This month’s research update focuses on cardiac rehabilitation and the inclusion of resistance training into the training protocol. Four key studies will be outlined.
Cardiac Study 1
Haslam DRS, McCartney N, McKelvie RR. Direct measurements of arterial blood pressure during formal weightlifting in cardic patients. Journal of Cardiopulmonary Rehabilitation. 8(6):213-225, 1988.
This was one of the first study of its kind that measured blood pressure (BP) responses to resistance exercise from directly within the artery. This breakthrough study helped the researchers and cardiac experts realize that RT is far safer for cardiac patients than originally believed. This study paved the way for more aggressive cardiac rehabilitation research and training protocols.
Eight male cardiac patients with an average mean age of 54 years (range 46-65 years) with coronary artery disease and history of myocardial infarction (heart attack) had a 20 gauge Angiocath needle (this is big) inserted into the brachial artery. Direct arterial BP was recorded before, during and after weightlifting activities. All subjects were monitored by electrocardiogram (ECG). All subjects performed a seated single-arm cable curl on a preacher bench using the non-catherized arm and a Global Gym leg press exercise (single- and double-leg). Subjects performed 1 set of between 5-15 reps at varying 1RM intensities (20%, 40%, 60%, 80%) with a 2 minute rest period. As the workload became heavier, the reps were decreased from 15 reps (lower body) and 10 reps ( upper body) to 5 reps at 80% of 1RM.
Subjects demonstrated clinically safe BP readings for all exercises up-to 80% of 1RM. BP increases were least with the lighter workloads and greatest with the higher workloads. The mean peak systolic BP at 80% 1RM for the single arm cable curl was 193 ± 10 mmHg; the single-leg press 204 ± 10 mmHg and the double-leg press 215 ± 7 mmHg; mean peak diastolic BP was 119 ± 8 mm Hg, 116 ± 6 mmHg and 124 ± 6 mmHg, respectively. Clinically acceptable maximum BP levels are generally considered to be 250/115 mmHg.
Another great outcome of this study was the information acquired regarding the effects of repetitions on Rate Pressure Product (RPP). RPP is the measurement used to determine the heart muscle (myocardium) oxygen demand and is calculated by multiplying systolic blood pressure with heart rate. Interestingly, performing more repetitions (15 +) with lighter workloads (50-60% 1RM) demonstrated a greater RPP than performing less reps with more weight. This means that the heart is working harder and requires more oxygen at lighter workloads, performed to fatigue, than when heavier workloads are used to fatigue. When performing more repetitions the blood pressure remains elevated and the heart rate continues to increase, thereby, increasing the heart’s requirement for oxygen. When performing low repetitions with a higher weight, the BP is much higher, however, the heart rate is much lower, since the set is finished before the heart has time to respond to the demand and the BP has dropped back to non-exercising levels. Other studies have shown greater ECG abnormalities during lighter workloads at higher repetitions than at higher workloads with lower repetitions.
The implications of these results suggest that (a) cardiac patients can perform resistance training safely without increasing the risk for experiencing a cardiac event and (b) it would be wise to use a workload between 50%-70% of 1 RM and limit the repetitions to twelve (see the next study)
Cardiac Study 2
Wiecek, E.M., McKelvie, R.R., McCartney, N., Comparison of Direct and Indirect Measures of Systemic Arterial Pressure During Weightlifting In Coronary Artery Disease. Am Journal of Cardiology. Nov 1990, (66) pp. 1065-1069.
This study compared arterial blood pressures of cardiac patients using the arm cuff method versus the direct invasive intra-arterial catheter method to investigate the relation of post-exercise pressures to the pressures that were generated during the actual lifting phases. This study also looked at the influence of overhead shoulder presses on BP. Five men, average age of 58 years, with a history of coronary artery disease (CAD) and myocardial infarction. Subjects had an intra-arterial catheter inserted into the brachial artery of the non-dominant arm and an arm cuff placed on the dominant arm. BP reading were taken at rest (once every minute for 5 minutes), immediately before, during and after each exercise set. Subjects performed seated single-arm preacher cable curl, single-arm overhead press, with the BP cuff arm and single- and double-leg leg presses. The order of the exercises was random. The subjects performed 1 set of 15 repetitions at 40% and 60% for the upper body and 1 set of 15 reps at 40% and 2 sets of 10 reps at 60% for the lower body exercises.
Their were no abnormal haemodynamic responses pre-, during and post-lift. BP dropped significantly within 1-2 seconds post-lift (both systolic and diastolic) suggesting that BP taken using the cuff around the arm were not of use when assessing BP after a lift. BP measurements by cuff method, during a lift, were not considered reliable due to the large fluctuations that occur in the readings as well as, noise interference. The arm cuff method demonstrated 13% less systolic pressures than the catheter method taken at the same time, however, diastolic pressures were similar
It was concluded that the arm cuff BP method for estimating systolic BP was significantly less accurate than the intr-arterial method. It was also noted that overhead shoulder presses incur a higher BP reading than lower body exercises and workload intensities should remain at or below 60% of 1RM.
