THE EVIDENCE FOR EXERCISE Combine Aerobic Exercise with Strength Training
Emphasizing one aspect of fitness at the expense of others may be a special concern for those exercising with weights who don’t do enough cardiorespiratory conditioning. Although exercise experts universally agree that resistance training is beneficial for a variety of reasons (as detailed in Chapter 4), it also has a downside.
A number of global studies have tracked the impact of weight training exercises on the cardiovascular system to find out if such training helps or harms the heart and blood vessels. These studies have shown that strength training poses short- and long-term risks to cardiovascular health and especially to arterial health.
Aside from the risk of injury, lifting weights has been shown to have the following adverse effects on the cardiovascular system:
• Weight training promotes short-term stiffness of the blood vessels, which could promote hypertension (high blood pressure) over time and increase the load on the heart.
• Lifting weights (especially heavy weights) causes extreme short-term boosts in blood pressure; a Canadian study revealed that blood pressure can reach 480/350 millimeters of mercury during heavy lifting. Over the long term, sharp elevations in blood pressure can damage arteries, even if each pressure increase lasts only a few seconds.
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• Weight training places stress on the endothelial cells that line blood vessels. Because these cells secrete nitric oxide (a chemical messenger involved in a variety of bodily functions), this stress can contribute to a wide range of negative effects, from erectile dysfunction to heart disease.
A variety of studies have shown that the best way to offset cardiovascular stress caused by strength training is to do cardiorespiratory endurance exercise (such as brisk walking or using an elliptical machine) immediately after a weight training session. Groundbreaking Japanese research showed that following resistance training with aerobic exercise prevents the stiffening of blood vessels and its associated damage. In this eight-week study, participants did aerobics before lifting weights, after lifting weights, or not at all. The group that did aerobics after weight training saw the greatest positive impact on arterial health; participants who did aerobics before lifting weights did not see any improvement in the health of their blood vessels.
Strength training does promote endurance fitness by improving nervous control of the muscles, increasing type IIa motor units (muscle fibers have a blend of strength and endurance capacity), and increasing tendon strength. These changes increase muscle strength and the rate of force development, enhance the economy of movement, and increase the speed that blood cells travel through the muscles.
The bottom line of all this research? Resistance training and cardiorespiratory exercise are both good for you, if you do them in the right order. So, when you plan your workouts, be sure to do 15-60 minutes of aerobic exercise after each weight training session.
The effects of high-intensity intermittent exercise training on cardiovascular response to mental and physical challenge.
