Resistance training is a critical component in the rehabilitation of individual’s post-cardiovascular event (CVE). However, restrictions on the amount of weight that can be lifted post-CVE limit overall health benefits that could be achieved through resistance training. Several components of health, such as muscular strength and endurance, and functional abilities, are significantly decreased. The loss of these health components substantially influences the rising cost associated with CVE by increasing patient readmission rates post-CVE. Numerous research studies have reported several health benefits of resistance training in cardiac rehabilitation, which includes increases in muscular strength and endurance, functional abilities, quality of life, and lowering the prevalence of muscle atrophy. These health benefits will positively affect an individual’s health post-CVE when safely implemented at earlier time-points. Therefore, the implementation of revised resistance training and weight lifting guidelines for cardiac rehabilitation could influence more significant health outcomes in patient’s post-CVE.

Keywords: Resistance Training; Cardiovascular Event; Cardiac Rehabilitation; Muscle Atrophy; Quality of Life

Resistance training (RT) is a vital part of physical reconditioning in cardiac rehabilitation (CR) programs. Utilizing RT increases muscular strength and endurance, functional abilities (FA), and quality of life (QoL) [1-3]. However, the early implementation of RT in CR is still not fully utilized. Currently, individuals who survive a cardiovascular event (CVE) are limited to very little physical activity (PA) for as much as 2 to 4 weeks after initial hospitalization. They are recommended to lift nothing >10lbs during this time [4]. Physicians and healthcare providers discourage the early implementation of RT in CR because RT increases blood pressure, heart rate (HR), and rate pressure product (RPP) during exercise [2]. There is concern that RT will induce the reoccurrence of a CVE by increasing stress on the heart. However, the risk of RT in CR patients is very low [5,6]. Weight lifting restrictions increase the risk of developing sarcopenia, muscle atrophy (MA), decreased muscular strength and endurance, decreased cardiovascular function, and impaired functional ability [2,7-9]. These risks apply to individuals with coronary artery bypass graft, valve replacement, percutaneous coronary angioplasty, myocardial infarction, and congestive heart failure (CHF). PA and weight-bearing restrictions allow for prolonged periods of skeletal muscle disuse, which causes MA to develop. Muscle atrophy has been shown to affect the muscles in lower body to a greater extent than the muscles of the upper body [10-15]. The rate of MA increases rapidly in the first three days of muscle disuse and continues to increase the longer muscles are inactive or immobile [11]. The loss of muscular strength is even more rapid than the rate of MA [16].

The early implementation of RT in post-CVE individuals is needed to reduce readmission rates, decrease recovery time, and lessen MA, and improve QoL [4,17,18]. The purpose of this review is to examine current recommendations of RT in CR and evaluate the benefits of implementing RT immediately post-CVE. 

Current American Heart Association (AHA) recommendations, outlined in Table 1, affirm that RT is a vital part of cardiovascular health [19]. Likewise, the American Association of Cardiovascular and Pulmonary Rehabilitation (AACVPR) recommendations for RT mirror those published by AHA [20]. American College of Sports Medicine’s (ACSM) current RT recommendations for CR is displayed in Table 2 [21]. Although similar to AHA and AACVPR recommendations, ACSM recommendations prescribe RT more specifically based on the type of CVE. ACSM also provides detailed progression and expected timelines for how long it may take to achieve different physical goals. There are also start time recommendations for when RT can be initiated post-CVE. However, the time periods provided are weeks and months after the CVE has taken place.
 

Table 1: American Heart Association and American Association Prescription of Cardiovascular and Pulmonary Rehabilitation Exercise Protocols/Recommendations. For Cardiac Rehabs Abbreviations: d = Day; wk = Week; Adapted from [19,20].

 

Table 2: ACSM Exercise Prescription Protocols/Recommendations.      
*Abbreviations: ADLs= Activities of Daily Livings; CVE = Cardiovascular Event; HRR = Hear Rate Reserve; E = Muscular Endurance; S = Muscular Strength; MVC = Maximum Voluntary Contraction; PCVE = Post Cardiovascular Event; RHR = Resting Heart Rate; RPE = Rate of Perceived Exertion; THR = Target Heart Rate; wk. = Week; ↑ = Increase; ↓ = Decrease; *Adapted from [21].  