This was a well-designed experiment that provided further insight and support for the inclusion of RT in cardiac rehabilitation. It helped cardiac specialist’s understand the BP differences that occur during different RT exercises and with varying workloads.
Cardiac Study 3
Potvin AN, Martin A, Ignaszewski A. The Effects Of Resistance Training During Early Cardiac Rehabilitation (Phase II) On Strength And Body Composition. UBC Research Thesis, 1998 (in press for publication).
This study was my own research. I wanted to:
- further support the international campaign to have RT included into clinical cardiac rehabilitation and Phase 4 community cardiac programs
- determine the magnitude of strength improvement possible with stable cardiac patients
- investigate the implications of aerobic-only cardiac rehabilitation programs on body composition
- investigate the optimal, safest and earliest point at which RT could be included into a cardiac rehab program
Based on my previous work and personal observations, it was clear to me that RT was a safe and important adjunct to the cardiac rehabilitation program (CRP), however, it was not being implemented in most CRP’s. I wanted to change this. I also noted that those patients that adhered to every aspect of a CRP including nutritional advice and exercise prescription, appeared to lose considerable body mass. Nothing in the literature adequately reported what exactly was being lost. I wanted to use the latest in body composition technology (DXA) to determine exactly what body compositional changes were occurring. Finally, I wanted to know what was the earliest point RT could be started in a CRP safely.
Twenty-seven male cardiac patients were assigned to one of three groups: aerobic only (AO), early-start resistance training (ESRT) and late-start resistance training (LSRT). All three groups participated in 16 weeks (32 sessions) of aerobic exercise. The ESRT started RT at the fourth week of aerobic training and lasted for 12 weeks (24 sessions) ; the LSRT group started RT after ten weeks of aerobic training and resistance trained for 6 weeks (12 sessions); both groups performed moderate-high intensity RT (70-79% of 1RM). The AO group did not perform RT other than during the four testing dates.
All three groups showed a significant decrease in deep abdominal (visceral) fat with no changes to skinfolds. The AO group also showed a numerical loss in muscle mass while both the RT groups showed a numerical increase. Strength changes were significantly different between groups with the greatest changes occurring in the ESRT group (27.9± 4.2%) followed by the LSRT group (25.5 ± 3.3%) and then the AO group (7.1 ± 2.6%). There was no significant difference between the ESRT and LSRT in strength suggesting that starting RT at 4 weeks or 10 weeks of a CRP will not have a significant physiological effect. However, a sub-study on self-efficacy showed cardiac patients that started earlier, gained a greater self-confidence in their abilities to perform strength type daily activities sooner and with less fear for re-injury.
These findings support the theory that those cardiac patients who follow all the eating, health and exercise guidelines of a CRP run the risk of losing active lean tissue, as well as fat, and the inclusion of RT can off-set this loss. Also, for those fitness professionals who focus on aerobic -only (AO) exercise with clients, they may run the risk of decreasing these clients active lean muscle. Another finding of this experiment suggests that combining aerobic exercise and RT into a client’s exercise program appears to be a safe and effective way of maintaining or building muscle mass while decreasing deep abdominal fat.
It appears that starting a cardiac patient on RT early (if cleared by a cardiologist) has no significant impact on strength performance when compared to those starting later in the CRP. However, the impact that early RT has on patients’ self-confidence and fear for re-injury is quite significant and makes for a strong argument to have cardiac patients start RT as early as possible. It offers them an opportunity to regain the quality of life that they were accustomed to sooner.
It is important that the reader note some limitations of this study. First, the sample size of each group was small, which statistically may influence the results; the greater the sample size the greater the power of the study’s results.
There is no way of knowing for certain whether those LSRT patients that started at the 10 weeks mark, actually refrained from RT on their own. This could have explained the high strength results, however, this is not likely to have occurred since, RT research shows that the greatest increases in strength performance occur in the first 4 weeks and are neurological in nature.
Although, the cardiac patients in this study trained between 70-79% of 1RM (8-12 reps to fatigue), it is not necessary nor always safe to RT cardiac patients at these intensities. It is recommended by experts to keep workloads below 70% of 1RM.
André Noël Potvin, M.Sc. is a trainer of fitness leaders for the BCRPA. He teaches in the School of Human Kinetics at UBC and lectures internationally. He can be reached by calling The Fitness Group at (604) 654-1725 Ext. 1104 or email: firstname.lastname@example.org