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Strength Training in Cardiac Rehab 1 Running Head: Strength Training in Cardiac Rehab Strength Training in Cardiac Rehabilitation Eric Coleman S.P.T. Wayne State University Strength Training in Cardiac Rehab 2 ABSTRACT With each passing day new discoveries are made which have the potential to reshape clinical practice. As scientists and clinicians it is important to be aware of both, past evidence that has molded current clinical practice, and emerging bodies of evidence that will shape the future of our practice. Over the past two decades strength training has been virtualy non existent in cardiac rehabilitation. If strength training was implemented into a Cardiac Rehabilitation Program (CRP) it was always left until Phase III and in more Traditional programs, not at all. More recent scientific research may soon establish early phase II as the appropriate time to begin strength training. Strength Training in Cardiac Rehab 3 Strength Training in Cardiac Rehabilitation “Cardiac Rehabilitation has been defined as comprehensive long term programme which ideally includes, in addition to prescribed, supervised exercise training, medical evaluation, risk profiling, education and counseling, and coronary risk factor modification by pharmacological and nonpharmacological intervention” (Leon, 2000). The role of the Physical Therapist within the scope of Cardiac Rehabilitation is to provide appropriate exercise prescription to address physical impairments of the patient in order to facilitate return to as normal a lifestyle as possible. For decades Cardiac Rehabilitation Programs (CRP’s) have addressed the needs of their patient population using primarily aerobic conditioning to improve cardiorespiratory endurance (Verrill, Ribisl., 1996). Many patients involved in CRP’s have deficits in muscular strength secondary to bed rest, administration of corticosteroids, and premorbid state of deconditioning. Historically “ Resistance, or weightlifting training, was not recommended, most probably because of the acknowledged pressor response induced by sustained isometric contraction.” (McCartney et al, 1998). Due to the role of muscular strength in the performance of a various vocational and recreational activities, many Cardiac patients are likely to have functional limitations (Maiorana., 1997). In the role of a Physical Therapist it is important that the needs of the patient are recognized, as well as, options available to fill those needs. Strength Training in Cardiac Rehab 4 Research Isometrics A study was performed by Atkins et al to examine the effects of isometric exercise as a stress test for left ventricular function. This research used forty-five cardiac patients of varying diagnosis and functional classes. Patients performed trials of isometric handgrip dynamometry at 25 and 50% of maximum voluntary contraction (MVC) for periods of 3-5 minutes and 30 seconds to 3 minutes respectively. Patients also performed aerobic exercise on a bicycle ergometer until reaching a symptom limited maximal load. Subjects were continuously monitored by electrocardiogram (ECG) during all trials. Results of this study showed higher systolic blood pressure, and greater incidence of arrhythmias during isometric exercise when compared with aerobic. The most significant difference was a high number of ventricular arrhythmias during isometric testing (Atkins et al., 1976). The major limitation of this research is that patients used in the study varied in functional classification, while data presented in the report does not identify whether or not patients in lower classes may have been more likely to experience adverse effects. Another study examining the effects of isometric resistance was performed by Sagiv et al 1985. The objective of this research was to compare left ventricular responses to upright isometric resistance in normal versus coronary artery diseased (CAD) men. Subjects used in this study were 14 men with CAD having history of myocardial infarction (MI) and ten normal men with no reported cardiac history. The tasks to be performed were upright isometric handgrip and dead lift. Trials were performed at 30% MVC for 3 minutes. During trials each subjects heart rate (HR), Blood Pressure (BP), Strength Training in Cardiac Rehab 5 left ventricular wall motion and left ventricular ejection fraction were monitored. The most significant finding in this study was the development of new wall motion abnormalities not seen at rest in CAD men, which researchers attributed to ischemia from increased rate pressure product or increasing dyskinesia in previously abnormal regions (Sagiv et al., 1985). A major limitation of this study is that nine of the fourteen subjects displayed wall motion abnormalities at rest, therefore, presence of abnormalities cannot be attributed to the testing (Sagiv et al, 1985) Findings of research examining physiological effects of isometric resistance like that which is described above, are commonly cited to discourage strength training for cardiac patients. However, the examiners in both instances studied acute effects of single bouts of prolonged isometric contractions. This cannot be generalized to all forms of resistance training. Some researchers would argue that all forms of resistance training have an inherent isometric component. However, the duration of isometric contractions used in most of the trials is not indicative of that which would be required in CWT training programs. Circuit Weight Training “Circuit weight training consists of performing a series of weight lifting exercises with moderate weight loads and frequent repetitions. Typically the subject moves to a station, performs the exercise, e.g. 30 sec and then moves to the next station to perform again” (Keleman et al., 1985). This method of resistance training utilizes short rest intervals between sets, thus maintaining increases in HR and has been proposed to facilitate increased strength as well as improved aerobic capacity. According to Verril and Ribisl, CWT either does not increased VO2 max or elicits only mild to moderate Strength Training in Cardiac Rehab 6 