Rationale For Resistance Training in Patients With HF
The intent of chronic exercise is to introduce a series of stresses that will cause the body to adapt, either structurally or functionally, to the physical stress. Ultimately it enables the body to respond better to subsequent stresses or exercise bouts. The benefits from aerobic training in improving muscle function in patients with HF are well established. However, most activities of daily living involve the use of the upper extremities more than the lower extremities in pushing, pulling, reaching, and lifting loads. Because disuse atrophy is a common finding in patients with HF, aerobic training may be insufficient to increase strength and muscular endurance in these patients. The American College of Sports Medicine61 recommends that resistance training be performed sufficiently to develop strength and endurance, as a part of an adult fitness program. This recommendation also should apply to patients with HF because of the deconditioning and muscle atrophy commonly seen in these patients. However, traditional cardiac rehabilitation programs for patients with HF do not focus on the strength development component in the same manner as they focus on the aerobic component.
A study by Ploutz et al. using REs showed that increases in strength could be obtained without hypertrophy of the muscle, suggesting that less muscle is used to lift a given submaximal load after training. Therefore, resistance exercises would be beneficial to patients with HF in preventing muscle atrophy and deconditioning, and the increase in strength would delay the early onset of anaerobic metabolism seen in these patients at high workloads.
Furthermore, researchers have demonstrated that resistance training in a population with advanced coronary artery disease may be as safe as, or safer than, graded treadmill exercise, as measured by blood pressure and peak heart rate response (rate pressure product or double product).[37,63,64] The same investigators noted that myocardial oxygen supply-to-demand balance is more favorable with maximal repetition weight lifting than with maximal treadmill exercises. Therefore, a combined aerobic and weight training program for patients with HF may be a more effective method of increasing aerobic performance and strength than traditional aerobic training alone.
Along with aerobic training, resistance training curtails the decrease in strength associated with aging. A study by Fiatarone et al. showed that resistance training caused significant increases in strength in very old (87-96 years), frail men and women. Subjects in this study exercised at an intensity of 80% of 1-RM for 10 weeks without complications, suggesting that resistance training at this high intensity was safe in this population. The noted increases in strength were associated with increases in gait speed, stair climbing power, balance, and overall spontaneous activity.
Because disuse atrophy is a common finding in patients with HF, and many of these patients are elderly, they may not be able to recruit motor units necessary to fully activate their muscles during voluntary contractions. Motor units are recruited according to their recruitment threshold (size principle) and firing rates. Low threshold or small motor units are recruited first at the onset of physical activity of low frequency and low intensity, as occurs in walking and long distance running. These small motor units are composed of fibers with slow myosin and high oxidative capacity. In contrast, large motor or high threshold units are composed of fibers with fast myosin and low oxidative capacity; these units are recruited infrequently. Maximum force production requires the recruitment of all motor units, including high threshold units, at a high enough firing rate to produce maximum force. Perhaps the main reason resistance training would be beneficial for patients with HF is that training adaptations would likely result in the ability to recruit all motor units when needed to perform a task.
Moreover, physical training decreases catecholamine levels, especially norepinephrine, associated with exercise at any given workload.[12,67] Serum norepinephrine levels are lower in trained than untrained individuals. A study by Green et al. showed that the time-dependent increase in catecholamine level was decreased significantly post-training. Study participants were untrained males who exercised (bicycled) for 120 minutes at a moderate intensity (65% of peak O2) on 3 consecutive days. The effects of resistance training on catecholamine levels in patients with HF remain to be determined. However, it is likely that chronic resistance training would favorably alter the increase in these hormones during exercise in these patients.
Resistance training also would be a significant adjunct to aerobic exercise (e.g., treadmill exercise) because the primary adaptation to endurance (aerobic) training is an increase in oxidative capacity. The primary adaptation to resistance training is an increase in strength. During aerobic exercise, the upper body is supported by isometric muscle actions of the legs. Upper body resistance training negates the decreases in type I muscle fibers associated with aerobic exercise.
Additionally, resistance training has been shown to have positive effects on glucose tolerance, insulin sensitivity, bone density, energy metabolism, and functional status. More importantly, RE may be one of the most effective and least costly interventions that can be used to preserve independence and functional capacity in patients with HF. REs can be performed in the home and the equipment required (hand-held weights, i.e., bar bells) is inexpensive.
Prog Cardiovasc Nurs. 2001;16(4) © 2001 Le Jacq Communications, Inc.
© 2007 Prog Cardiovasc Nurs
Cite this: The Effects of Resistance Exercise on Skeletal Muscle Abnormalities in Patients With Advanced Heart Failure - Medscape - Oct 01, 2001.