Currently, RT recommendations used in CR are somewhat vague and provide little or no information regarding RT being implemented at earlier time-periods (e.g., 1 to 2 days) post-operation/hospitalization. Specific considerations for a patient’s age, gender, occupation, or current PA level are not factors involved in the type, time frame, or progression of RT. These factors play a critical role in decreasing the rate of MA and rehabilitation time, increasing QoL, and diminishing healthcare costs. The generalized protocols allow healthcare providers to be aggressive or passive when prescribing RT, negatively affecting the recovery time of patients. The occupation and leisure activities of the general population have become more sedentary than in previous years [4]. The occupation of CVE individuals can serve as an indication which specific RT protocols should be used and the amount of time before the start of rehabilitation. In a clinical research study, six firefighters were given the option of normal CR or participating in RT known as HIOST (High-Intensity Occupation-Specific Training). All six firefighters completed HIOST with greater strength and endurance gains than traditional CR with no adverse symptoms [22].

Studies that looked at muscle disuse or immobilization over different periods showed a rapid decrease in muscular strength, mass, and cross-sectional areas [11, 13]. In a 10-day study that observed immobilization of the lower limb, subjects exhibited a loss of 41.6% of muscle strength, and 11.8% decrease in cross-sectional areas [11]. In a similar 10-day bed rest study, muscle protein synthesis was shown to decrease at a rate of 0.027% per hour of bed rest [15]. The influence of isometric exercise has also been investigated in subjects randomized to undergo either 20 days of complete bed rest or 20 days of bed rest with added bilateral isometric leg extensions while lying in bed [12]. The exercising group maintained knee extension force, while the non-exercising group experienced an 11% decrease in knee extension force. Additionally, cross-sectional area of the vastus lateralis decreased only 4% in the exercising group compared to 8% in the non-exercising group [13]. Muscle disuse produces significant negative effects on muscle torque. Unloading of the leg muscles for two weeks resulted in 13-22% loss of torque in the knee extensors and 3-14% loss of torque in knee flexors [12].

Implementing RT at earlier periods than currently utilized in CVE individuals involves different levels of risk, depending on the individual. Patients are classified as low-, moderate-, or high-risk depending on physiological risks [23]. For example, sternal tenderness and weakness are risks when the chest has been opened up for coronary artery bypass graft (CABG) or valve surgery. There is the potential for RT to reopen the percutaneous coronary angioplasty incision sight to the arm or the leg. There is also the risk of cardiovascular complications (e.g., hypotension, hypertension, arrhythmias) developing. Muscle soreness is very common with RT, especially in individuals who are sedentary and do not participant in regular PA or exercise [24]. Pollock et al. stated that RT in moderate- to high- risk patients in CR requires more research to prescribe RT safely and effectively [25]. Previous studies that were reviewed reported that RT with higher weights could be added three months post-CVE. In conventional exercise prescription, it is suggested that RT not be initiated for 4 to 6 months in myocardial infarction patients [26]. This conservative recommendation is based on the concern that RT will cause the occurrence of another CVE by increasing stress on the heart after the initial CVE. However, these recommendations were made 20 to 30 years ago, and factors influencing these recommendations (e.g., age, lifestyle, occupations, and research) have since changed.

The risk of a cardiovascular complication occurring during RT is considered low, according to the ACSM in low- to moderate-risk individuals. In high-risk individuals, the possibility of having a cardiovascular complication is still considered low. In low- to high-risk CR patients, the occurrence of a cardiovascular complication is considered marginal [28]. When calculating the occurrence of cardiovascular complications in phase II and III CR, one occurred every 58,451 patient exercise hour. Phase I is different from phase II and III in that it is considered by healthcare professionals to be high-risk for potential complications. Table 3 outlines 15 studies that examined RT beginning 6 to 24 weeks post-CVE. In these studies, only eight individuals reported any adverse symptoms. The reported adverse symptoms included two chest pain episodes in a single patient, three reports of musculoskeletal pain or soreness in two patients post-exercise, one reported episode of vasovagal response, and two reported arrhythmias in two different patients (only one occurred during exercise). Increases in strength and endurance were reported with improvements of 10 to 55% in the upper body and 15 to 50% in the lower body. All participants completed RT safely with no significant adverse effects in the reviewed studies. When studying 24 post-CABG individuals who participated in circuit training (CT), there appear to be no negative effects [29]. Featherstone et al. conducted a study on twelve men with a history of coronary artery disease [30]. The men were exercised at 40, 60, 80, and 100% of their maximum voluntary contraction (MVC) of the skeletal muscle, and their results were compared to their maximal treadmill tests. Greater significance was seen in myocardial oxygen supply and demand in the RT group when compared to the treadmill group [30].
 

