Aerobic Exercise Part 8
The take-home message from the first seven installments of this series is that resistance training is of little benefit if your heart isn’t strong enough to keep your bigger muscles up and running. Therefore, the heart must truly be the strongest muscle of them all. But there is a lot of indecision about the best way to train the heart and contradictory messages are even present when you consider guidelines suggested by experts who call the shots in the world of exercise.
It is universally recognized that cardiovascular training is synonymous with aerobic (endurance) exercise, which is any physical activity that requires rhythmic contractions of a significant portion of the body’s larger muscle groups at a sustainable percentage of the peak force they can produce. Therefore, exercise modes including walking, jogging, cycling, rowing and elliptical stepping can be used to train the heart. But there is far less unanimity regarding how hard you should work when you perform these maneuvers. “A sustainable percentage of the peak force a muscle can produce” comprises a wide range of intensities including strolling on the beach at sunset. But if this was all that was required to train the heart, cardiovascular disease wouldn’t be the biggest cause of death in the U.S. today!
The American College of Sports Medicine’s 1998 position stand suggests that once a minimal intensity level is surpassed, the cardiovascular training effect will be dependent upon the total amount of energy you expend. Energy expenditure is a function of both intensity and volume; therefore, this means that if you exercise long enough, you can get significant gain sans pain. However, recent research suggests otherwise. In an article published in the Journal of Applied Physiology in 2005, a research team that included exercise physiologists from the U.K. and Australia assessed changes in cardiorespiratory fitness and coronary heart disease risk factors in two groups of subjects following 24 weeks of endurance training. These researchers set up training protocols so that regardless of the group that a subject was in, the overall quantity of energy they expended would be similar. Specifically, they performed three aerobic sessions per week and expended 400 calories each time they trained. However, one group worked longer at a less challenging pace while the other spent less time, but more sweat during their workouts.
In the study by O’Donovan et al., 42 previously sedentary men completed the program and when post-training tests were performed, some interesting differences were found. A non-exercise control group was also included in the investigation and the good news is that both groups that exercised improved their fitness (as indicated by VO2 max, which is the maximum amount of oxygen a person can consume) compared with those that did not. However, the degree of improvement in the two groups was also different. After week eight when exercise intensity was increased from 60 to 80% VO2 max in the high-intensity group, those subjects experienced greater increases in VO2 max compared to the ones who continued to train at 60%.
For an endurance athlete, an inquiry regarding VO2 max is equivalent to the “How much can you bench?” question that is typically asked of those who lift weights. So, the finding of a greater increase in this parameter by expending the same amount of calories in less time is definitely important for those who concern themselves with such matters. But if you’re not a Lance Armstrong wanna-be, you might be wondering if there is a similar rationale for you to work harder. After all, if you can strengthen your heart to keep yourself alive without “killing” yourself in the gym, why not go for it? Well, the answer lies in another critical finding from this study. After 24 weeks of endurance training, pre- to- post-training changes in coronary heart disease risk factors were not significantly different in the moderate-intensity group compared to the control group. However, the high-intensity group decreased total cholesterol, LDL cholesterol and non-HDL cholesterol to a greater extent!
In addition to proving that high-intensity cardiovascular training provides greater health benefits, O’Donovan et al. also addressed one of the key contentions that had been forwarded by those who advocate caloric expenditure instead of intensity as the end all and be all. It had been suggested that expending the requisite amount of calories by working easier and longer promotes exercise adherence by decreasing burnout and/or injury. In other words, most people don’t stick with an exercise program to begin with, so we must sugar coat the requirements to make exercise as palatable as possible. The problem with this approach is that it does a severe disservice to those who are ready, willing and able to work harder, but believe they don’t have to. Sure, if I thought I could derive the same benefit from a 30-minute relaxing walk plus 30 minutes of gardening as I do from 20 minutes of pure agony on the treadmill, I would choose the easier route also. But this study suggests you don’t! Instead, it indicates that changes in cardiovascular risk factors are influenced by exercise intensity and what is more, O’Donovan et al. found no difference in injury or dropout rates due to the different intensities of training.
This article was originally published in New Living Magazine, which can be accessed on-line at www.newliving.com.