increases (4-15%) with greater improvements being seen in less fit individuals (Verril et al, 1996). In a study comparing 20 subjects in traditional phase III cardiac rehab (aerobic exercise only) to 20 subjects participating in a combined program (CWT and aerobic). The control group performed a 10-minute warm-up, 20 minutes of walking or jogging at 85% of maximum HR (based on treadmill test), and 20 minutes of recreational volleyball. The combined group performed the same warm-up and aerobic activity, but substituted two complete circuits of weight training using a ten-station circuit in place of recreational volleyball. Training for both groups occurred three times weekly for ten weeks. The CWT protocol required subjects to perform 10-15 repetitions per station at 40% of one repetition maximum (1 rm) in 30 sec at each station with 30 seconds of rest between stations. Results of this study show an average 24% increase in strength, 12% increase in total treadmill time for the combined group. No significant changes in either strength or endurance were noted for subjects in the control group. Radiotelemetry was used to monitor HR, and the presence of arrhythmias. No new arrhythmias were produced in either group (Keleman et al 1985). Case studies have been describedin which cardiac patients experience significant improvements in symptoms and/or function following relatively short bouts of resistance training (McCartney, 1998) Research initiating weight training with patients in phase II cardiac rehabilitation yielded results following data collection indicating that weight training was safe for low risk patients during phase II cardiac rehabilitation (Squires et al., 1991). The major limitation of this study is that experimenters did not control variance by establishing a uniform number of treatment sessions for participants in the study. Due to the large Strength Training in Cardiac Rehab 7 variance in number of sessions for different participants individual results cannot be pooled and statistical power for this research is very low. In a study of CWT in phase two cardiac rehab using subjects 6-16 weeks post- MI. Researchers found that Not only was CWT safe for these patients, but produced fewer adverse responses to exercise including: hypotension, hypertension, Angina, Arrhythmias, and ST segment depression. This study also compared combined protocols using three intensities of CWT to a control group using a more traditional model. All groups trained three times per week performing 40 minutes of walking or cycling, with the Combined groups performing an additional 15 minutes of CWT following aerobic activity. The CWT protocols for Combined groups are described as follows: Group 20; performed 20 repetitions at 20% of 1rm, Group 40 performed 10 repetitions at 40% of 1rm, Group 60 performed seven repetitions at 60% of 1 rm. The amount of weight to be used was determined at the onset of the study and remained constant throughout the ten- week training period. All three groups participating in the circuit weight training displayed significant increases in strength following the ten-week training period, while the control group showed no significant increase in strength. There was also a stepwise trend that suggests that the groups training at higher percentage of 1rm showed greater improvements, however, that data did not prove statistically significant. All four groups in this study showed significant increases in VO2 max, yet none proved to be significantly greater than any other group (Daub et al., 1996). Limitations of this study are: mean age of subjects was 49.3 years of age, CWT excluded lower body, Experimental groups had more training, and no protocol was assigned for progression of weight training. Age of greater than 61 years was one criteria for exclusion from this Strength Training in Cardiac Rehab 8 study and the mean age of subjects at 49.3 makes it difficult to generalize this research to older cardiac patients. If CWT were likely to facilitate improvements in aerobic capacity as tested using a Bruce treadmill test, it would be beneficial to include the lower body in the CWT protocol. The experimental groups received 15 minutes more training per session, which may have skewed the results of this study in favor of the groups participating in CWT. The failure of this study to show significant differences in strength gained among the three CWT groups may be due to the lack of a protocol for progression of the strength training. Had specific instructions been given for CWT progression the trend that is evident in the data may have been more significant. Later research on CWT in phase II cardiac rehabilitation compared a middle aged group (mean age 48 +/_ 7) to an older group (mean age 68 +/_3). All subjects had suffered a recent MI (4-12 weeks) and had undergone angioplasty while hospitalized. Both groups in this study performed a Protocol of combined CWT with aerobic exercise. CWT was performed at 50% of MVC for ten repetitions; training was progressed using specific guidelines related to the Borg scale of perceived exertion. CWT sessions took place over an 11week period, 3 times weekly for 10-15 minutes per session. Aerobic training began 1 week prior to CWT and continued throughout the 11 week trial (Fragnoli-Munn et al., 1998) The results from this study reported no adverse reactions to training in either patient group. Both groups displayed significant increases in strength and maximal oxygen uptake post-training (Fragnoli-Munn et al., 1998) Stewart performed a study “To determine if weight training used during cardiac rehabilitation as soon as four weeks after myocardial infarction (MI) is safe, and if weight Strength Training in Cardiac Rehab 9 training combined with aerobic exercise improves aerobic fitness and muscle strength more than aerobic exercise alone” (Stewart et al., 1998). This research used 23 male subjects who had experienced an uncomplicated MI as soon as 4 weeks, but not greater than 6 weeks previously. The control group performed aerobic exercise only, using a schwinn airdyne bicycle. Total training time for the control group was 30-35 minutes, consisting of