We are being told that short bursts of high-intensity training are better for body composition than slow and steady cardio training.  Ok, nothing new here.  However, one must use common sense. 

The American Heart Association has issued a statement that outlines the benefits and risks of vigorous exercise. Physically active people have a reduced risk of a sudden heart attack.  That we all should know.  Be aware that intense exercise training can have risks to new exercisers or people with undiagnosed cardiovascular conditions or prior cardiac episodes. 

I see so many people who rush into intense training and either get injured or so sore that they can not work out for days. They may stop exercising entirely because of this.  Slow and steady wins the race, folks.  When you build a routine over time, the body will adapt and adjust to a higher intensity.  Do increase intensity if you are cleared by your physician, in order to have increased benefits.  

I've often mentioned the number of people I know with joint pain from high-impact exercise.  I have some hip and knee pain myself from injuries when I was younger.  Pay attention to your body!  Increase intensity in ways that do not impact the problematic joint.  Pay attention to the surface that you are exercising on and the temperature.  Hot yoga and exercising in extreme temperatures is not smart!  My goodness, I'm on my soapbox again.  :) 

The American Heart Association has these recommendations for anyone starting an exercise program.

Warm-up by doing the planned activity at a slower pace.  The heart rate should rise gradually.

Increase intensity and length of exercise gradually.

Be mindful of conditions when you exercise such as humidity, temperature, elevation, etc.

Cool down after exercise to let the heart rate return to normal.  

Seek medical attention if you experience any heart-related symptoms such as shortness of breath, chest pressure, or lightheadedness.  

Again, most of this is common sense but I have seen common sense go out the window way too many times.  We forget we are over 45, haven't exercised in years, or are impatient to see the results we are seeking.  Be kind to yourself by pacing your progress and balancing nutrition and stress.  A little less intensity and putting down the candy bar may be the right choice and still give you the body composition that you desire.  

Reference:   Exercise-related acute cardiovascular events and potential deleterious adaptation following long term exercise training. Placing the risks into perspective- An update from the American Heart Association.  Available in Circulation (2020;141,e705-36)