Posts Tagged ‘high-intensity exercise’

Irregular Heart Rhythm in Men Associated With Exercise Intensity Over Time

Young men who undertake endurance exercise for more than 5 hours a week may increase their risk of developing an irregular heart rhythm later in life, according to the results of a new study.

“Physical activity contributes to prevention of several diseases, and in general is good for the well-being of your body and mind.

However, frequent high-intensity exercise during many years could increase the risk for atrial fibrillation (AF),” lead author Dr Nikola Drca, Department of Cardiology, Karolinska Institute, Karolinska Hospital, Stockholm, Sweden, said in an interview.

The increase in risk is real, but quite small, he added.

The researchers presented their results online in the May 14, 2014, issue of the journal Heart.


In the Swedish study, the researchers quizzed more than 44,000 men aged 45 to 79 years about their leisure-time physical activity patterns at the ages of 15, 30, 50, and during the past year, when their average age was 60.

They tracked the participants’ heart health for an average of 12 years from 1997 onward to gauge how many developed AF, which is a known risk factor for stroke.

The men who had exercised intensively for more than 5 hours a week were 19% more likely to have developed AF later in their lives than those exercising for less than 1 hour a week.

The level of risk rose to 49% among those who did more than 5 hours of exercise a week at the age of 30, but who subsequently did less than an hour by the time they were age 60.

But those who cycled or walked briskly for an hour a day or more at age 60 were about 13% less likely to develop AF than those who did virtually no exercise at all.


“It seems that moderate doses of physical activity are enough to get the positive effects without acquiring the negative effects, while these benefits are lost with very high intensity and prolonged efforts,” Dr. Drca noted.

There are several possible mechanisms by which frequent endurance exercise could increase the risk for AF, he said.

These include enlargement of the left atrium, enlargement of and left ventricular hypertrophy, inflammatory changes in the left atrium, and an increase in the activity of the parasympathetic nervous system.

“In our study, the men who had the highest risk of developing atrial fibrillation were those who were very physically active when they were young, but stopped being physical active.

I think that moderate intensity regular physical activity that you continue throughout your life is the best way to maximize the benefits obtained by regular exercise while preventing undesirable effects.”

He added: “Physical inactivity and a sedentary lifestyle is a far bigger problem in the general population than excessive physical activity.

However, frequent high-intensity exercise during many years is associated with an increased risk of AF.”

Interval training advice from A Woman’s Guide to Muscle and Strength

Some years ago before a meniscus tear curtailed my jogging, my friend Jack and I set out for a run in East Hampton.

Jack, a well-trained triathlete, quickly got ahead of me, so he easily adapted his run into a fartlek, the Swedish term for Speed Play.

He ran hard for a few hundred yards, then jogged the next few hundred as he waited for me to plod along and catch up.

A fartlek is a less structured way of doing interval training.

Interval training involves higher-intensity exercise followed by recovery periods in a very specific time frame.

“The purpose of performing short bouts of high-intensity exercise is to reach overload, or uncomfortable intensity levels, throughout your training routines,” writes personal trainer Irene Lewis-McCormick in her new book A Woman’s Guide to Muscle and Strength.

“Obviously, it would be impossible to exercise at such high intensity levels for an entire 30-minute workout.

This is why there are built-in rest periods – not enough to allow you to fully recover, but enough to challenge you appropriately during these quick-paced, time-efficient workouts.”

In the book, Lewis-McCormick provides examples of work-to-rest ratios, that is, how long you exercise compared to how long you recover.

For example, she provides a sample for a 1:1 work-to-rest ratio:

Treadmill: Alternate 5 minutes of running (at 5 mph, or 8 km/h, or faster) with 5 minutes of walking (at 3.5 to 4 mph, or 5.6 to 6.4 km/h) for a total of 30 to 45 minutes.

Elliptical trainer: Alternate 2 minutes at a high intensity (as hard as you can work while still maintaining good form, posture, and control) with 2 minutes at a moderate intensity for a total of 30 to 45 minutes.

You can change the intervals to suit your needs or how you feel on a particular day.

Perhaps you exercise twice or three times as long as you rest.

Or if you’re not feeling in top shape, switch to twice as much rest as exercise.

“Most important with interval training is to remain consistent,” she writes.

“If you decide to run on the treadmill at a 2:1 work-to-rest ratio, you need to stay true to the intervals and not decide halfway through that you need more time to rest or can wait another minute.

The training benefit comes from the overload that results from the consistency of the ratios.

For example, if you decide that the hard part will take two minutes and your recovery will take one minute, stick with that routine during the entire workout to the best of your ability.”

If you’re more into fartlek sessions, which are designed to break up the monotony of interval training on a track, try these The Top 6 Favourite Fartlek Sessions.

As I recall, Jack and I finished our run, both satisfied with our workouts.

With less cartilage and more arthritis in my right knee, my aerobic training is now limited to the exercycle, where I do 30 minutes of interval training, usually at a 1:1 ratio: after 5 minutes of warm-up at a slow pace, I go hard for 5 minutes, then easy for the next 5, hard for 5, easy for 5, ending with another 5 minutes of cool-down.