Cardiopulmonary Resuscitation

Slettalokken Gunnar, Rehn Tommy, Munkvik Morten, Rud Bjarne, Nymark Bernt, Lunde Per Kristian, Sjaastad Ivar, Sejersted Ole, Halle Jostein, Normal training response in skeletal muscle of post-infarction heart failure patients, European Journal of Sport Science
, 2013. 2 (13), 231-239.

Introduction/Purpose

Congestive heart failure patients express an inability to exercise at the capacity of healthy individuals but more precisely experience reduced muscle fatigue resistance. This study was designed to elicit a clearer understanding as to whether skeletal muscle in CHF patients has a normal training response relative to both Coronary Artery Disease patients and healthy subjects following induced bouts of endurance training. Directly comparing the variables of a CHF group to a control group, in respect to aerobic capacity adaptations through endurance training, was the primary objective of this research. Researchers hypothesized, both CHF patients and normal subjects, would increase the aerobic capacity of the muscle in a similar manner.

Methods

10 patients with post–infarction CHF and 13 healthy subjects were included in the study. An additional 9 people with coronary artery disease (left ventricular systolic function), were included as a second control group. Various quantitative measurements were collected, such as, ejection fraction, VO2 peak, mean peak torque, heart rate, CSA (cross sectional area of muscle), muscle fiber circumference/area and capillary length, to be used for comparative analysis. Subjects used a custom designed electromagnetic braked ergometer to engage in 6 weeks of one-legged knee extensions. Each participant’s initial VO2 was collected using a cycle ergometer, which used continuous electrocardiography readings to enhance the quality of measurement. In addition, CT scans helped determine muscle cross sectional area and muscle biopsies were used to determine muscle fiber type and capillary length. This 10 week training program was coupled with a multitude of quantitative tests preceding each week, with each test differing based on the week of the program. All measurements contributed to increasing the external validity of this research, further enhancing the study.

Results

Training responses were evaluated by comparing the trained leg and control leg at the conclusion of the training period. The 1-KE isokinetic contractions indicated CHF patients were less fatigue resistant in the control leg, but not the trained leg. Peak power and peak oxygen uptake yielded a significant disparity in results with a 10-16% higher number in the trained leg than the control leg. After using muscle biopsies to help delineate between fiber type composition in the vastus lateralis, it can be concluded there was no difference in % values between trained leg and control leg in CHF patients. Interestingly, after training, capillary density accrued and showed approximately a 6.5% higher concentration in the trained leg than control leg in CHF patients, when all groups were compared. Results obtained from this research confirmed the initial hypothesis in that more fatigable skeletal muscle of CHF patients would respond equally to endurance training as those of CAD and healthy patients.

Discussion

Through extensive endurance training specific to the quadriceps, 6 weeks of dynamic 1-KE endurance training diminished muscle fatigability to a level that was comparable to healthy subjects. Although CHF is linked to degradation in various physiological components such as cardiac function, capillary density, oxidative enzyme activity, and mitochondrial volume, this study revealed compelling similarities in rate of development in respect to exercise capacity and muscle metabolic capacity between CHF, CAD and healthy patients. Essentially, a strong correlation exists between fatigability of skeletal muscle and rate of development in terms of response to endurance training in CHF patients, to the point where development may supersede that of CAD and healthy individuals.

Reflections

Empirical research of this magnitude facilitates a better understanding of the physiological nuances that are linked to various heart diseases. Before doing this research analysis, I would have never surmised that skeletal muscle of congestive heart failure patients would display the propensity to adapt at a rate similar to that of coronary artery disease patients and healthy patients. Through strenuous endurance training, I speculated accrued physiological inefficiencies would manifest in CHF patients, leading to a large disparity in % values between the 3 groups. With a total 32 participants and meticulous structuring of prescribed exercises, this study certainly adhered to the empirical research demands needed to qualify this study as legitimate. As far as recommending this study to those interested in cardiovascular disease and its relationship with exercise training, I would suggest it.