.min.sup.-1] (s = 1.21). Although this was a statistically significant difference, it is doubtful that it would be clinically significant. In view of the difference in resting means, [VO.sub.2] during each exercise was adjusted using an ANCOVA, with resting [VO.sub.2] as the covariate, to allow for a statistically valid comparison. No significant difference was found in [VO.sub.2] between the two groups during the exercises.

The Newman-Keuls multiple-range test was used to determine whether a significant difference existed between the four exercises. The only exercises that did not differ significantly were sitting knee extension and lateral trunk flexion. All other differences between the means of [VO.sub.2] were found to be significant.

Discussion

No significant difference was found in [VO.sub.2] during exercise between the two groups of subjects in this study. This finding may be due to the wide variation found between subjects. Within the CAD Group, the standard deviation was 22% to 29% of the mean, whereas in the Control Group the variation was even greater (37%-44%). Several authors have reported large variations in energy expenditure between subjects performing calisthenics. Greer et al reported variations of 13% to 25%. [4] Amundsen et al found coefficients of variation of 12% to 29% for calisthenics [3] and 19% to 27% for exercises using wall pulleys. [2] Many of the women in our Control Group attended aerobic dance classes, where movements are sweeping and quick. In almost all Control Group subjects, it was necessary to slow their movements to match the beat to the metronome. This tendency may have contributed to the wide variation found within the Control Group.

A second possible reason for finding no significant difference between the two groups is the level of physical exertion at which [VO.sub.2] was measured. Information is lacking in the literature on comparisons of [VO.sub.2] between healthy subjects and CAD patients during submaximal activities. Energy expenditure can be measured in METs, where the energy expenditure at rest is approximately equal to 1 MET. The levels of energy expenditure at which these subjects were measured were 1.6 to 2.9 METs. It is conceivable that these levels of exertion were not stressful enough to demonstrate a significant difference between the two groups. A significant difference may exist at more strenuous work loads.

The MET levels of various exercises have been listed in the literature; however, these studies have involved healthy, predominantly young subjects. Our study demonstrated that, at intensity levels below 3.0 METs, women with CAD had a [VO.sub.2] response to exercise quite similar to that of healthy, young subjects. It should be kept in mind, however, that the subjects in the CAD Group were currently participating in, or had completed, an early convalescent rehabilitation program. [13] Their exercise tolerance was greater than that of patients with cardiac disease who are still in the hospital or have not participated in such a rehabilitation program.

Upper extremity exercises in cardiac rehabilitation programs have been used with less frequency than lower extremity exercises because of a concern that arm exercise involves a greater amount of isometric (static) contraction. [13] A strong isometric contraction results in a marked increase in arterial blood pressure as well as an increase in both cardiac output and heart rate. [16-18] At a given submaximal power output, arm exercise results in a greater relative [VO.sub.2] (percent of [VO.Sub.2 max]) than leg exercise. Consequently, cardiac rehabilitation programs rely heavily on lower extremity activities and less on arm cranking, pulley, or other upper extremity exercises. [9,19] As evidenced by the energy cost demonstrated in our study by the arm exercise and the hip exercise, however, the specific movement itself must be analyzed. During the arm exercise, the CAD Group and Control Group reached [VO.sub.2] levels of 5.76 and 5.87 [mL.kg.sup.-1..min.sup.-1], respectively, whereas during the standing hip flexion exercise, they reached levels of 6.86 and 7.47 [mL.kg.sup.-1..min.sup.-1], respectively. The hip flexion exercise required a significantly greater amount of energy than did the upper extremtiy exercise. Not only does the hip exercise use more muscles, but a greater muscle mass is involved. wehn choosing graded calisthenics to be used in a cardiac rehabilitation program, the degree of isometric exercise must be analyzed as well as the muscle mass involved. An evaluation of each particular movement, together with the cadence at which the movement is performed, is warranted.

[beta]-Adrenergic blocking agents are often administered to patients with cardiac disease to treat hypertension, angina, or cardiac arrythmias. Along with decreases in heart rate, systolic blood pressure, cardiac output, and resting stroke volume, [beta]-blockers reduce [VO.sub.2 max]. In studies by both McGhee et al [20] and Wilmore et al, [21] however, these drugs have not been found to alter the training response without submaximal exercise in patients with CAD. In our study, we found no consistent difference between the eight women in the CAD Group who were taking [beta]-blockers and the seven women who were not.

Summary

The results of this study demonstrate that no difference in [VO.sub.2] exists between healthy women and women with CAD when they are performing calisthenics in the range of 1.6 to 2.9 METs. During exercise below 3.0 METs, the women the CAD had [VO.sub.2] values similar to those of young, healthy subjects. We found significant differences in [VO.sub.2] between the four calisthenic exercises studied. Standing hip flexion was found to be the most strenuous, followed by standing bilateral arm exercises, and then standing trunk bending and sitting knee extension. Wide intersubject variations found in response to these activities suggest that, even with careful supervision, it is difficult to precisely predict how any one individual will respond to calisthenic exercise.