a 5-minute warm-up, 20-25 minutes at target heart rate, and 5 minutes of cool down. The combined group also utilized the airdyne bicycle, performing a 5-minute warm up, followed by 8 minutes of cycling at target heart rate prior to completing 2 circuits of a six station program. CWT was performed at 40% of 1rm with the goal of completing 10-15 repetitions in 30 sec. Subjects were allowed 30 seconds of rest between stations. Amount of weight lifted at each station was increased when subjects were able to complete 15 repetitions easily within 30 seconds. Both training groups performed exercise three times weekly for 10 weeks on nonconsecutive days. Duration of exercise sessions for the control and experimental group were equal (Stewart et al., 1998). Results of this study showed a 14% increase in maximal oxygen uptake, 10% increase in exercise duration, 31% increase in leg strength, 20% increase in arm strength, and 23% increase in total strength for the combined group. The control group did not display statistically significant increases (8%) in VO2 max or exercise duration (Stewart et al., 1998). Future Research Considerations Further research should be conducted to explore physiological effects of isometric training. The research previously cited explored only acute effects of single bouts of Strength Training in Cardiac Rehab 10 prolonged isometric resistance. New research should be conducted to explore whether or not a training effect can be achieved using repeated isometric contractions (<30sec) over a ten-week training period. Would maximal Isometric strength improve and if so, would this increase result in a diminished hemodynamic response to isometric resistance and subsequent increase in patient safety? There are many variables to be considered when designing and implementing a program of CWT “Unless all of these variables are either controlled or manipulated as part of experimental design, it is not possible to accurately compare energy cost, evaluate hemodynamic responses between protocols, or assess the safety of different protocols for use with a cardiac population” (Degroot et al., 1998). More research using Combined CRP’s in phase II targeting specific populations and program parameters is necessary. Comparative analysis such as Number of circuits, repetitions, frequency of training, type of exercises included in CWT program should all be performed. Research has also suggested that patients that are the most deconditioned may display the greatest improvement following CWT or combined CRP’s. This is a direction that research should explore in order to determine at level of VO2 max would patients benefitthe most from Combined and or CWT CRP’s. Quality of life measures have been used in attempts to quantify effects of treatment on life following Cardiac care (Taylor et al., 1998). Attempts to implement this sort of measure with Cardiac Patients pre and post CWT may provide valuable information. Strength Training in Cardiac Rehab 11 Summary Changes in the traditional model of Cardiac Rehabilitation have been slow. Research used in arguments against integrating resistance training into CRP’s, although valid, is not applicable to the topic of CWT. There are many possible adverse effects to isometric exercise for cardiac patients including: dangerous increases in end-diastolic pressure and end systolic volume of the left ventricle, decreased end-diastolic volume and ejection fraction, exacerbated wall motion abnormalities and dysrhythmias (McCartney, 1998) There is a growing body of research proving the safety and effectiveness of Combined CRP’s utilizing CWT and aerobics in early phase II for specific populations. Not only is this proven to be a safe and effective approach to achieve desired increases in maximal oxygen uptake, but also, increases in strength often necessary to facilitate optimal function. “The majority of CAD patients are senior citizens; several surveys have shown that the elderly are often excluded from exercise training in spite of reconditioning” (Perk et al., 2000). Whether strength training begins within the Physical Therapy outpatient setting during Phase II, or during Community based Phase III it is the duty of the Physical Therapist as a health care provider and educator to inform the patient of possible benefits and appropriate resources. The role of the Physical Therapist as an educator does not end with the patient, but extends to our peers, other health care professionals and into the community. Strength Training in Cardiac Rehab 12 Bibliography (2001). "Recommendations for exercise training in chronic heart failure patients." Eur Heart J 22(2): 125-35. Atkins, J. M., O. A. Matthews, et al. (1976). "Incidence of arrhythmias induced by isometric and dynamic exercise." Br Heart J 38(5): 465-71. Daub, W. D., G. P. Knapik, et al. (1996). "Strength training early after myocardial infarction." J Cardiopulm Rehabil 16(2): 100-8. DeGroot, D. W., T. J. Quinn, et al. (1998). 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"Cardiac rehabilitation: applying exercise physiology in clinical practice." Eur J Appl Physiol 83(4 -5): 457-62. Sagiv, M., P. Hanson, et al. (1985). "Left ventricular responses to upright isometric handgrip and deadlift in men with coronary artery disease." Am J Cardiol 55(11): 1298-302. Shephard, R. J. and G. J. Balady (1999). "Exercise as cardiovascular therapy." Circulation 99(7): 963-72. Squires, R.W., Muri, A.J., Anderson, L.J., Allison, T.G., Miller, T.D., Gau, G.T.(1991). "J Cardiopulm Rehabil 11: 360-364. Stewart, K. J., L. D. McFarland, et al. (1998). "Safety and efficacy of weight training soon after acute myocardial infarction." J Cardiopulm Rehabil 18(1): 37-44. Taylor, R., B. Kirby, et al. (1998). "The assessment of recovery in patients after myocardial infarction using three generic quality-of-life measures." J Cardiopulm Rehabil 18(2): 139-44. Verrill, D. E. and P. M. Ribisl (1996). "Resistive exercise training in cardiac rehabilitation. An update." Sports Med 21(5): 347-83. ABSTRACT Research Isometrics Circuit Weight Training Future Research Considerations Summary
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