Resistance weight training improves aerobic capacity in the elderly

Shelley Wood

March 29, 2002

Fri, 29 Mar 2002 19:25:41

Gainesville, FL - In an unusual study that saw elderly men and women doing bicep curls and leg presses, researchers have found that resistance weight training can improve aerobic capacity in older adults. The finding appears to fly in the face of the traditional view that cardiorespiratory fitness - with its beneficial impact on early mortality, CV disease, hypertension, and stroke - can only be achieved through endurance exercise and not by doing so-called "resistance" exercise, typically using weight-training machines.

"Physicians always think, if people need to exercise, tell them to go for a walk," lead author Dr Kevin R Vincent (University of Florida Health Sciences Center, Gainesville, FL) told heartwire . "What I want them to start thinking about is also getting their patients active in resistance training. People are always asking what will be the 'best' exercise: aerobic or weight training. What you really need to do is both, because each has its own type of benefits in terms of weight loss and healthier heart, or strength, bone density etc."

Vincent and colleagues published their study in the March 25, 2002 issue of the Archives of Internal Medicine.

Sixty-two men and women between 60 and 83 completed the study, which spanned 6 months. Subjects were tested at baseline then randomized to a high-intensity or low-intensity program involving 1 set of 12 different exercises; 16 subjects were randomized to a control arm that did no training. In the training groups, subjects exercised strenuously during the sets, then rested for only 2 minutes between exercises. Strength, muscle endurance, and treadmill time to exhaustion was measured at baseline and again at the end of the study period.

Both training groups improved, compared to controls

The authors report that muscle strength, oxygen consumption, and time to treadmill exhaustion increased significantly in both of the training groups, but not in the control group. The low-intensity group had trained at either 50% of their one repetition maximum for 13 repetitions while the high-intensity group had trained at 80% of their one repetition maximum for 8 repetitions, 3 times per week for 24 weeks. Of note, however, training results appeared equal between the two groups.

Percentage change from baseline in control, low-intensity, and high-intensity groups

Outcome

Controls

Low-intensity group

High-intensity group

p value**

-1.1%
17.2%
17.8%
<0.05
no change
23.5%
20.1%
<0.05
6.2%
26.4%
23.3%
<0.05
*TTTE=Treadmill time to exhaustion; ** p values were similar for both the low-intensity and high-intensity groups, compared with controlsTo download table as a slide, click on slide logo below

"These data suggest that resistance exercise of either or both low or high intensity may be a valid means of increasing cardiorespiratory endurance in older adults," Vincent et al write. They hypothesize that resistance training may increase oxidative enzyme activities or build leg strength such that muscle weakness does not prevent older exercisers from reaching their peak oxygen consumption. "Older adults don't have very good leg strength. So when they're on a treadmill or whatever is being used to test their aerobic fitness, they don't have enough strength in their legs to perform to their maximum potential," Vincent explained to heartwire .

Curiously, no such findings linking muscle strength to aerobic ability have been observed in younger adults, something Vincent believes is likely a result of improperly designed studies. "Younger people might already be fit, they may not be doing a strenuous enough resistance training program, or even an appropriate program with short rest periods.... If you studied resistance training in a younger person and used an appropriate regimen, you'd still see an increase [in aerobic capacity], but it might not be as dramatic."

The upshot, say the authors, is that frail elderly people may experience greater improvements in endurance and aerobic capacity following resistance training than younger, more able-bodied people.

In older adults, the authors conclude, "Increased leg strength may allow aerobic exercise training bouts to be performed at a greater intensity or for a longer duration, also leading to improvements in aerobic capacity." They propose that resistance exercise should be incorporated into exercise regimens for elderly women with no physical or cardiovascular contraindications, "to increase muscular strength, cardiorespiratory endurance, and physical function."

Elaborating to heartwire , Vincent emphasizes that resistance exercise might even be more important than aerobic activity in the elderly. "Something that you lose as you get older is your balance - which is partly a function of leg strength - as well as your ability to live independently in terms of getting in and out of chairs, carrying groceries, going up and down stairs etc. And strength training helps with that."

Linking directly to CVD endpoints

Linking resistance training directly to cardiovascular morbidity and mortality endpoints is tricky, Vincent admits, partly because resistance, and even aerobic training studies, are rarely conducted over the long term, leaving retrospective and epidemiologic studies to provide some clues.

That said, Vincent states that some strides have been made. For example, research indicates that people who have done some resistance training do not experience the same dramatic blood pressure rise in response to exertion as do people who do not weight train. "Think of it this way," he explains. "If you're going to pick up a 30-pound box, you pick it up and you get a blood pressure response that's really in response to how strong you are and how heavy that box is to lift. If you do some strength training and you pick up that box, it's lighter to you, your blood pressure response is lower, and a lot of cardiovascular events occur in people when they have that big spike in blood pressure."

In a separate study coming out later this year, Vincent and colleagues found that resistance training can boost the body's ability to fight free radicals. "So I think that we're going to start to see data that's directly making the link between resistance training and cardiovascular health."



Related links

1. [HeartWire > News; Nov 1, 2001]

2. [HeartWire > News; Jul 18, 2000]


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