Acknowledgements

We wish to thank Judy Accrocco, RN, and the staff of the West Houston Cardiac Rehabilitation Center for their advice in the planning of this study and for their cooperation in providing access to their patients.

(*1) MET = 3.5 mL [O.sub.2..kg.sup.-1..min.sup.1].

(*2) Precision Scientific, 3737 W Courtland St, Chicago, IL 60647.

(*3) Beckman Instruments, Inc, Electronics Div, 3900 River Rd, Schiller Park, IL 60176.

References

[1] Scheer SJ: Calisthenics: What level of stress? Abstract. Arch Phys Med Rehabil 59:524, 1978

[2] Amundsen LR, Takahashi M, Carter CA, et al: Exercise response during wall-pulley versus bicycle ergometer work. Phys Ther 60:173-178, 1980

[3] Amundesen LR, Takahashi M, Carter CA, et al: Energy cost of rehabilitation calisthenics. Phys Ther 59:855-858, 1979

[4] Greer M, Weber T, Dimick S, et al: Physiological responses to low-intensity cardiac rehabilitation exercises. Phys Ther 60:1146-1151, 1980

[5] DiCarlo S, Leonardo J: Hemodynamic and energy cost responses to changes in arm exercise technique. Phys Ther 63:1585-1592, 1983

[6] Jones WB, Finchum RN, Russell RO, et al: Transient cardiac output response to multiple levels of supine exercise. J Appl Physiol 28:183-189, 1970

[7] Wasserman K: Physiology of gas exchange and exertional dyspnoea. Clin Sci 61:7-13, 1981

[8] Nutter DO, Schlant RC, Hurst JW: Isometric exercise and the cardiovascular system. Medical Concepts of Cardiovascular Disease 4:11-15, 1972

[9] Froelicher VF: Exercise and the Heart: Clinical Concepts, ed 2. Chicago, IL., Year Book Medical Publishers, 1987, pp 72-75, 438-441

[10] Pollock ML, Foster C, Schmidt D, et al: Comparative analysis of physiological responses to three different maximal graded exercise test protocols in healthy women. Am Heart J 103: 363-373, 1982

[11] Freyschuss U: Comparisons between arm and leg exercise in women and men. Scand J Clin Lab Invest 35:795-800, 1975

[12] McCarthy RT: Heart rate, perceived exertion and energy expenditure during range of motion exercise of the extremities: A nursing assessment. Milit Med 140(1):9-16, 1975

[13] Atwood JA, Nielsen DH: Scope of cardiac rehabilitation. Phys Ther 65:1812-1819, 1985

[14] Sinning WE: Experiments and Demonstrations in Exercise Physiology. New York, NY, Holt, Rinehart & Winston General Book, 1975, pp 35-40

[15] Huck SW, Cormier WH, Bounds WG: Reading Statistics and Research. New York, NY, Harper & Row, Publishers Inc, 1974, pp 132-140

[16] Bevegard S, Freyschuss U, Strandell T: Circulatory adaptations to arm and leg exercise in supine and sitting positions. J Appl Physiol 21: 37-46, 1966

[17] Jensen JI: Neural ventilatory drive during arm and leg exercise. Scand J Clin Lab Invest 29: 177-184, 1972

[18] Mitchell JH, Wildenthal K: Static (isometric) exercise and the heart: Physiological and clinical considerations. Annu Rev Med 25:369-381, 1974

[19] Cain HD, Frasher WG, Stivelman RS: Graded activity program for safe return to self-care after myocardial infarction. JAMA 177:101-115, 1961

[20] McGhee JS, Siconolfi SF, Bouchard MS, et al: Proprandolol therapy does not prevent an exercise training response in patients with coronary heart disease. Journal of Cardiac Rehabilitation 4:445-449, 1984

[21] Wilmore JH, Ewy GA, Morton AR, et al: The effect of beta-adrenergic blockdale on submaximal and maximal exercise performance. Journal of Cardiac Rehabilitation 3:30-36, 1983

P Gleeson, PhD, PT, is a physical therapist, Westside Orthopaedic and Sports Medicine Associates, 3807 FM 1092, Suite 104, Missouri City, TX 77459. She was a student, School of Physical Therapy, Texas Woman's University, Houston, TX, when this study was completed in partial fulfilment of the requirements for her master's degree. Address correspondence to 139 Haversham, Houston, TX 77024 (USA).

E Protas, Phd, PT, is Coordinator and Professor, School of Physical Therapy, Texas Woman's University, 1130 MD Anderson Blvd, Houston, TX 77030.

This article was submitted June 26, 1987; was with the authors for revision for 49 weeks; and was accpted November 28, 1988.