Physical Fitness and Heart Disease in Men

Summarized by Hannes B. Staehelin
December 20, 2002 (Reviewed: December 16, 2004)

Introduction

In spite of medical progress, heart attack and stroke remain in first place as the leading cause of death in the developed world. Men are affected and die at an earlier age from these conditions than women. In recent years, onset is often later in life, and the numbers of sufferers are fewer. On the other hand, the number of diabetics has increased during this period. In view of the worldwide obesity epidemic, it must be feared that cardiovascular disease, stroke, blood flow disturbances in the legs, and some types of dementia will all increase in frequency.

Preventive behavior is therefore an important goal for everyone. It's well known that physical activity protects one from cardiovascular disease. What's uncertain, however, is how much exercise is necessary to achieve the desired effect. It's been shown that, in women, regular brisk walking, or a similar level of activity, reduces their risk of cardiovascular disease (see first link below).

Like almost no other activity, the amount of physical exercise undertaken is largely dependent on the individual's motivation and doggedness. The two studies summarized below should help improve people's motivation.

Physical activity and blood lipids

In their so-called "Studies of Targeted Risk Reduction through Defined Exercises" (STRIDE) scientists from Duke University, USA, examined the effect of various exercise programs on blood lipid levels in 85 overweight men and women. They compared the results after 6 months with those of a control group who didn't undertake any exercise. The participants were between 40 and 65 years old, with a Body Mass Index (BMI) between 25 and 35; they all had a lipid problem -- either elevated low-density lipoprotein cholesterol (LDL) or lowered high-density lipoprotein cholesterol (HDL) levels.

The active participants were allocated to one of three different types of exercise program, as shown in the table below. They were instructed to try to keep their weight constant, in order to lessen possible effects of weight loss on the results of lipid profiles.

Intensity of Activity	Type of Activity	Effect after 6 Months
A lot, and intensive	20 minutes jogging daily, = 20 miles (32 km) per week(or equivalent)	Lowered triglyceride and IDL* Increased HDL Improved O2 uptake
A little, but intensive	12 minutes jogging daily, = 12 miles (19 km) per week(or equivalent)	Lowered triglyceride Increased HDL Improved O2 uptake
A little, and only moderately intensive	12 miles (19 km) brisk walking per week(or equivalent)	Lowered triglyceride Increased HDL Improved O2 uptake

* IDL = Intermediate Density Lipoprotein, which are breakdown products of LDL.

The chief conclusions to be drawn from this study are:

• Regular physical activity has beneficial effects on the blood lipid profile
• The more intensive the effort, the better the result
• Even when body weight remains unchanged, intensive activity leads to favorable effects on the risk of vascular disease

Can intense physical activity decrease cardiovascular disease?

This is a similar question to that raised in the first section, above. What amount of activity is necessary to produce significant benefits? We know that brisk walking for 30 minutes daily, 5 days a week, is effective in women, but how about men? The answer comes from an analysis of results from the "Health Professional Follow-up" Study recently reported in the Journal of the American Medical Association.

Over 44,000 male health professionals had their physical activity monitored every two years over a 12-year period. Their activities were classified as jogging, walking, heavy outdoor work, or sports such as tennis, soccer, cycling, or swimming. Weight training was added for the final 8 years. In order to be able to compare results of different activities, the amount of oxygen each consumed was expressed in a unit called a "MET" (metabolic equivalent task). This allowed the following classification:

Marked physical activity	Jogging Running Tennis Squash Rowing	6 METs or more
Moderate physical activity	Walking Garden work Weight training	Less than 6 METs

To ensure the appropriateness of this classification, detailed energy expenditure studies were done on different subgroups in each class. In the course of these exams, it was confirmed that physical activity led to an increase in HDL cholesterol levels.

About 40% of the subjects in the study expended fewer than 8 METs a week, while 40% expended between 17 and 69 METS a week. It was noticeable that the greater the level of activity (i.e. those with higher METs), the smaller the percentages of smokers and subjects with high blood pressure, and that high-activity subjects were more likely to consume vitamin supplements, fruits, and vegetables.

Physical activity reduced the risk of cardiovascular disease. The results also confirmed the importance of known risk factors such as smoking, high blood pressure, and high cholesterol levels. As was seen in women, the protective effect of exercise was not dependent on body weight.

Running for an hour or more per week was associated with a 42% reduction in the cardiovascular risk -- in fact, it was just as effective as most medicinal treatments! Rowing led to an 18% reduction, and weight machine use for more than 30 minutes a week caused a 23% reduction -- a new and important finding.

Type of Activity	Reduction of Risk*
Running more than 1 hour/week	- 42%
Rowing more than 1 hour/week	- 18%
Swimming	No effect
Bicycling	No effect
Weight training more than 30 minutes/week	-23%
Walking more than 3.5 hours/week	-18%
Brisk walking more than 30 minutes/week	-45%

* Risk reductions adjusted for other factors, e.g. smoking, BMI, diet, etc.

Again, this result for men corresponded with that for women, where brisk walking led to a reduced risk of - 39% to - 49%. Regular quick walking is therefore the simplest and, at the same time, the most effective way of preventing cardiovascular disease for both men and women; a brisk tempo -- over 5 km/hour (about 3.1 miles per hour) -- is more important than the duration.

The conclusions from this second study are:

• The greater the physical effort, the less the risk of cardiovascular disease
• Brisk walking, running, rowing, and weight training are effective
• The classical risk factors for heart disease are still important (smoking, weight, high blood pressure, etc) and must be taken into account in planning a healthy lifestyle

Sources

• Effects of the amount and intensity of exercise on plasma lipoproteins WE. Kraus, JA. Houmard, BD. Duscha,  et al., N Engl J Med., 2002, vol. 347, pp. 1483--1492



• Exercise type and intensity in relation to coronary heart disease in men M. Tanasescu , MF. Leitzmann, EB. Rimm,  et al., Jama, 2002, vol. 288, pp. 1994--2000

Related Links
Walking for Heart Health
Penn State Cooperative Extension: Starting a Simple Walking Program
Tool: Find Out Your BMI
Fitness Helps Men Avoid Stroke

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