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Least Fit Adults Benefit Most from Modest Exercise

Modest regular physical activity significantly reduces the risk of dying in the least fit individuals, a new study suggests.

The study was published in this month’s Medicine & Science in Sports & Exercise, the official journal of the American College of Sports Medicine.

The study involved 4,384 participants with an average age of 56 years and a body mass index (BMI) of 28.6. Participants were followed for an average of almost 9 years.

Tread mill testing was conducted to assess fitness levels at baseline. Study participants were divided into five groups (quintiles) of fitness based on metabolic equivalents (METs)† achieved. The least-fit group was designated Q1; the next-least fit level was Q2, etc. The most-fit group was designated Q5. Only subjects with normal exercise test results and no history of cardiovascular disease were included in the study.

Physical activity data of participants was collected between 1993 and 2006. Based on weekly caloric expenditure levels, participants were classified as sedentary (<1,000 calories), moderately active (1,000 – 1,999 calories) or active (>2,000 calories).

During the study, 655 deaths occurred. The number of deaths from all-cause and cardiovascular mortality decreased significantly with higher fitness levels (all cause mortality was 25% for Q1 and 6% for Q5; cardiovascular mortality was 5.3% for Q1 and 0.9% for Q5). However, the greatest difference was between the least-fit and next-least fit quintiles – all-cause mortality and cardiovascular mortality rates dropped by about 50 percent from Q1 to Q2.

Risk factors lowered and use of cardiovascular medications decreased as fitness levels increased. But, the biggest differences were seen between the least-fit and next-least fit group. The least fit group had greater use of cardiovascular and blood pressure medications (ACE inhibitors, calcium channel blockers) and had a higher incidence of diabetes compared to the next-least fit group.

Age adjusted weekly energy expenditure levels differed across the five groups for recent (past year) and lifetime (adulthood) recreational activity. However, the difference in activity levels was more pronounced when comparing recent recreational activity between the least-fit and next-least fit groups. The least-fit group expended 40 percent fewer calories per week on average (1,129 METs for least fit; 1,566 METs for the next-fit group).

At higher fitness levels, peak heart rate, peak blood pressure readings and METs improved (e.g., Q1 METs were 4.4; Q5 METs were 14.4). Significant differences in maximum heart-rate, systolic blood pressure and exercise capacity were also observed between Q1 and Q2.

After adjusting for age, risk factors, cardiovascular medications, reduced peak exercise capacity (METs) was the strongest predictor of mortality. Each 1-MET increase in exercise capacity conferred an 11 percent risk reduction for all cause mortality and a 13 percent risk reduction for cardiovascular mortality for all participants. If just Q1 and Q2 were considered, the risk reduction improved to 21 percent for all cause mortality and 24 percent for cardiovascular mortality.

†Metabolic Equivalent of Task (MET) or Metabolic Equivalent. One MET is defined as the ratio of metabolic rate (the rate of energy consumption) during a specific physical activity to a reference rate of metabolic rate at rest. MET values of physical activities range from 0.9 (sleeping) to 18 (running at 17.5 km/h).

The Bottom Line

This study demonstrated that it was the sedentary lifestyle in the least-fit group that accounted for the differences in mortality – not the differences in health status (e.g., cardiovascular risk factors or age).

It also showed that it is the most recent physical activity that offers protection against mortality. This reiterates the importance of maintaining physical activity levels throughout adulthood to lower this risk. Importantly, those who are the least-fit can benefit the most from starting an exercise program.

If you don’t consider yourself a jock or a gym rat, that’s fine. By engaging in just 30+ minutes of moderate-intensity physical activity, on 5 or more days a week, you can substantially lower your mortality risk. A good example is a brisk walk.

As physical activity levels increase beyond this threshold, you can expect to not only improve your fitness levels but prolong your lifespan.

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