Table 3: Cardiac Rehabilitation Resistance Training Research Studies.
Abbreviations in Alphabetical Order: B = Butterfly; BC = Bicep Curl; BE = Back Extension; BF = Back Flexion; BP = Bench Press; CB = Chest Butterfly; CR = Calf; Raises; D = Dips; LB = Lower Body; LC = Leg Curl; LE = Leg Extension; LF = Leg Flexion; LR = Lateral Raise; LP = Leg Press; LPD = Latissimus Pull Down; E = Muscular Endurance; MP = Military Press; S = Muscular Strength; pt = Patient; RCB = Reverse Chest; Reps = Repetitions; SF = Shoulder Flexion; SP = Shoulder Press; SR = Shoulder Raises; TE = Triceps Extension; UB = Upper Body; VR = Vertical Row; 1-RM = 1 Rep Max; ↑ = Increase; ↓ = Decrease; ? = Male; ? = Female; * = Gender sample size not reported.

Many post-CVE patients are middle-aged to elderly. Thus, research was conducted in these populations to evaluate the safety of participating in RT. The evidence suggests RT is a safe and effective way to decrease HR and blood pressure in the aging population [31-33]. An RT study was conducted involving 14 participants who were 46 to 72 years old and were 1 to 3 months post-CABG or percutaneous coronary angioplasty [31]. They were able to complete the RT program safely and successfully. Heart rate and systolic blood pressure were shown to be lower during RT in older participants as well as in several other studies when comparing RT against aerobic exercise [27, 29-34].

ADL help to gauge post-CVE patient’s QoL and assess their overall fitness levels [35]. Adams et al. found that determining a patient’s fitness level before the start of CR was beneficial to prescribing RT [4]. CHF patients, who were over the age of 65, participated in RT for six months and increased their 1-RM by 50-80% [2]. Also, a Continuous-Scale Physical Functional Performance Test (CS-PFP) was used to assess participant functionality [1]. The results of the study found that strength, balance, coordination, endurance, and overall functional ability increased with RT [2]. Maintained or improved FA are beneficial for individuals wanting to get back to ADL and allows them to be more independent. There is a strong correlation between muscular strength, endurance, and decreased mortality (36). Individuals who complete RT are stronger on average than those not completing RT, and they exhibit superior FA. RT helps to increase daily FA, which include (e.g., chores, walking, balance, and yard work).

QoL is a mental health dimension that is an important part of CR. Individuals often feel scared, timid, angry, or depressed after they experience a CVE. Sometimes the fear of having another CVE causes them to be timid when doing everyday activities. These feelings can decrease the amount of PA that individuals participate in, and their overall QoL is decreased. Beckers et al. randomly assigned 58 CHF patients to 6-months of combined endurance-resistance training (n = 28) or endurance training only (n = 30) [35]. After completing the study, 42 of the 58 participants filled out self-reported, health-related QoL. Nineteen of the 42 patients (42%) reported a significant decrease in noticeable cardiac symptoms (e.g., angina, shortness of breath, pain, numbness, weakness or coldness in your legs or arms). There was a greater decrease in cardiac symptoms in the RT group (60% decreases) versus the aerobic group (28% decrease). With a decrease in cardiac symptoms, individuals feel more confident, less depressed, and are more likely to return to ADL [35]. Other studies reported that by increasing muscular strength in cardiac patients they could reduce the perception of the effort exerted during daily tasks [4, 37].

Research evidence suggest that greater physiological benefits can potentially be obtained by implementing low amounts of RT immediately post-CVE. Resistance training has been proven to be beneficial and safe for individuals who have experienced a CVE ¬¬[4]. PA restrictions that are placed on individuals for days and weeks post-CVE hinder them from benefiting their future health. The first three days are shown to have the greatest loss in skeletal muscle and strength [11]. The greater the decrease in muscle mass, strength, and endurance, the greater decline in FA. Decreases in strength and FA can cause an increasingly sedentary lifestyle, which leads to further health issues and prolife rates the probability of readmission. 

In conclusion, there is compelling evidence that by implementing RT earlier, readmission rates in CVE patients will decrease. There are few clinical studies that have evaluated exercise in CR phase I [38, 39]. To my knowledge, currently there are no studies that have investigated RT immediately post-CVE. Future research is needed to examine the physiological effects of RT during the period immediately (1-14 days) post-CVE. Also, research is needed in occupational differences and outcomes from participation in CR phase I and II.

Acknowledgments: None

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Corresponding Author: Dr. Jeffrey S. Forsse, One Bear Place, Baylor University, College of Health & Human Sciences, USA.

Copyright: © 2021 All copyrights are reserved by Jeffrey S Forsse, published by Coalesce Research Group. This This work is licensed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.